89 5.0 Hunts For Idle

[Zach Ferreira]

Hello my name is Zach and I have 89 foxbody 5.0 automatic just picked up a couple months ago and I've been driving it daily ever since with minor issue the engine burns a little oil and water pump leaks a little water but the other day I was letting it warm up and i heard the engine turn off. Started it back up and it's constantly searching for the right idle. I pulled the plugs and they're cover in oil/fuel so I do a basic tune up plugs, wires, cap, rotor and ignition module on the front of the distributor it seemed to help because the car no longer dies but still searches for idle. I checked fuel pressure and it's at 34-39 psi depending on if I rev the engine up. I went ahead and replaced the fuel pressure regulator since it was the original regulator. I had to pull the intake manifold to do so I replaced both throttle body gaskets and the upper intake gasket I also replaced all the injector o-rings and one injector cap that was broken. Also checked ignition timing and reset it just to be sure and still no change engine still hunts for idle but no popping or back firing when I snap the throttle. I have a 4 wire maf sensor and I have good power and ground and signal wire to and from the sensor and when I measure the voltage coming out the maf sensor with the engine running its 1.1 - 3v (I think that was wide open throttle but I was working alone and couldn't see the gauges from the engine bay) the voltage then steadily climbs down and steadies off at 1.2 at an idle. I pulled the IAC motor off and made sure the plunger isn't sticking there is a little bit of carbon built up on it but the plunger moves freely and so does the little motor and when the IAC is unplugged with the engine running it immediately stalls out. Also when the MAF sensor is unplugged the idle gets very choppy so I believe both of those work but I didn't actually measure the voltage coming in and out of the IAC. I assumed because the engine burns oil that maybe the 02 sensors are fowled out so I pulled those out and they're not wet but definitly have a good coating of suit on them. So I plan on replacing them in the morning when the parts store opens just for good measure plus I plan on keeping the car for a long time so I'm not too bothered by replacing parts that could be failing even if they're not the root cause of the problem. Just wondering if anyone has run into a similar problem like this and what they did to fix it. Also the ignition timing is where it has been for the past two months I've been driving it and I never pulled the distributor but I marked it before replacing the ignition module on the front because I had to turn it in order to remove the little set screws. I have a code reader and after i change the 02 sensors in the morning I'm gonna pull codes with it running. Any suggestions as to where to go from here would be greatly appreciated

 

[a91what]

Check for vacuum leaks. These cars are getting old so sometimes the plastic lines tend to break. Do a visual on the vacuum lines if that turns up nothing you can use some carb cleaner to spray around the lines to help, if the engine revs then you have a leak.

Clean the MAF sensor, (never touch the MAF element you will damage it) use only maf cleaner or non-chlorinated brake clean and spray the element down. Do this with the MAF disconnected and out of the car.

 

[Noobz347]

http://www.stangnet.com/mustang-forums/threads/help-me-create-the-surging-idle-checklist.698148/

 

[Mustang5L5]

Search for "Mustang idle reset procedure"

 

[General karthief]

You got a good jump on things, let us know what codes you get, there is also a procedure for cleaning the egr valve, it gets pretty messed up.
Is the car stock?
Pull the codes thats always number one on the list of things to do.
Welcome to stangnet, you'll get good advice if you post pics of you stang.

 

[Zach Ferreira]

So I replaced the 02 sensors today and the idle is a little better but when I pulled codes I got code 33 for EGR valve not opening properly I just went ahead and ordered a new one should be here in a couple of hours. I did drive the car today just down the street and it runs fine at wide open throttle, a little black smoke when I punch on it. Also when the car warms up and runs long enough the idle eventually gets worse and smoke starts coming out from the back of the engine near the firewall. Mostly white smoke except a little black out of the exhaust pipes. I pulled the EGR valve off and it's all gummed up. The idle is a little better now that the 02 sensor are replaced but only when cold

 

[Zach Ferreira]

Forgot to mention I did pull the maf sensor out and clean it with maf sensor cleaner as well as replaced the IAC gasket and sprayed carb cleaner all over the engine bay and air intake tube and vacuum lines and the idle never improved. The car is 100% bone stock to the best of my knowledge and I double check and all my vacuum lines are hooked up including the line to the pcv valve and the valve itself is hooked up.

