steven storch

I've had a slight stumbling problem for a while, usually when warmed up...a slight hesitation on acceleration. Not noticeable much while moving. Very erratic.

Yesterday, took her out (1985 928s) for a short ride. Parked it. When I restarted, engine would surge to 1400 rpm, back down to 500 or so, back and forth, back and forth. Was able to get home but noticed lots of unburned fuel. Engine would stall when hitting the low end of the surging, especially when stopped.

I've replaced the spk plug wires, plugs, caps, rotors, and ignition coils a year or so ago to try to solve the hesitation problem. Found a few minor vacuum leaks as well but now...I'm just scratching my head.

Idle speed was high last year at inspection (over 1000 rpm) so I readjusted using factory procedure to 650rpm.

Any suggestions?

Completely perplexed 928 owner, Steven Storch
Durham, NC

I don't drive it much...1,000 miles a year or so (want to sort things out with suspension and get interior redone). Just filled up with premium.

rixter

hey Steven, did you ask the local guys about this? there is an excellent place in Durham to take your car and have it checked, and another here in Cary
driving only 1k miles a year can play havoc with a 928, they need to be driven regularly
could be old gas still in the lines, wur or csv issue?

steven storch

csv= cold start valve
wur?

what's the place in durham? there used to be a great mechanic in hillsborough (team stuttgardt) but he left the area. millersport?

thanks
steven

rixter

wur = warm up regulator
contact Brad Moyer, he owns the Digital Chassis in Durham, or you can bring it to Cary and talk to Jimmy at European Performance... I have numbers for both of them if you want to pm me, they are both well known and respected

Tommy928

Steven, if you noticed a lot of unburned gas then it is ignition related. Since you already have new coils, etc, the only remaining items to check are the two ignition control units in the front of the car and the brain. If it turned out to be the ignition control units I have two good used one you can have for cheap. PM me.
Tommy

H2

Idle control valve? Vacuum Leak? My idle improved quite a bit when I replaced the conrol valve but it didn't idle as bad as yours.

Drewster67

Check your cap and coils - (again) Just went throught this last week.

goodspeed928

few minor vacuum leaks
No such thing!

steven storch

I'll try replacing the fuel filter (I did run it very low when the crazy idle started). God only knows when it was replaced last. I also have a fuel pump and check valve ready to go in. I've been meaning to replace these for a while now.

I know brad at digital chasis (he did a great alignment for my 944). If I can't sort through this, I'll run it by him in a few weeks.

In the meantime, got to replace the leaking radiator on the 944 (just started leaking yesterday)

I'll check the caps/rotors for moisture or cracks.

Tried spraying the base of the intake manifolds with carb cleaner but didn't notice any change.

Next warm couple of days that come up might allow me the opportunity to take off the manifold tubes and install a new set of gaskets and check for any hidden vacuum leaks. While I'm under there, I might as well replace the idle control valve.

Thanks for the feedback guys. If you can think of anything else, post it to this thread.

Steven

deliriousga

I'm a newbie w/ my 928, but had a similar problem with a previous car. If it's surging, my other car had a bad oxygen sensor. It was reading too low so the engine surged to compensate. Don't know if it's similar, but just a place to look....along with the million other ones.

Good Luck!!

Let us know when it's all better so we can celebrate

John

John Struthers

85' has a WUR???
Might as well try the WD-40 attack on the flappy while your at it.
Don't think it's the fuel filter, nor pump/check valve -running rich-
but if they are on hand, I suppose, it can't hurt.

Rich9928p

An 1985 928 has no WUR (only found on CIS 928, only 1978 - 79 for US models) and the "flappy" only exists on 928s from 1987 and newer.

Scott M.

Steven;

Sounds like it could be the begining of the end for your LH box. I'm sitting on an 86.5 that had the exact mode of problems. Try to locate someone w/ an 85-86 car to borrow a brain from.

Scott

borland

" I don't drive it much...1,000 miles a year or so (want to sort things out with suspension and get interior redone). Just filled up with premium."

Car sitting usually spells "Bad gas", "clogged injectors", "dirty MAF/AFM".

murarie

Steven;
As Tommy said one ignition control module may have failed,
Do you notice a significant loss of power?
My ignition control modules would work properly at idle and part throttle but one would cut off in load.