Guys-
Ok it's been a saga - bear with me.

Two weeks ago I poured some fuel injector cleaner into my fuel tank that only had a few gallons - went for a rip and the car was running awesome (as it has for years - with one exception noted below). Then added about 1/2 tank of gas to the almost 1/4 tank. Within a few minutes the car was running poorly. It would idle ok but stutter a little as soon as I gave it some gas then smooth out, and it would hesitate/stutter pulling from a stop and sputter just a little at high rpm/high boost. Thought I got bad gas - went to another station and added about 1/4 tank - car _seemed_ to run a little better so that supported my bad gas theory.

I had no way of draining an almost full tank so basically went out on the highway and cruised out in eastern Colorado in 4th gear for a few hours until I had about 1/8 tank - then filled up. No change. damn. So much for bad gas.

So. I went home and the next night started digging. In the past I've had multiple issues with the plug connectors on this Beru wire set I got 5 years ago (this is the only running issue (engine related) I can think of I've had with this car in the last 5 years). Cracked, broken connectors. Arcing. No arcing noise this time (I think one of the other times there was no clicking from an arc either, other times there was a clicking from the arc). So I removed the connectors. They all looked good. So I removed the plugs (no more than 15K on them) - they looked great. Put new ones in anyway.

While I was in there I removed the injectors - took them to a shop and he tested the spray pattern - they looked great. Went home with 6 graduated cylinders and tested volume - all 6 flowed the same. Hooked up CIS gauges - I think system pressure was 86 - spec is like 88-98 I think.

While in there I found the intake manifold nuts to be not totally snug (not loose tho) - didn't make them super tight as I don't want to crack the spacers but gave them a small snug down.

No smoking gun but now the car had fresh plugs - and maybe the injector test cleared up a tiny clog? So I put the car back together. It ran the same. Damn damn damn. Turned the car off after several minutes.
Waited a few minutes then turned it back on. Within a few seconds it cleared up. Maybe it was bad gas afterall and the good stuff had not gotten from tank to motor yet?? shut the car down again. Waited for a few minutes and started it back up. Ran and revved smoothly. So I went for a test drive. Ran great on my 15 minute test loop. Did another short drive the next day and another test loop a day or two later - ran great every time. Problem solved! Not sure what fixed it but oh well it was running great!

So. Saturday morning. Left from Denver for Rennsport with a few others. Car is running great. Except I did get one small hesitation at high rpm high boost. Other than that running great. Fast forward a couple hours and now we are in Glenwood Springs. The stutter is back - same as before. We stop for 20 minutes. Get back in car is running great. For about 15 minutes and the hesitation comes back intermittently (kinda hard to say as we were just cruising - it was pulling away from stops where it was most evident). We took a detour off I-70 on a great curvy road and no issues really. We get to Grand Junction (3 1/2 hours from Denver) and now it's consistently stuttering pulling away from a stop - but cruising fine. Eat lunch for an hour. Car runs great for I don't know... 5 minutes. Then hesitation etc back. But now it's starting to happen while cruising and for sure a little when I try to accelerate. We pull off in some road side shade.

I told you this was long.

So I swap in a different EZ-69 and a different known-good coil. Test drive - good for a couple minutes then stutter.

So I swap in a new cap. Old one looks bad I think - not an expert but my guess is it looked bad. Same with the rotor. Black carbon all over the tip. A small crack in the enamel looking stuff. I don't have a spare. So we clean it up - very gently with a file. We start driving and the car is running GREAT. Previously (when I swapped the EZ and coil) the stutter came back in about 2 minutes I'd say. But then after about 10 minutes the stutter is coming back. I make a decision - our route was taking us to much more remote (awesome) roads - but I could not go on - the car was getting worse.

The Gruppe went on and I turned around . I decided to limp the car back to Denver - 250 miles. After a while my AFRs were looking whacked out. I was very careful and eventually got home late last night after a slower, stressful night drive.
And get this - I decided to call the local Porsche shops (knowing nobody would be there on a Sunday) - just in case. Guess what. Somebody answered. Storz Garage (old school air cooled shop 5 minutes from my house). And he had the correct rotor!!! 30 minutes later car was buttoned up. I also tested the resistance of the coil wire - just under 1000 Ohm. This is where I got lazy - Storz said that was about right but I did not check the manual. Quick shower, fresh ice in the cooler and I made my Rennsport Departure #2 my test drive. Car was running perfect. I was flooring it from low rpm. I was giving it the beans up hills. I was trying to pull from low rpm up hills. The car was great. 5 minutes. 15 minutes. 30 minutes. I'm headed to Rennsport.

Until I got 45 minutes away up in the mountains - the stutter was coming back - albeit definitely not nearly as bad as last night. It was pretty small really But still - I wasn't going to run solo to California unless car is running perfect.
On the way home I swapped in another coil wire I have. No change.