 

[Zach Ferreira]

I've replaced the egr valve and no change the code for the egr valve did go away but the idle problem is still present. I now have a code 19 failure in EEC (PCM) internal voltage

 

[jrichker]

Code 19 - Engine off - No Vehicle Power (pins 37 + 57) or bad PCM VPWR Diagnosis. This is a wiring problem that is from a bad ECC power relay, bad connection, bad fuse link, bad ignition switch or a bad computer. The ECC relay is located on top of the computer under the passenger side kick panel. Pull the connector off any fuel injector and measure the voltage on the red wire: if its 12 volts or better, the ECC relay is OK. If the ECC relay is OK, pull the kick panel off and measure the voltage at pins 37 & 57. If it is 12 volts or more, then the computer's diagnostic firmware has taken a dump and is defective.

Engine running - Erratic idle during test (reset throttle & retest) - Idle Set Procedures .
See http://www.stangnet.com/mustang-forums/698148-help-me-create-surging-idle-checklist.html#post6855020 for the best way to set the mechanical base idle and cleaning procedure for the IAC/IAB.




Do the checklist....

You guys with idle/stall problems could save a lot of time chasing your tails if you would go through the Surging Idle Checklist. Over 50 different people contributed information to it. The first two posts have all the fixes, and steps through the how to find and fix your idle problems without spending a lot of time and money. It includes how to dump the computer codes quickly and simply as one of the first steps. I continue to update it as more people post fixes or ask questions. You can post questions to that sticky and have your name and idle problem recognized. The guys with original problems and fixes get their posts added to the main fix.

It's free, I don't get anything for the use of it except knowing I helped a fellow Mustang enthusiast with his car. At last check, it had more than 200,000 hits, which indicates it does help fix idle problems quickly and inexpensively.

 

[Zach Ferreira]

Thank you I appreciate the help and advice. I didn't know about the surging idle check list until you mentioned or I probably would have started there. I started with the basics and I was a little impatient I guess but I also didn't have a code scanner until last night and by the time I had it I already had parts of the car apart and didn't want to run the vehicle with old gaskets I'm sure you understand. Plus most of the parts I replaced were in need of replacement, although they may not of failed at the moment I'm sure they would have failed in the not too distant future. The previous owner hadn't done a lot matenice to the car since he bought it. I was also very unaware of the fact the obd1 system on this vehicle was actually capable of KOEO & KOER tests or I most certainly would have started there. I did the pull the computer out of the vehicle and I'm going to have it tested but I did find quite a bit of corrosion on the outside of the case and near the terminal where the wiring harness plugs in but no corrosion on damaged pins on the wiring harness itself. I will check the voltage on the wiring harness tomorrow and continue on from there until the problem is solved

 

[Joe B]

I had the same problem recently. Car wouldn't idle and would stall. It was a bad MAF sensor. Changed it and the car is running like a million bucks!!

 

[Zach Ferreira]

Sorry it's been a few weeks since
I posted anything but today has been the first day I've done any work to the car. So I had my computer sent off and tested and the company said they found an internal problem in the pcm (didn't say what it was though) but I went ahead and had them rebuild it. I assumed that was problem and re installed it and the car ran the same. I went ahead and pulled out the pcm relay and just replaced it, it was only 20 bucks no big deal. Cleared the codes out of the computer and car fires up and runs the same and then kicks the same code 19 for the pcm and a code 11 saying the OBD 1 system is ok so idk what to do now. Possible bad wiring harness at this point?

 

[Zach Ferreira]

I tested the power at the fuel injectors and I'm getting 12v at the injectors with the pcm unhooked from the car so that tells me the relay is working fine and I've got 12v at pin 37 and 57 for the harness that goes into the pcm itself. Not sure what to do, maybe send the pcm back to the company that just rebuilt it and have them double check and make sure nothing screwy happened

 

[jrichker]

Ford ODBI codes often have a two definitions.
1.) The engine is not running - KOEO (Key On, Engine Off)
2.) The engine is running KOER ( Key On, Engine Running)

If you got the code 19 with the engine running, it is a idle problem

If you still have idle problems, do the Surging Idle Checklist. Otherwise you may spend a LOT of time and money and not find the problem.