James L.

Hello Porsche engine lid lifters!

I have a 03/1987 euro 3.2 (imported to New Zealand where I am based). It has no cat or O2 sensor. 88,000 mile on the clock.

Recently the car has developed a 'surging' or 'bucking' problem at 2350rpm exactly. It happens in 3rd, 4th and 5th as the car is cruising.
The car idles perfectly and under acceleration is fine.

The problem has been there for sometime now but only recently has it started to get to a stage where it is now annoyingly bad.....ie it's getting worse.

It is fitted with a K&N filter, new plugs at 82k mile, serviced every 6-8 months.

Any clues most appreciated :-)

James L.

Stuttgart951

Try having the injectors tested - I had a similar problem and it turned out I had a bad injector.

BER

James,

I had a similar problem in my '84 Carrera (3.2 ltr) a couple of years ago.

The bucking and surging was eliminated by leaning my idle mixture using the idle bypass screw (bottom of the AFM). My idle mixture had been set way to rich. I used a Gunson CO Meter and reset my idle CO to approx. 3%. All my surging and bucking problems went away.

Bruce

purrybonker

These responses are becoming a bit of a dog's breakfast, but in contrast to BER's comments - my situation is supposed to be exactly the opposite.

I have the same car as you (except mine is a June car and has a cat) and have experienced the same surging problem. My local dealership pointed to my K & N filter/Authothority MAF/chip combo as the culprits that were causing an "over-lean" situation. They concluded that the surging was related to this lean condition caused by the chip & MAF.

I suspected this to be BS and have left the add-on parts alone.

I have found that the problem has moderated with switching fuels - I had been running an ethanol blend (the highest octane, 94, available in these parts). Running Shell 91 seems to have all but eliminated the surging down to a minor annoyance.

I was waiting on my next spring "tune-up" to address the issue further. I look forward to hearing if you find a solution to the problem.

Ken

art

I have been fooling with EFI on my 2.2E for a few years, and anytime I have surging/bucking it has been from too rich mixtures. I realize this is a very different animal from yours, but that's my experience.

You may want to add an 02 senso to monitor things. They are dirt cheap here.


Art

Bob Prosser

Hi Ken.

Here's an anecdotal story relating to my long time daily driver -- a 1987 Carrera, presently with 125K miles on it.

For many years, I had noticed a surging at about 4250 RPM -- not your exact problem I know, but a surge all the same. I assumed I had to live with it, since everything about the engine and its tuning checked-out fine (good electricals, no intake leaks, good injectors, etc.)

Then, about nine months ago, I contracted to do some marketing and advertising work for a company named Powerchip (an aftermarket chip/ECU programming company originally from Australia). If you read Excellence, R&T, C/D, you've probably seen some of my/their ads.

Anyway, during my learning about their fuel mapping techniques, etc., I told them about my surge. They suggested that I replace my chip with one of theirs, so they can evaluate the old one. I took them up on their offer.

After replacing the chip, I immediately noticed that the surging was gone! In fact, the engine ran smoother across the entire rev range. When I spoke to them later, they told me that after evaluating my old chip, it was not OEM and whomever did the programming was an amateur -- it had very aggressive settings that, under the right circumstances, could have damaged the engine.

Huh, all this time I assumed it was stock. When I purchased the car from the original owner (many years and over 100K miles ago), he had neglected to tell me that there was an aftermarket chip in it.

How does this relate to your problem? I am not sure, other than it couldn't hurt to take an hour or so and swap out the existing chip with another good quality unit to see if it makes a difference. It certainly did in my case.

Regards,
Bob Prosser

PS: This is not an endorsement of Powerchip, per se. No doubt, any professionally programmed chip could have made a difference.

purrybonker

Thanks for the comments Bob, you've inspired me to pursue this issue sooner, rather than later. I'll play around with some chip options...

Thanks

Ken

James L.

Thanks everyone, tips most appreciated.

One thing I forgot to mention; I used 100octane during the weekend at a track day (with Ferrari's present,a couple of which, shall we say 'retired' but the Porkers trucked on.....); this fuel I believe made the 'problem' worse but now back to 96 and the car is better behaved.

CO/mixture test will be done and injectors will be serviced regardless in the next week or so.
:-)