Setting Base idle

[Loubaruch]

After 18 months laid up ( body off chassis restoration) a few things that were previously OK needed sorting.

It ran like a bag of bones and Frank Wilson ( Blazeaway) looked at the Rovergauge Log files and identified a few problems:

The first was the MAF, Frank suggested cleaning with MAF cleaner.
Checking the Stepper motor
Checking the TPS voltage

After cleaning both the MAF and the steppermotor the car was transformed and perfectly usable. What a great chap Frank is I know he has helped many owners by reading their Logfiles.

So I then decided to set the base idle.
The air feed from the stepper was blanked off but the car refused to start and would only run with the throttle opened, the base idle adjuster did nothing.
Carb cleaner was directed into the bleed hole by the idle adjuster and removed a lot of black stuff. But even after a great deal of cleaner the car would not start without some throttle. I tried to pass a thin wire from the adjuster hole through to the main plenum but it hit solid, I wonder if the plenum casting has always been faulty with no bleed hole from the air inlet side to the main plenum as I would have expected a wire to pass through. This would be consistent with a refusal to start without some throttle. Any thoughts very welcome!

Edited by Loubaruch on Wednesday 18th June 22:33

[Belle427]

I cant really answer what route the bypass port takes or how big it is but have you checked the basics first such as ignition timing?
The bypass screw is usually 1.5 to 2 turns out and using rovergauge if all is well the stepper at idle sits around 30% as a guide.

[Loubaruch]

Thanks, the car now runs really well so things like ignition timing are spot on. It is just that I wanted to set base idlle to be 100% but the adjuster has no effect,
Am taking the Plenum off today to have a closer look.

[Belle427]

I have never tried taking one of the adjusters all the way out but may help clean the passage out.

[Loubaruch]

I took the adjuster right out and gave the bleed hole a good soaking with carb cleaner and there is now a passage through to the plenum inside. It was quite clogged with black stuff.

About to set Base idle again and the car would not fire, Dont you just love TVR's !! No spark so next job

[blaze_away]

I worked with Richard Pearce last year and via the logfiles identified the base idle as needing to be opened up s bit. No amount of adjusting fixed it.

We came up with a remedy as follows.

Remove the plenum turn it on its side.
Remove the base idle screw completely
Inside the body of the plenum is the air inlet to base idle screw airway.
Block it of with eg A bit of blue tack.
Squirt carb cleaner etc in the hole where the screw goes.
Keep pumping and soaking with the fluid until all the crap is flushed out
You can see the crap exit into the plenum neck just beyond the throttle butterfly. Flip the butterfly open using the linkage.

Hope that helps

Edited by blaze_away on Thursday 19th June 13:45

[Loubaruch]

Thanks Frank, I removed the plenum to the bench and used about half a can of carb cleaner until it ran clean inside the Plenum. After sorting out the ignition fault (rubber Ignition amp plug wrong side of Aluminium mounting) .it would idle without the ICV in circuit so progress. Had to abondon for lunch and take the dog for his pm walk.

Thanks again Belle and Frank.

[Belle427]

Always good to check the important basic settings so it can operate correctly.
Should run sweet as a nut when your done.

[Loubaruch]

Even after clearing the airway adjusting the base idle screw did nothing. Even with the screw completely removed it still would not idle with the ICV blanked off.
Reading Mark (Blitz) notes again he states that for catalyst cars the base idle screw should not be adjusted. so now I am completely confused.

Thanks all.

Paul

[eliot]

I've had a number of these plenums on the bench when doing the 72mm conversion - they do get gummed up. Must admit, I should really remove the screw completely and clean it out - but people get anxious when they see the blanking plug removed.

[Belle427]

Loubaruch said:

Even after clearing the airway adjusting the base idle screw did nothing. Even with the screw completely removed it still would not idle with the ICV blanked off.
Reading Mark (Blitz) notes again he states that for catalyst cars the base idle screw should not be adjusted. so now I am completely confused.

Thanks all.

Paul

Think he may be referring to the adjustment on the AFM but I have not read it.

[Loubaruch]

Thanks all.

Yes, Belle Mark was referring to the CO trim on the MAF sensor not the base idle. I must be going senile!!

Thanks Eliot I will pull the plenum off again and give the air way a good blast of air.

Edited by Loubaruch on Friday 20th June 12:22

Edited by Loubaruch on Friday 20th June 12:23