Cranks OK, but No Start Checklist for Fuel Injected Mustangs

Discussion in 'Fox 5.0 Mustang Tech' started by jrichker, May 22, 2006.

  1. Have you figured out your issue with the no start? I am having a heck of a time getting my 92 5.0 to run! I just posted for help with my problem, and i hope someone can help me figure it out. :( Can you read my post and see if you have any suggestions.?. thank you! Happy New Year !
  2. 5.) Fuel pressure OK, the injectors are not firing.
    A.) The PIP sensor in the distributor tells the computer when to fire the injectors. A failing PIP sensor will sometimes let the engine start if the SPOUT is removed.
    A noid light available from any auto parts store, is one way to test the injector circuit to see if the injectors are firing. The noid light plugs into the fuel injector harness in place of any easily accessible injector. Plug it in and try to start the engine: it will flash if the injector is firing.
    B.) I like to use an old injector with compressed air applied to the injector where the fuel rail would normally connect. I hook the whole thing up, apply compressed air to the injector and stick it in a paper cup of soapy water. When the engine cranks with the ignition switch on, if the injector fires, it makes bubbles. Cheap if you have the stuff laying around, and works good too.
    D.) Pull an injector wire connector off and look for 12 volts on the red wire when the ignition switch is on.
    E.) No power, then look for problems with the 10 pin connecter (salt & pepper shakers at the rear of the upper manifold).

    See the graphic for the 10 pin connector circuit layout.

    Sorry, the 10 pin salt & pepper fuel injector wiring harness connector diagram disappeared with's website. The lawyers ate it up... :(

    It's Back

    The injector power pin is the VPWR pin in the black 10 pin connector.
  3. Thanks for reminding me that I need to update the sticky. This is the current graphic for the 10 pin connectors.

    The injector power pin is the VPWR pin in the black 10 pin connector. [/b]
  4. That was my intention.
    You may want to expand the checklist. You can have correct pressure & not enough flow, which is my situation. It takes an incredibly long time to pressurize my new pressure tester, even with the fuel pumps running continuously with the jumper to ground on the Test Connector, by grounding the contact where the dotted red line joins the tan/green in the pic below. This info is in my Ford Service Manual. With the KOEO, grounding the contact will run the fuel pump continuously. BTW, fuel filter is new, old one looked normal when it was replaced several months ago.
  5. Low flow and normal pressure would suggest a restriction in the fuel path somewhere or low voltage at the pump. Or the pump could just be dying. The stock pump is 88 Liter Per Hour, or 1.47 Liter per minute. Therefore, minimum flow would be about 2 liter bottle full of fuel every 82 seconds. You might want to check my math:) Since it is a positive displacement pump moving an incompressible fluid, the volume should remain constant throughout the pump's pressure range.
  6. My in-tank pump is a 155 lph, installed about 20 years ago, as a replacement for the stock 88 lph. It feeds an 80 gal/hr Hypertech power Pump #4018. Can easily disconnect the relay for the Hypertech.
    Your math is good. I should be filling a 2L bottle in 46 sec or less. A very rough estimate is that my flow is about 1/10 of that. I'm almost surprised it starts & idles at all. I have to assemble some hoses to attach to the rail for flow testing. It's pumping about 20 oz/min. with the 155 only, with both pumps, about 32 oz/min.
    Walbro now has 255 lph pumps which can replace both of these. If the restriction is the Hypertech, it's coming out, & the new 255 will replace the old 155. If the restriction is the old 155, the new 255 will replace it & the Hypertech can be disconnected from power or removed. Either way, the tank will have to come out.
  7. Replaced fuel pump with Walbro 255 lph HiP. Old pump sock looked very bad. Boost pump is removed.

    Car was running 6 days ago, enough to get to the gas station. It was running rich, but making good power & idling fine. Pulling vacuum line from FPR had no effect on gauge reading 40psi, even though FPR has dedicated vacuum line & vacuum is 18-20 inHg. Removed FMU & now vacuum line connected to FPR has desired effect of reducing fuel pressure. Not sure what FMU has to do with it because it doesn't begin to close until pressure builds in vacuum line. It's all new except for the housing. Bench testing verifies it's all good.

    Take it out again 1 day ago, & engine is breaking up under load like nothing was ever done.

    Today. disassemble FPR, all looks good. Disconnect return line fitting at tank & blow out entire line with compressed air from the FPR. Then blow from disconnected hose to tank where it seemed it dislodged a blockage in the hose. If there was something in there, it's now in the tank. Reassembled FPR, connected remote Fuel Pressure Gauge to the Schrader valve & road tested. Power is good, fuel pressure is good, but now it won't idle.

