1990 928 GT with chronic 4 cylinder mode issue

SeanR;5990 wrote: Good news on the MAF connector. This can absolutely be the cause of the issue and for some reason I thought we'd been through that. Hope it fixed the issue.

Before the most recent service attempt I had swapped MAFs. I do not recall a cracked boot, so never checked the wires beneath.

SeanR;5990 wrote: On the PSD/ABS, check the barrel connectors at each wheel for condition, a broken ground wire can cause this. If those are all good, get under your seat and check the inertia switch, these can get unplugged, or inside they need to be cleaned. Don't think about buying a new one, they are expensive. Search on R-list for inertia switch in both the 928 and the 964 sections.

Will check these, thanks.

SeanR;5990 wrote: It also could be a crappy relay, that has a loose component when hitting a bump.

I will re-seat the relays in play, thanks.

928mac;5991 wrote: Hi Stan, I have a different idea.
Since you are having more then 1 gauge problem, try this.
Well driving, put your right hand under the pod and feel for the wires where they go into the pod.

Move them around, push them tight, and see if this changes the volt gauge issue.
I know that I have a bad contact on 1 of my connectors as well as when I squeeze the right side of the cluster, my problem goes away.

I’m not saying anything but this is a quick check that will help locate loose wires if there are any in that area.

I need to pull mine apart and tighten the pin grip as mine looses connection as the dash and wires warm up.

Brad:)

Sounds like a simple enough idea, and fortunately my under dash bolster is still off, so should be possible. Thanks.

My optimism was inappropriate, @10 miles of driving today and 3-4 limp mode occurrences withe one separate ABS and PSD light. If these were somehow connected it would seem more likely to be a ground, or at least a fuse panel issue, thus the suggestion to review and clean it all (by Malcolm as I recall) might be next on the list....

If nothing else cleaning the fuse/relay panel eliminates it from the tshoot equation.....good luck.

Oh man that is a pisser. it still must be an electrical problem and you may have to inspect the entire LH/EZK to engine bay harness.
Sean or Malcolm maybe able to say which circuits, but at this point if you dont find anything behind the CB panel, you may have to visually inspect every inch of harness looking for any scraping or bulging in the wires/harness.
sounds like you have done everything else.

www.tmworld.com/file/4479-6436546.pdf?force=true

Stan,
I had a very similar problem on my '89. It would run great, then I would go over a bump and it would not run or not run well. I had gone through just about everything (I thought) and had narrowed it to what I thought was the engine wiring harness. WRONG! In the process of eliminating issues, I was going to check each wire from the computers to the engine end with a test light AND a multimeter. When I tried to use the ground, I found that my engine WAS NOT GROUNDED AT ALL! I checked the main engine ground (the one under the car on the passenger side)and it was hooked up and tight and everything, but not one electron was getting throught the braided cable. I removed the cable, cleaned it (and the engine mount and the frame mount) checked continuity and reinstalled. It has run great since. I did clean and tighten the coil grounds and both grounds at the back of the "V" just for good measure.

Your airbag and PSD warnings are probably related to ground issues as well.

My thoughts are that the computers and the car would work just fine as long as they could find a ground, but when they had to search for a ground, all kinds of wacky stuff would follow.

Good Luck