no doubt

1988 928 automatic suddenly started idle surging/cycling slightly by about 50 rpms either way, then flooring the gas caused her to only barely climb a hill.

Won't rev above 4600 rpms in any gear, but will rev to redline in Park/Neutral when warm.

Car feels "weak."

Shifts are harsh, and only coming above 3500 rpms even with partial throttle. Definitely staying in gear far longer today than normal city driving yesterday.

Any help/tests/experience would be appreciated.

Other than that, she's been fairly trouble free for at least the past 6 months of daily driving.

dprantl

One half of the ignition system not running? Check the coils and coil wires.

Dan
'91 928GT S/C 475hp/460lb.ft

Stromius

+1 on Coil/Coil Wires. Any change at idle by wiggling the Temp2 plug on the coolant bridge. I found this week mine was giving me rich, rough idling.

auzivision

Could it be a weak fuel supply? Mine acted somewhat goofy like this and ended up being the fuel pump relay. Swapped with horn realy and now both work fine. Might be worth a try.

blitz928

I had some similar symptoms when my LH failed, my post here...

https://rennlist.com/forums/928-foru...h-andrade.html

Dean_Fuller

Where are you located?

no doubt

I'll get that diagnosis pdf, thanks.

Birmingham.

Hilton

Look in the Workshop Manual - volume 1A at the tail end is a subvolume on LH-EZK-Diagnosis - labelled as "DME Diagnosing" in the table of contents.

Page D24-9 has a large table that shows the possible causes for symptoms, and describes the tests for each point.

Check the row for "Low power output" or "Poor pick-up" and start testing

The Temp II sensor (passenger-side connector on the water bridge) is a likely cause - but test it before replacing as its not the only candidate

Mrmerlin

warning after starting the car look at the cats and make sure they are not glowing red if so then dont run the car for more than 3 mins , this can cause a fire also inspect the trans cooler lines that run above the cats if they are damp the lines should be removed and the flex portions of the hoses replaced , this will also cause a fire if left to leak

AO

Official LH and EZK car test point thread

You don't even need to look it up.

Dean_Fuller

My car ran like that. I had bad spark plug wires. Changed out and all was well. Just a thought.

no doubt

I swapped the fuel pump relay, replaced the badly corroded/blackened fuel pump fuse, put electrical cleaner and marine contact enhancer on the pins for the EZK, LH, and MAF plugs, as well as removed the MAF and cleaned it with MAF cleaner, then reinstalled it.

Initial startup was rough for 3 or 4 seconds, then the idle stabilized and a brief warmup drive went fine.

Too early to tell if the half-power issue is gone or just hiding, but so far, so good.

Thanks for everyone's help and input!

Thanks!

Thanks!

Thanks!

no doubt

I changed out the original spark coils, the original distributor caps, and the original distributor rotors. This likewise increased my power as above.

But she still wasn't back to normal. Power was up from before, but she was still seeming to peak at 4600 rpms, and the shifts were taking way too long to engage.

A buddy came over, looked at my motor, and instantly said "you've got a loose throttle cable."

Well, it turned out that I had TWO loose throttle cables, one of which seems to go to the transmission. 30 minutes tightening up the cable adjustments and suddenly I've got SHARK POWER again!



Hoo rah!