Running problems....HELP!!

[plhorner]

Right, I could really do with some help on this one.
I had SSI's fitted over the winter, the job took about 12 weeks longer than anticipated which left me little time to get my brakes re-build before Le Mans. Anyway, I finally got some miles on the clock to settle things down prior to going back to the specialist to have the mixture adjusted once things had settled down. Anyway, the car had been running really well, however when we put it on the analyser we found it to be running a little lean. The chap at the garage started to adjust mixture and turn the slow running down, we got nearly there and then found that the engine wouldn't rev. It ticked over just fine, but open the throttle and you could hear the induction roar but the engine just spluttered badly. Said specialist diagnosed air flow meter problems, adjust things back to where we had been...but not quite! On the drive home, on very light throttle openings, the car hesitated, if I put my foot down it would surge forward after a slight pause. Anyway, for various reasons I had to leave the car for a couple of days after which it appeared fine and I couldn't repeat the fault. Said specialist reckoned it would be fine for the trip to France......I only got 15 miles before it finally packed up (and fortuately this side of the channel)!

So symptoms are: When fully warmed up (after 15miles / 10/15 mins) the car hesitates and sometimes looses all power. It won't stall and it ticks over fine, how ever if you put any load on the engine it really struggles. If you lightly touch the throttle you can get the revs up and it will go, if you really get the revs up it feels like nothing is wrong! If you floor the throttle from tickover, the engine coughs and won't pick up.

I've had the airflow meter out and checked by a bosch specialist, apparently fine. I've done the checks in the Bentley, I've got power to the meter and the temp sender is OK and in spec.
Having had a look at the engine, it appears that a new cylinder head temp sensor has been fitted recently (without my knowledge - I've had the car 6 troble free years!) ANyway, the sensor is the new 2 wire variety and is in spec. resistance wise.

Could it be a dicky DME relay? Fuel pump dying? ECU failure??
Really lost now and don't want to take it back to the specialist, lost a lot of confidence in the place and feel like I've been spun a yarn or two....I'll say now more!

Help, all ideas greatfully recieved!
Cheers,

 

[bones]

I don't know the 3.2 well enough Phil but this is what I would do find a Bosch diagonostic specialist and have him first check the least complicated thing, that is the electrical system. Get him to check that the plugs are getting the correct current all the time. If that checks out you are into fueling problems which means doing pressure tests. I would think if these tests are performed systematically a diagnosis should be possible in a hour, two at most. It might be worth checking out the dizzy too as it is possibly sticking.

 

[plhorner]

Pete, good call, I'd not considered ignition. The chap who's checked over the AFM is a Bosch specialist, I might give him a try for it. I just wondered if there was anything simple I was missing before shelling out again.

Cheers,

 

[bones]

They should have checked spark and fuel from the getgo, it's basic stuff really. Keep us posted , hope you get it fixed soon.

 

[Richard Savage]

ORIGINAL: plhorner
So symptoms are: When fully warmed up (after 15miles / 10/15 mins) the car hesitates and sometimes looses all power. It won't stall and it ticks over fine, how ever if you put any load on the engine it really struggles. If you lightly touch the throttle you can get the revs up and it will go, if you really get the revs up it feels like nothing is wrong! If you floor the throttle from tickover, the engine coughs and won't pick up.

Phil - I had exactly these symptoms on mine, but it was also more noticeable in damp / wet weather. I went straight for the Distributor Head, expecting to find condensation. There wasn't any. However, the distributor head was questionable, so I replaced it anyway but the Rotor Arm was totally, and I mean totally, shot! [ 59,500'ish miles ] Replaced the rotor arm. [ Obtained Both from Local Auto-shop - Not Original Porsche, but what the hell! ] - Sorted!

Also had the same symptoms on a Vauxhall Cavalier SR1 and a VW GTI - On both occasions, Plug Leads!

The problem with Electronic Ignition is, that since Contact Breakers don't need to be replaced / set any more on a service, nobody ever bothers to look inside the distributor!

I have my fingers crossed for you!

R.

PS - Had the engine 'tuned' shortly afterwards, just to make sure everything was back in order!

 

[dtunnicliffe]

Phil,

Reckon Bones and Richard are on the money. Simple things first and first stop for me would be the Dizzy. Ages ago now but a duff condencer on my works Imp gave similar symptoms. Ran fine on idle, give it gas and it threw a wobbly.

Can't be much more than a tenner from Eurocarparts and a pukka Bosch part at that. I'd still get the rest of the ignition tested. If one part is down you can almost be sure something else will be in need of TLC in the ignition department. Cheers

Dave

 

[plhorner]

Cheers lads, I'll take a look.

 

[Guest]

Hi Phil,
I had almost the same symptoms as you describe, would be just getting up to
operating temperature then missing as you describe, when the problem first
started, it would clear and then run fine the rest of the day, sometimes not
happening at all, this would happen intermittently but after a while got
worse and eventually would not run at all.
It turned out to be the lambda sensor I believe, it's a
American import '88 Cab. and someone had put a cat bypass pipe
on and not changed the sensor, I'm not very mechanically minded but it seems
as the engine was getting up to operating temperature this sensor was
sending out all sorts of wrong info to the ECU because it thought there
was still a cat fitted.. Hope this makes some sense.
Cheers.

 

[plhorner]

Well, after much checking of fuel and ignition systems I finally found the problem. A broken wier to the AFM, it was obviously giving an intermittent signal to the ECU which was then upsetting the fueling (it was part of the resistance circuit giving feedback from the flap). I've actuallt fitted a new connector block as there'd odviuosly been an issue in tee same area before, looks like somebody had butchered the back of the connector to solder wires back in...a real mess!
Hopefully all sorted now, gave her a good run yesterday without any problems....fingers, toes and anything else crossed![8|]