BornToFord

I've been working on my 2002 GT with 93k miles to get it running well enough to pass emissions here in TN. Only mods are a K&N CAI and older Magnaflow exhaust. It was my son's car and I never thought it ran right. The engine is in very good shape, and after replacing the coil packs, PCV valve, and vacuum hoses, cleaning the MAF and IAC, it runs pretty well. It runs awesome before it hits full operating temp. However, after it warms up it runs a bit rough.

I took it to the dealer and had them run diagnostics. The mechanic said it was running perfectly and that these cars just run on the rough side. Is this true?

I have an SCT TSX tuner and have flashed the performance tune to try it out, but am running the stock tune now.

I also have a P1000 code that I need to get rid of. I have put about 60 miles on it since resetting the ECU, and it's still there. Any ideas how to get rid of it?

Thanks, Andy

FormlessGT

I also have a 2002 GT. From my experience up to 113,000 miles, mine runs smooth.

BornToFord

Yeah, the mechanic said the air/fuel ratio was about 11.5 to 1. That sounds way rich, although he said it was acceptable. I'll bet a good dyno tune would have it running great. It's not terrible, and like I said it runs awesome before it hits full operating temp. As soon as I pass smog I'll get it corrected.

Still need to clear that P1000 code!

cliffyk

If the front O² sensors are failing they can still output sufficient voltage and switch as they should, however when the PCM switches to closed loop mode (after the engine warms up over 175° or so) the low output will be interpreted as the AFR being lean. The PCM will compensate by adding fuel until the failing sensors report a proper AFR of 14.7:1 (the actual process is a bit more complex than this).

This adding (or subtracting) of fuel is called the Short Term Fuel Trim (STFT), and as long as it stays between -25% and +25% the PCM will not throw a trouble code.

So the first thing I would do would be to data log a cycle from start-up to engine hot and see what the STFTs (there's one for each bank) do. If they push up into the 15%+ range when the engine is hot then the front O² sensors are almost certainly on their way out. At 93k miles this would not be unusual.

One last comment, if the engine was running 11.5:1 at idle or under normal loads (I.e. not 70% or more throttle) then it is not acceptable nor normal--find a new mechanic. In closed loop it should cycle between 14.4:1 and 15.0:1 one to 3 times per second, maintaining an average of 14.7:1.

The P1000 code is being thrown because the OBD2 I/M (Inspection/Maintenance) readiness tests have not been completed. Their completion does require some specific conditions, here is a description of the Drive Cycles needed to force the I/M tests to run...

1slow67

Tennessee has emissions testing?

cliffyk

Yup, Hamilton, Davidson, Rutherford, Sumner, Williamson and Wilson Counties...

BornToFord

Some counties do. It's a good way to make money.

Thanks Cliff, I have been checking out your posts for a while. You are the main reason I signed up and posted.

I forgot to mention that the car was running poorly when I got it, and the first thing I did was replace the O2 sensors with NTK's based on your posts. I believe one sensor was worse than the other as it was black and the other was light brown. The plugs looked like one bank was running richer as well.

Fuel trims are running from .8 at start up, then drops to .65 for a short time, the up to around 1.05 at max when at full operating temps. This is off the Datalog Graph read off the TSX tuner module. I'm not sure how that relates to percentage.

I did replace my thermostat after this logging. I was running about 180 deg on the highway as read off the ECU, and I run about 190-195 deg with the new thermostat. Both are 195 degree versions.

BornToFord

Bump

Thanks Cliff, I have been checking out your posts for a while. You are the main reason I signed up and posted.

I forgot to mention that the car was running poorly when I got it, and the first thing I did was replace the O2 sensors with NTK's based on your posts. I believe one sensor was worse than the other as it was black and the other was light brown. The plugs looked like one bank was running richer as well.

Fuel trims are running from .8 at start up, then drops to .65 for a short time, the up to around 1.05 at max when at full operating temps. This is off the Datalog Graph read off the TSX tuner module. I'm not sure how that relates to percentage.

I did replace my thermostat after this logging. I was running about 180 deg on the highway as read off the ECU, and I run about 190-195 deg with the new thermostat. Both are 195 degree versions.