Engine won't rev over 3000rpm. Any ideas.

Engine won't rev over 3000rpm. Any ideas.

Author
Discussion

gromit wedge

Original Poster:

94 posts

107 months

Friday 18th May 2012
quotequote all
My 350i wont rev past 3000rpm when I drive it but will rev freely when parked. Its like it has a rev limiter fitted.
I had a problem with it misfiring last month and changed most things including plugs, HT leads, coil, ignition module, rotor arm, distributor cap, fuel pump, fuel filters and finally changed the temperature sensor and it sorted the misfire and I didn't really drive it hard so didn't notice the failure to rev freely. It starts perfectly hot and cold and idles really nice. Really need this fixed ASAP.

Any ideas or suggestions.

350zwelgje

1,811 posts

200 months

Friday 18th May 2012
quotequote all
Had something like you, but not exactly....
During the time my ECU was less and less functional idle was perfect, but performance was less and less. No rev limiter type of experience, but in the end any throttle would nearly kill the running of the engine. Got an ECU to use over time: no issues, felt like a power upgrade. Had the old ECU resoldered and while waiting for it got a spare that I used until then.
After this long story, has your ECU been resoldered? If not perhaps worth to have it done and perhaps it solves the rev limiter type of issue.
Not into wedge camshafts myself yet, but missing lobes can do funny stuff and this could be one of them.


Rob

gromit wedge

Original Poster:

94 posts

107 months

Friday 18th May 2012
quotequote all
Pretty sure its not the camshaft as it was running perfectly then one day wouldn't rev. It hasn't been getting worse over a period of time it just stops at approx 3000 rpm and then you have to change gear and it accelerates fine until it hits 3000rpm again.

350zwelgje

1,811 posts

200 months

Friday 18th May 2012
quotequote all
Distributor and rotor combinations for RV8s are like a lottery. Had some issues tracking the right ignition parts down myself in the past. Kept the old original stuff and if it didn't run ok used these parts to rule out ignition stuff as well as after installing new 'correct' parts.
Hope you find the source of the problem quickly,

Rob

TVRleigh_BBWR

6,534 posts

152 months

Friday 18th May 2012
quotequote all
gromit wedge said:
Pretty sure its not the camshaft as it was running perfectly then one day wouldn't rev. It hasn't been getting worse over a period of time it just stops at approx 3000 rpm and then you have to change gear and it accelerates fine until it hits 3000rpm again.
If once a camshaft looses it hardness, is can wear out in less than an hours, so you can't rule it out, but it's unlikely.

What happens when you hit 3k, does it just stop or start to miss / back fire.
Advertisement

GarryA

4,700 posts

103 months

Friday 18th May 2012
quotequote all
Exhaust collapsed?

TOPTON

1,514 posts

175 months

Friday 18th May 2012
quotequote all
Check the rotor arm, if you haven't got like for like maybe you have bought one with a built in rev limiter. 3k revs is a bit low for that but you never know

vampire222

428 posts

88 months

Friday 18th May 2012
quotequote all
could also be ur timing is way off or advance is way off so it drifts so far it wont fire the mix anymore at 3k

Wedg1e

26,736 posts

204 months

Friday 18th May 2012
quotequote all
Trigger sensor for the ignition module, in the distributor, could be dying. If it is, then it could go for months like this before suddenly packing in altogether one day.

gromit wedge

Original Poster:

94 posts

107 months

Friday 18th May 2012
quotequote all
It missfires a little but the power just dissapears. Parked up it revs over 5000rpm with no problem.
TVRleigh_BBWR said:
What happens when you hit 3k, does it just stop or start to miss / back fire.

adam quantrill

10,685 posts

181 months

Friday 18th May 2012
quotequote all
In that case I would start with the timing first - lack of torque over 3k fits in with lack of advance.

