4500 RPM weirdness

[mookers]

I had my car serviced last week, and it has been Not Quite Right since then... my mechanic is going to take another look at it anyway, since the Great Spark Plug Part Number Fiasco meant he didn't get to finish the job properly. Unfortunately he's booked out this week and understaffed due to one of his employees taking paternity leave.

Anyway...

The car drives just fine when I pedal gently - in fact I'm getting awesome economy from the current tankful. However, when I hit it hard it does this funny "flat spot" thing at about 4000-4500 RPM, where the revs pick up FAST but the acceleration doesn't seem to match. It behaves like a slipping clutch or something, but it doesn't FEEL like a slipping clutch, and it seems fine below 4000 RPM.

It's much more noticeable in 3rd gear than in 1st or 2nd. I haven't tried revving that high in 4th or 5th because I don't want to go quite that fast on public roads...

It didn't do this before I had the oil, oil filter, and air filter changed. It's still running the old spark plugs (to be changed next week I hope) but has new leads. My mechanic double checked the turbo plumbing the day after the service but won't have time to look at it thoroughly until I take it in for the spark plug change. Does it sound like he missed something?

 

[jungle]

I know what you are talking about. Expand on what happended with the plugs?? If the gap is too wide( the anodes have burnt out like mine were having been in there from probably new) then its quite possible the car is breaking down due to the spark "blowing out"

I changed my plugs last week and went one colder- fitted 7's and the difference is amazing!

It sounds to me that when your car is loaded up, its just the spark breaking down.
change the plugs, or check the gap isn't stupid wide, set them from 0.8mm to 1mm and she'll run like a champion

 

[Leggs]

I had the same problem in my GSR Turbo and it ended up being a leaking cooler pipe. Is it shuddering at all in the flat spot or making irregular whistling noises?

 

[bradc]

4500rpm is peak torque, so if it was a slipping clutch, logically it would happen then, but I'd be inclinded to think it was something else. Perhaps have another person in the car to see if they think the car is going a bit slow around that point.

4500rpm in 4th is only 125, I can't see the danger if you're just briefly accelerating?

 

[mookers]

Expand on what happended with the plugs?? If the gap is too wide( the anodes have burnt out like mine were having been in there from probably new) then its quite possible the car is breaking down due to the spark "blowing out"

Long story short: I ended up with the wrong replacement plugs so my mechanic couldn't change them. He put the old plugs back in. Maybe one of them suddenly started going wonky after being removed and reinstalled?

4500rpm in 4th is only 125, I can't see the danger if you're just briefly accelerating?

I'm just being careful - on the fastest road around here, 125 is only 5 km/h away from losing my licence! Not to mention I'd be rear-ending someone quick smart if I tried that during the times when I'm normally on the road. I haven't had a chance to drive it on a really empty stretch lately.

 

[Guest]

It definately sounds like a slipping clutch to me. If it was a problem with your spark plugs, piping, AFM, etc it would start surging irratically, a similar feeling to boost cut I suppose.

The fact that it continues reving but feels like it's going nowhere sounds 100% to me that it's a clutch issue. If the clutch slips then the engine is basically free-reving (like it would do in neutral) and your revs would increase faster than usual.

 

[mookers]

It definately sounds like a slipping clutch to me. If it was a problem with your spark plugs, piping, AFM, etc it would start surging irratically, a similar feeling to boost cut I suppose.

The fact that it continues reving but feels like it's going nowhere sounds 100% to me that it's a clutch issue. If the clutch slips then the engine is basically free-reving (like it would do in neutral) and your revs would increase faster than usual.

I'm worried that this may in fact be the case. But wouldn't it do it in every gear? It doesn't seem to do it nearly as much, if at all, in 1st or 2nd gear.

Oh well, if I need a new clutch... it's only money lol

sigh...

 

[Guest]

Not at all, as Brad said, it's slipping where the peak torque curve is. There's minimal torque when you're putting around in 1st and 2nd gear. Next time try changing up to 4th before 4500rpm and see when it slips there.

I had the same thing happen to me in the Z. 1st, 2nd and 3rd were all fine, but when I went to accelerate in 4th the clutch would start slipping at around 3500rpm and I'd go nowhere.

 

[Dr_Josh001]

Long story short: I ended up with the wrong replacement plugs so my mechanic couldn't change them. He put the old plugs back in. Maybe one of them suddenly started going wonky after being removed and reinstalled?




I'm just being careful - on the fastest road around here, 125 is only 5 km/h away from losing my licence! Not to mention I'd be rear-ending someone quick smart if I tried that during the times when I'm normally on the road. I haven't had a chance to drive it on a really empty stretch lately.

Come up here and test it; the speed limit is still 130.

 

[bradc]

ohh yeah thats right, victoria is the stupid place where 3kmh above the speed limit screws you.

 

[M0R81U5]

Derek, did you end up finding a resolution to this? Cause I have exactly the same problem and would be very grateful for a shove in the right direction.

Right now I'm preparing myself to do a full service and the bank balance for a new clutch