For the past couple of months, I have been having a problem with my engine severely stuttering on wide open acceleration, from a dead stop. It would cause the trans to act strangely, and really had me scratching my head. It was suggested that I had a plugged fuel filter(I changed it), my fuel pump was bad(I checked the pressure), or my exhaust was plugged. I was so desperate, I ran a bottle of catalytic converter cleaner through it. I was getting close to running her through the auction.

The only 3 codes she would spit out were P1638-Can Link ECM/INSTM circuit/Network, P1642-CAN link circuit, and P1797-CAN TCM/ECM circuit malfunction. My voltages were all good, with the battery at almost 13 volts, and charging at 14.2 volts. I was also unable to erase these codes for more than a minute or so. These codes led me to believe either I lost an ECM, a TCM, my ABS, or I had mice eating wiring somewhere. I read the tech lines, and they were shotgunning everything from a bad ABS module, to replacing the instrument cluster.

The car went from running great, to being a dog overnight. Last weekend I decided to go back and read a basic fuel injection manual.(even old mechanics do this) It pointed me towards either a throttle body(throttle position sensor), or the mass air flow sensor.

With the car off, I disconnected the mass air flow sensor, and the bog almost completely disappeared, when I restarted it up until it hit 3500 rpm. I realize that this was due to the presets in the ECM, to get you home in case of a component failure.

I replaced the mass air flow sensor, and the car runs great again. She will chirp the tires off the line. I was even able to reset the check engine light. According to the codes the mass air flow sensor should not have even been a culprit. Scan tools are nice, but sometimes a little common sense goes a long way. Thank you all for the help you have thrown my way...........Take care.......Mike

 

Thanks for posting this I'm sure others will run into it sometime too. In summary it sounds like reseating the MAFIA connection cleared the problem. Whew nice job.

 

Glad to see you solved your problem, you didn't try cleaning the MAFS and connector? Sometimes that is all it takes. Just as a PM I pull the MAFS out every six months or so spray cleaner in it and the connector.

 

I had some special mass air flow sensor cleaner, made by B and G, and it didn't help. The new sensor cured the problem......Thanks.....Mike

 

I'm wondering how a changed MAF can be relevant to always-occurring CAN faults (MAF isn't on the CAN bus). Chafed harness or the like maybe. Expect the CAN faults to return.

 

That is why I wrote this. If I kept following what the scan tool said, I would still be looking for a reason for the poor running condition. We don't know how the control units are laid out, and there should have been no reason for a mass air flow sensor to be the repair for my problem. Sometimes common sense overrides technology. For the life of me I don't know why it fixed it. The controller area network should have had little to do with a launch issue, and the faults should not have gone away after replacing a sensor. They would not go away before the sensor change.

I went through every accessible inch of the harness looking for a ground or short, over the past couple of months, to no avail. I probed the plugs, and cleaned every connection....I am just saying this fixed it. All the CAN harness is is a communication line between the control units, and the sensors. Maybe this one sensor was enough to throw things off.

In all my years I don't think I have replaced more than 3 mass air flow sensors, so this came as a real surprise. I will take small victories when I can get them.......Mike

 

I had the opposite experience with my last car (1995 Corvette) that was somewhere between OBDI and OBDII. The problem that I had was a quite noticeable missing at low rpm under load (like at idle with A/C on) as well as a horrible miss/stumble under full throttle. There were NEVER any codes thrown and it was basically a case of guessing what might be wrong and changing out parts. This was not isolated to my car since there were dozens of similar posts to other owners on the Corvette Forum with miss/stumble/hesitation without any codes being thrown (this was a chronic problem with the LT-1 engine).

I am not sure what is worse--having an obvious problem without any codes coming up or having codes come up that are erroneous and point to the wrong things.

I miss the days when you can drive in to your local guy and by listening to the engine for a few seconds knew what was wrong.

Doug