Fnic99

Hello. Since I bought my car in Nov (91 S4 Auto) the car has been running really rich and going through cycles where it surges at idle sometimes stalling. The O2 sensor, ISV, knock sensors, temp sensor, MAF, and an intake rebuild have all been done recently by the PO. My mechanic went through the car in detail and could not find anything wrong with the parts that were changed although he is getting error readings. He is experienced in 928's and presently owns 2. The theory was that the LH might be damaged and needed a rebuild. I sent it out myself and installed it tonight. The car now turns over but stalls immeditely. I checked all the connections and the LH seems to be in there correctly. Any ideas?

Thanks.

Tom. M

My 89 was behaving weirdly (idle issues) a while back. Ended up being both my temp II sensor and the wiring harness that runs across the front of the engine. It was frayed really badly where the harness goes through the block near the Alt..(down to the oil pressure sender and starter).. Check that harness for continuity...

good luck

Hilton

Have you done all the tests outlined in the WSM at the LH plug to make sure the harness is ok between the various sensors and the LH?

How's the MAF sensor connector?

GregBBRD

Not a good sign that it apparently ran (although it ran rich) before the LH rebuild and now it will not run at all.

Pretty much like everything, in this world: There's a few people that can rebuild these things properly.....and then a bunch of people that should never touch them. What you "got back", depends on how careful you were, in your selection process of a rebuilder. I can help you with this, a bit. The cheapest rebuilder should not have been part of your selection process.

If your mechanic owns 2 of these cars.....testing pieces should be a snap....why not have him "test" your rebuilt LH in one of his cars? And then your MAF. If he has the wrong models (your LH will fit and run in anything made from 1987 to 1995), tell us where you are at and perhaps there is someone that is on Rennlist that lives close to you and will help you with testing the parts....or send them to me and I'll plug them in a car.

The problem with what you have described, is that all of the pieces that control the fuel mixture have been replaced. So, unless you have a bad wiring loom....you don't have a problem and things should be working fine.

Fnic99

Thanks for the advice. Before sending out the LH I researched rebuilders on this board and decided to send it to Louis Ott (nice guy btw). He tested my old LH in his car and did find any problems. I decided to have it rebuilt anyway since I read they fail often and I wanted to eliminate the LH as the source of the problems.

My mechanic has an 84 and 86 1/2 so we couldn't test the LH. He did test all of the parts changed by the previous owner and said they appeared fine although he was getting error codes for the temp sensor and knock sensor. The car was stalling a lot before I took the computer out and the check engine light would come on frequently.

I sent the computer out myself since it was easy to remove and seems like an easy DIY item to save money.

GregBBRD

Louis Ott sells LH units rebuilt by John Speake. Some of the very best.

Send me the computer and the MAF. I'll plug them into a vehicle and see how they work. Easy for me to do.

Fnic99

Greg, thank you very much for your generous offer. I sent you an email to your AOL address.

Fnic99

Decided to send the LH back to have it tested. Most likely, the LH is not the source of the problem but just wanted to eliminate it. Before I sent it, I swaped the relays for the fuel pump and LH with new ones and the problem continued. Checked fuses, ground in the trunk and everything looked good. Battery is fully charged.

Landseer

Ground in trunk?
How about ground for the computers, located elsewhere.
Speaking of which, where are you located, maybe there is somebody nearby who can help with the electrical troubleshooting.

Fnic99

I am located in central New Jersey. Admittingly, I am better in Excel than auto mechanics but I am spending a lot of time reading on this board, google, youtube, 928intl Repair Tip section and other sources to learn as much as possible.

I read on a few other threads that the ground strap that runs under the tool kit sometimes corrodes and causes electrical problems. I also read that many problems are relay related so I decided to check those (XXII, XXV, XXVI).

Mrmerlin

you would do well to test the temp 2 sensor at the computers connectors.
its quite common for the wires that go to this sensor to short together
so cutting the wires a few inches back from the connector and installing a new connector will restore performance

Landseer

OK.

edit, of course first do what Mr. Merlin suggests. But I'm one with zero trust of previous owners; if it doesn't solve it, establish your own new baseline.



Who was the previous owner? I assume nobody from rennlist?

I'd verify timing marks. Clean / re-fuse and re-relay the electrical panel. Disassemble and clean the 14 pin connector. Check with mirror / clean carefully with dremel flex extension and wire brush the ends of coils inside right and left fender wells. Clean with same tool the grounds deep beneath the air cleaner, on either side of V at back top of block. For starters. And remove two distrib caps, very carefully clean the rotor and the inside cap contacts, wipe clean.

I also think you have an intake refresh in your near future, not a bad thing, but TPS and knock sensors and vac connections are all suspect.

Then try it.

NoVector

I’m probably the last guy to give advice on a no-start as I dorked around with mine for almost 2 months. But, if you don’t already have them or you want a visual of what MrMerlin is saying about the Temp II sensor, you can get the workshop manuals here: http://www.ligeti.com/928/

Volume 1A, section 24 is fuel injection. Surprisingly, you can check a lot with a cheap volt ohm meter and some small blade connectors that will fit into the 35-pin connectors. Or, you can jump to Andrew Olsen’s LH/EZK test points here: https://rennlist.com/forums/928-foru...nt-thread.html

While your LH is out being tested, if you want to clean ground points, a good thread with pictures is here: https://rennlist.com/forums/928-foru...y-grounds.html Any test plan starts with a good battery and good ground points, so doing them now is money in the bank.

Good luck!

Fnic99

NoVector, thanks for the links. The last one especially with the ground points should be helpful. I will see tomorrow if I can follow Mrmerlins advice.

I was looking through my mechanics last receipt and he wrote:

Fault Codes

EZK 14 Eng Temp
31 Knock Sensor 1
LH 14 Engine Temp Sensor
Alarm 12,13,14,15,16,17

"Cooling fan runs regardless"

He also wrote that he tested Temp II Sensor, Temp Sensor, and wiring to ECU.

From the Service History, There was a full intake refresh in April of 2012 including all gaskets, hoses, knock sensor, and Idle Control Valve.


Just want to get this car on the road.

jcorenman

With both LH and EZK giving temp sensor errors, I would check the temp-II sensor again-- it is easy to get fooled.

The temp-II sensor lives on top of the water-bridge, just behind the cross-brace. It has two wires, but those are not the usual signal and ground wires. The sensor is actually two separate temperature sensors, one for the LH and one for the EZK, and each with its own wire. The ground is via the threaded connection to the water-bridge and engine block.

If sealer or teflon tape is used to install the sensor, it is quite possible to insulate the ground connection-- but it will still measure OK between the two terminals (typically 4-5K ohms), and measure OK to the sensor-body.... but NOT to the engine block or chassis ground. With the connector off, use a multimeter and measure resistance (ohms) from each sensor terminal to the engine block-- they both should be ballpark 2.5K ohms at around 60F (higher for colder temps).