This can't be normal? (idles rough/volt gauge jumpy)
 

My Idle has been stumbling especially when I turn on indicators especially when the engine is fully warmed up.

I have also found that the volt meter starts pulsing up and down in sync with the flasher from the indicators by almost 2V. I would guess that this would be enough to through the A/D circuits out in the LH brain.

I will get my trusty multimeter out in the morning and start hunting but has anyone had similar problems?
Tips ?

Thanks in advance!!!

Check and clean your battery terminals, grounds, and power leads to the fuse box first. Also check and clean the wires on the jump post and alternator. If this doesn't help have your battery load tested... it may be marginal. later 928 fuel/spark brains can be very sensitive to input voltage, which could account for the idle stumble.

Grounds need cleaning. Also, investigate the wires inside the large harness running across the front of the engine to the 14 pole connector on the pass side, near the jump start lug. These harnesses carry a lot of current, and are known for melting adjacent wiring.

Many thanks for the tips so far.

I checked the battery terminals and cleaned them, no difference. The batterty is only a few months old.

I should add that this only appears to occur with the indicators on. Turning the headlights on makes no noticible difference on the volt meter or the idle but it does get worse when both the headlights and indicators are on.

Good point will clean all the grounds.

I am wondering if there is a possibility of the flasher/relay unit being faulty and drawing to much current.

Will investigate further.

Picky point, I think we all know what you mean, but keep in mind his passenger side is different from yours.

SteveG I could just kiss your arse for illuminating the dreaded 'passenger side' syndrome!!!

Colin. 89GT. RHD!

Hmmm.

Yes that connector, not a pretty sight, lots of oxidisation and low and behold one of the wires is no attached to its pin.

Well better start cleaning it all up and repairing and somehow find out which circuit the lose wire is from.

Gulp, never like it when there is so much oxide even after cleaning the connector will reoxidise quickly and suggestions as to try and prevent this.

I hope this fixes the problem but if not it may help in other areas.

Try applying some electrical contact grease commonly found at electrical supply stores, it's a light (usually redish colored) grease designed to prevent oxidation at electrical contacts between dis-similar metals, but also allows good continuity.

Ben Burris

86.5 Indischrot AT #1459

Dilectric grease is probably not a bad idea when you reassemble the thing...

I have this syndrome too, but not so severe. Probably not a bad idea for me to do a little cleanup on the jum post and vicinity.

I added an additional ground strap from chassis to block last year and had some gremlins go bye-bye. 6 bucks and 15 minutes investment.

Thaddeus wrote:
"I added an additional ground strap from chassis to block last year and had some gremlins go bye-bye. 6 bucks and 15 minutes investment."

Interesting Idea. Where to where, please?

Thaddeus

As I understand you just put in a ground strap from the engine block to the body. What gremlins did this solve? Would be of interest for everyone.

DeoxIt or Corrosion Block would be much better than grease on the connectors.

DeoxIt is available at electronic supply houses and some Radio Shacks, while Corrosion Block is available at most better boat supply places.

Well, the gremlin is still around. I have spent a number of weekends trying to resolve this problem, I have cleaned all the grounds that I could find may be missed one somewhere. I replaced most of the pins in the big connector near the jump post and tidied it all up nicely. Still no difference.

An update in what I am finding. The voltage pulses with drops of 1.5v with the indicators on. Turning almost anything electrical on also drops the voltage dramatically, e.g. rear window demister. Now for the good one. If I put my auto box into reverse a big drop almost 2v, I guess due to the reversing lights coming on and something else? Also in reverse the idle really starts to stumble.

Had the battery load tested and its fine.

So either something is is draining alot of current, or its not being regulated properly.

Ideas how to track this down would be much appreciated.
As have all the suggestions till now.

Many thanks to all.

How are you measuring the voltage? If you are using the meter guage on the pod, it's not very accurate. Better to use a volt meter. One thing you can do to see if the alternator is putting out enough charge is to put the volt meter on the jump terminals in the engine bay with the engine off. It should read something like 12.5v. Then start the engine and re-check. It should read about 14.2 or 14.3. If it reads much less, then your alternator is not pumping out enough juice. Check the alt. belt and if that's okay, remove and have it tested.

First noticed the problem from the dash meter guage and then verified it with a DMM. With the engine off 12.6v and with the engine running 14.06 - 14.13 depending on the RPM dropping as soon as anything is turned on such as the indicators etc to 13.2 - 13.9v. Measured engine block to body as 0.004 - 0.011v, which I am not sure but does indicate an imperfect ground. Or is the DMM to sensitive.

Alt belt checked and replaced a few weeks ago, no change.