Replaced TPS, four dead cylinders

Esten N

New Member
Dec 19, 2015
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Hey all--I have an 03/04 cobra swapped 99 GT with a twin turbo kit and an 01 cobra intake manifold (for reference). I recently had a CEL display for p0122, a TPS failure. I replaced the TPS, and ever since replacing it, the car has idled on only the rear four cylinders, not even on the same bank. I've put two more new sensors in the car, replaced the harness for the TPS, and reinstalled the old sensor only to continue having the same problem. All 8 cylinders have spark, but the front four injectors aren't firing as far as I'm aware. TPS is adjusted at .99, is properly grounded, sweeps properly with the throttle body opening and has 5v of power. The same is true for the pin on the PCM. Fuses are all good, TPS is responding, compression is good, new plugs and brand new FIC 1440 injectors. Leaning towards issues with the PCM/ECU, it's just super odd it would suddenly fail at the same exact time I replace the TPS. Thank you in advance!
 
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wmburns

SN Certified Technician
Aug 14, 2009
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Houston Texas
I have helped someone with a 4V DOHC with fuel injector "issues". It turned out that one of the fuel injectors pig tails got pinched between the COP cover plates. The fuel injector was grounding out to the motor via the pinched wire.
 

Esten N

New Member
Dec 19, 2015
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I have checked, no wires are pinched or could be pinched during the installation of the tps. There are also no wires grounding out around the coilpacks or injectors as far as I can see.
 

wmburns

SN Certified Technician
Aug 14, 2009
5,878
514
204
Houston Texas
IMO it's short sighted to focus your inspection of the wiring harness on just the wiring to/from the TPS.

If this were my car I would put a test light between a fuel injector and ground to VERIFY there is constant power to the failing fuel injector, Next I would put the test light across the fuel injector to VERIFY that the injector continues to pulse when the problem occurs.

Start with the basics. Confirm power and grounds are present at the devices experiencing problems.
 
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