Shunting/power loss

[Chimp871]

I know its been covered and have tried several the ideas but no go.

450 98 serp top end rebuild with a stealth cam fitted, bedded in, and timed in. Take it for a spin and the first 200 metres i can give it the full beans and complete rev range.

After 200 metres immediate power loss above 1800 rpm with it only coming back in at 1000 rpm. Limp mode i suppose.

It does reset after being left for a few minutes then repeats ie. Full beans for 200 metres is ok then instant power loss.

Fyi - I measured tappet preload and was out 75 to 100 thou so installed 30 thou shims (48 thou at rocker cover) to get it back close to spec

So far I've tried, one step a time,with no improvement (exact same cycle as above):

Clean rotor
Remove fuel vacuum
Remove dizzy advance
Disconnect stepper (engine then idles at 1800 so constant powe loss)
Reset ecu

The obvious engine changes are the cam and shims - is there anything obvious I'm missing or is a fuel remap required due to stealth cam?

Cheers. Matt

[Chimp871]

cheers blitz and qbee, especially for the loan of a chip.

No MIL light came on but will get a rovergauge cable and software and so what it shows up. I'll buy one of the classifieds.

I should add that whilst static and during cam bed in it'll rev to the max quite happily, so only under load does it limp.

I'll give V8D A call tomorrow and see if Rob/Ray have any ideas and if stealth cam 450 cars need a set up.

The previous owner had put on a straight through exhaust with large bore tail pipes. In case back pressure can cause a fault.....

[Chimp871]

Cable ordered. Not a fan of guesswork either.....

Would fuel delivery problem create limp mode? I understand fuel starving would result in power loss but the engine is still turning not cutting out. I admit i have no idea on fuel flow rates under load.

I take it to test fuel pressure you connect a gauge up to fuel rail valve point. Ok at idle but whilst driving take it rovergauge can monitor fuel flow.

Forgot to say before that the oil warning light is always on but reading from a mechanical gauge I've got good pressure (electric one confirmed this too) would a faulty oil sender switch put car in limp mode as it assumes oil isn't circulating? I'd be surprised if this were true though.

Edited by Chimp871 on Sunday 26th June 18:06

[Chimp871]

New fuel filter less than 1000 miles ago but intake hose unchecked

I'm back Thursday and will check fuel rail pressure and rover gauge it. Will find a way to measure pressure on the move. Something like this may help
http://www.ebay.co.uk/itm/252419059081

[Chimp871]

Chimp - I understand any of those reasons could kick in but laying up a car, change cam and then have power failure is hard to put down to various tvr quirks or gremlins.

Besides iffy design, controversially, I feel the servicing garages are part to blame for not pointing out points to fix improve on. I read somewhere over 50% of chimps are on SORN

[Chimp871]

update:

Rovergauge plugged in and working well (nice bit of kit too).

Fault codes thrown were 17 (throttle pot) and 19 (hi flo MAF and throttle pot).
Reset codes & reset ECU.
Back in car and went to set off but fault 17 showed again and would not clear
Went for drive to get to power loss problem, but I noticed throttle position does not move off 11% mark (non adjusted) whilst driving.

So the throttle pot looks knackered but before I go and get one is a broken throttle pot consistent with such power loss?

I did log it all but it's in txt file format which looks weird.

Edit - from this post i!may be getting close. He had 11% (and not moving) and limp home mode too
http://www.pistonheads.com/gassing/topic.asp?t=126...

Edited by Chimp871 on Thursday 30th June 11:04

[Chimp871]

got it thanks.... TPS is a constant 11% (also lambda's are at zero).

Focusing on TPS and link above explains ecu can get stuck

[Chimp871]

Gives you an idea of RG results. You see the throttle pot stuck at 11%.

I'm getting 4.9v at the TP connector engine side.
Throttle pot shows 6k ohms but doesn't budge when rotating.

[Chimp871]

davep said:

A few comments:

The ECU is running with Fuel Map 5, closed loop, but there are no Lambda Trim values, this could be a connectivity problem or your car has been de-catted and the probes removed/disconnected.

hmm...they are both connected. Battery is low due to amount of starts whilst testing, but will charge and check.

just scraping myself off the floor after seeing how much tps are!!! £150..

edit - it seems my TPS is a pre-serp version despite having a serp engine!#. Current knacked one is stamped 215SA, variant 70408A a lucas part(LR - ERR2263).

£130 for original serp one from tvr parts - http://tvr-parts.com/tvr-parts/part-details/tvr-e0...

Just for fun I rang LR dealer who said it was £280 + vat........

Will come back if it sorts my problem out.... but pleased ecumate shows TPS problems as throwing car into limp mode

Edited by Chimp871 on Thursday 30th June 15:15

Edited by Chimp871 on Thursday 30th June 15:21

[Chimp871]

Blitz - you appear to be a guru on electrics, when i get a new tps do you want old one to break apart and see fault?

[Chimp871]

blitzracing said:

Still too much- but better:

http://www.rimmerbros.co.uk/Item--i-ETC8495A

Edited by blitzracing on Thursday 30th June 16:14

Blitz - would you know which is +ve, -ve and trace wire from link you sugested - which is coming tomorrow?

[Chimp871]

Frustrating day. The rimmerbros tps was faulty, ohm reading went from 1.8 to 35 and had the correct sweep angle but if you slightly pulled the pivot out a smidgen or it was centred perfectly it would read open loop and times 130 ohms. Basically fickle.

Rang RB who told me I ordered the wrong part but advised them the test was on the bench not the car. TBH took sometime to persuade them the part was faulty and had nothing to do vehicle fitting. Its gone back but sense a battle to!get my refund.

Frustrating day........

Edited by Chimp871 on Tuesday 5th July 21:19

[Chimp871]

I think it maybe their standard response to avoid a refund, it'll be back with them today so we'll see. The body didn't have any markings only the box it came in. It looked and felt cheap enough low wire gauge.

I stumped up the TVR tax and got one from Performance and just fitted it. Works great and build quality significantly better with the brass pivot fitting snugly onto butterfly female stem, even has spacers I assume for different throttle bodies.

Has slots under spacers and can be adjusted, using RG was not able to get throttle to 100%, only 93% with idle at 13%. Obvious is to increase idle % but not sure which is more important smooth idle or WOT?

After 6 months off road for top end rebuild, new cam etc. Feels good to have her back.