[carbed 85 gt]

I have a problem not with surging but high idle. It will idle low as I want it to until I try to set the TPS to around .9 it will idle to about 1200 and this is with 2 different TPS sensors. If I bring it back to .6 or less it will idle where I set it.

[leveling]

[jrichker]

Originally Posted by leveling

Some troll has left his trash behind... The link is an advertisement for some easy money scam

[BLKBELT]

I went through the checklist .The car ran good for about two weeks without a hitch.Then it started bucking like it was losing fuel pressure ,I installed a pressure gauge and it matains 36 pds.The scanner reads 29,54,66,87and 96 .Any ideals? Thank uou

[jrichker]

Originally Posted by BLKBELT

I went through the checklist .The car ran good for about two weeks without a hitch.Then it started bucking like it was losing fuel pressure ,I installed a pressure gauge and it matains 36 pds.The scanner reads 29,54,66,87and 96 .Any ideals? Thank uou

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 54 – ACT sensor out of range. Broken or damaged wiring, bad ACT sensor. Note that that if the outside air temp is below 50 degrees F that the test for the ACT can be in error.

Check the resistance of the black/white wire to battery ground. If it is less than 1 ohm, it is good. If it is more than 1 ohm, the black/white wire has bad connections or a broken wire. Always take resistance measurements with the circuit powered off.

Then check the resistance of the ACT sender located in the #5 intake runner on most 5.0 stangs.

ACT & ECT test data:

The ACT & ECT have the same thermistor, so the table values are the same

Pin 7 on the computer - ECT signal in. at 176 degrees F it should be .80 volts

Pin 25 on the computer - ACT signal in. at 50 degrees F it should be 3.5 volts. It is a good number if the ACT is mounted in the inlet airbox. If it is mounted in the lower intake manifold, the voltage readings will be lower because of the heat transfer. Here's the table :

68 degrees F = 3.02 v
86 degrees F = 2.62 v
104 degrees F = 2.16 v
122 degrees F = 1.72 v
140 degrees F = 1.35 v
158 degrees F = 1.04 v
176 degrees F = .80 v
194 degrees F = .61

Ohms measures at the computer with the computer disconnected, or at the sensor with the sensor disconnected.
50 degrees F = 58.75 K ohms
68 degrees F = 37.30 K ohms
86 degrees F = 27.27 K ohms
104 degrees F = 16.15 K ohms
122 degrees F = 10.97 K ohms
140 degrees F = 7.60 K ohms
158 degrees F = 5.37 K ohms
176 degrees F = 3.84 K ohms
194 degrees F = 2.80 K ohms

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).

The MAF output varies with RPM which causes the airflow to increase or decease. 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.

For voltage measurements, the red & back wires are used as a test pair, and the dark blue/orange and tan/light blue are a test pair. That means you measure the voltage using only using the test pair as + & -. Do not measure between the colors and ground for this test.

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 and ground.

See the following website for some help from Tmoss (diagram designer) & Stang&2Birds (website host)

http://www.veryuseful.com/mustang/te...nks-ign-ac.gif

http://www.veryuseful.com/mustang/te...1eecPinout.gif

Code 87 – fuel pump primary circuit failure. The fuel pump lost power while the engine was running. Check fuel pump relay, check inertia switch, wiring to/from inertia switch, red wire going to inertia switch for +12volts. Check the other side of inertia switch for +12 volts.

To help troubleshoot the 87 code, follow this link for a wiring diagram for 89-93 cars [urlhttp://www.autozone.com/servlet/UiBroker?ForwardPage=az/cds/en_us/0900823d/80/19/59/5a/0900823d8019595a.jsp [/url]

For 79-88 cars use, http://www.autozone.com/servlet/UiBr...3d8016713c.jsp

The following test path covers two different wiring schemes. Make sure you are following the one for your model year car.

Code 96 – KOEO- Fuel pump monitor circuit shows no power - Fuel pump relay or battery power feed was open - Power / Fuel Pump Circuits. The fuel pump lost power at some time while the ignition switch was in the run position.

Look for a failing fuel pump relay, bad connections or broken wiring. The fuel pump relay is located under the Mass Air Meter on Fox bodied stangs built after 91. On earlier model cars is under the passenger seat. On Mass Air Conversions, the signal lead that tells the computer that the fuel pump has power may not have been wired correctly. See http://www.stangnet.com/tech/maf/massairconversion.html

To help troubleshoot the 96 code , follow this link for a wiring diagram for 87-90 models http://www.veryuseful.com/mustang/te...nks-ign-ac.gif

for 91-93 models see http://www.autozone.com/images/cds/g...3d80195960.gif

Look for power at the fuel pump - the fuel pump has a connector at the rear of the car with a pink/black wire and a black wire that goes to the fuel pump. The pink/black wire should be hot when the test connector is jumpered to the test position. . To trick the fuel pump into running, find the ECC test connector and jump the connector in the lower RH corner to ground. http://www.mustangworks.com/articles...-iv_codes.html for a description of the test connector. it. No voltage when jumpered, check the fuel pump relay and fuse links.

