We took my SRT-4 to a local AEM Factory Trained Tuner Friday to get the AEM dialed in. After 5 hours of dyno time (and more $$$ than I care to mention), the car pulled 412 whp and 407 lbs-ft torque at around 21 lbs of boost. Engine info is:
- Stock engine (top & bottom)
- 50-trim AGP DBB turbo
- Tial wastegate
- Aeromotive fuel pressure regulator
- Wallbro in-tank fuel pump w/return line
- 750 cc RC injectors
- AEM MAP sensor 3.5 bar
- AEM intake air temp sensor
- AEM fuel pressure sensor
The car ran real strong throughout the pull. Unfortunately, at the end of the last run, we noticed the idle had gone haywire. It stumbled right after start-up, and then revved and died repeatedly, until it finally settled in at around 1100 rpm. We pointed this out to the tuner, and -- for whatever reason, maybe it was closing time and he wanted to go home -- he claimed he hadn't done anything to cause the change. He said it must be something like a manifold leak or somewhere else around the throttle body, not his AEM tune that was causing it. Yet neither I nor my mechanic friend (who had done all the mods on the car) had noticed any problem with the idle prior to the last run. Since this tuner has a pretty good reputation, and it was late, we accepted his disclaimer and took the car home. The idle fluctuated considerably and the car wanted to die as we pulled it onto the trailer. This weekend, my friend went over the car. He pressurized the system to 35 psi and couldn't detect any leaks. He sprayed soapy water over all the seams around the throttle body, TB spacer, IM gasket & head, AIC motor, TPS, and found nothing. We searched this forum for "high idle" and found a DIY thread on the TPS harness. Unfortunately, that fix didn't correct the problem. Finally, after coming up completely blank on the cause of the problem, he hooked up the stock ECU (actually a Stage1), and the idle was fine (around 900 rpm). It seems like the problem is related to the AEM tuning. At this point the car is not very driveable.
Do any of you AEM experts out there have any suggestions or thoughts as to what might be causing the idle problem? I'm not sure I want to go back to this tuner, especially if it means paying him more $$$. After all, he claims his tune didn't cause the idle problem. Does it typically take 5 hours and 15 runs to tune a car? I'm planning on trying another tuner.
Thanks in advance for your input.
