IanM

A weird issue has recently reared it's head with my car. It runs fine on the street, can run WOT without any issues. BTW, I'm running a Vitesse MAF setup, plus lots of other mods.

A couple weekends ago during a track day, the car suddenly and temporarily bucked (engine cut out then came back to life) shortly after exiting a sharp 180 degree corner. It didn't sputter or hesitate anywhere else on the track, but did it in that one spot a few times. I figured it was fuel starvation, as I was running only 1/4 tank of gas. I filled the gas tank up and didn't notice the problem for the rest of the day.

Last weekend I had the same problem occur during an autocross, also while on a straight away following a tight corner. I was running just under 1/2 tank of gas, but went and filled it up anyways. The problem didn't go away. Looks like it's not fuel starvation.

Today I was at another autocross. The car did it several times today. Same conditions, on a straight immediately following a tight corner. Also, it only seems to do it at WOT, if I go half throttle out of a tight corner it doesn't seem to happen (although this has not been thoroughly tested).

So...any ideas? When it happens, my wideband temporarily shows a very rich condition. My fuel pressure gauge is steady, no drop seen. The last time I had a problem like this it was happening only while on track when the engine was very hot, and I solved it by replacing the engine wiring harness - problem was likely a short that only occurred when things got hot. This problem is different, and so far only happens after exiting a very tight 180 degree bend. I've never had it occur on the street, so far only on track and autocross.

Opinions appreciated.

Thanks,

- Ian

ehall

My opinion is that you have a hot wire that is arcing due to the cornering load shifting the actual wire. Either that or a ground is moving around or coroded and changing positions for the same reason. This happened to me. I looked at every stinking known gremlin, before I got fed up and took it to a guy. He checked the usual and then checked to battery hot lead, running to the starter. The casing was AFU. He replaced it, just because it needed it. He took it for a drive and the problem was solved. Under heavy boost, the wire was getting close enough to arc.
I've never had the issue again.
That's my opinion. It could OBVIOUSLY be a huge number of other possibilities.

xsboost90

i had a similar issue at the last DE- entering a corner i started to roll onto the gas and there was nothing. In the straight it would take off hard and then in the corners it was like the pedal did nothing. Ended up my recirc valve (forge) was loose at the top- dont ask me i tightened it down and back out on the track no more issues.

aelliott

I had this exact problem in the exact same circumstances: on exiting corners, car would stumble/buck but resolve itself. Figured it was just "acting up". Then the car went totally dead... took me a while to notice the battery getting very hot. Full-out short from the (now blown-apart) starter cable to the body behind the bellhousing. I was lucky: no fire, no damage to starter, alt, or electrics, and the battery's even working okay again after a jump. Sometimes you catch a break.

Adam

IanM

Thanks guys. I'll take a very close look at the starter and alternator cables and report back. I don't *think* it's a ground, at least not the main grounds. I'm running ground straps from the late-great Dan Wray, and the connections onto the bellhousing are in excellent shape.

Adam - doesn't look like you post much. Four posts in four years! I thought I was a slacker.

thingo

Left or right corners ?

Rich Sandor

Ian, where the hell did you dissapear to yesterday?

IanM

Rod - Previously (last track day and subsequent autocross) it was only doing it after taking a hard right turn, but at autocross yesterday it was doing it coming out of hard left turn.

Hey Rich - I had to run...sorry for not sticking around. Thanks for setting up another great autocross.

thingo

I had a similar problem with my 968 on right turns(though I only drove it on one clockwise circuit).Found out later the fuel return hoses(the ones that run on the top of the tank)were being pinched, fuel tank had been out of the car at some point.There is a lot of hoses in that area.

sweanders

To much fuel when the throttle opens fully? Does the same thing happen both when you feather the throttle and when you slam it?

IanM

Rod - thanks for the idea, I'll try to take a look at things when I put the car up in the air.

Anders - No, it doesn't seem to do it when I feather the throttle coming out of a corner, only when I floor it. It doesn't happen 95% of the time though, only out of a sharp 180 degree corner. I haven't been able to get it to do it on the street (yet) - who knows, problem could get worse.

IanM

I jacked the car up the other night and took a look around. The smaller of the two main power cables that go to the starter had a small fray in the plastic sheathing immediately before it bolts to the starter. I think this is the cable that goes from the starter to the alternator. It looked like it could very well have been grounding out against the bell housing head shield on the body. I also found that the lead from one of my reference sensors was partially melted - had come too close to the turbo downpipe. Swapped out the sensor for a used one I had, and fixed the fray in the starter cable. Hopefully that cures the problem! Thanks everyone for your insight.

- Ian

Red!

Sounds like it might - I had EXACTLY the same problem - turned out to be a malfunctioning kill switch - when I wired around the kill switch suddenly the car was perfect - it started up instantly (used to need to crank a few times) and has run great ever since - now I need to buy a new killer - I'm leaning towards the LR Electronic one for $200 - I figure a relay is less likely to have problems than a manual switch which seems to die over time (when I speak to others they say "oh yeah, I replaced my kill last year"

jwlester

Forgive me dredging up this old thread. Any "after the fact" info on this issue? Any other suggestions? I'm having a very similar problem. I'll look into the electrical issues this weekend. Thanks.

https://rennlist.com/forums/924-931-...ed-corner.html

Josh

ehall

I had exactly the same issue on my 86. I replaced both.