Q – I have an 86 Carrera Targa with about 38,000 miles. Recently when it drove it about 10 miles, it started to sputter and then it died. I had it towed in and when it got to the shop, it started and ran fine! I hate that! They replaced the DME relay, checked fuel pump draw, all other relays and fuses, and could not get it to fail again. They even test drove it about seven miles without a hiccup.
I was warned that problems that cannot be duplicated cannot be conclusively solved and sure enough, I got about eight miles away and it started cutting out again. Just before it did this, the idle began hunting up and down. Now it is stuck in my garage versus along side the road, but that is little consolation. What’s next? Karl
A – First of all, the DME relay was a good guess but if it won’t act up for the shop, you are at a serous disadvantage. The other problem is that, unlike modern cars with on board diagnostics, this generation car cannot give you any clues electronically. So you are left with S.W.A.G. (aka: Sophisticated Wild A** Guess) Yes Karl, intermittent failures suck!
Here’s what I suggest: In the engine compartment, there is bracket on the left side of the engine compartment that has two or three fuel injection plugs on it. One of these plugs is for the temp sensor. If the temp sensor has a two connector female terminal plug, but the temp sensor has only one terminal, replace the temp sensor. This is a good diagnostic hunch since these have been known to fail for years.)
The next thing I would check is the main harness plug that connects the engine harness to the body. These rarely give any trouble but you never know and they are easy to check. If the plug is not full seated or if the terminals look funky, that could be it. The next thing I would look at is the Motronic control unit located under the driver seat. Since you have a Targa and since Targas and Cabrios leak, it is possible that the computer got wet. I know of no clever way of getting the computer out without removing the seat, so, have at it! Look for dusty white residue on the circuit board, the connector and harness plug. If you see any, use contact cleaner, then plug and unplug it numerous times to scrape a fresh surface into the terminals.
If none of this works, SWAG dictates parts swapping with a known good car. (Ideally, the owner of the donor car is aware that his is being used for test purposes and you have his permission to infect his car with your problem.) It is not as bad as it sounds since the infection is easily cured by removing the infected part once the problem is nailed down. Good luck. – MC