86-90 Models:
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 drivers 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. Good voltage there, then the fuel pump is the likely culprit since it is getting power. 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. Good voltage there & at the Pink/black wire, swap the relay.

91-93 Models:
Using the diagram, check the dark green/yellow wire from the fuel pump relay: you should see 12 volts or so. If not the relay has failed or is intermittent. Check the inertia switch: on a hatch it is on the drivers 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. Good voltage there, then the fuel pump is the likely culprit since it is getting power. No voltage there, check the Pink/black wire, it is the power feed to the fuel pump relay & has a fuse link in it. Good voltage there & at the dark green/yellow wire, swap the relay.

[BLKBELT]

Thank you jrichker,I was sure that you would try to help me out.I will let you know how this information goes. Thanks again.

[vikingpower]

Can a leaky header/h-pipe flange cause surging? I got a pretty loud leak from under there and I was wondering if air is getting in there and contaminating the exhaust around the O2 sensors. I've got BBK LT's and h-pipe, and the o2 sensors are only about 3 years old (Bosch). Also is there any way to stick a gasket in the ball flange?

[jrichker]

Originally Posted by vikingpower

Can a leaky header/h-pipe flange cause surging? I got a pretty loud leak from under there and I was wondering if air is getting in there and contaminating the exhaust around the O2 sensors. I've got BBK LT's and h-pipe, and the o2 sensors are only about 3 years old (Bosch). Also is there any way to stick a gasket in the ball flange?

No.

There is always pressure inside the exhanust system. There is no way you can suck air into the exhaust on a running engine. The exhaust will be pushing gases out any leaky joint it can find.

[rideapony]

Well this is my first interaction in these forums. Thank you for this thread I've been fighting with surges for a long time now. I tried all what is mentioned with non or little success and my next move will be to splice once and for all the "Salt/Pepper" connectors to eliminate any loose, wet or corroeded connections.

[vristang]

JR - just a suggestion for some clarification on the first post in this ultra cool thread.

Item 13 reads
13.) Mismatched MAF and injector size. The MAF must have a matching flow rating for the injectors. If you have 24 lb in injectors, you need a 24 LB MAF. The Cobra computer is the exception to this rule, since it uses a 19 LB MAF & internal tables to modify the fuel curve. Some aftermarket devices can modify the mismatch, but they are not very common.


This could be somewhat misleading as...
In the 93 Cobra setup the MAF, MAS, fuel injector size, and the actual Calibration File in the Cobra computer were all different than the A9* series computers. The 93 Cobra is its own beast.

Of course running an aftermarket MAF or larger injectors will change things, as you already stated.

Off topic -
I am about to find out how well this applies to an SD N/A 2.3L 87 Mustang.

jason

[vanwilder692]

ok the iac, or idle air control valve, you said, unplug it, start car, adjust to 600 rpms? well my car wont even idle with it unplugged. so should i turn the iac upside down? it is an aftermarket sensor so maybe thats why since replacing it, my cold idle sucks!

[vanwilder692]

ok the iac, or idle air control valve, you said, unplug it, start car, adjust to 600 rpms? well my car wont even idle with it unplugged. so should i turn the iac upside down? it is an aftermarket sensor so maybe thats why since replacing it, my cold idle sucks![/QUOTE]

[vristang]

Originally Posted by vanwilder692

ok the iac, or idle air control valve, you said, unplug it, start car, adjust to 600 rpms? well my car wont even idle with it unplugged. so should i turn the iac upside down? it is an aftermarket sensor so maybe thats why since replacing it, my cold idle sucks!

[/quote]

You may have to turn the throttle set screw a little to get to where you can idle.

[jrichker]

Originally Posted by vanwilder692

ok the iac, or idle air control valve, you said, unplug it, start car, adjust to 600 rpms? well my car wont even idle with it unplugged. so should i turn the iac upside down? it is an aftermarket sensor so maybe thats why since replacing it, my cold idle sucks!

Originally Posted by jrichker

This isn't the method Ford uses, but it does work. Do not attempt to set the idle speed until you have fixed all the codes and are sure that there are no vacuum leaks. Warm the engine up to operating temperature, place the transmission in neutral, and set the parking brake. Turn off lights, A/C, all unnecessary electrical loads. Disconnect the IAC electrical connector. Note the engine RPM: use the mechanical adjustment screw under the throttle body to raise or lower the RPM until you get the 600 RPM mark +/- 25 RPM. When you are done, reconnect the IAC electrical connector. Changing the mechanical adjustment changes the TPS, so you will need to set it.