    Found Schrader adapter for remote pressure gauge to be defective, too tight or too lose would not allow fuel to pass through it; modified it & now works as it should.

    Bad Codes, all codes were cleared before testing today.
    29-C -Insufficient input from vehicle speed sensor. Not connected to EEC, don't care.
    66-C - MAF sensor went below 0.4 volts during the last 80 warm-up cycles.
    67-O - Neutral safety circuit failure.
    95-C - Fuel pump secondary circuit failure. The EEC senses infinite resistance to ground from the fuel pump on the Fuel Pump Monitor circuit.

    67 & 95 make no sense at all. 66 may account for the no idle condition.

    Every time I fix something, another gremlin appears.
  8. Code 29 - Vehicle Speed Sensor (VSS) is an electronic sender mounted on the speedo pickup gear on the trans. It works the cruse control for both 5 speed and auto trans cars. The VSS is used to tell the computer to speed up the idle as you slow to a stop. This helps keep the engine from stalling when you slow down for a stop sign or stop light.

    Check to see if the electrical connector is plugged into it. Clean the connector & contacts with non flammable brake parts cleaner prior to replacing the sensor, as that may fix the problem. The sensor cost is under $30 and it is easy to replace.

    Code 66 MAF below minimum test voltage.
    Insufficient or no voltage from MAF. Dirty MAF element, bad MAF, bad MAF wiring, missing power to MAF. Check for missing +12 volts on this circuit. Check the two links for a wiring diagram to help you find the red wire for computer power relay switched +12 volts. Check for 12 volts between the red and black wires on the MAF heater (usually pins A & B). while the connector is plugged into the MAF. This may require the use of a couple of safety pins to probe the MAF connector from the back side of it.

    There are three parts in a MAF: the heater, the sensor element and the amplifier. The heater heats the MAF sensor element causing the resistance to increase. The amplifier buffers the MAF output signal and has a resistor that is laser trimmed to provide an output range compatible with the computer's load tables.

    The MAF element is secured by 2 screws & has 1 wiring connector. To clean the element, remove it from the MAF housing and spray it down with electronic parts cleaner or non-inflammable brake parts cleaner (same stuff in a bigger can and cheaper too).

    Changes in RPM causes the airflow to increase or decease, changing the voltage output.. The increase of air across the MAF sensor element causes it to cool, allowing more voltage to pass and telling the computer to increase the fuel flow. A decrease in airflow causes the MAF sensor element to get warmer, decreasing the voltage and reducing the fuel flow.

    Measure the MAF output at pins C & D on the MAF connector (dark blue/orange and tan/light blue) or at pins 50 & 9 on the computer. Be sure to measure the sensor output by measuring across the pins and not between the pins and ground.

    At idle = approximately .6 volt
    20 MPH = approximately 1.10 volt
    40 MPH = approximately 1.70 volt
    60 MPH = approximately 2.10 volt

    Check the resistance of the MAF signal wiring. Pin D on the MAF and pin 50 on the computer (dark blue/orange wire) should be less than 2 ohms. Pin C on the MAF and pin 9 on the computer (tan/light blue wire) should be less than 2 ohms.

    There should be a minimum of 10K ohms between either pin C or D on the MAF wiring connector and pins A or B. Make your measurement with the MAF disconnected from the wiring harness.

    See the following website for some help from Tmoss (diagram designer) & Stang&2Birds (website host) for help on 88-95 wiring

    Ignition switch wiring

    Fuel pump, alternator, ignition & A/C wiring

    Computer,. actuator & sensor wiring

    Fuse panel layout

    Vacuum routing

    Code 67 –
    Revised 5 Jan 2012 to add warning of possible idle surge condition due to code 67

    Cause of problem:
    clutch not depressed (5 speed) or car not in neutral or park (auto) or A/C in On position when codes where dumped. Possible neutral safety switch or wiring problem. This code may prevent you from running the Key On Engine On tests. External evidence from other sources claims that a code 67 can cause an idle surge condition. Do try to find and fix any issues with the switch and wiring if you get a code 67.

    The computer wants to make sure the A/C is off due to the added load on the engine for the engine running tests. It also checks to see that the transmission is in Neutral and the clutch depressed (T5, T56, Tremec 3550 & TKO)). This prevents the diagnostics from being run when the car is driven. Key On Engine Running test mode takes the throttle control away from the driver for several tests. This could prove hazardous if the computer was jumpered into test mode and then driven.

