5ktq electrical problems update (not fixed)

[Ameer Antar]

So where are you measuring the voltage at? Just b/c it's 13V at one point, doesn't mean it's the same everywhere... Try measuring the voltage at the low-voltage side of the ignition coil and also check those connections for corrosion/loosness. I've had problems from these connections before. Also there are more than one ground points for the engine. There's also one that goes to the intake manifold and maybe a couple more. You should really consider getting the 2nd Bentley since it will help w/ lots of wiring issues and will help when you want to add or upgrade some electtrical stuff. Also check the connections at the battery and body (ground and positive). I would also check for any corrosion underneath the fuse panel area and ECU. How bout checking the alternator grounding? You may also want to measure the voltage coming from the high-voltage spark-plug wires. There is a special spark tester at many auto places that tells you what voltage you have. This will be helpful in monitoring your progress through this problem. Godd luck.

-Ameer

---Original Message---

From: "Cody Forbes" <cody at craincorporated.com>
To: "Audifans Q-list" <quattro at audifans.com>
Subject: 5ktq electrical problems update (not fixed)
Date: Tue, 23 Sep 2003 09:15:58 -0400

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I'm still having electrical issues on the new '87 5ktq. The problem is that when ever the voltage gets to 12.8v I get a missfire, and 12.6v basically shuts off the motor unless I hold it full throttle. Normal voltage is in the 13.5 area. Problem is completely ignition related for sure. The voltage usually goes down to that range with the headlights and/or with the rad fan on. No, I can't just take the fan out and not use the headlights, :-).

I have replaced the voltage regulator (yeterday, Eric's suggestion), and last night I found corrosion on the main engine ground, so I cleaned all of the connections there and cleaned the chassis where it bolts up and even used a new bolt. Didn't make a slight differeance. Then I went to the alternator. I took both wires off and cleaned them, then started the car up and it was fine. I could use the headlights, even the highbeams, so I went for a 20 minute drive. It would still miss just slightly with the rad fan AND the highbeams on, but thats about it. So I went back to the shop to get my tuning computer because I was way rich on the EFI (on purpose). Went to go for another drive with the tuner and it was back to the same thing as before. I assumed there had to be something loose near the alternator, so I went to the starter and cleaned all the wires and contacts. I didn't have the chance to test it after cleaning the starter wires, but does this at least sound like I'm the right track? I did order a new ignition switch too, figured it couldn't help. I should be able to test it later today and install the ignition switch. I'll let you know what happens.

My issure though is that ok with all of the charging system good I shouldn't ever go below 13v which would cure it, but shouldn't the ignition work fine well below 13v? Even if cleaning all the contacts get the charging voltage up to 14v it will fix my immediate problem, but I will still have weak ignition and loose power. I don't have the 2nd volume of the Bentley which is electrical stuff, so I don't have any wiring diagrams. I do get full battery voltage @ the coil.

-Cody Forbes
Black Forest Racing
2x '86 5ktq
'87 5ktq
'88 80 4cyl

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