Okay. Here is the car, its a '97 Cobra with o/r x-pipe, MIL eliminators, flowmasters, 4.10's. Other than that its pretty much stock. I bought it a few months ago from a friend. Its got 95,000 miles on it and wasn't taken very good care of, but the price was right. The CEL has been on from the day he bought it, 3 years ago. So he just drove it around like that for 3 years and the car feels very slow for a Cobra. I haven't had much time to do anything to it, other than replacing the AC compressor. But now I am in the UAE and I left the Cobra with a friend so he could fix and drive it. He's a competent mechanic and owns an '04 & '05 GT so he is somewhat familiar with mustangs.
So here is where it started a week ago. He has a code reader so he downloaded the code and it was a P0171. So first we changed the front O2 sensors (because they have 95k on them). The P0171 came back. Also because the car is old we Seafoamed the intake. After Seafoaming and clearing the codes, the P0171 came back and now a P0174 came up. Common sense would tell you that if you got both codes, there must be a vacuum leak. So after a short check, it turns out the Seafoam worked too good and cleaned out all the gunk that had been sealing the intake. So we changed all the intake manifold gaskets and cleaned the IMRCs and checked the exhaust manifolds for leaks and tried again. This time the P0171 and P0174 came back and then a P1443. Good thing is all the lost power is back, now the car pulls smoothly all the way to redline. He checked the Charcoal Canister and all the vacuum lines, the EGR system , gas cap and PCV valves. Found a cracked up line and replaced it and the 1443 went away and hasn't come back but the P0171 & P0174 where still there. So we checked for intake leaks again and found small leaks at the ends of the IMRC's. So we pull the intake back apart and replaced the seals on the IMRC shaft and put it all back together.
After rebuilding the IMRC's and finding the IMRC cable had broken so he fixed that and now only the P0171 came back and its only tripping at idle. We're going to wait a couple days and put some miles on it and make sure only the P0171 is there. I'm going to have him check/clean the MAF and if that don't do anything, we are going to pull the fuel injectors and clean them or possible just replace them.
So that's it. After all this, we started with just a P0171 and have worked our way back to just a P0171. But after all this the Cobra acts like a completely different car, pulling hard from idle to redline. Unlike before. It still has an issue with the idle, after the engine is warmed up, and you drive it around. When you come to a stop the RPM comes down to about 1000-1100rpm and after about 5 seconds drops to 600-800rpm.
So has anyone had something like this before? Any help, advise or opinions would be greatly appreciated. Thanks.
So here is where it started a week ago. He has a code reader so he downloaded the code and it was a P0171. So first we changed the front O2 sensors (because they have 95k on them). The P0171 came back. Also because the car is old we Seafoamed the intake. After Seafoaming and clearing the codes, the P0171 came back and now a P0174 came up. Common sense would tell you that if you got both codes, there must be a vacuum leak. So after a short check, it turns out the Seafoam worked too good and cleaned out all the gunk that had been sealing the intake. So we changed all the intake manifold gaskets and cleaned the IMRCs and checked the exhaust manifolds for leaks and tried again. This time the P0171 and P0174 came back and then a P1443. Good thing is all the lost power is back, now the car pulls smoothly all the way to redline. He checked the Charcoal Canister and all the vacuum lines, the EGR system , gas cap and PCV valves. Found a cracked up line and replaced it and the 1443 went away and hasn't come back but the P0171 & P0174 where still there. So we checked for intake leaks again and found small leaks at the ends of the IMRC's. So we pull the intake back apart and replaced the seals on the IMRC shaft and put it all back together.
After rebuilding the IMRC's and finding the IMRC cable had broken so he fixed that and now only the P0171 came back and its only tripping at idle. We're going to wait a couple days and put some miles on it and make sure only the P0171 is there. I'm going to have him check/clean the MAF and if that don't do anything, we are going to pull the fuel injectors and clean them or possible just replace them.
So that's it. After all this, we started with just a P0171 and have worked our way back to just a P0171. But after all this the Cobra acts like a completely different car, pulling hard from idle to redline. Unlike before. It still has an issue with the idle, after the engine is warmed up, and you drive it around. When you come to a stop the RPM comes down to about 1000-1100rpm and after about 5 seconds drops to 600-800rpm.
So has anyone had something like this before? Any help, advise or opinions would be greatly appreciated. Thanks.