Idle Issue

[92Patrol5.0]

It runs fine when I first start it up. It idles normal. But sometimes after driving for a while when I come to a stop it will start to lope, like a cylinder isnt firing or something. The car rocks like I have a loppy cam, but it revs normal, doesnt cause any driveability issues or anything. Just when it settles into idle it drops in rpm and starts to chug and lope. If I keep driving after a while when I come to a stop again it idles normal and no problems. Or if I shut the car off when it does it, and restart it the idle is back to normal. I haven't checked codes yet. I get no CE light, but there could still be codes. Any idea what could be causing this? I hope I explained it clear enough cuz I don't really know how to explain it. *** I should also add that I have dumps and I can usually smell exhaust when I drive. However, when it starts to do this idle issue, I can smell fuel also.

 

[ram360]

definetly check the codes. I had a similar problem. My vehicle speed sensor was bad and causing the idle not to drop once I can to a stop.

 

[92Patrol5.0]

Ttt

 

[87'GTstang]

How coated is the intake tract from your throttle body on? When was the last time you cleaned your IAC? Have you tested your TPS?

 

[ram360]

Pull the codes

 

[HISSIN50]

it is also worth checking your plug wires real quick - given how this happens a bad wire is not real likely, but it could be allowing a cylinder to drop out.

Good luck.

 

[olymaster]

idle rich
get dyno tune

 

[smokenda22s]

having the same problem with my 91 gt vert, dies at idle. I've cleaned the EGR, IAC, MAF element, set the TPS. All the vacuum lines look too be good. Car runs good, sometimes it bucks, problem seems too happen when i come too a stop or slow down below 5-10mph..... havent pulled codes, went too a-zone but they said the car was too old, and i dont know how too pull them myself...any help appriciatied....thnx.......

 

[smokenda22s]

one more thing, doesnt matter if its hot or cold, i could start it up and about after a minute or two, it will just die.....

 

[Darkwriter77]

I share your pain. I've got a seemingly endless thread running with regards to almost the EXACT same symptoms. If you find a fix for it, by all means, let me know. PLEASE, let me know! So far, I've tried (in no particular order)...

1. EGR valve
2. TPS
3. IAC valve
4. Cleaned all ground cables (those that I could find)
5. TFI module (tested good, but going to replace tonight, anyway)
6. PCV valve
7. 10-pin connectors
8. Exhaust leaks
9. Seafoam treatment (twice)
10. Full tune-up (plugs, wires, cap/rotor, all filters/fluids, reset timing)
11. Replaced all vacuum hoses
12. Injectors (all 8 of 'em)
13. Swapped out cone filter for stock airbox
14. Cleaned MAF wires
15. MAP/BAP sensor
Plus some other stuff I can't remember right off hand...

I've yet to replace the O2 sensors, but those are next on the list. While some of these did improve the situation slightly, the problem isn't entirely gone. I think it's a culmination of several factors, and not necessarily just one quick fix. Might give any/all of the above a shot, either testing or cleaning them, and see if that helps. Good luck!

 

[92Patrol5.0]

This just started happening to me within the last 2 weeks or so. I normally do a tuneup(plugs, wires, cap, rotor) every spring but I didn't get to it this year. So that may be my problem. My car has almost 170k on the clock. It very well could be a sensor of some sort. I will have to pull the codes and see if I get anything out of that. It runs great, and then all of a sudden out of nowhere when at idle it will start doing this. Like I said, if I shut the car off and restart it right away it idles fine. Or if I keep driving for a bit it will eventually not do it anymore when I sit at idle. Thanks for all the ideas. At least I'll have a place to start if nothing else. Keep the ideas coming though.

 

[Nutzy19]

Please help with this as it is the same going on here.....Very coincidental.... alot of people with the SAME problems

 

[jrichker]

Here's the link to dump the computer codes with only a jumper wire or paper clip and the check engine light, or test light or voltmeter. I’ve used it for years, and it works great.

See http://www.troublecodes.net/Ford/
OR
See http://www.mustangworks.com/articles/electronics/eec-iv_codes.html

IF your car is an 86-88 stang, you'll have to use the test lamp or voltmeter method. There is no functional check engine light on the 86-88's except possibly the Cali Mass Air cars.

Codes have different answers if the engine is running from the answers that it has when the engine isn't running. It helps a lot to know if you had the engine running when you ran the test.