    The following is for 5 speed cars only.
    The NSS code 67 can be bypassed for testing. You will need to temporarily ground computer pin 30 to the chassis. Computer pin 30 uses a Lt blue/yellow wire. Remove the passenger side kick panel and then remove the plastic cover from the computer wiring connector. Use a safety pin to probe the connector from the rear. Jumper the safety pin to the ground near the computer.
    Be sure to remove the jumper BEFORE attempting to drive the car!!!

    Code 95 Key On, Engine not Running - the following test path is for 86-90 model Mustangs.

    The 95 code is because at one time or another, the fuel pump relay hiccupped and didn't provide power the pump when the computer told it to run. Sometimes this is a one time thing, other times it is a no run or runs poorly condition.


    Using the diagram, check the red/black wire from the fuel pump relay: you should see 12 volts or so. If not, check the inertia switch: on a hatch it is on the driver’s side by the taillight. Look for a black rubber plug that pops out: if you don't find it, then loosen up the plastic trim. Check for voltage on both sides of the switch. If there is voltage on both sides, then check the Pink/black wire on the fuel pump relay: it is the power feed to the fuel pump. No voltage there, check the Orange/Lt blue wire, it is the power feed to the fuel pump relay & has a fuse link in it. If there is good voltage there & at the Pink/black wire, swap the relay.

    Some Mass Air conversions neglect to run the extra fuel pump wire, and they always have a 95 code. See for more information on the Mass Air wiring conversion.

    See the following website for some help from Tmoss (diagram designer) & Stang&2Birds (website host) for help on 88-95 wiring Everyone should bookmark this site.

    Ignition switch wiring

    Fuel, alternator, A/C and ignition wiring

    Complete computer, actuator & sensor wiring diagram for 88-91 Mass Air Mustangs

    Complete computer, actuator & sensor wiring diagram for 91-93 Mass Air Mustangs

    Vacuum diagram 89-93 Mustangs

    HVAC vacuum diagram

    TFI module differences & pinout

    Fuse box layout
  9. Looking at the bigger picture. all these weird codes, here today, & gone tomorrow & different ones the next day can only mean 2 things EEC or 60-pin connector. I have no faith that any of these codes have any true meaning, individually, but collectively, they point to the EEC or the connections to it. The wires will always ohm fine backshell to backshell. If you de-mate the connector, the conditioned have changed so the test is not valid
    It's a computer, therefore, Garbage In = Garbage Out. The S&P connectors have never been separated in 24 years & look new, but will tighten them up as much as possible. Will do the same for the 60-pin.
  10. Maybe I am missing something regarding the NOID light. I have been to the local parts stores and check the usual online places. No one that I can find has any NOID lights that connect to the fuel injector harness. Do you have a place to get them or am I wrong about them plugging into the FI harness?
  11. The noid lights plug into the individual fuel injector connectors in place of the fuel injector.

  12. jrichkter, you sure this is correct in step 1??
    Don't you mean remove the coil wire from the coil and see if it sparks using your test method??
  13. No. Do it as directed. Remove the high voltage wire from the center of the distributor cap and leave it connected to the high voltage connector on the ignition coil and hold it 3/8” away from the engine block Then crank the engine as described above.
  14. Hey Steve, wanted to say THANKS!!! for your post,You were right on the money with you post,I went ahead and replaced the 10uf,and the two 47uf caps fixed my problem(ie:"fuel pump constantly runs")

    Thank You Very Much!!!
    jrichker likes this.
  15. Hi guys, great post and info for no start conditions. I too am having to troubleshoot my baby also, she is an 87 5.0 foxbody stang. I've read and followed jrichkers checklist, but im getting stumped when it comes to troubleshooting the fuel delivery system. I'm getting spark from the coil and at plug number 1, so I moved on to testing the fuel pump, when I jumper the eec test connector tan/grn wire the fuel pump doesn't constantly run. The key is turned on, but the fuel pump comes on whenever it wants to or just randomly. I'm new guys so any help is appreciated.
    I also tried spraying starter fluid in the throttle, but it still just cranks. Thanks in advance.
  16. No start when starting fluid is sprayed in the throttle body - remove the SPOUT from the TFI harness and try that starting fluid trick again. If it fires off briefly, the PIP sensor in the distributor is marginal or going bad. Plug the SPOUT back in the TFI harness before doing the next step. Use a noid light plugged into any one of the fuel injector wiring connectors, turn the key & crank the engine. If the PIP sensor is OK, the noid light will flash. If it doesn't, the PIP is probably bad.

