burp at 6k rpm

[warpig]

engine runs strong and quick up to 6k then feels like its hitting a rev limiter. kicks and farts for 500 rpm then off she goes again to 7.5k
any ideas chaps
cheers dan

[boardinscotland]

Mine does the same thing. Seemed to lose it for a while when I ran it on V power but occasionally comes back. No idea why.

Would love to have an answer to it

Greig

Edited by boardinscotland on Tuesday 24th June 21:54

[Peppe]

Hi !

Check the routing of the HT leads compared to the engine loom. Had the problem and it was the HT leads that where routed together with the crank sensor wire.
If this ain´t the problem it could be badly balanced or worn throttles.

Peppe

[Night Rider]

Yep, join the club. Have changed plugs, leads, coil, fuel brands & tune but no change.

If I accelerate hard the hesitation occurs every time but if you accelerate slowly it's perfect. Is that the same with your engines? Someone did mention the fuel chip in the ECU....there was an upgrade at some stage. I am looking into this today.

The investigating continues.......

[Night Rider]

.....and my solution was new fuel chip. Drives like a new car!! All problems gone.

[Peppe]

Night Rider said:

.....and my solution was new fuel chip. Drives like a new car!! All problems gone.

Do you have the version number of the chip ?

[VYT]

hmm, wasn't the fuel chip a "fix" for worn throttle bodies?

[Night Rider]

Peppe said:

Night Rider said:

.....and my solution was new fuel chip. Drives like a new car!! All problems gone.

Do you have the version number of the chip ?

Contact Power for that (if you want to wait for weeks for a reply) or maybe CT. But soz I don't have the Ver#.

[johnbear]

I've spent a fortune fixing this problem.

Numerous sources on PH and else where have helped.

The first suggestion was interference from the HT heads to the crank sensor. Try moving the HT leads away from the crank cables.


The actual solution for me was a throttle pot - as it got to 6000rpm at full throttle the ecu recieved mixed signals from the worn pot and cut the fuel. I'd try this next as it very cheap to replace.

The most expensive solution to the problem was to chanmge the ECU to a new version. This cost £250 for nothing.

Another ideas was the HT leads but this does cost £60 or so.

I also changed the Coil Pack but this around £70. If you ruled everything else I ould lend you my old coil pack to test on your car.

[s6boy]

Yep, all of the above especially the coil pack and leads, but also worth a mention is to make sure you're up to temp before full throtle. Had this once on the motorway on a cold day and tried to overtake in fourth and hit an invisible brick wall, back off and try again smoothly- no probs. I believe, but happy to be corrected, an engine management fail safe.

[warpig]

put a lovely set of 10mm magnecor leads on a while back to cure a bad missfire
that sorted that out.
while the car was off the road sorting out a few other problems, i fitted a new chip from tvr power.
hadn't driven it in serious anger in the month or so it had been back on the road.then one day while having a tussle with an aston i noticed it holding back at 6k. initialy thought it was the chip as previously it was ok.refitted the old chip,burp still there. no problems any where else though the rev range, just at 6k.think i'd better buy a lead and hook it up to see if any thing shows up

[tail slide]

IMO Johnbear's suggestion of throttle pots is worth checking out, and they sometimes need resetting not replacing.

Mine were behaving fine a few months ago, but showed up faults even at low revs at recent dyno session - could instantly see the resulting smoother running the moment they were re-set.

[Targarama]

Mine was missing under load when hot after its last service. Turned out to be the HT leads (Magnecor ones - been on 3 years). Re-fitted the std TVR leads and all is well again.

[tail slide]

Targarama said:

Mine was missing under load when hot after its last service. Turned out to be the HT leads (Magnecor ones - been on 3 years). Re-fitted the std TVR leads and all is well again.

Hmm that's interesting, now have Magnecor on mine. With the frequent diagnostic checks we're doing as part of development at least we'll find & report any misbehaviour early!

For info a knock-sensor is being added Thursday (just a visible indicator type but high quality, but we'll soon link to the MBE ECU as well). Not that an S6 needs it when everything's set up & working correctly, but a useful early warning that many other engines have if fuel/ignition/anything else starts deteriorating.

Edited by tail slide on Tuesday 8th July 20:31