So to revisit.
Tested injector spray pattern - good
Tested fuel flow - even amongst cylinders
System pressure might be 2 psi low (this was with car off, fuel pump jumped - not sure if car running and sending 14V instead of 12V will change that..?
I have never changed fuel pumps (had car 12 years, 60K miles)
I also have not tried swapping in a new fuel pump relay

new plugs
new cap
new rotor
swapped known good coil
swapped known good EZ-69
Swapped coil wire

The delay in performance degradation leads me to believe heat is involved. And the BIG difference from new cap and rotor - and how bad the old ones looked (30,000 miles on them, FYI) - I'm thinking it has to be ignition.

so....Wires? These crappy "new" Beru wires (5 yrs/30,00 miles) with connectors that have caused issued already several times (3 or 4 of the 6 connectors failed in some way)

What else? Thoughts?

I'm thinking Clewitt is the way to go. Steve (bwe) I know you asked about wires a while ago - what did you get?
Anthony you like Clewitt, right? I'm definitely leaning toward these.

What else? What am I missing, not checking? Thoughts?

Total bummer - this car has been sooo good - bad timing for this issue.

Input appreciated - thanks for reading my book.

Brandon
'91 Turbo

 

I have Clewitt wires and they are great quality.

Sorry about your issue, looks like a process of elimination,

Check your turbo control unit for bad relays or soldering - so you can check it off the list..

https://rennlist.com/forums/964-turb...ml#post6129847

 

one more note:

I have seen weird inconsistent issues with flaky fly wheel sensors - issues from hard to start , cut out and die, or rough running.

 

Best to get direct from Clewett? Pelican Parts? Pelican web site says they have the right set but the guy says no. That set is for XDi ignition. Admittedly I don't know what I'm talking about here....

link?

EDIT - nevermind - talked to Clewett.

EDIT #2: I also talked to Patrick Motorsports. They also do wires (same wires as Clewett possibly - same supplier I'm told - but Patrick was doing them first). Our wires are same as a 3.2 Carrera EXCEPT the coil wire.

thanks!

Brandon
'91 Turbo

 

I always go straight to Clewett - So you can speak directly to THE Man

 

https://www.clewett.com

 

man that's frustrating Brandon. I feel for ya Bud.

I never did replace my Beru wires. They were not the problem. My problem (this is almost 2 yrs ago now), was the flywheel sensor. It had essentially disintegrated. Replaced that and everything has been fine ever since,... albeit last summer I broke a head stud, so I had the entire engine pulled apart, heads re-conditioned, new clutch,.. etc etc. $20k spent (just to get the better 993 Turbo head studs in the motor, Lol).

anyway,... sorry to report that I never went with Clewitt. Fingers crossed that my original Beru's continue to perform without failure.

Oh, and also, most recently I did have a fuel relay that was intermittently giving me problems. Replaced that, & I have been good all summer. But ironically, my symptoms from a "starting-to-go-bad" fuel relay, seem very similar to what you are describing. It only really acted up when the car got fully hot.

 

I don't know of any case in which a faulty fuel relay or TDC sensor would have caused the symptoms described. If errors occur in these components, they behave digitally, yes, no, runs, doesn't run.

Replacing the ignition cables is certainly not a mistake, but I'm afraid it won't solve the problem.

I would first try to determine if it is an ignition or fuel problem. I don't know your possibilities but an AFR measurement is best suited for this. If it is a fuel problem the AFR value should change significantly when the fault occurs.

Fritz

 

I have purchased 2 sets of Beru wires in the past 3 years from Pelican Parts for both 965s. Both sets say "Made in France" on the packaging, and "Germany" on the wires & caps themselves. P/N: 0300 890 295 They are pretty darn good wires!

I have also purchased Clewett wires for my twin plug hotrod; P/N: CE-9192-22-B and CE-9192-24-B (upper and lower with hold-downs.)

I am heading west to San Diego on Saturday with a 2-car trailer...if you are stranded some place, let me know I will pick up your 965.

Question: You said that you ran fuel cleaner in your car on a low tank. Is it possible that you killed your O2 sensor? Could that cause these issues --> Impacting AFR?

 

Is the issue at all related to a specific RPM range? I had a number of issues coming on to boost when I first bought my car that created stumbling. We narrowed it to a loose intake manifold and rolled O ring on the intercooler.

I also hit most of what’s on your list as well.

Sorry you have to deal with this before RS7!

 

really Fritz? ... this is a surprise to me, as even my local Indy shop mentioned that the fuel relay can intermittently go out, then come back, then go out again,... causing these type of symptoms.

Are you saying that when a fuel relay fails, it fails completely all at once, never able to return to a operating state?

... Maybe I just heard my guy wrong, cuz I certainly do not fully understand the internal electronics on those relays

 

I've never experienced this, but what would actually be conceivable would be for the ralay to drop and close again every part of a second. This would cause the fuel pumps to cycle on and off at rapid intervals. If the relay behaves like this, you should be able to hear an audible ticking sound coming from the fuse box when the trunk is open.

Fritz

 

did you just replace the relay in the fuse box (53 on top) off to left side looking from front?

 

Hi Brandon, Sorry hear about your car, Here's a couple of other things to look in to that you have not covered,

A leaking or bad Blow off valve or a bad WUR.

I hope this helps

Helio

 

yes