Have you got a timing light?

gromit wedge

Original Poster:

94 posts

107 months

Friday 18th May 2012
quotequote all
I will have to borrow a timing light. Don't have one anymore because all newer cars need a laptop!!!!
I have a replacement distributor so will try fitting that and reset the timing.

vampire222

428 posts

88 months

Friday 18th May 2012
quotequote all
gromit wedge said:
I will have to borrow a timing light. Don't have one anymore because all newer cars need a laptop!!!!
I have a replacement distributor so will try fitting that and reset the timing.
Hurray for oldskool mechanical ignition huh? wink

ThePunisher

2 posts

2 months

Monday 21st January
quotequote all
This is identical to what my car is doing at the moment, and can't seem to figure it out.

Did you fix the issue?


mrzigazaga

18,213 posts

104 months

Monday 21st January
quotequote all
Sounds like an over-fuelling issue, especially if its on a motorway or A road and you cannot go over 50mph...Do you have an adjustable fuel pressure reg?
Could also be the Coolant Temperature Sensor failing....if its reading backwards then will be throwing fuel in when its hot instead of cold.

adam quantrill

10,685 posts

181 months

Tuesday 22nd January
quotequote all
Have you checked the timing? Especially the advance when revved?

ThePunisher

2 posts

2 months

Tuesday 22nd January
quotequote all

See there are just so many variables to solve this which is so annoying when all you want is to have your car back :/

@mrzigazaga not sure if I have one. Can this cause fuel restrictions?

Context about my car symptoms

My car drives fine at lower revs (low speeds) and feel that the engine can only go upto 3000rpms, if I try to go more than that I can feel it hesitate little. Overall I feel its reached its max performance at 3000 rpm, which isn't right because when I bought the car I was hitting 80-100mph easily in 5 gear without any restrictions in a 6 speed gearbox and now I only get up to 90 using all gears. Like Gromit wedge mentioned once I change gear it then accelerates until I reach 3000rpm. I do feel that the power response feels different, before it would be so instant I could reach 80mph in 4th gear so easily and now I feel its like transitional power lacking performance.

I have had a diagnostic test to test the turbo which checked all good. My injector 1 injector (cylinder1) quantity at idle was -0.70 and the other 4 injectors were in above 0 to compensate the deviation. Soleniod activation on injector was also -6. Could possibly be that an injector is not injecting enough fuel at higher revs and my car is possibly running on three cylinders? But I'm not too sure if the above injector values mean a lot at idle. All I know is my car does wobble/shake when I'm at idle. I'm thinking either injectors, maf, map, or a vacuum leak ... I have had fuel, air, glow plugs and cam belt changed and still have the same issue. Probably will have to see live data when the car is underload to pinpoint exactly where the problem is.

btw I drive a 2006 Audi A3 2.0 TDI (140bhp)

If you have any other suggestions that would be greatly appreciated

BIG DUNC

1,483 posts

162 months

Tuesday 22nd January
quotequote all
The engines on a 2006 turbo diesel audi and petrol V8 tvr which is approx. 20 years older will be so different that I am not sure whether the cause of the original problem would be relevant, even if we did know how it was fixed.

eesbad

1,283 posts

141 months

Tuesday 22nd January
quotequote all
ThePunisher said:
btw I drive a 2006 Audi A3 2.0 TDI (140bhp)
You do realise that you are posting on a TVR Wedge board? You might have better luck on the "Audi, VW, Seat & Skoda" board... We're all a bit "old school" on here... smile Good luck!

QBee

16,408 posts

83 months

Tuesday 22nd January
quotequote all
eesbad said:
ThePunisher said:
btw I drive a 2006 Audi A3 2.0 TDI (140bhp)
You do realise that you are posting on a TVR Wedge board? You might have better luck on the "Audi, VW, Seat & Skoda" board... We're all a bit "old school" on here... smile Good luck!
I could suggest broken intercooler, which caused by Merc 320 CDI to go into limp home mode exactly as i was half way past any 38 tonner on a single carriageway with something coming the other way, or various clogged valves etc. You definitely need to be on a diesel page for this one. Diesel engines tend to get very sooted up. Good luck