Carrera stalls when I give gas...

Rick Lee · Rick Lee's Garage

Just about everything on this car is new and Charlie (kstylianos) and I just can't get it to run right. It starts and idles very nicely. When warm it stumbles and then dies as soon as he gives it gas. We tested idle control valve - fine. AFM is new and barn door opens just fine. O2 sensor is 9 mos. old. DME relay is a year old, swapped it with another and same problem. Fuel pump is 10 mos. old. Head temp sensor is new. Alt. is new. Fuel filter is a year old. What the hell is left?

kstylianos · 06-24-2003, 08:13 PM

With a little help from John Walker........

We disconnected the O2 sensor, nothing...
Checked the alt was putting out good voltage at idle and high RPM's, good...
Checked connections to all fuel injectors were fine as well as the 6 pin connector near the firewall, good...

BTW: I noticed the problem first at higher RPM's, around 4-5k. Felt like the fuel system would just plain cut out. Kinda like hitting the rev limiter. The problem eventually progressed (within about 1 mile) to not being able to accelerate at all, it would buck, backfire, etc. and not be able to keep RPM's higher than idle.

It does sound pretty damn sweet at idle though

Milu · 06-24-2003, 08:57 PM

You've almost certainly already looked at plugleads, distributor cap and rotar? If not might be worth a look.

john70t · 06-25-2003, 12:03 AM

Check the fuel pressure-could be just enough to hold an idle.
Check the grounds-the injectors may not be getting enough juice to open enough.
Check the coil-may be breaking down with any kind of load.

Rick Lee · Rick Lee's Garage

Forgot to add that plug wires are 10 wks. old, cap and rotor are 4 mos. old too. I don' know about fuel pressure regulator, but it was checked when I had it in the shop in March. That may need a second look. BTW, as always, JW came to the rescue when those on the East Coast were closed. Thanks again.

jpnovak · 06-25-2003, 04:50 AM

I think its just sad to be replaced with a newer model.

Rick Lee · Rick Lee's Garage

I think it may be a little more mechanically related than that Jamie. Charlie has been stretching her legs regularly and has kept her looking nice too. She's not even around my 993 very often, so I doubt she knows I'm with someone else now.

Thomas Owen · 06-25-2003, 05:01 AM

Have you ruled out the DME? If you want to try another one I will send you a known-good spare I have...

s_wilwerding · s_wilwerding's Garage

I knew someone who had a similar problem. It turned out that the ignition advance on their car wasn't working properly. I'm not sure how advances work on newer cars (I know there's a vacuum advance on my SC), but it's something you might check.

Rick Lee · Rick Lee's Garage

Thanks Thomas. I can borrow one locally to try out. But it's probably getting towed to the shop before that, as I don't have time to fool with it much more and I have a very interested buyer. Can Warren chime in here?

BGCarrera32 · 06-25-2003, 05:36 AM

Ask shop to check the speed sensor and reference sensor with a scope (plugs labeled BG and DG that sit right below the CHT sensor plug). I had misadjusted mine after I did the clutch, and the car idled but would crap out when pushing the throttle. Most reliable sensor on the car I hear but can and does go south...

ALSO, FYI the DME check and sensor check for these two sensors in the Bentley manual is incorrect, and I can prove it wrong...their resistance check is misleading and you do in fact need the speed sensor to start the car.

jpnovak · 06-25-2003, 05:37 AM

My vote is a fuel delivery problem.

Rick Lee · Rick Lee's Garage

Quote:

Originally posted by BGCarrera32
Ask shop to check the speed sensor and reference sensor with a scope (plugs labeled BG and DG that sit right below the CHT sensor plug). I had misadjusted mine after I did the clutch, and the car idled but would crap out when pushing the throttle. Most reliable sensor on the car I hear but can and does go south...

ALSO, FYI the DME check and sensor check for these two sensors in the Bentley manual is incorrect, and I can prove it wrong...their resistance check is misleading and you do in fact need the speed sensor to start the car.

I'm sure speed and reference sensors were set correctly when we installed the engine in Jan. Otherwise, we would have had this problem long before now, no? Is engine R&R required to replace these?

kstylianos · 06-25-2003, 08:29 AM

Quote:

Originally posted by jpnovak
My vote is a fuel delivery problem.

Jamie,

I tend to agree. The fuel filter was replaced last year, so i doubt its that. Plus the tank has not been run down enough to pick up muck from the tank bottom.

It was a slow progression from cutting out at higher RPM's to eventually only able to hold idle. Dosent sound like a switch going south, which usually corresponds to instant and consistant problems/symptoms.

A local shop seems to think its a munged fuel pressure regulator.

My .02....