84 erratic quits

[hrscrk]

84 carerra w/84000 miles

in an earlier post i described her running.....dying...running...dying...etc

porsche dealer put her on the box and sez the dme is a goner

a second source says its unusual for the entire dme to give up the ghost; could be a connection, component.

third source at used parts house says they sell a lot of these

since i'm about as mechanical as a newt i don't know who to belive.

thoughts, gents?

tx

ed

[nesslar]

Might be the DME relay going bad; $25-$30 fix. Mine acted up a bit before dying completely years ago. In time, you might not get it restarted if it is going out. Likely it is, but at any rate, this is a good place to start. ONLY the black relay, NOT the whole control module! Lar

[rlw]

The way I noticed my DME relay was going bad was one little blip while accelerating one day. It was like the engine turned off for a split second then back on. It was so fast I thought I made it up. Drove around, car restarted fine. That next morning, car would not start. Changed relay and that fixed it. Its an easy/cheap thing to try plus best to carry an extra anyway if that is not the problem.
RW

[Joe Bob]

That's the first fix.....if it doesn't do it, you have a spare for when it DOES go.

There are more than a few Motronic/DME diagnostic threads. Mine ended up being a switched power short on the fuse box.

Could also be a short on the sensors.

Usually they fail all at once. Intermittent shorts suck to track down.

[twin plugged targa]

'Intermittent shorts suck to track down'
- Tell me about it!

[kidrock]

DME relay replacement should be checked first.

If that doesn't do the trick, a series of diagnostic checks should be followed, such as checking for fuel and spark.

[DonMo]

My 84 had a intermittent transistor failing inside and did exactly what your is doing. When cold, starts and runs, once hot, shuts down. I am talking about the DME getting hot, not the relay. Sent it off for rebuild and ECU and less than a week later. Clean start, steady idle, great performance. They also test, you can do the easy volt/resistence checks but don't start easter egging parts.

[450knotOffice]

Believe it or not, these DME's can also develop cracks in the solder connections on the mother board, which can cause shorts to develop when the DME warms up. I had this EXACT issue crop up on me one day while out driving. It popped and quit. It would start again after cooling down, but refuse to run properly. I replaced the DME relay first, but still had the same issue. I borrowed a fellow Pelican's DME and it fired right up. Anyway, I called Steve Wong and told him about it and he told me to come on over so he could take a look at the DME. The next day I brought it to him and he subsequently found MANY bad solder joints. He resoldered all of them and it was good to go.

Interestingly enough, it seems I'm having this issue again, as this literally JUST happened to me again an hour ago. I did manage to nurse it home though.

[hrscrk]

here's the latest.

the dealer is convinced the dme is shop, so i decided to replace it and found a rebuilt. car was at dealer #1 but dme was at shop #2 and no swap between shops was possible so i had to get from point a to point b.

interesting that the prob. is associated w/fuel pump. mechanic at the dealer jumpered two slots on the box under the hood (though the dme is under the seat) that control the fuel pump. ran like a charm. they said that's not a permanent fix because over time could screw up other parts of the program if i redlined the engine because the rev limiter would not be working.

result: she's at shop two which is gonna run another diagnostic before installing a rebuilt dme.

man, it's tough not knowing a thing about how this stuff works. high anxiety.

thanks for your input; i'll keep you posted.

[Drisump]

You may want to try to get in touch with ischmitz on the forum, seems like he's "the guy" pertaining to all things DME. Cheers

[plharr]

Take a look here. I had a similar problem a while back. What they did with the fuses bypassed the DME, I beleive, and provided current to the fuel pump. Hope it helps and they get you back on the road quickly.

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