Hi,
New member here.
Got problems with my 87 Cimarron 2.8 V6. The KOEO check gives the normal code 12 indicating the system is working, but the engine running check gives only a continuous rapid series of flashes. Drivability symptoms are fast surging idle, frequent stall at idle, frequent stumble under road load.

I wonder if bad grounds can cause the check engine light problem. There have been a few other things crop up recently which could be consistent with ground problems, such as radio loosing memory, digital dash not lighting, windows not working unless switch is jumpered to body ground. I have cleaned and tightened the body ground strap on the driver's side fender well (the one from the battery ground terminal). I know some other things that can cause the drivability problems, but have not yet checked them. My 1st priority at the moment is to learn what can cause the continuous flash.

Thanks,

Floyd Pickering

 

Are trying to start and run engine with aldl jumped to flash codes?

 

The procedure I'm following is this:

jumper ALDL terminals A to B
turn on key Result is code 12, normal operation.
turn off key
remove jumper
start engine
replace jumper Result is continuous rapid flash. Once I counted 30+ flashes, and still going, before I pulled the jumper and gave up.

It's probably worth mentioning that the engine running test is not occurring at idle, as I am now having to apply a modest throttle to keep the engine running. I would have thought that would just cause it to set a TPS code, not a contnuous flash.

Floyd

 

Check engine light should flash, but not rapidly. It indicates O2 sensor switching from rich to lean. It does sould like you have a ground problem. Check grounds at engine including where cable attaches.