    Once you have eliminated the PIP sensor, check the fuel pump. The computer depends on the PIP sensor to tell if the engine is running so it knows when to turn the fuel pump on and leave it turned on.

    Fuel Pump Troubleshooting for 87-90 Mustangs

    Revised 11-Mar-2014 to add new fuel pump wiring diagram.

    Clue – listen for the fuel pump to prime when you first turn the ignition switch on. It should run for 1-3 seconds and shut off. To trick the fuel pump into running, find the ECC test connector and jump the connector in the upper LH corner to ground.



    Turn the ignition switch on when you do this test.

    If the fuse links are OK, you will have power to the pump. Check fuel pressure – remove the cap from the Schrader valve behind the alternator and depress the core. Fuel should squirt out, catch it in a rag. A tire pressure gauge can also be used if you have one - look for 37-40 PSI. Beware of fire hazard when you do this.

    No fuel pressure, possible failed items in order of their probability:
    A.) Tripped inertia switch – press reset button on the inertia switch. The hatch cars hide it under the plastic trim covering the driver's side taillight. Use the voltmeter or test light to make sure you have power to both sides of the switch

    B.) Fuel pump power relay – located under the driver’s seat in most Mustangs built before 92. See the diagram to help identify the fuel pump relay wiring colors. Be sure to closely check the condition of the relay, wiring & socket for corrosion and damage.
    C.) Clogged fuel filter
    D.) Failed fuel pump
    E.) Blown fuse link in wiring harness.
    F.) Fuel pressure regulator failed. Remove vacuum line from regulator and inspect
    for fuel escaping while pump is running.


    The electrical circuit for the fuel pump has two paths, a control path and a power

    Control Path
    The control path consists of the inertia switch, the computer, and the fuel pump relay coil. It turns the fuel pump relay on or off under computer control. The switched power (red wire) from the ECC relay goes to the inertia switch (red/black wire) then from the inertia switch to the relay coil and then from the relay coil to the computer (tan/ Lt green wire). The computer provides the ground path to complete the circuit. This ground causes the relay coil to energize and close the contacts for the power path. Keep in mind that you can have voltage to all the right places, but the computer must provide a ground. If there is no ground, the relay will not close the power contacts.

    [b[Power Path[/b]
    The power path picks up from a fuse link near the starter relay. Fuse links are like fuses, except they are pieces of wire and are made right into the wiring harness. The feed wire from the fuse link (orange/ light blue wire) goes to the fuel pump relay contacts. When the contacts close because the relay energizes, the power flows through the contacts to the fuel pump (light pink/black wire). Notice that pin 19 on the computer is the monitor to make sure the pump has power. The fuel pump has a black wire that supplies the ground to complete the circuit.

    Remember that the computer does not source any power to actuators, relays or injectors, but provides the ground necessary to complete the circuit. That means one side of the circuit will always be hot, and the other side will go to ground or below 1 volt as the computer switches on that circuit.


    Now that you have the theory of how it works, it’s time to go digging.

    All voltage reading are made with one voltmeter lead connected to the metal car body unless otherwise specified

    Check for 12 volts at the red wire on the inertia switch. No 12 volts at the inertia switch, the ignition switch is turned off or faulty or there is no power to the EEC (computer) power relay. To be sure look for good 12 volts on the red wire on any fuel injector.
    Good 12 volts means the EEC relay is working. No 12 volts and the ECC wiring is at fault.
    Look for 12 volts on the red/green wire on the ignition coil: no 12 volts and the ignition switch is faulty, or the fuse link in the ignition power wire has blown. No 12 volts here and the ECC relay won’t close and provide power to the inertia switch. Check the Red/black wire on the inertia switch, it should have 12 volts. No 12 volts there, either the inertia switch is open or has no power to it. Check both sides of the inertia switch: there should be power on the Red wire and Red/Black wire. Power on the Red wire and not on the Red/Black wire means the inertia switch is open. Push the button on the side of it to reset it, and then recheck. Good 12 volts on one side and not on the other means the inertia switch has failed.

    Look for 12 volts at the Orange/Lt. Blue wire (power source for fuel pump relay). No voltage or low voltage, bad fuse link, bad wiring, bad ignition switch or ignition switch wiring or connections. There is a mystery connector somewhere under the driver’s side kick panel, between the fuel pump relay and the fuse link.

