Paulyy

Okay i'm seriously sick of this same / similar issue.

Tonight just quietly drove to a mates house, on the way there i noticed my tacho bouncing around on the freeway and at the time i was thinking, ahh probably ground issue behind the cluster. Then i noticed my car was jumping a little, barley noticeable, then it got worse. i pulled over to the servo and just took the dme out and noticed it was wet (may be the issue, not sure) inside had 1-2 drops of water, dried it up and the car wouldn't start. no ignition. took it out looked at it again put it back in and it started, ok i pulled a U Turn to go home, it got a lot worse (like last time), during the drive home a few hundred meters the car stalled. i opened the bonnet and heard a noise from the cap, i took the coil plug off the cap and got zapped 5-6 times... ehhhh? (ignition was in the on position motor not running) the tacho was bouncing all over the place.

It got worse and worse every minute i tried to get home. so bad it backfired. the afrs where 8 - 11 trying to cruise.

I'm thinking reference sensors?

Can a fault chip board cause this? Josh?

On the drive there, the only boost i hit was 2 psi, I will check the ic pipes and vacuum leads tomorrow if its not raining.

What have i missed?

Thanks for taking the time to read.

kombatrok

Water in the DME = not good

Is your battery tray intact?

hp18racer

The DME runs the tach. If the tach is bouncing with the car not running but key on I'd be thinking bad DME.

86 951 Driver

If your DME is getting wet I would look into that. I have never heard of that unless your battery tray is rusted out. The DME getting wet is very bad. Do you see any corrosion?

How is your coil? Do you have a coil tester?

Reference sensors can cause this if they are not gapped properly or the connections are loose. Maybe try and disconnect them and spray that with electric connection cleaner.

Paulyy

Note: my battery is in the boot.

The dme had a few drops, it wasn't soaked inside. the outside was moistish. but still might be the issue.

Coil is good. i've changed it out once with a known good spare and no difference. (last time i had an ignition issue)

mudbuddha

I am thinking bad dme as well- moisture and water droplets can and will short out electronics. I'd put in a used dme to see if that's the issue. FWIW my first 944, an 86 turbo had similar issue wherein I had water not draining well from the battery tray area so it leaked into the passenger compartment and onto the dme area. I also had water leaking into the area behind the driver seat too but that maybe from the sunroof. Anyway, the car sat outside so when it rains or moisture got to the dme, I'd experience no start and/or car would die while cruising. I'd park the car for a few hours or let it dry off then it would start again. I think you have drainage problem so look into that before it rots out the car.

Paulyy

The only problem with putting a known good dme in my car is the only person i know that can get to me (cyberpunky) has an 86 (yes same as mine) but i'm running the M-tune wish uses a 28pin DME.

This is the 2nd time water has gotten in that area in 2 years. my car sits outside in the rain most of the time. I'll definitely be looking into that problem.


What i don't understand is that it just got worse and worse every minute. it got to the point i probably had flames shooting out the exhaust. that's how loud the back fires where.

Black51

Was the car running flawlessly right up to that point?

Based on the information at hand, I too am jumping on the DME bandwagon. It could be that as everything was getting worse, the chipboard was shorting.

fortysixandtwo

I've been towed home because of a wet DME. There was enough water to actually pour out of the holes in the DME case. I opened both the DME & KLR, washed the residue off of the solder side of the PCBA (chip board), let them dry, reinstalled. I never had a computer related problem after that.

It's been about 10 years since that happened, so I don't recall if the tach was acting up. Plus it wasn't a slow onset, the car bucked a few times and shut off in the course of a few seconds. While trying to restart, it was shooting fire ***** out of the exhaust.

I would open the computers and let them dry for a couple of days. If you see any water marks on the PCBA, clean them off. They can be conductive and cause the computers to act erratically.

Adonay

Did you notice the DME beeing wet the last time you had these issues . If i remember correctly you had a faulty KLR then ? I had similar issues years ago i got so fed up i almost bought a standalone to replace the ancient Motronic . Sold that car never found the issues as it was always ok when searching for the problem.

Would be interested to see what is causing your problems. Best of luck

Bri Bro

Water isn't the problem, it is water combining with the flux used to solder the DME that causes the problem. Water isn't conductive until it combines with other elements, which it is very good at doing. Combine it with salt, it turns into a great conductor, combine it with an acid (flux) it turns into a great conductor. I am not surprised it got worse with time.

Take some >90% alcohol and pour it over the boards, then let it dry. The alcohol will absorb the water and it will evaporate quickly. Look at the boots going through the firewall. I am guessing they are leaking. Putting a water hose on the car while looking inside will ID the source.

Rogue_Ant

Re: chipboard - they usually work or they don't, not much room in-between...

Try going with Brian's advice.

Paulyy

I'm going to try the alcohol and report back.

I'll start it first, see what happens.

Then the alcohol, when it's dry i'll try again.

Bri Bro

Your call, I would clean it first, then start it.

Paulyy

Well i started it with out touching anything, and it started with out any worries.
I let it idle, then i noticed the tacho bouncing all over the place. i turned the car off got the camera and recorded me starting it. idling and revving it and showing the tacho bouncing all over the place.

The video is being uploaded right now, it's a huge file so it'll take a bit. soon as it's done i'll post it. (i'll give it an hour and a half to upload 250 mb )

I'll be going down to the shops to get some methylated spirits to give it a clean.