Turning the IAC upside down won't help much if you can't set the mechanical base idle speed.

[HISSIN50]

Originally Posted by vanwilder692

ok the iac, or idle air control valve, you said, unplug it, start car, adjust to 600 rpms? well my car wont even idle with it unplugged. so should i turn the iac upside down? it is an aftermarket sensor so maybe thats why since replacing it, my cold idle sucks!

You do have a hot motor and all accessories turned off when you try to let it idle with the IAC disconnected, right? I had to ask.

Good luck.

[vanwilder692]

Originally Posted by HISSIN50

You do have a hot motor and all accessories turned off when you try to let it idle with the IAC disconnected, right? I had to ask.

Good luck.

yea i turned everything off, and im not finding any codes for it. so im gonna try it again.

[89-notchback]

My car has the hanging idle and a tiny surge, the idle hangs for like 2 to 5 sec, I notice when i unplug the IAC the idle does not change, so i'm assuming this might be part of the problem, the IAC looks to be from a parts store and looks brandnew. Should i try another local parts store one , Or is the ford one from the dealer really better?, I was looking in cj pony parts catalog and it says they need a code No. from inside the door jamb when ordering one from them, do i really need this code to order one? becuse my car was converted from a 4cyl when i bought it.

[jrichker]

The first post contains all the updates to the fixes. I continue to update it as more people post fixes or ask questions. Pay special attention to the setting base idle speed section.

[Nicoleb3x3]

does anyone know if the ACT sensor will creat surging idle and driving too??? like driving slowly in 1st gear?

I've had limited time with the car because it's been in and out of the tranny shop...so I've lost allot of time to narrow this checklist down...

[jrichker]

A surge/bucking in first gear is not uncommon at just off idle. The engine may try to stall and speed up. Any tendency to surge may be amplified by the load of moving the car with light or no pressure applied to the throttle.

[Nicoleb3x3]

I think I found my surge issue:

15.) EGR leaking or partially open. An EGR that doesn’t seal or has vacuum applied when the engine is at idle can cause rough idle. Look for EGR code 34 in this case. Disconnect the EGR vacuum and cap the line and observe if the idle improves.

Carbon between EGR the pintle valve and seat can hold the valve off its seat. Remove the EGR valve and clean it with carbon remover. Prior to re-installing see if you can blow air through the flange side of the EGR by mouth. If it leaks, there is carbon stuck on the pintle valve seat, replace the EGR valve ($85-$95).

If I take the vacume line off and plug the vacume line, then my idle is perfect now. So; can I just replace the EGR Sensor/EGR valve? is there both the sensor and the valve in this assembly?

[jrichker]

Follow the instructions and see what happens. If you can blow through the EGR after cleaning it, replace it. The EGR vavle is $85-$95 and the sensor is $15-$25.

The EGR system has a vacuum source (line from the intake manifold) that goes to the EVR, computer operated electronic vacuum regulator. The EVR is located on the back of the passenger side shock strut tower. The computer uses RPM, Load. and some other factors to tell the EVR to pass vacuum to open the EGR valve. The EGR valve and the passages in the heads and intake manifold route exhaust gas to the EGR spacer (throttle body spacer). The EGR sensor tells the computer how far the EGR valve is open. Then computer adjusts the signal sent to the EVR to hold, increase or decrease the vacuum. The computer adds spark advance to compensate for the recirculated gases and the slower rate they burn at.

There should be no vacuum at the EGR valve when at idle. If there is, the EVR (electronic vacuum regulator) mounted on the backside of the passenger side wheelwell is suspect. Check the vacuum line plumbing to make sure the previous owner didn’t cross the vacuum lines.

Diagram courtesy of Tmoss & Stang&2birds.

[Nicoleb3x3]

I have a vacume line comming form the back of the upper intake going directly to the EGR...so that's wrong then!

so; I found the EVR and it has a rubber vacume piece w/ one not being used, and two valcume lines going to similar canister like vacume things, and then from there it goes to the in the fender vacume ball, and then to the 3 tier vacume piece, and then to the vacume tree which is then hooked up to the intake.



so; should there be a vacume line where there's a blank vacume part here not be used, and go to the EGR?

[Nicoleb3x3]

btw; my car is a 93

[jrichker]

On your picture of the EVR, the red vacuum line should connect to manifold vacuum. The green vacuum line should conncet to the EGR valve.

On my car, there is a 4 way rubber splice connector. The red line connects to a black vacuum line that goes to the manifold vacuum. The green line connects to a white line that goes to the EGR valve. You car is a conversion, so the splice may not be present.