    Turn on the key and jumper the fuel pump test connector to ground as previously described. Look for 12 volts at the Light Pink/Black wire (relay controlled power for the fuel pump). No voltage there means that the relay has failed, or there is a broken wire in the relay control circuit.

    Pump wiring: Anytime the ignition switch is in the Run position and the test point is jumpered to ground, there should be at least 12 volts present on the black/pink wire. With power off, check the pump ground: you should see less than 1 ohm between the black wire and chassis ground.


    The yellow wire is the fuel tank sender to the fuel quantity gage. The two black wires are grounds. One ground is for the fuel tank sender and the other is the fuel pump. The ground for the fuel pump may be larger gauge wire that the fuel tank sender ground wire.

    Make sure that the power is off the circuit before making any resistance checks. If the circuit is powered up, your resistance measurements will be inaccurate.

    You should see less than 1 Ohm between the black wire(s) and ground. To get some idea of what a good reading is, short the two meter leads together and observe the reading. It should only be slightly higher when you measure the black wire to ground resistance.

    The Tan/Lt Green wire provides a ground path for the relay power. With the test connector jumpered to ground, there should be less than .75 volts. Use a test lamp with one side connected to battery power and the other side to the Tan/Lt Green wire. The test light should glow brightly. No glow and you have a broken wire or bad connection between the test connector and the relay. To test the wiring from the computer, remove the passenger side kick panel and disconnect the computer connector. It has a 10 MM bolt that holds it in place. With the test lamp connected to power, jumper pin 22 to ground and the test lamp should glow. No glow and the wiring between the computer and the fuel pump relay is bad.

    Computer: If you got this far and everything else checked out good, the computer is suspect. Remove the test jumper from the ECC test connector located under the hood. Probe computer pin 22 with a safety pin and ground it to chassis. Make sure the computer and everything else is connected. Turn the ignition switch to the Run position and observe the fuel pressure. The pump should run at full pressure.
    If it doesn't, the wiring between pin 22 on the computer and the fuel pump relay is bad.
    If it does run at full pressure, the computer may have failed.

    Keep in mind that the computer only runs the fuel pump for about 2-3 seconds when you turn the key to the Run position. This can sometimes fool you into thinking the computer has died. Connect one lead of the test light to power and the other lead to computer pin 22 with a safety pin. With the ignition switch Off, jumper the computer into self test mode like you are going to dump the codes. Turn the ignition switch to the Run position. The light will flicker when the computer does the self test routine. A flickering light is a good computer. No flickering light is a bad computer.
    Remove the test jumper from the ECC test connector located under the hood.

    Fuel pump runs continuously: The fuel pump relay contacts are stuck together or the Tan/Lt Green wire has shorted to ground. In extreme ghetto cases, the pump relay may have been bypassed. Remove the fuel pump relay from its socket. Then disconnect the computer and use an ohmmeter to check out the resistance between the Tan/Lt Green wire and ground. You should see more than 10 K Ohms (10,000 ohms) or an infinite open circuit. Be sure that the test connector isn’t jumpered to ground.
    If the wiring checks out good, then the computer is the likely culprit.

    Prior to replacing the computer, check the computer power ground. The computer has its own dedicated power ground that comes off the ground pigtail on the battery ground wire. Due to it's proximity to the battery, it may become corroded by acid fumes from the battery. It is a black cylinder about 2 1/2" long by 1" diameter with a black/lt green wire. You'll find it up next to the starter solenoid where the wire goes into the wiring harness

    If all of the checks have worked OK to this point, then the computer is bad. The computers are very reliable and not prone to failure unless there has been significant electrical trauma to the car. Things like lightning strikes and putting the battery in backwards or connecting jumper cables backwards are about the only thing that kills the computer.

    See the following website for some help from Tmoss (diagram designer) &
    Stang&2Birds (website host)
  17. Thanks a lot jrichker. That's much clearer I will try unplugging the spout connector, to try the starting fluid again. and follow the next steps. I will report back any issuses or progress. Thanks again for the help because I was stumped
  18. What a great forum. I was running the no start checklist in hopes of running down my issue with this stock transplanted 1986 5.0 that ran fine for 10 years, but then sat for the last 10 with no real run time for nearly the last 7. I need a fresh perspective and hope that someone could chime in. With my initial checks and probing the fuel pump relay I shorted the fuel pump control circuit and damaged the EEC. Ironically I was able to get it started in what appeared to be a limp mode that blew smoke horribly and allowed me to drive it around the block, but it was clear it was still in need of help and a new computer, but at least I thought I was past the no start issue, or so I thought.