Trouble codes are either 2 digit or 3 digit, there are no cars that use both 2 digit codes and 3 digit codes.

For those who are intimidated by all the wires & connections, see http://www.actron.com/product_detail.php?pid=16153 for what a typical hand scanner looks like. Normal retail price is about $30 or so at AutoZone or Walmart.

Or for a nicer scanner see http://www.midwayautosupply.com/detailedproductdescription.asp?3829 – It has a 3 digit LCD display so that you don’t have to count flashes or beeps.. Cost is $35.

 

[smokenda22s]

pulled my codes, and what i pulled off were mostly related with voltage, or circuit problems. Codes 22,24,31,34,61,72,81, and 82, the last 2 are vacuum realted. do i need to adjust all these things or is there one particular thing that is not providing enough voltage???? alt, vol regulator, etc???

 

[smokenda22s]

engine was not running......

 

[Darkwriter77]

Haven't driven through a full tank of gas yet since the changeout, but it appears the cause of my car's similar demons was the combined work of a defective IAC (that I'd only had on for four days) and an ancient, crappy TFI module. I've put 30 miles on this since then, lots of short stop-and-go runs and re-starts in there, and the symptoms haven't showed a hint of returning at all. Adjusting my timing a little bit seemed to help, as well. Even though my TFI module tests good on a bench test, it still seems to have been one of the two main culprits, so if yours is over a year or two old, you might as well give it a swap.

Now, to see if I can actually get better than 13.6 MPG since the fix...

 

[92Patrol5.0]

I found my culprit

I believe I found what was causing my idle issue. I started the car today and heard a vacuum leak. I found the hose that runs from the charcoal canister up across the engine and into the intake had a big hole in it. It must have gotten hot and weakened and it split. I cut the bad piece off and reconnected it and no problems so far.

 

[olymaster]

ok i had those problems
and it was my e303 cam
tuner set my idle up to 850
and its good
no more studdering stalls
plus the tune tho
all fixed

 

[jrichker]

pulled my codes, and what i pulled off were mostly related with voltage, or circuit problems. Codes 22,24,31,34,61,72,81, and 82, the last 2 are vacuum realted. do i need to adjust all these things or is there one particular thing that is not providing enough voltage???? alt, vol regulator, etc???

Code 22 MAP (vacuum) or BARO signal out of range. The MAP or BARO sensor is pretty much the same sensor for both Mass Air & Speed Density cars. The main difference is where it is connected. Mass Air cars vent it to the atmosphere, while Speed Density cars connect it to the intake manifold vacuum. Its purpose is to help set a baseline for the air/fuel mixture and changes in barometric pressure. The MAP or BAP sensor puts out a 5 volt square wave that changes frequency with variations in atmospheric pressure. The base is 154 HZ at 29.92" of mercury - dry sunny day at sea level, about 68-72 degrees. You need an oscilloscope or frequency meter to measure it.

Baro or MAP test using frequency meter - run the test key on engine off. The noise from the ignition system will likely upset the frequency meter. I used a 10 x oscilloscope probe connected from the frequency meter to the MAP/BAP to reduce the jitter in the meter's readout.

If it is defective, your air/fuel ratio will be off and the car’s performance & emissions will suffer

Code 24 - Intake Air Temperature (ACT) sensor out of range. Bad sensor, bad wiring. The ACT for Mustangs built before 95 is in the #5 intake runner. It measures the air temperature in the intake to help computer the proper air/fuel ratio.

Note that that if the outside air temp is below 50 degrees F that the test for the ACT can be in error.

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: 31 (KOEO) - EVP circuit below minimum voltage. Vref (5 volt reference voltage supplied by the computer) missing or broken wire or bad connection in circuit. Use a DVM to check for 5 volts on the orange/white wire. If it is missing, look for +5 volts at the orange/white wire on the TPS or MAP sensor located on the firewall near the center of the car. Use the black/white wire for the ground for the DVM.
With the sensor removed from the EGR and still connected, press the plunger and watch the voltage change on the brown/lt green wire. Pull the passenger side kick panel and measure the voltage at the computer. You will need to remove the plastic cover over the wires and probe them from the backside. A safety pin may prove very useful for this task. Use pin 27, EVR input (brown/lt green wire) and pin 46, signal ground (black/white wire) to measure the voltage. The orange/white wire is Vref and should always be 5 volts -/+ .25 volt. Be sure to measure Vref at the EGR sensor to rule out any broken wires or bad connections.

