Won’t rev past 5k rpm
Discussion
Evening all
New to this forum but not to TVRs being a long term wedge owner
Anyhow, my son recently bought himself a Griff 4.0 precat - nice car needing a few electrical bits and bobs sorting. It does however Have a running issue that it won’t rev over about 5000 rpm. It starts ok idles ok and runs well at low revs With good torque (although may be down on power as it doesn’t seem to have much of a step up in performance over my 350i which I was expecting) But once you get to 4,500 it starts to run out of urge and then plateaus at 5000. It doesn’t falter or misfire or anything just stops revving any higher
This afternoon we had an hour to have a quick look for anything obvious
Checked to see if it’s firing on all 8 - plug leads removed one by one resulting in a slight drop in rpm each time which came back up when lead refitted
No 1 plug removed- slightly sooty so over fuelling a bit but not enough to worry me
TDC mark on front pulley confirmed as correct by the “bit of wire down no.1 plug hole” method- not entirely accurate but a good starting point - TDC Mark looks bang on
There’s tippex on the pulley at TDC and 8deg btdc so it’s been timed up before at least at idle (tippex looks as if it’s been there a while maybe a couple of years)
That’s as far as we got
So my thoughts are this :-
Fuelling is a little rich but not enough to cause this issue
Timing needs to be checked once I get my paws on a timing light but is about right at idle but could possibly be a problem with the distributor mechanical or vacuum advance
Or it could possibly be a worn cam - (I’m thinking it’s this but hoping it’s not!!)
Just wondering if my thought processes are correct and have I missed anything??
Thanks Ron
New to this forum but not to TVRs being a long term wedge owner
Anyhow, my son recently bought himself a Griff 4.0 precat - nice car needing a few electrical bits and bobs sorting. It does however Have a running issue that it won’t rev over about 5000 rpm. It starts ok idles ok and runs well at low revs With good torque (although may be down on power as it doesn’t seem to have much of a step up in performance over my 350i which I was expecting) But once you get to 4,500 it starts to run out of urge and then plateaus at 5000. It doesn’t falter or misfire or anything just stops revving any higher
This afternoon we had an hour to have a quick look for anything obvious
Checked to see if it’s firing on all 8 - plug leads removed one by one resulting in a slight drop in rpm each time which came back up when lead refitted
No 1 plug removed- slightly sooty so over fuelling a bit but not enough to worry me
TDC mark on front pulley confirmed as correct by the “bit of wire down no.1 plug hole” method- not entirely accurate but a good starting point - TDC Mark looks bang on
There’s tippex on the pulley at TDC and 8deg btdc so it’s been timed up before at least at idle (tippex looks as if it’s been there a while maybe a couple of years)
That’s as far as we got
So my thoughts are this :-
Fuelling is a little rich but not enough to cause this issue
Timing needs to be checked once I get my paws on a timing light but is about right at idle but could possibly be a problem with the distributor mechanical or vacuum advance
Or it could possibly be a worn cam - (I’m thinking it’s this but hoping it’s not!!)
Just wondering if my thought processes are correct and have I missed anything??
Thanks Ron
The mixture is set with a hex head screw on the side of the AFM, but it only has an effect up to about 2400 rpm, above this mixture is purely done on the fuel map, so the screw won't affect full power. Possible fuel restrictions will make it go flat at wot, but difficult to detect as you don't have lambda probes to read the mixture, so you would need a rolling road session. As mentioned check the timing advance, and replace the fuel filter anyway. Worth opening up the ECU and check it had a TVR chip in it, for the correct map.
Has the air filter been replaced?
2 part question. If no then inspect it to see if it is blocked.
If yes then try removing the pipe where it goes into the AFM.
Some makes of air filter are supplied with a chavy sticker which you may or may not want to use.
If you don't want to use it you may not have spotted that it is nicely packaged in a poly bag and posted down inside the filter.
When you start the car the bag flies up the pipe and partially blocks the AFM.
Ask me how I know.
Steve
2 part question. If no then inspect it to see if it is blocked.
If yes then try removing the pipe where it goes into the AFM.
Some makes of air filter are supplied with a chavy sticker which you may or may not want to use.
If you don't want to use it you may not have spotted that it is nicely packaged in a poly bag and posted down inside the filter.
When you start the car the bag flies up the pipe and partially blocks the AFM.
Ask me how I know.
Steve
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