Hello, I'm working on a 1994 5.0 Mustang GT 5 speed manual. It's all stock with just a few modifications. I know little of it's history, but it appears to have had a somewhat recent tuneup just by looking at the cleanliness of the distributor cap and wires. It has EGR and AIR systems deleted, and exhaust work with no cats. The EGR pipe to the exhaust has a cap and welded on, and it has a blockoff plate on the intake manifold. It does NOT have the plug in thing to the EGR harness to trick the computer, and is of course throwing codes for it. It had a charging issue that I have resolved (broken harness connector at voltage regulator). It also had a rough idle, I have done the following: Cleaned the MAF, IAT, IAC (which appears to be recently replaced also), and also cleaned the TB. I went through the whole procedure of setting base idle (whoever worked on it prior completely backed the set screw out), I did the IAC relearn, then set TPS voltage to ~0.98 volts. After all that, the car idles and runs awesome, but only when fully warmed up. On a cold start, it has a rough idle (idle fluctuates a few hundred rpms), and if you try to drive it it bucks and surges like crazy. It's essentially undriveable until fully warmed up, then runs almost like new.
So, would the computer thinking there's still EGR cause this issue? I don't know enough about these cars and the computer logic to know. I am tempted to buy the plug in to trick the computer just to see, plus eliminate the codes.
Any other ideas? I will list all the codes it's throwing below, but none seem to be related to any of this issue in my opinion. I also did the cylinder balance test or whatever it's called and it flashed the CEL 9 times, which I believe means it passed with no issues/codes.
This is my first experience with obd1 which has been a bit of a learning curve to get the codes lol. I'm used to working on obd2 and mainly GM/LS engines. Would love some helpful hints here, I've about exhaust everything I know to do.
Here are my ideas before I give up:
- Wrong spark plugs? (heat range way too cold, causing it to load up when cold)
- Unplug IAC during a cold start and see how it idles/runs. If much better, try replacing the IAC. Maybe it's not working properly only when cold? (doubt it...)
- Try the EGR plug tricker thing. Maybe this is messing up the fueling/tuning when cold? Maybe!?!?
- I've read about the ECT sensor causing issues like this. It doesn't appear to be bad, the coolant temp rises as expected slowly and steady. But maybe....?
One other symptom, which may be normal, I'm not sure, as I don't drive this car regularly. When shifting gears, the rpms actually jump up a couple hundred rpms when letting off the gas and pushing the clutch in. Seems odd, like the IAC is opening up when shifting. The rpms will fall again, just seems odd. Maybe this is normal???
That's about all I got, lol, any help appreciated!!! Below are the codes:
KOEO Codes:
327 - DPFE or EVP circuit below minimum voltage of 0.2 volts (I assume this is due to the EGR/AIR delete and may go away with the plug in tricker thingy)
564 - Electro-drive Fan circuit failure (no idea why this is triggering, when the car does the self test I can hear it run low and high speeds. Not too worried about this one...)
Continuous Memory Codes:
212 - Loss of IDM input to EEC or SPOUT circuit grounded (I had pulled the SPOUT thing to check static timing, this may be why this one was set. Also, I pulled codes multiple times prior to checking timing and this is the first time it's set. So not worried about this one right now, I'll clear them next time I pull codes...)
327 - Same as above
Engine Running Codes:
314 - Thermactor air system inoperative - left side (I assume this is due to the EGR/AIR delete and may go away with the plug in tricker thingy)
311 - Thermactor air system inoperative - right side (I assume this is due to the EGR/AIR delete and may go away with the plug in tricker thingy)
327 - Same as above
Cylinder Balance Test:
CEL flashed 9 times (believe this is a pass)
So, would the computer thinking there's still EGR cause this issue? I don't know enough about these cars and the computer logic to know. I am tempted to buy the plug in to trick the computer just to see, plus eliminate the codes.
Any other ideas? I will list all the codes it's throwing below, but none seem to be related to any of this issue in my opinion. I also did the cylinder balance test or whatever it's called and it flashed the CEL 9 times, which I believe means it passed with no issues/codes.
This is my first experience with obd1 which has been a bit of a learning curve to get the codes lol. I'm used to working on obd2 and mainly GM/LS engines. Would love some helpful hints here, I've about exhaust everything I know to do.
Here are my ideas before I give up:
- Wrong spark plugs? (heat range way too cold, causing it to load up when cold)
- Unplug IAC during a cold start and see how it idles/runs. If much better, try replacing the IAC. Maybe it's not working properly only when cold? (doubt it...)
- Try the EGR plug tricker thing. Maybe this is messing up the fueling/tuning when cold? Maybe!?!?
- I've read about the ECT sensor causing issues like this. It doesn't appear to be bad, the coolant temp rises as expected slowly and steady. But maybe....?
One other symptom, which may be normal, I'm not sure, as I don't drive this car regularly. When shifting gears, the rpms actually jump up a couple hundred rpms when letting off the gas and pushing the clutch in. Seems odd, like the IAC is opening up when shifting. The rpms will fall again, just seems odd. Maybe this is normal???
That's about all I got, lol, any help appreciated!!! Below are the codes:
KOEO Codes:
327 - DPFE or EVP circuit below minimum voltage of 0.2 volts (I assume this is due to the EGR/AIR delete and may go away with the plug in tricker thingy)
564 - Electro-drive Fan circuit failure (no idea why this is triggering, when the car does the self test I can hear it run low and high speeds. Not too worried about this one...)
Continuous Memory Codes:
212 - Loss of IDM input to EEC or SPOUT circuit grounded (I had pulled the SPOUT thing to check static timing, this may be why this one was set. Also, I pulled codes multiple times prior to checking timing and this is the first time it's set. So not worried about this one right now, I'll clear them next time I pull codes...)
327 - Same as above
Engine Running Codes:
314 - Thermactor air system inoperative - left side (I assume this is due to the EGR/AIR delete and may go away with the plug in tricker thingy)
311 - Thermactor air system inoperative - right side (I assume this is due to the EGR/AIR delete and may go away with the plug in tricker thingy)
327 - Same as above
Cylinder Balance Test:
CEL flashed 9 times (believe this is a pass)