Revs drop, engine out

[timewind]

Hi there

My chim really is behaivng nasty lately.

Newest challenge is, that very often when I drive backwards the revs will go down to around 300 and then eventually stalls. This also happens if I slowly approach a roundabout and let the car roll. Exactly the same. Revs go down, seem to stop at 900-1000 (as usual) but then they very often are dropping to zero and engine out.

The very odd thing is, that if I steer full lock (when stationary) to the left or right, the revs drop around 400 revs.

any ideas? I have a friend coming over tomorrow with his new Porsche and I really don't want to stall the chim at every junction or roundabout.

Thanks

[miniman]

Presume it has power steering?

[timewind]

HI

Yes, power steering...

[blueyonder]

Have you tried cleaning the stepper motor? A dirty stepper is often a cause of poor idling.

[kenny chim 4]

timewind said:

Newest challenge is, that very often when I drive backwards the revs will go down to around 300 and then eventually stalls.

As far as I'm aware every RV8 TVR struggles (from cold) in reverse gear without approriate pressure on the throttle. I have always reversed the car to park it -other than have to reverse the car from cold.

[miniman]

timewind said:

HI

Yes, power steering...

Most cars with power steering will drop revs when full lock is applied when stationary. It's just maximum load on the power steering pump so it drags the revs down a bit.

[timewind]

Hi

Thanks for the information about the power steering and the help so far. Stepper

Motor is only 2 years old and has been cleaned 1 month ago.

This morning now, the idle rpm is not steady at all, it's fluctuating around 200 - 300 rpm. from 800 to 1100.

Thanks.

[tvr keith]

Try resetting the stepper motor;

Yesterday (07:47)
--------------------------------------------------------------------------------
I cleaned the stepper motor and the idle was then wrong. It would slow to about 1200 rpm, then speed up briefly to about 1600rpm then slowly drop to about 800rpm where it would remain.
I originally asked Dream Machines and was told that if the stepper motor has been disconnected it must be set up again. I did as instructed and all was well, stupidly forgot to write the procedure down.
Recently went through the same procedure again and asked Chris Baldock at James Motor Sports (he is ex workshop manager for Walldonway ex TVR main dealer).
When told the procedure I remembered it from before to be the same so I'm thinking it must be right.
Procedure is;
With engine at operating temparature,
Disconnect stepper.
Ignition on for 10 secs (do not start engine).
Connect stepper.
Ignition on for 10 secs (do not start engine).
Ignition off for 10 secs.
Restart engine.

Interestingly Chris Baldock also told me that it is best to clean the throttle pot with carb cleaner at the same time;
Remove the pipe that links the Stepper motor to the throttle pot and clean it out,
Remove the pipe that connects the air flow meter to the throttle pot.
Screw the base idle screw right in, recording the number of turns. Then remove it.
Clean the hole that it sits in and also the butterfly and neck around it using a bit of rag to soak it up so not much goes into the engine.(Mine had a fair bit of gunge here)
Reassemble making sure the idle screw is wound right down and then out by the number of recorded turns.
It sounds a lot but only took about 1/2 hour and now idles perfectly.
Strange that the re setting procedure is not mentioned in the Bible

Edited by tvr keith on Friday 20th April 09:00

[timewind]

Thank you Keith.

I lost my patience and I've brought the car to the TVR dealer and he did some analyses at the ECU. We have found, that there have been several error-codes like engine misfire, Stepper motor failure, lambda error etc.in addition to that the air-bypass was blocked. We also found out that the car is running too rich (3.5ms and should be around 2.8ms)

We cleaned the airbypass and the steppermotor and things improved but still the car would stall especially when in reverse gear (but also on roundabouts). We then tried two brand new stepper motors but strangely enough, none of them seemed to worked on my car, while mine seems to work. Things really are getting unreal.... And the ecu doesn't find any errors anymore. We also made a reset after the whole procedure.

Dealer asked me if he can keep the car the car over the weekend in order to have a closer look. I asked him about the road speed sensor, but he said he would be suprised and this certainly has nothing to do with it.

Since we have beautiful weahter here in Switzerland and I would like to have the car over the weekend, does anybody have another idea.

Thanks for your help anyway

[miketvr]

The reset sounds a bit unnecessary to me. The Stepper resets itself back to fully home (can't remember wether its fully in or fully out) every time you switch the ignition off - so the most you should need to do before starting is to turn the ignition on and off.

I fully agree with the removal of the gunge around the butterfly and possibly the base idle screw. However the base idle will need to be reset properly if tampered with. The procedure may be in the bible, but it's fairly simple. At normal engine temperature start the engine. Clamp off the rubber pipe that feeds the stepper motor with air from the other side of the plenum. When the base idle screw is set correctly the revs will drop to about 500 RPM (from memory).

Mike