Mark Brook

Guys,
Need some help please.
Last night I started the car from cold, accelerated away and went through the gears, using no more than 3000 rpm. On changing from 3rd to 4th, the revs increased on their own to 4500. I dipped the clutch, pulled off the road and turned the engine off immediately. Pulled the mats away from the accelerator pedal, and tried to start the car again. The revs went straight up to 4500 again, so I turned off again. Opened the hood and opened and closed the throttle manually, wiggled the cable around a bit, and noticed nothing untoward.
Walked home to consult Adrians book to search for inspiration, and when I went back to the car, the damn thing started fine.
So, I'm worried about 2 things now. Is my rising rev thing down to a stuck/frayed cable or someting more worrying ? How tough is it to change a 964 throttle cable ? Also, will the engine have suffered any damage as a result of such high revs. I drove for a while after and noticed that at tick-over on warm engine, the oil pressure seemed very low 1.2 ish as opposed to 2.2 usually.
Can anyone put me out of my misery ????

Cheers

Mark. 90C2

DaveK

I wouldn't worry too much about damage to the engine - doesn't the owners manual say you should keep revs below 4K or 4.5K when cold? So you were about there anyway. Not ideal, but I doubt you've done anything serious.

As for cause - someone posted that their accelerator jammed once before - think it was about 6 months ago (and hopefully they will read this). If I recall - I think it was something to do with the cable around the pedal assembly but can't remember exactly.

When you say you opened / closed the throttle assembly manually - did it look like it was open when you first popped the lid?

Mark Brook

Dave,

No, I noticed nothing at all. All spring etc seemed fine. Thats what is so strange. I've done a search and can't find anything relevant.

Cheers,

Mark

gilessav

Hi Mark,

not to sure about the cause of the throttle problem but idling at 1.2 bar at warm should'nt be an issue as my car had always done this and can dip down below 1bar when very warm in traffic. I still show almost fullbar oil pressure (4-5) when driving normally so i think your engine will be fine. I've only had throttles stick on cars as a result of the floor mats jamming the return but this does'nt sound like your case so cant help on that i'm afraid.

Good luck
Cheers
Giles.

Jeff Curtis

Mark, oil pressure is fine.

The revs your engine experienced that fine evening are "OK".

As for throttle jamming, just a stab in the dark - if the throttle cable or your pedal assembly is not causing the issue (i.e. BINDING) - consider the cruise control circuit if you have cruise.

...you did say that the revs increased "on their own" to 4500??

jrb964

I was the one who had the throttle sticking. But mine stuck at redline. When ever I depressed the peddle all the way to the floor it would stick and the engine would redline. It really scared the you know what out of me the first few times.

Just prior to this the speed control had stopped working.

To temporarly fix the problem I could "bip" the peddle and it would return to normal. So I drove like this for a few months, I just got used to the situation and lived with it.

Took the car in for some work and asked that this problem be looked at. As it turned out they were one in the same problem. A plastic connector that attaches to the speed control had broken. When I put the peddle all the way to the floor it caught on something and left the throttle all the way open. The replacement connector is now metal and cost about $10 with no labor as it sit right on top of the engine in back of the fan.

Hope this helps.

Mark Brook

Jeff,

I don't have cruise on it . I guess the effect of me putting the clutch in to change from 3rd to 4th could be why the revs went up, if the cable was trapped. It didn't seem like that when it happened though !
It's weird, I was only thinking yesterday how nothings gone wrong with it for ages !!

Cheers,

Mark.

Mark Brook

Guys,

What I did notice, was that about 6 inches down the cable from the cables connection to the throttle body was a concertinaed rubber sleeve. I presume that this should go right the way up the cable. Can't be more precise because it was getting dark !
JRB, sounds like the same problem to me. At least I'm not so worried about the high revs now.
Stupid thing is, I was thinking only yesterday that nothing has gone wrong with her for ages !!

Cheers,

Mark.

DaveK

It sounds like the rubber sleeve is just the sleeve to keep dirt out from the cable outer sleeve. So it should be over the end of the cable outer, but doesn't need to be to the end of the cable inner - i.e it doesn't have to reach to where the cable meets the throttle body (if that makes any sense!).

DavidI

I once had this happen on a Sierra Cosworth - it just decided it wanted to idle at 4,500rpm. Turned it off, let it cool down and it never repeated the party trick again. I put it down to a temperamental ECU (that car's 'brain' was mush at the best of times), but couldn't the problem just be a momentary mis-read of one of the monitored conditions, such as air pressure? Not very reassuring, granted, but is occasional brain-fade unheard of on the 964?

Jeff Curtis

Mark...THAT is what I was looking for, the "revs went up when I depressed the clutch pedal" comment!

The gremlin, without doubt...lives in your pedal cluster. Worn bushings and loose/chaffing connections will be the fault.

Let us know what you find down there...besides loose change, sand/gravel, grass, etc.

Wikkid911

I'm sure John Boggiano also had a similar thing happen to him.
I think he posted some photos as to what his fix was.

DaveK

Yes - I'm pretty sure it was John Bs post I was thinking of. I searched for it but couldn't find it.

Mark Brook

Thanks for your help fella's. John B, can you shed any light on whats happening here please ??
I'll have the floor-board up tomorrow and have a poke around, but took it out last night and nothing noticably wrong. I'm not worried about the sleeve thing now either , I over-estimated the amount of wire not covered, it's only about 2 inches.
Any more help would be appreciated !

Cheers,

Mark

John Boggiano

Hello there.

My apologies, I did spot this thread and knew it was me you were thinking about, but pressure of time meant I hoped someone would find the thread...

My throttle stuck about half way open which, I think, was due to some grit entering the cable at the pedal end. I 'fixed' it at the roadside by forcing the throttle linkage at the engine until it'clicked' and freed itself. No more trouble since...