Mongo

Fuel regulator and dampeners. Replaced all mine and the warm start issue went away. I used to have to press the gas to get it to fire.

928s4forme

Replaced fuel pump, regulator, dampers, starter, cleaned all ground points, checked flex plate (endplay in spec), replaced all "53" relays, changed temp 2 sensor with a good spare, unplugged O2 sensor after unhooking battery to compare running when warm, swapped the LH and EZK with an spare from my 88 model parts car, new plugs, new thermostat, new battery, and she still will:

-start perfectly when cold
-run and idle perfectly when cold to warm
-idle at 675 until it warms up, then while in gear idle drops to 400-500 when in gear.
-after idling for 30 minutes or so, she idle hunts and will stall if you give her gas and let her try to stabilize idle again.
-if you try to start her when she is hot, the battery is dead or weak, wait 5-10 minutes and she will crank up and idle low (400-500)

The only thing I have left to check is MAF and cleaning the ISV, and will be doing that this evening (have a good spare MAF)

Does anyone have any ideas?

928s4forme

UPDATE - cleaned ISV and swapped MAF...trouble still exists..

928s4forme

Swapped MAF and recleaned ISV with half a can of WD40 and the idle hunting is gone.

Only have a low voltage when warm issue now...will be doing an alternator voltage drop test tomorrow to see if its the alternator or wiring. Should be good to go now.

Thank you everyone for your help....I believe I am close to having her on the road again. Will know tomorrow for sure....

jnaarnold

Reviving an old thread....

I bought this car....it does have issues still...set the throttle cables up and put some techroline in and did regapped the plugs..made a world of difference, still idles low though, with occasional stalling...

ollieleven

Hi there did you ever remedy this issue my 87 S4 does the same going to change my CPS this weekend

Mongo

CPS may not do it. If your car is an automatic, I recommend a crankshaft end play check after releasing the pinch collar bolt for the torque tube to flexplate.

ollieleven

I've had that checked and have a flex plate clamp fitted http://www.ritech-systems.com/928_flexplate_clamp.html
so i'm pretty sure it electrical.