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Exhaust leak will contribute to lean condition. Fix leak first. Lean condition with hard starting… check fuel pressure. Weak fuel pump.
High LTFT with rough idle that improves with RPM point to vacuum leak. LTFT that get higher with RPM is fuel related. Need trims to to diagnose.
if the EGR turns out to be the problem and after you make the repair and your trims come back to normal range but you still get a P0400 (EGR problem)… I have read that a bad or failing supercharger actuator can cause a P0400 code to trip.
I only have a DVOM and basic Autoenginuity.
Is it a fix with the new 02? no more codes fuel trims Ok?
Ok… I have gone back and re read all your posts on this… we have ruled out the fuel system and EVAP as being the problem.
On to the EGR… the EGR will cause a rich condition as it is introducing hot exhaust gases into the intake, the PCM will note the extra oxygen via the 02 and start adding fuel. With the EGR open even a little, idle will be off and get better at higher RPM.
You had mentioned that you blocked off the EGR and the trims went positive (2%) and when a hold developed in the block off plate, the trims went back negative. But in blocking off the EGR you get a P0400.
Lets get into the EGR. If you have not already done, clean the EGR seat and pentel. Check the pentel spring, it should hold the pentel in the closed position firmly (you should not be able to move it by hand). Try and pass air through the passage way, no air should pass. If the EGR is Ok, install it on the car. With the engine running, disconnect the vacuum line(plug off the vacuum line so it does not leak) and apply vacuum manually. Idle should be smooth then get rough as you apply vacuum. Check trims with EGR in closed position your trims should go positive like when you had it blocked off. Re attach the engine vacuum line, note any idle change.
Does your Jag have a supercharger?
Andy
I believe you have checked the pressure regulator and fuel pump and should be satisfied that they are working properly. the purge valve if leaking can allow gas fumes to be pulled into the intake and cause a rich condition and idle problems. check the purge valve. no air should pass in the closed position. best way to check would to be to remove the valve and try and pass air through the valve. you do not want any air to pass.
to totally rule out the regulator… do a throttle snap test. With the engine running, snap the throttle to full wide open then let off. What are the readings… at idle, then wide open then back to idle.
first, respectfully, stop firing that parts canon… that’s what this site is about. Use scan data to diagnose the problem.
What are the STFT and LTFT fuel trims for both banks and the voltage reading for the 02’s.
By unplugging the 02 the ecm is compensating by running the engine rich. unplugging the 02 will setoff more codes.
Because the 02’s are in closed loop, that tells me that one or both are not reaching operating temp (600 degrees). if an 02 voltage stays or goes above 450mv for over 2min, the P0132 or P0136 will set. Most likely B1S1 02 has failed. Check your wiring first before buying a new 02. If the wiring failed or shorted the new 02 will not work.
check your fuel pressure. 44-54psi key on engine off. key off engine off, psi should stay the same and not drop more than 1psi is 15-30min. engine running at idle, snap the throttle, psi should go up then down just below static psi and then level off at static psi. if psi goes down instead of up you have a pressure regulator or fuel pump issue.
is the computer throwing any codes?
forgot to mention… the coil pack on the V6 mustangs from 94-2000 were known to be really bad and cause much of the problems you described. You mentioned that the ignition coil was good, but make sure, test the pack, make sure you have a good strong spark coming from each coil tower. You might consider taking it to a professional and having it checked out.
at this point no diagnostic can be done until you have the engine back together and running. fluctuating RPM is usually due to a vacuum leak. had an engine with a blown head gasket between two cylinders idle and sound the same as yours but vacuum reading was very low. normal vacuum is between 17 and 22 and steady.
I would throw out all previous thoughts as to what is wrong until the engine is running again. if it was a head gasket, low readings on 1 and 6 are suspect, you’ll know it when engine running again. check all vacuum lines. one that is pinched or collapsed but not cut open can cause problems.
looks like you found the problem. you should not have a loss in fuel pressure after de-energizing the system… especially 5psi that quick.
your problem is leaking fuel injectors or a failing fuel pressure regulator. with the engine running, pull the vacuum line on the fuel pressure regulator. check for fuel in the vacuum line or at the nipple of the regulator. leave the vacuum line off for several min and check for fuel coming out of the regulator. this could take a few seconds or a few min so be patient and run the engine for 10min or so. if you get fuel, replace the regulator.
