Idle broken after exhaust install

Hydrocarbon · Jun 4, 2004

Is My Computer Fried?

Ok here's the problem. My car has a miss at idle. It started after I got it home from putting exhaust on it, and letting it sit for an hour or so.

If the car is moving faster then 3MPH its fine, otherwise it misses like crazy. I found out it will only to this while its warm, and I can seem to aggravate the problem by shutting the car off for a few seconds and restarting.

I pulled codes before and after installing the exhaust, both times I got:
22 KOEO
91 KOER
33 KOER
and sometimes I got code 41 KOER
One really strange thing is that my code scanner reports a 6 cylinder during the KOER test.

When I checked the timing I forgot to remove the SPOUT connector and the timing mark was jumping quite a bit. After I removed the SPOUT it stopped missing and the mark stayed at 10 degrees BTDC.
I'm replacing the BARO today, but I don't think that's the problem.
I'm going to test the O2s (both new) but I have to get a analog meter.
As for the EGR I'm not sure where to start.
Please help guys. Thanks.

Schlodes · Jun 4, 2004

What all did you change on the exhaust??? Did you change to an off road H pipe? I see your Stang is an older one... did you change the piping where the 02 sensors screw into? I ask because I had some problems when I installed an X pipe a while back. Below is the thread, and what was wrong with my car.. and how I finally figured it out.. This may be of no help to you but I hope it is Good luck.

http://forums.stangnet.com/showthread.php?t=463132

jrichker · Jun 4, 2004

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: 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. With the sensor removed from the EGR and still connected, press the plunger and watch the voltage change on the brown/lt green wire. Check for the same results on pin 27 on the computer.

If replacing the Baro sensor doesn't fix the problem, you have some bad wiring. The Orange/white wire supplies power for both of these sensors. The Black/white ground wire is also common to both sensors.

See the following website for some help from Tmoss (diagram designer) & Stang&2Birds (website host) for help on 88-90 wiring

http://www.veryuseful.com/mustang/tech/engine/images/88-91eecPinout.gif

Hydrocarbon · Jun 4, 2004

UPDATE:

Well my BARO sensor came from Schucks (Karagan) as a TPS (right box, wrong part). So I wasn't able to replace that today. So I decided to check my plugs. I found that #1 plug had a pice of carbon stuck between the tip and the electrode. The rest are white at the tip with black sooty deposits up inside the insolator.

I then focused on the EGR. It turns out that the EVR tested ok, but it wasn't opening. So I replaced that, and I have no more EGR codes.

I retested and now I get codes 44 and 94 (KOER). I don't have the smog hooked up, but I do have the Ron Morris eliminator kits for both the EVAP and TAB/TAD (here). So I'm not sure if I should be getting these codes or not. The funny thing is I never got them before today.

As for my exhaust. When I first started the engine it had open longtubes and it was running fine after I fixxed a vacuum leak. I drove it to the exhuast shop and put duel 2.5" Magnaflows with a O/R H-Pipe. It ran fine on the way home, but after I restarted the idle turned to poo.

OK I just test drove it and it still misses. My current codes are:
22 KOEO Will be fixed tomorrow if Schucks gets their s**t together.
44 Sec air injection (Not hooked up).
94 Same as above

Hydrocarbon · Jun 4, 2004

Now I'm pretty sure its a heat related problem.

I let the car cool down and restarted it. It ran fine for about 10min of idling, and about 15min of driving. After that It started missing again. I'm pretty sure that the computer reached closed-loop before it started missing.

Thinking that it may be heat related. I unplugged the o2 sensor harness and restarted...no change. I did the same thing to the MAF...nothing.
So it doesn't matter if its in open or closed loop, it still misses. It just has to be warm.

BTW I have a A9P ECC-IV computer.

Hydrocarbon · Jun 5, 2004

TTT

Am I going to be left to figure this out by myself?

Hydrocarbon · Jun 5, 2004

To whom it may concern.

I replaced the BAP today so no more code 22. I'm starting to think my computer is bad. I noticed my fuel pump was making a lot of weird noises, like it was losing power. When I tried to start the enigne the FP clicked on for 1sec (like it should), but when I tried to start the engine, it died after just a second, and the FP kept running until I turned off the key. After messing with it a little bit. The FP comes on after you turn on the key, and stays on until you turn it off. I can't even pull codes anymore.

I checked all the wiring and checked for 12V at the battery side of the relay, and the VPWR side, both checked out. I also tested pin/wire#22 for shorts, and got nothing. I tried replacing the realy, and it didn't help.
So what do you guys think? Replace the computer?

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