Engine dies momentarily

[colin129]

Don't know if this one has come up before.

I was driving into London the other day. 20 miles on motorway with no problem, approaching the Hammersmith flyover the engine suddenly died for literally a second and then came back. Revs droped immediately to zero then just as quickly back to normal. This happened a few times over the next mile or so, I thought I'd better stop and see what was happening.

Engines started fine, and revved smoothly round to the red line, instead of settling immediately to idle it overshot, somtime stopping sometime coming back to idle. This happened a few times whilst stationery.

I toyed with the idea of call out the AA, but a) They know nothing about our cars and b) It wasn't really broken down. So having revved the engine a few times and having stalled few (less) times I decided that valour was the better part of discretion and continued my journey into Central London with no problems.

On the way back I had the same problem, this time on the motorway. It happened a few times then continued to run with no problem until I got home.

Subsequent shorter trips the following day, although long enough to completely warm the engine and no reoccurance. Also my trip to work (9 miles) was without incident.

Some of you may know from earlier posts that I have owned my car for 9 years, I've never had anything like this before. I thought about the DME relay but that has always shown itself as a starting problem in the past and it starts fine.

Thanks for getting this far...any ideas?

 

[PRJ]

Colin - I had something a bit similar happen a couple of months back. Think the thread was something like 'engine misfiring occasionally' if you search. My problem started with some random, very short cut-outs and over a couple of weeks, things got progressively worse, although there were many days when there was no recurrence.

In the end the culprit was identified as a dodgy connection on the AFM. Just needed the connector pushed further on. Hope this helps.

 

[colin129]

Thanks for your help...but what is an AFM? (Am I supposed to know this?)

 

[PRJ]

Found it:
http://www.porscheclubgbforum.com/tm.asp?m=154675

 

[PRJ]

Sorry - Air Flow Meter

 

[colin129]

I've read the thread and I do not appear to be getting a misfire...engine just dies...

 

[Guest]

did you have to let the clutch out to start it again, or did it just drop to zero and *start* again of it's own accord?

Oh, and which year/model is it? (you may want to stick it in your signature for future reference...?) Alyhough on this it probably won't make much difference.

I'm thinking it may be something to do with the throttle body area. Either a leaking body, position switch error of some description, stuck throttle cable, or maybe even a lost return spring....

 

[Guest]

Hi

The absolute first thing to try with this sort of problem is the DME relay. Any Porsche specialist worth the name will sell you one for about twenty quid.

In the early 944s, all the relays are in the passenger footwell. Look for the one that has "DME" printed on it, and change it for a new one. I do not know where it is on the later cars - it could be anywhere! (In a 3.2 911 it is in a totally undocumented location all on its own under the driver's seat - so you might have to look for a while.)

I have had to do this on all of the 1980s Porsches (944x2, 911x1) I have owned, and the signs have been just as you describe. What will happen is that the periods on engine stoppage will increase, and become more frequent. Eventually, the stoppage will be indefinitely long. When I first encountered this, I was in the west of Ireland on a Friday evening. Only after the car was re-patriated on the back of a transporter, was the problem diagnosed by the parts department of my local OPC over the telephone in 15 seconds flat!

I have carried a spare ever since, which was handy when the same happened on my second 944 and my 911 3.2! I am waiting for my 964 to do the same...

A

 

[colin129]

ORIGINAL: pikey7

did you have to let the clutch out to start it again, or did it just drop to zero and *start* again of it's own accord?

Oh, and which year/model is it? (you may want to stick it in your signature for future reference...?) Alyhough on this it probably won't make much difference.

I'm thinking it may be something to do with the throttle body area. Either a leaking body, position switch error of some description, stuck throttle cable, or maybe even a lost return spring....

I'd like to put a signature on, but I'm not sure I know how (or maybe been bothered to find out!!) It is a 1990 944S2, nearly 170K mikes.

The engine restarts of its own accord, I guess you would say it jump started itself.

This morning I had a 90 minutes journey of mixed driving (no motorways) traffic jamming and country roads, no reoccurrence of the problem.

Re DME, I have had two fail on me before but it doesn't feel like the same problem, although I don't discount it. With the DME the engine would shut down and coast to a stop, and as it got worse not restart until the engine was coldish. I'll keep an open mind on this one as it would be a cheap and convenient fix.

 

[Diver944]

ORIGINAL: colin129

I'd like to put a signature on, but I'm not sure I know how (or maybe been bothered to find out!!)

Please do bother, it's really hard to help people when we don't even know what car they've got []

Click 'profile' at the very top of the page, scroll haf way down and fill in the box labelled 'signature'. Click on apply and then save - job done []

I would always try a new DME relay for any electrical type problem and always keep a spare as they do wear out (mines gone twice in 8 years). Andrew at Promax will send you one for tomorrow for under £20 all inclusive

 

[colin129]

Done!!

 

[Guest]

Done???!!

Did you fix your car?

If do, what did you do?

A

 

[Guest]

Now, I have had two different situations.

1 in 944 Lux 2.5: Engine cuts and re-starts after 1second, and this period lengthens over time.

2 in 911 3,2: Engine never cuts out when running, but sometimes does not restart when warm, but does not seem to have a cold start problem. (The ablsolute nightmare was trying to escape from Tesco on a Friday afternoon in Inverness, and the bloody thing would not start in front of hundreds of leery chuchters).

Both problems solved instantly and 100% with a new DME relay.

This is not the first, it is the zeroth thing to try!

A

 

[colin129]

ORIGINAL: eurgain

Done???!!

Did you fix your car?

If do, what did you do?

A

No, I mean 'Done', I've put a signature on, do you like it?

No reoccurance of the problem so far, I guess its a case of wait and see...

 

[Diver944]

I reckon it was the lack of signature causing your problem []

 

[colin129]

Just as an update, I have still had no reoccurance of the problem, despite making a similiar trip this saturday.

Watch this space...