my friend has a 94 M6 Z28. he bought it about 1 month ago. the engine since he bought the car is running rough at all RPM's and there is big time of lost power. he did a tune up i.e. cleaned injectors, new spark plugs, new spark plug wires, new optispark, new O 2sensors, rockers were adjusted right 1/4 turn, and still that thing doesn't want to run right still running excatly the same way not even improved by even a hair. what would be that? coil? some defected injectos? by the way the PCM showed the follwing DTC's :

DTC22, DTC29.

any one can help?

 

DTC 22 - Throttle Position (TP) Sensor Circuit (Signal Voltage Low)
DTC 29 - Secondary Air Injection (AIR) Pump Circuit

 

Dr.Mudge, i tried today the following :

1- good coil from my car but still my friend's Z is running rough.

2- tried a good TPS sensor and still the same thing.

by the way the cruise cable small black plastic piece is brocken and not installed but i think that will affect how the engine runs.

how to check for the TPS? are the plug loose and not plugged in tight with the TPS sensor? how to fix DTC22? what to do?

 

Have you done a compression check, you may have a dead hole. The pcm sends a 5v ref signal to the tps, at idle the tps sends a .5v +/- back to the pcm, at wot it sends a 4.8 +/- back to the pcm. The voltage should increace smoothly as the throttle is opened. If you have any logging software, you should see the tps readout on it.

 

i used freescan to moniter engine data and the TPS is showing that something is not working on my friend''s Z.

on my car the TPS readings are normal they increase as i increase the throttle but on my friend's Z as i can remeber it was stuck at 0.23 or so and as i mentoined the car has DTC22 (TPS voltage low) so there is something wrong with the TPS but it is not the sensor as i tried a good TPS sensor with no change, is that a loose connectoin, bad ground, bad wire or what?