what could cause the rpms to jump 3k rpms on the datalogger and on the tach in the car, but the engine doesn't idle up it spits and sputters and pops like it is on a revlimiter.

on hte datalogger the spark advance doesn't go up, the map values stay the same. the LTM and BLM are at 128 since the o2s or programmed out.

this is with the car in park and reving hte motor. it doesn't do it until hte car is warm.

what does the cylnder ID # do in datamaster? what should they range?

the injector duty cycle also goes up when hte rpms jump.

HELP

Built350camaro on AOL IM

 

Need basic info like the year of the car, engine, and major mods (including any other changes to the PCM beyond the open loop programming). Since you're using DataMaster we can assume its a 93-95. The fact the tach and the RPM indicated on the scanner jump together would seem to indicate a faulty pulse signal from the Opti. Injector duty cycle would jump in proportion to a faulty RPM signal IF you are running speed-density?????

 

it is a 95 TA.

mods are

224/230 cam
ported heads
forged motor
longtubes
3500 stall

u say it is a faulty pulse signal from the opti? which pulse the high or low res? i got no codes.

is there any way i can test the signal on the harness with a dvom with hte car running and what should the values be?

the opti is about 2 weeks old, but it is a reman unti from AZ.

seriously thinking about getting a new GM unit from summit, since i have had nothing but problems out of the reman units.

i have also thought about changing the opti harness.

car has a new coil, and new icm.

i am getting good at replacing this damn thing, this makes about the 4th one in a year.

 

4th opti in a year? Did you check the length of the cam dowel pin when it was installed?

 

I'm just suggesting one possibility. If the low res pulse is erratic, it can lead the PCM to think the RPM is different that it really is. That wouldn't necessarily set a code, since the PCM just looks to make sure there is a pulse pattern being received. Has no way of knowing whether the pulse pattern is correct. Interference on the harness would cause the problem, either pulses leaking frmo the high res circuit, or RFI interference on the harness due to a nearby high voltage ignition wire, or arcing.

Is the car programmed for speed-density or are you running an MAF? Knowing that might help verify the impact on the injector duty cycle. Does the pulse width increase with the false RPM signal, or only the duty cycle increases? If its only the duty cycle, its jumping because the scanner software calculates the duty cycle from the pulse width and the RPM. If its getting a false RPM increase, its going to calculate a false higher duty cycle. In a mass-air setup, the pulse width will not change, in a speed-density system the pulse width should increase roughyl proportional to the RPM input signal.

 

i think i figured it out. the wiring going to the opti was messed up at hte opti end. anyone have the p/n on it?

shoebox, yeah i checked hte dowel pin, the first opti was the factory on with 130k on it, the second one i drowned with water from the water pump, the third on the opti wheel was warped and ate the sensor for lunch, and this one is the forth one.

on hte opti connector harness, the clip is broke on the opti end and the prongs on the end are all screwed, when i pulled it out one of hte wires came out of hte end.

i put the connector back together and fixed the prongs on the end and just tried it in the car and it has no wierd rpms anymore so that has to be what it was, but i need a new one anyway since the end is screwed.