Code 42 driving me nuts...

[Orlando_87GN]

I keep getting intermittent problems seemingly related to the ignition system. My GN has a miss at part throttle and an occasional Code 42. It's hard to pinpoint what is happening because sometimes the car drives around perfect and then other times it goes into its fit. It seems like if you turn the car off and then turn it back on the symptoms go away until next time. The symptoms are part throttle miss, occasional code 42, bucking, changed exhaust note and sluggishness due to the timing switching in and out of some default value in the IGN module.

Over the weekend I used this troubleshooting chart at Steve's site:
http://www.vortexbuicks-etc.com/code_42.htm

Here is my technical question:

On step 4 of the above test, when I test the resistance from 'B4' to ground while applying 12v to 'D5' I am only measuring ~4600ohms, not 8000ohms like the chart states. I am wondering how critical this is and what the 8000ohms really means. I have tried 2 different ignition modules and currently I am using a brand new Wells Garner from the parts store. I am also using a known good coil pack but I am not sure if that could even be an issue here. I installed a wire loop in place of the Translator timing wire so the harness is essentially back to stock for test purposes. The B4 wire and D5 wire check out fine and are not shorted, open and they don't have high resistance.

The chart basically leads me to 'check for intermittent connections' and I have. Needless to say I am stuck and at this point I guess I'll just start throwing more parts at the problem like plugs, wires, more coil packs, EST modules, cam sensors and maybe even the rear bumper.

Anyone been through this troubleshooting chart before with similar results?

Thanks,

[turbo nasty]

4 whatever reason I cant get the link to vortex to work on my end. But here is a few helps from my head

Have you taken your ecm and checked the connections there??

Check the chip and calpac double check the connections in the ECM.

Have you double checked your wires on the plug and tower ends to verify no corrosion etc or maybe they are just getting tired?

[salvageV6]

Have you gotten the code since you bypassed the timing control wire?

Over at Full Throttles tech. website there's some code 42 fixes for certain translator boxes.

I've never found mine but I'm thinking it's more the translator/chip than the wiring or module.

I get the code about 6 times a year, it's a pain to reprogram the chip and clear it but it runs great after doing so.

Mine won't go into boost at all when it shows up it runs crappy, driveable but no boost and power beyond 0, and the service engine light comes on at that point too which is kinda odd, it's like a 0 boost switch and light.

And yes I'd check the chip socket connections too.

I'm going to try another ECM someday when I get another one modified for LO-Z injectors.

[Orlando_87GN]

I haven't gotten the code since bypassing the T+ timing wire, but that was just done Saturday. It will started missing at part throttle yesterday and acted like it was going to code. I was disgusted with the car and just parked it because I thought after all the troubleshooting over the weekend and cleaning of the connectors I would have it licked. If I would have drove it around more I am sure it would have coded eventually as the symptoms were exactly the same right before it would throw the code.

[Orlando_87GN]

Oddly enough, my other car with the same chip, ECM, Translator, injectors started doing the same thing. Intermittant code 42's, studdering, popping through the exhaust and I can tell it was driving around with the wrong timing. That is for another thread and another day, but may be related.

I have had some bad luck with exhaust leaks and ignition on these cars.

[V-6 Vegatex]

Could the ESC itself be bad? When I had the Code 41 it turned out to be my cam sensor cap.

[NM Tom]

Are you running direct scan? When I used direct scan with a unshielded cable my car would code 42 and miss and buck at high boost. As soon as I put on a newer shielded cable all problems went away.

[Orlando_87GN]

No Direct Scan plugged in but the Power Logger is. The USB cable isn't even hooked up to the PL when the problems occur though.

[NM Tom]

Not sure about the power logger, but mine would have problems even with cable not plugged into the laptop. The cable would basicaly act as an antenna and send RF interference into the ECM causing the problem.

[GNVYUS 1]

My code 42 stopped after many hours on a Sun Machine, the darn cap would occasionally miss and cause the car to run in limp mode and throw a code. They showed me the screen after saving it and you could clearly see the one line was was lower.

Worth swapping out cam sensors to see.

[Doc1of7]

Try reburning the chip. I've had some that were sort of *flakey* that would code 42 for no apparent reason. Burning the same code on another chip cured it.

[earlbrown]

Try backing off the bolt that holds the harness to the ign module 1/4 turn and pulling the plug back a little. That's what it took to fix my flaky car a few years ago.

[Hafrod]

I had BAD LUCK with the Wells ignition modules! I tried 2 in one week! BOTH JUNK!!!! I also tried a Echlin from NAPA and had to go back twice. I had many different symptoms from-would not start after driving(engine warm), part throttle miss, bucking at WOT, not reving over 3800 RPMs. I finally bought GM ignition module and coil pack. Kirbans is selling original coil packs for 59 bucks! Limited supply. I bought a spare cause the price is tough to beat! after installing them, the car run really good! On one of my other Grand Nationals, I found a bent prong on the module plug in. That car was missing BAD but straightening the prong cured that! Dan

[GN Mistress]

Mike,swap in a new cam sensor for test.

[Scott GN231]

Originally Posted by Doc1of7

Try reburning the chip. I've had some that were sort of *flakey* that would code 42 for no apparent reason. Burning the same code on another chip cured it.

I had a bad chip cause this once as well.

I also had a module that would get hot and intermittently produce the same results-- bucking, stumbling, sometimes with code 42, sometimes without. Tested fine when not hot, intermittent problem was a real PITA to find.