Code 34 Or 334 - EGR voltage above closed limit - Failed sensor, carbon between EGR pintle valve and seat holding 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 the blow by test passes, and you have replaced the sensor, then you have electrical ground problems. Check the resistance between the black/white wire on the MAP/BARO sensor and then the black/white wire on the EGR and the same wire on the TPS. It should be less than 1 ohm. Next check the resistance between the black/white wire and the negative battery post. It should be less than 1 ohm.

Note that all resistance tests must be done with power off. Measuring resistance with a circuit powered on will give false readings and possibly damage the meter.

Let’s put on our Inspector Gadget propeller head beanies and think about how this works:
The EGR sensor is a variable resistor with ground on one leg and Vref (5 volts) on the other. Its’ resistance ranges from 4000 to 5500 Ohms measured between Vref & ground, depending on the sensor. The center connection of the variable resistor is the slider that moves in response to the amount of vacuum applied. The slider has some minimum value of resistance greater than 100 ohms so that the computer always sees a voltage present at its’ input. If the value was 0 ohms, there would be no voltage output. Then the computer would not be able to distinguish between a properly functioning sensor and one that had a broken wire or bad connection. The EGR I have in hand reads 700 Ohms between the slider (EPV) and ground (SIG RTN) at rest with no vacuum applied. The EGR valve or sensor may cause the voltage to be above closed limits due to the manufacturing tolerances that cause the EGR sensor to rest at a higher position than it should.

This will affect idle quality by diluting the intake air charge

Code 61 - Engine Coolant Temperature (ECT) sensor is or was too low. Failed sensor or bad wiring for the ECT. 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. Check the resistance of the Lt green/yellow wire at the sensor connector and Pin 7 on the computer. It should be less than 1 ohm. If it is more than 1 ohm, the Lt green/yellow wire has bad connections or a broken wire.

Code 72 - No MAP or MAF change in "goose" test - retest, check for frequency or voltage change. The MAP sensor or MAF sensor has failed or has some bad wiring or bad connections. Look for code 66 for MAF problems and code 22 for MAP problems to show up as well.

Code 81 – Secondary Air Injection Diverter Solenoid failure AM2. The solenoid valve located on the back side of the passenger side wheel well is not functional. Possible bad wiring, bad connections, missing or defective solenoid valve. Check the solenoid valve for +12 volts at the Red wire and look for the Lt Green/Black wire to switch from +12 volts to 1 volt or less. The computer controls the valve by providing a ground path on the LT Green/Black wire for the solenoid valve.

See http://www.veryuseful.com/mustang/t...ng5.0Vacuum.gif for help on the vacuum line plumbing.

Code 82 – Secondary Air Injection Diverter Solenoid failure AM1. The dump valve air diverter valve (front vacuum operated valve) isn’t working on the Thermactor Air System (smog pump). Look for broken or missing vacuum lines on the solenoid valve to the diverter valve Check the solenoid valve for +12 volts at the Red wire and look for the Red/White wire to switch from +12 volts to 1 volt or less. The computer controls the valve by providing a ground path on the Red/White wire for the solenoid valve.

I would look very closely at the possiblity of some wiring problems with the VREF circuit (orange/white wire) that supplies 5 volts to the sensors. It may be missing or low.

See AutoZone wiring diagrams for your car model year.

http://www.autozone.com/servlet/UiB..._us/0900823d/80/16/71/3c/0900823d8016713c.jsp for 79-88 model cars

http://www.autozone.com/servlet/UiB..._us/0900823d/80/19/59/5a/0900823d8019595a.jsp for 89-93 model cars

http://www.autozone.com/servlet/UiB..._us/0900823d/80/1d/db/3c/0900823d801ddb3c.jsp for 94-98 model cars

 

[90mustangGT]

I believe I found what was causing my idle issue. I started the car today and heard a vacuum leak. I found the hose that runs from the charcoal canister up across the engine and into the intake had a big hole in it. It must have gotten hot and weakened and it split. I cut the bad piece off and reconnected it and no problems so far.

I was thinking "vaccume leak" until that post, good job.

Clear codes and reset the memory and drive it a couple times and then re-run your codes, the other codes may have been caused by the vacuum leak but the ECT (engine coolant temp) is being detected as having a short. That can really effect drivability and MPG.