90 964 Trouble Lights

Porsche_monkey · 01-19-2009, 01:38 PM

All my lights are coming on in the dash. There are no real 'faults'.

I think my battery is kaput, and the voltage is dropping too low?

Hamptonsam · 01-20-2009, 01:46 AM

I believe a bad coil/coils can do this as well.

Newsboy · Newsboy's Garage

Check your battery voltage 1st. Should be around 12.6 with engine off 13.5-14 with engine running. Search for"Christmas Tree effect", bad coils, even those that test within recommended spec's often cause this.

Porsche_monkey · 01-20-2009, 05:52 AM

Okay thanks. Every car I bought before was supposed to have trouble. This car was supposed to be 'sorted'.

New battery later today.

Porsche_monkey · 01-20-2009, 09:41 AM

Now I am seriously pissed. Car fired right up in really cold weather this morning, so the battery is NOT the problem. Went around the block and a serious misfire/$hit running occurred. Limped home (barely) and the car is now stuck blocking the effing street. Will start and run for ten seconds. Won't take any throttle. Battery is now run down to almost zilch. Tow truck on the way.

Back to the repair shop.

I guess a coil might be gone?

Newsboy · Newsboy's Garage

When"The Christmas Tree" happened to me, it would go away for a while after the car was re started. But then, it started sounding the warning gong, and finally it would hardly run. This is called the "limp home mode". Coils are not hard to replace, if you want to try it yourself. Of course, it could be other things like a bad ground.

Porsche_monkey · 01-21-2009, 05:31 AM

Too cold here to work on my car here. I can get it to my workshop, but I do not want to have to tow it to my workshop, then find out I can't fix it, then tow it to a real shop. So it went straight to a real shop.

I am hoping it is just water in my gas line, but my symptoms are exactly the same as what you described. Progressively worse until it died.

Should know later today. More cha-ching expected.

Porsche_monkey · 01-23-2009, 07:50 AM

Hamptonsam and Newsboy move to the front of the class.

While I was hoping it was water in my fuel, it was actually a bad coil.

Both are being replaced as we speak.

Twin plug double cha-ching anyone, with a side order of tow-truck fees?

Oracle · 01-24-2009, 11:53 AM

Bad coil or broken solder in the dash clock can give that xmas tree effect.
the limp mode is just the computer trying to get you home..
Also I read that sometimes the connection of the harness and computer sometimes needs to be re-settled.

Henry964 · 01-25-2009, 02:11 PM

Sorry to be late, but in my car, with a bad case of christmas tree, replacing both coils solved the issue

Porsche_monkey · 01-25-2009, 05:25 PM

Picked up my car a few days ago. Very expensive, but two new coils did the trick. Runs great now. Enjoying it a lot in the snow.

Porsche_monkey · 02-07-2009, 05:53 AM

Two new coils a few weeks ago. Christmas tree happened again last night.

Oracle · 02-07-2009, 04:59 PM

Take a look at the broken solder in the dash clock.. same xmas effect...

Newsboy · Newsboy's Garage

Did you check all the grounds, battery, transmission. Could also try unplugging & re-plugging in the computer under the drivers seat.

Steve W · Steve W's Garage

Sounds like you have hardware problems with the ignition side of your system. Could be the ignition modules, broken distributor belt, or bad spark plug cables. Electrical interference/RFI from the ignition system causes the DME to do a reset each time. With a twin plug ignition, try isolating the problem side by disconnecting the plug from one ignition module (next to the ignition coils) and start and note how the car revs and idles. Turn off, plug back in, and unplug the other module and repeat. If there's a difference between the two sides, you've isolated the side with a problem.

colo964 · 02-08-2009, 06:24 PM

Any loose acing can do this. Could be worn rotors and caps, or bad plug wires. Mine had a small arc (can see a blue spark when idling in the dark). Put your radio on AM, if it buzzes proportional to the RPM, you have an electric leak in your ignition system. They could have been the cause of your coil failure - check it soon before you burn your new ones.

Porsche_monkey · 02-09-2009, 05:39 AM

Thanks for the suggestions. I will start looking into this issue today/tonight.

Porsche_monkey · 02-12-2009, 01:23 PM

Voltage from the alternator is correct. Ground strap looks good.

Moving on to clock solder joint and ignition next.

Problem is not going away, partial failure again today.

Question: Any reason I can't run for a week on one coil and see if the problem goes away? That would indicate the problem is in the 'other' circuit, right?

Porsche_monkey · 02-13-2009, 10:07 AM

Quote:

Originally Posted by Oracle

Take a look at the broken solder in the dash clock.. same xmas effect...

Not sure what this means. Where would this be? I took the clock out today, but aside from finding out is difficult to remove, and even harder to replace, I did not accomplish anything.

I also checked the battery ground (it's like new) and re-seated the ECU plug.

Newsboy · Newsboy's Garage

With reference to the clock, look at this
http://p-car.com/diy/clockrepair/