    With a new EEC and all other tests appearing to checking out it wouldn't fire at all. With the only error code for a out an of range air intake temperature (expected from what I understand as it is cold) , I was fearing that all of the injectors were simply shot from sitting and the limp mode just somehow overcame this, so then I fed it some starting fluid and it ran smooth as a top for 5 seconds and died again seeming to confirm my guess. With a great pulse on the noid light for injector #1, I am about to start pulling injectors...but instead have a friend feed it starting fluid to keep it running for 3 or 4 min while I wiggle wires and check for vacuum leaks and fuss with the idle screw. I tell him to stop with the starting fluid and low and behold it keeps running for about 2 minutes with stretches of perfect idle of 5 seconds at a time, and the rest of the time surges and hunts , and nearly stumbles and dies, and then revs again, idles nice for another five seconds and then eventually gives up the ghost and stumbles to a stop. Now that the block isn't cold (guessing) I can crank it without any aides for 2 or 4 seconds and can now get it to run as long as I want with a dance of the throttle, but it has no response and bogs out if you just open the throttle. There is no chance to drive it at all like this for reference. It is still a total mess and only "runs" in the technical sense of the word.

    So now I am conflicted, and welcome any recommendations. It seems that I need to recheck the TPS and IAC valves to make sure they are playing nice, but I find it hard to believe that it could magically idle perfectly for 5 or 8 seconds at a time if all of the injectors were messed up. I find all grounds and reference voltages appear fine and am wondering if I could be dealing with a PIP or TFI issue, though that seems unlikely with it perfectly happy to run on starting fluid.
  19. @Jjmcay
    How fresh is the gas in the gas tank? Old gas will do a lot of the same things you are seeing happening. Consider replacing the fuel filter if you haven't already done so.

    What sort of fuel pressure are you getting - beg, borrow or rent a fuel pressure test gauge.
  20. Again all great stuff. I had pumped out the tank and put a new filter on at the beginning of my effort with a couple fresh gallons of gas last month, but did both again this afternoon at your prompting and my own concerns that I may have not got all of the old gas out. I am glad I did so, as I am now able to get it to start after 10 to 20 seconds of cranking and pedal play. It isn't pretty, but fuel was definitely part of the issue (and still may be), and once it was warmed up it actually idled...almost. I have a fuel gauge on the rail, and it reads good at 40 psi, good prime and correct FPR response, no leaks.

    As some more back ground, I used the old in tank pump that had been sitting for years to empty the tank last month and put a couple gallons of fresh gas in at that point, but then I realized the pump was totally fried. I put in a new pump and sock in the tank as part of the no start tests along with a dozen other things. Letting a car sit does it no favors. I can do the pump from the trunk (as I can access it without dropping the tank) but it never really dawned on me until now that the dead pump likely meant I didn't get all of the old gas out, and sure enough upon emptying it this time I had well over 3 gallons in there so at least a gallon+ of old fuel, plus the left over the pump can't get. I'll likely drain it one more time and drop a couple more gallons in there with some injector cleaner and maybe some condensation remover just in case. The tank does look clean on the inside from when I changed the pump, but bad fuel for sure.

    Having read through the idle and surging tests I took the opportunity to disconnect the IAC and inline timing connectors while it stumbled/ran this time. Before the engine was warm, removing the IAC allowed the engine to idle better... as it would die out in 5 or 10 seconds with it connected, but once it was warmed up, neither seemed to make any notable difference. The one notable symptom is that it has no throttle response. Open the throttle slowly and it just gasps and dogs out. Cycle the throttle from zero to 75% in a quick manner and you can get it to rev up to 4K, but there is no power behind it. I didn't get much further than this today, but did check the TPS voltage response which seems good and lowered the idle screw back down to where the TPS reads 1.0v, and removed the IAC valve and inspected it. This did help it idle a bit better, though it still verged on stalling while it hunted and surged for it's idle point.

    On the IAC valve, should it be 100% closed when disconnected? Mine is slightly open at rest which would seem bad. If I remove the IAC motor actuator, the valve closes 100%. Both the actuator and valve move and are clean and smooth so just wondering if it is bad or good mechanically with the open state at rest. Going to pull EGR valve on next effort and flush the gas again and see where I am. Thanks for your input and great resource.
    #40 Jjmcay, Nov 5, 2014
    Last edited: Nov 5, 2014