Hey guys,
I've got a strange problem with my 1991, 90, FWD, Auto, I5 engine dying while driving, either highway speeds or slow city street speeds.

The engine acts like it was just shut off. Just quietly quits. No codes show.

The fuel pump is a brand new Bosch, less than a year old. The fuel filter the same. It gets driven about 8,000 miles a year, so not heavy use. New spark plugs. ISV is newish (about two years old) and clean. Replaced the big rubber boot to the throttle from the air filter / air sensor within the last year. Rubber tubing to the ISV is OK. Metal pipe for the crankcase vent to the rubber boot. I keep the maintenance up probably even better than necessary, including oil and transmission fluid changes, etc.

Once you stop the car, just wait about 3-4 minutes and it starts right up again. Runs great on the highway. Doesn't act like it is starved for fuel. Idles smoothly.

Has done this 4 times now in about two weeks.

Today when it happened, I noticed that the oil pressure gauge stayed up, just like the engine was running, even though the Tach said zero while I was coasting. The oil pressure warning symbol on the little image panel came on, as though there were low pressure. Gauge says pressure, while light says No ? ? ?

Also, funny thing, when I pressed on the throttle, I got a bit of a roar as though the engine was running, but the Tach said 0 and I obviously had no power as I coasted to a stop.

Well, I'm stumped. I've checked the fuses, the computer codes, the relays are mostly all new.

What makes an engine die like that, then work fine in 3-4 minutes and run for days w/o a problem? Then die an the next unexpected time?

Seems maybe electrical to me, but no idea where else to look.

 

check your grounds, it dose sound like something electrical just cutting out

 

Thanks, CR, I'll take a look at those. The ignition switch is new too... replaced with Audi-bought switch, not after-market, just to be sure.

Frustrating when there are so few signs of just what it is. Especially when it always starts up each day. I'm just afraid of losing power at some important moment or on a bridge or whatever.

Still looking.... If there are any other ideas out there, I'm all ears. Thanks again!

 

i would also take some contact cleaner to all the connections in the engine compartment, it might resolve the problem its kinda difficult to troubleshoot a random problem like that. have you pulled any codes?

 

You know what?

A buddy of mine had an old Honda CB550 Four that used to do the EXACT SAME THING. Drove us nuts. We did everything to that damned bike... adjusted the carb floats, jetted it rich, jetted it lean, no luck.

Turns out, it was the gas cap! The little pin-***** hole in the gas cap had rusted internally. The gas tank, when filled up, would drain to vacuum, and the fuel wouldn't flow efficiently. The motor would chug and eventually die. After a few minutes it would fire up again.

I think the reason it works for a few days is because your tank level has dropped enough to allow a "cushion" period of slow vacuum build-up. Remember, air is compressable (read: stretchable for this purpose) fluid NEVER is.

Try pulling your gas cap RIGHT away the next time it dies (likely with a full tank). See if it starts right away.

 

You mentioned the tach read zero when you were coasting to a stop. You had the clutch in, so you know the engine wasn't turning? The reason I ask is that I had a similar propblem on our '88 90Q. At 40 mph, the engine would die, but even with the clutch out and the engine turning, the tach would drop to zero. (No sparking action) That gave me the impression it was electrical. I swapped an entire distributor from my parts car and never had a problem again. I think it was the Hall sensor. The rubber grommet where it passes under the dist. cap was broken, maybe the wire was cracked, too.

Bruch

 

Well, that's what it was.

The Hall Sensor. The whole distributor had to be replaced, which was fine by me as I was anxious to fix this once and for all.

I was driving on the highway, passing a semi when it happened again - BAM, no power, no nothing, no tach (auto transmission), dash full of warning lights.

Just as I was about to say, "Oh what the heck..., panic!" the freaking engine *started* running again all by itself (never seen anything like that) and I passed the semi. It was "dead" about 10 seconds.

So, I get to the store, go buy a trunk-load of stuff to take home and it won't start at all. Nothing I can do to make it start. Just turns over and over. And nothing.

Frustrated at this long-running dying problem, I give up and have it towed to the dealership, which is actually a pretty decent place although it costs a fortune.

They went to start it the next morning and it started right up. Thankfully, the mechanic believed me and investigated. Eventually, he found that as the engine got warmer, there would be weaker sparks here and there. And, eventually, he tracked that to the Hall Sensor which would fail, slightly, at higher temperatures.

So, there's one to add to the list of things to suspect about dying cars.

Hasn't died again in about 6 months.