1990 928 GT with chronic 4 cylinder mode issue

where did you buy them Brad?

SeanR;5947 wrote: Here's another thing to consider, and would not have given it a 2nd thought if it had not happened to my car yesterday.

The ignition modules. My car just started to do what you you are experiencing. Now I know everything on my car is new and these are not, so I swapped a new set in and the car ran great. For $40.00 each, cheap insurance.

I haven't got to any of these tests yet, trying to prepare the M3 for a Lime Rock track day tomorrow.

Just a quick note, that I had previously swapped ignition modules with varied results, as well as the coils. I ended up replacing all of them for both sides (20+ year old car why not). The varied results might be indicative of one of the wiring issues previously suggested. I am particularly interested in checking the O2 sensor, as I replaced it, but haven't looked at it in some time, and did at one time install an RMB, so perhaps tweaked some wiring then.

I am hoping the grounds were previously checked, as it is one of those items I paid to have done, and the intake has been off 3 times since. Nonetheless, I am taking *nothing* for granted, and will check everything one item at a time.

Thanks so much for the suggestions so far!

I had a few minutes, so I:
1. Cleaned the ground by the ignition modules, the one that has 4 brown wires coming to it.
2. Swapped the cable connectors from ignition module 1 to ignition module 2 and ignition module 2 to ignition module 1.

I started the car and nearly immediately the green light lit on the IMS relay (as it has been). This indicates the problem is in ignition circuit 2 (cylinder 2,3,5,8. I would conclude the ignition module is not the problem.

As a side note the dash voltage gauge started working again, this has been an intermittent problem.

Good news, that will be $928.43 split 3 ways please.

I think you misunderstand Brad, since both ignition modules are new, I didn't expect they would be bad anyways. Finding the cause is what will make me happy, not eliminating as suspect known good parts.

It was a joke Stan.
That you owe us all some money for helpng you fine your 4 year gremlin

I thought $928 was a nice number