ThePhoenix74

Hello All,

I did a lot of search on this forum in regards with sudden power loss, but I'm not sure I found something exactly alike mine.

Last summer, this problem arose a couple of times where while i was driving along the highway, I would suddenly lose power (but the engine wasn't stalling) it felt like no combustion. As I wasn't letting the accelerator go, it would suddenly come back with a burst (as if the fuel was finally burned).

This spring, it started again, to the point where it's happening on a daily basis. Today, I was doing city driving, and it started to act in a very similar way and the only was to get power back was to downshift in 2nd gear and reapply the accelerator. When it's happening, it feels like the car is not getting all the power back.

i did change the DME relay, got the O2 sensor checked-out, and no changes. The computer error codes were checked, but nothing meaningful this problem came out.

Any idea where I should be looking next?

Thx,

Yvan

Duck

Are the coils in your car original? I was having issues with mine hesitating and I was able to fix mine with new coils.

klr10

Seem to vaguely recall some posts like this where it turned out to be an engine ground strap loose.

Rocket Rob

The DME relay and O2 sensors are the common culprits. Since you have already checked those, I would look at the main power cables at the battery and engine. Verify that those are solid.

springer3

Read the diagnostic codes. The DME should have the reason.

elbeee964

hmmm...

Well, here's a long shot, but is yours an '89, or '90?
(I think I spy flag mirrors on yer avatar...)

If so, see if this factory tech bulletin fix was done to your airflow meter's wiring harness.

It's an easy fix.
If not already done, you can do it yourself.

BGLeduc

I have had the problem cured by the TSB procedure, and when it happens. all hell breaks loose. The car will buck violently. Trust me when I say that you will know it if happens. :-0

I also have had a problem that sounds similar to what is being described by the OP. For me, it will happen when descending a very shallow grade, with steady, but only part open throttle. It is like the throttle pedal is just dead. When that occurs, if I floor the throttle, everything will go back to normal.

There has been discussion of this from time to time, and I think one of the suggested fixes was cleaning the contact areas of the airflow meter itself, as there could be corrosion and other contamination that caused a dead spot in the sensor's range. I never carried that out, so I can not speak to its effectiveness.

Brian

Richard Curtis

FWIW, when I had similar problem, simply cleaning the battery cables and all battery/ground strap connections did the trick.

ThePhoenix74

I looked at the code, nothing relevant whatsoever to the problem I'm experiencing.

gchristofi

+1 check the ground straps 1st, then the AFM wiring mod (purely because straps are easier to reach)

yellowducman

+1. Mine does the same thing at the same place on the same road. Every time. Sounds like maybe the mass air meter gets out of calibration and the only good fix is to replace it. If you could get your hands on another one and try it that would narrow it down.

911Jetta

Yvan,
Very good advice above.

I had a similar situation last year.

My car would randomly stall while driving or suddenly jerk and cut out for a second. It would always start right back up (even while driving on the highway). In the beginning the problem was random, but the situation was getting progressively worse...

I also received similar advice. I thought it was my fuel pump...I almost replaced it but that just didn't feel like that was the answer so I threw-in the towel and had it towed to the shop.

They scratched their heads for a bit but eventually traced the problem down to me incorrectly seating my Steve Wong chip. I installed the chip months and months earlier and the car drove really well but the chip slowly unseated itself and this would cause the car to randomly stall.

https://rennlist.com/forums/showthre...ferrerid=19642

ThePhoenix74

Very interesting. I bought this used Porsche 2.5 years ago, and I don't know if it's using a stock or aftermarket chip. Is it easy to figure by opening the DME ECU?

My problem also happened last summer (2 or 3 times) and never re-occurred, I thought it was a fuel gremlin problem and that it went away. 1.5 month into this summer, it already happened 20+ times and I'm also getting into the nervous zone where I don't want to take the car for a long ride and get stuck in the middle of nowhere without any cellular coverage.

I already suspected that it might be a DME ECU problem and will get to try a replacement unit for a couple of weeks and see if the problem is caused by this component. I can't believe the a fuel pump would behave this way (re: intermittent problems).

On another note, I did see error #21 Hot Film MAF... Any possibility that this could be linked? My mechanic told me that it's very unlikely and that error is probably triggered by the aftermarket air intake (Evolution Motorsport) installed in the car. Any idea?

Thx,

Yvan

ThePhoenix74

Quick Update: I finally got a check engine light that went on for about 5 seconds. Looked at the error code and it's pertinent to temperature. Mechanic think it might driven by the EVO intake cone that was installed in the car when I purchased it.

Did review the Technical Bulletin with him, he confirmed that the mod was done on my car.

johnsjmc

My 3.6 from a 964 is in a 1980 SC. I chased a similar "hiccup condition" last year. I replaced both crank sensors,DME relay ,plugs ,rotors and caps. Finally I replaced the plug wires. The plug wires fixed it. I believe there was always at least one spark in a cylinder so a miss was not detected but the other one mis firing causes the computer to reboot.