1990 928 GT with chronic 4 cylinder mode issue

SeanR;5938 wrote: Yes, sounds like bad ground, intermittent ground and I think I know which one it is.

Pull the air box and MAF. Right side in the V, under the throttle cable pulley is a block ground that is the grounding point for the EZK/LH. There is also the ground for the MAF and a CPS on the left side, in the V. Check those and ensure they are grounded.

Man I wish I had your knowledge.

Brad.....you were there also.........under the intake, back of the v in the block the throttle cable is there, the CPS just beyond thats where the grounds are that Sean references......they get very warm due to location and also are under the fuel lines and close to coolant ports....all contaminate the grounds as well age.

malcolm;5940 wrote: Brad.....you were there also.........under the intake, back of the v in the block the throttle cable is there, the CPS just beyond thats where the grounds are that Sean references......they get very warm due to location and also are under the fuel lines and close to coolant ports....all contaminate the grounds as well age.

Except I no longer have a stock harness and my grounds are on the back of the head.
nothing in my V except Knock sensors. even the crank sensor loops back towards the firewall and all three attach level with the right head just under the AC line.

I guess I should doc my harness into a schematic so that if the car ever goes to a different owner they will have a map to follow.


One of the knock sensor connectors

Had thought the stock harness was on before the mods?

Stan.....whats the current draw on the battery with everything off?

malcolm;5942 wrote: Had thought the stock harness was on before the mods?

Stan.....whats the current draw on the battery with everything off?

Yes the car was stock when I got it before the mods and I do remember some grounds there.

The current draw should not be above 100 mil volts.
I think I have mine down to 23 mil volts and will last for 3 or 4 months easy
but I have seen caddys has high as 320 mil and the bat will be to dead to start it in 10 days or less

Most modern vehicles will shut down the modules with in 20-40 sec after the key is removed and will drop to 20-70 mil volts

here is a good step by step
www.aa1car.com/library/battery_runs_down.htm

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.