Acceleration probs '87 Cab

I wonder if anyone can help .....

I've just started having problems with my '87 Carrera Cabriolet. Annoyingly it's an intermittent cutout under acceleration that seems to only start once the engine is warm, at first manifesting itself as a power drop at around 4500 rpm but then quickly developing into a brief cutout before curing itself.

It only happens under acceleration - at idle its fine and at a constant throttle position it's fine at any speed. What's more baffling is that it comes and goes - sometimes making the car almost undriveable and at other times (in the same journey) completely dissappearing.

I'm guessing an dodgy sensor or fuel injector is to blame or some part of the ignition system is playing up.

Has anyone had a similar problem? Any advice would be most gratefully recieved.

Many thanks

Christian Stewart

'87 Carrera Cabriolet

christian.stewart@dmstewart.com

the single wire head temperature sensor is a source of problems, as is the DME relay under your seat.

Christian:
Check to see if you have the "old style" head temperature sensor. Looking into the engine compartment from the back, at the top of the engine on the left hand side, there are three connector plugs held by a metal rack. The one on the top (the white one) holds the connection for the temp head sensor. Pull the connector apart. Look at the part of the connector that's on the rack. If it has two prongs, it is the new style head temp sensor. If it has only one prong, its the old style and should be replaced with a new one. The new sensor will cost about $60.00 (US). This may or may not be your problem, but it wouldn't hurt to replace it now if it's the old style. Good luck
regards,
jlex.

Fairly obvious thought would be crap in the fuel lines or a clogged up fuel filter. For the cheap fix, I'd do this anyway unless you've already done so recently. Never hurts. Just a thought. Dave

Mnay thanks for the above advice guys - will check head sensor type and operation DME relay. Fuel filter replacement a priority too (docs which came with car seem to indicate it hasn't been replaced recently).

Will keep you informed of results....


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Christian Stewart
@87 Carrera Cabriolet

christian.stewart@dmstewart.com

Any harm in replacing the plugs and checking your ignition cables?

Joe

Sounds like it could be the air flow meter as well. I had trouble with mine. After dinking around with it once, I got it to cut out at around 4500 rpms.
The bentley manual has a testing procedure for it, testing continuity for the full range of the gate. Mine had flat spots which I addressed by pulling the black connector out (gently out), and making sure the slide contacts reinsert correctly.


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Kurt B
'84 Carrera Cab.
carrera_cabriolet@yahoo.com

Just to keep those who were so kind to offer advise updated and reassure you that i'm not a splash and dash forum type, I've done multimeter tests on most of the available sensors as per bentley manual and nothing discovered.

Single wire sensor present but seemingly working - rotor and distributor cap replaced - annoyingly seemed to cure the problem for 50 glorious miles during which the car has never run better, but then back to square one - still waiting for new DME relay and fuel filter to try but meantime have been recommended a Bosch specialist who is going to give it the full checkover on Wednesday.

Most recent run i had showed more distressing symptons with the car cutting out for 2-3 seconds and not just on acceleration before picking up again - got me baffled especially as it's a complete cut out and semes to be initially provoked by going past 4000 - 4500 revs and only after 10 - 20 miles.

I wonder if it could be a worn fuel pump - but i've never experienced intermittent failures on one before.

Again many thanks for all your help - will keep you informed of any results after Wednesday.



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Christian Stewart
'87 Carrera Cabriolet

christian.stewart@dmstewart.com

My 87 Turbo would cut out briefly on hard acceleration occasionally, and also was difficult to start; it would turn over but not fire consistently. It turned out to be a bad relay in the engine compartment that was interrupting the ground to the fuel pump relays. I diagnosed it by grounding the fuel pump relay independently and the car started perfectly and stopped cutting out. Once the relay was replaced, the car was fine. Something to ponder.

Vic
88 Carrera

It would make sense Vic - a lot of the symptons are of a "loose connection" or similar that is cutting in and out or out and out as the case may be - I'm not good on electrics - can just about wield a multimeter as the book instructs after much head scratching. The only difficult thing to reconcile is the rev "trigger" of 4500 - which seems consistent.

I've checked as many of the ground wires and electrical connections that i can find - being an 87 carrera cab the only relay in the engine compartment is the heater blower. I'll add the independent grounding of the DME relay onto the list of helpful suggestions to the specialist on Wednesday.

Many thanks


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Christian Stewart
'87 Carrera Cabriolet

christian.stewart@dmstewart.com

i would replace the head temp sensor first, if it's the old single wire in the plug type. it's helpful to have a shop plug in a computer temporarily to rule that out.

Thanks John, it's top of the suspect list I'm giving them - out of curiosity how much can they tell with a laptop hooked up? Am i right in thinking the car doesn't have a dedicated diagnostic hook up?



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Christian Stewart
'87 Carrera Cabriolet

christian.stewart@dmstewart.com

Christian,

Christian,

Christian,

Christian,

Christian,
Mine, an 87, cutout when I hit a bump. The DME relay was vibrating loose. I put a new relay in and a wad of paper beneath to support it and am now living happily ever after. Look at the relay and you can see how it is not properly supported, vibration will tend to separate the relay from the plug.
Ned Monaghan

Looks like I've got the hesitation cured - took the car to a Bosch specialist in Edinburgh last week and despite Bosch's best efforts to lose parts etc have got it back today and it's running better than ever.

DME checked out fine - no fault codes on normal running and of course he couldn't re-create the hesitation himself - however delivery / flow rate on the fuel was down and a new fuel pump seems to have cured it. At the same time a cracked CV boot was discovered so that was replaced too.

In the course of the whole drama of trying to troubleshoot the car I've got further to the bottom of it's history - which might be of interest to other euro car owners or those trying to source their P-cars from Germany. The car was originally a stock 1987 euro non-cat 98 ron only vehicle. But in 1992 it was fitted with a catalyst, O2 sensor and DME remapped. The Porsche card included in the handbook describing the changes shows the power dropped and the fuel requirement dropped to 95 ron unleaded. Apparantley no Super Plus 98/97 ron unleaded was available at the time so this had to be done. Rather than replace the DME they have simply remapped the original. The only other changes are an unleaded only filler setup.

It seems that at the time laws changed regarding emmissions and this is a common conversion - how many different conversion types (Porsche/Non-Porsche) there might be I'm not sure.

Many thanks to everyone for all the help in getting to the bottom of this.



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Christian Stewart
'87 Carrera Cabriolet

christian.stewart@dmstewart.com