So this problem only manifested itself AFTER the car was getting tuned? Everything mechanically is checking out - I would guess something with the tune isnt right. Have you tried sticking a stock tune in the PCM and running it? What happens? If that fixes it, build off of the fresh file.

What about your previous tune? Tried putting that back in?

 

The tuner said he double and triple checked the tune and couldn't find anything. He tried putting a GM factory tune in there and it did the same thing, MAF reading spiked under a barely open throttle and car almost died. Unfortunately I don't have my old pcmforless tune anymore.

 

Won't make a significant difference, but you should be measuring relative to the PCM ground. The PCM ground itself you should measure relative to battery negative.

Given the large number of weird readings I would:

1) remove PCM, check all harness pins for shorts to power or ground

2) install a known-good PCM with a known-good tune, and recheck the output voltages

If I was being really careful, I'd disconnect the sensors/actuators that connect to the weird readings before connecting the new PCM. Like, everything that connects to 5V reference. But I'm usually not that careful...

 

Pin A7 is the fuel pump relay control = fuel enable signal. The chart contains note (2) for that pin. EXACTLY what I typed for you.

Where did I go wrong? Why the "magical chart" sarcasm? I was only trying to help you?????????

 

I interpreted your response as mostly passive aggression, Injuneer. As if I was wasting your, and everyone else's precious time that could've been saved if I wasn't such a chart hater. As if my problem is some kind of burden on everybody right now. Or maybe I'm way off.

The "fuel enable signal" is A25, not A7 which is the "fuel pump relay control". How can they be the same thing? A25 is a dark blue wire and A7 is a dark green/white wire.

I talked with my tuner this morning about all this. I asked him about the MAF signal wire being at .01 when the reference says it should be 5 and he said to measure the frequency like was mentioned earlier in the thread. I don't want to drop $80 on a frequency meter so I'll see if I can find a shop around here to measure the frequency tomorrow.

He also wants me to bite the bullet and get a cable and data logging software as well as Tunercat. I won't be able to do that for about 2 weeks until my roommate comes back with his laptop. Frown town.

 

OK.... sorry I offended you. I'll drop out and let more friendly people help you.

 

Are there any more helpful or more friendly people out there? I don't think so. Without you, Shoebox, and Rich too, this board would die. Anyone would be hard-pressed to disagree.

 

I took the car to the local "electrical specialist" shop and they said it was the PCM. Apparently with the engine off and they key on, the signal on the wire from the PCM to the MAF would randomly spike. They said the MAF and the wire were ok.

Before, when I was on the dyno, we tried a different PCM with no luck. But what the hell, might as well try yet another PCM.

 

Did you try a new PCM? Did it work out?