V8S revs oddly..

[Psychobert]

Odd problem just emerged with the new V8S, (I know, I know, will take pics and update the profile)..

Couple of days ago the revs started not dropping as quickly as they used to when I changed gear. Also, when I slowed for a junction, they would either hover at 900, or 1100, or drop so low I thought it would stall, then pick up again. Lunchtime today, I hopped in the car and as I started her, revs jumped straight to about 2500 and wouldn't drop below that. I could accelerate above it, but the revs wouldn't drop below until I switched off and restarted.

Any ideas?

While I think, used to have a Sierra manual for the V6 that detailed the engine reasonably well, is there an equivalent for the V8?

[HarryW]

I will say most RV8's do have odd days where things like this do happen, TADTS .
Failing that, clean the stepper motor, re-set the ECU after cleaning though so it forgets any bad manners learnt. If it returns in a matter of minutes then it could be fecked and or something else.
Other areas are the induction pipes, if original it could be a partial blockage whereas the innner liner ballons forming a blockage.
Any ECU derived faults should show up as fault codes if you have access to a code reader and your loom has the test plug fitted, not all early cars do AFAIK.

H

[nawarne]

Psycho,
I'm sure someone will be along soon enough if I'm wrong, but my first shot would be to remove and clean the stepper motor.
Locate on top of the plenum, close to the bulkhead, a black, large (27mm) nut with 4 pin multiplug coming off it. Undo said nut and clean valve end with meths or carb cleaner - not forgetting housing in plenum!

Re-assemble using PTFE tape on threads to provide airtight seal. Do NOT over tighten. Re-connect multiplug and apply grin to mouth.
Nick

[Psychobert]

thats 2 votes for the stepper motor so will give that a once over..

Probably give the old girl a thorough thrashing on my way back to the hotel tonight, can't have been good for her to crawl along sodden motorways for the last couple of days..

[brioss]

I have found that if I dont use Optimax petrol , the idles is poor, too low/ too high (thats after cleaning the stepper motor)

Always try to fill with Optimax

>> Edited by brioss on Tuesday 2nd August 19:16

[cobra kid]

Hi Mr Bert, noticed it was missing from your car park and hoped it hadn't gone AWOL. May seem daft but what about the mass air flow sensor if it has one??? Hope to see and hear it soon!

[Monkeylegend]

Do you have to reset anything after cleaning the Stepper motor, or do you just put it back in and everything else is ok?

Sorry about what is probably a silly question but know very little about this.

[keithyboy]

I had exactly the same problem recently which was manifesting itself more frequently. It was the stepper motor. After removing the wiring conmnector, unscrew the motor from the plenum chamber and keep the sealing washer (providing it's intact and in good nick). I cleaned the barrel end and spring up carefully with a squirt or two of WD40 and a soft cloth - it wasn't too bad as it's only been on there a couple of years following the rebuild. Carefully replace it with the washer in place (apparently you can use PTFE tape if you dont have a washer). Screw it in handtight first to avoid cross threading and tighten just enough to ensure an airtight seal. DO NOT OVERTIGHTEN as the motor can and will crack - they are £80 plus or so to replace! Mine runs fine again now

>> Edited by keithyboy on Wednesday 3rd August 10:51

[tvrgit]

You mention loads of wet weather - could it also conceivably be water in the electrical connectors between the stepper motor and the ecu? My V6 suffered from similar symptoms in wet weather...

[Monkeylegend]

keithyboy said:

I had exactly the same problem recently which was manifesting itself more frequently. It was the stepper motor. After removing the wiring conmnector, unscrew the motor from the plenum chamber and keep the sealing washer (providing it's intact and in good nick). I cleaned the barrel end and spring up carefully with a squirt or two of WD40 and a soft cloth - it wasn't too bad as it's only been on there a couple of years following the rebuild. Carefully replace it with the washer in place (apparently you can use PTFE tape if you dont have a washer). Screw it in handtight first to avoid cross threading and tighten just enough to ensure an airtight seal. DO NOT OVERTIGHTEN as the motor can and will crack - they are £80 plus or so to replace! Mine runs fine again now >> Edited by keithyboy on Wednesday 3rd August 10:51

Sounds pretty straight forward, will be doing the same to mine tonight.

[Psychobert]

tvrgit said:

You mention loads of wet weather - could it also conceivably be water in the electrical connectors between the stepper motor and the ecu? My V6 suffered from similar symptoms in wet weather...

Thought I'd test that out by going for a decent drying out session/hoon last night. Bristol to Gloucester on the back roads, return via somewhere once slepy in the Cotswolds, (sorry about the car alarms I set off )

Have to say, no such problems this morning..

[silverback mike]

I'll join you soon for a little exercise.

[Psychobert]

silverback mike said:

I'll join you soon for a little exercise.

Excellent!