More High Idling trouble

[Rob]

It does have an original Pete Betts delimiter/convertor on it.

Putting wiring back to stock would involve dash removal and re-soldering. Would just unplugging the convertor be Ok?

 

Oh, Chris where's the water temp sensor on the NA?

 

I'm also thinking of some electronic signal that resets when ignition is killed.

 

The earlier stuff about being able to press the throttle body shut, applies equally to Scooter's TB, in his case it killed the engine, so I guess thats normal for the NA TB.

[Rob]

Simply disconnecting the speed delimiter so the speedo had no reading at all caused no change. I presume you are thinking the only difference when the car is rolling is the speed signal to the ECU?

[Rob]

Another idea, has it got a spedo convertor on it? If so, remove it and put the wiring back to standard, see what that does.

 

Finally got round to doing that.

 

It doesn't appear to have made any difference, except I've now got Error code 42 but thats probably my soldering.

 

Still confused now, only other thought is that the spark plugs are a bit over 120k miles now, and they were last changed at 60k, could this have any effect?

[Dr_Doom]

Finally got round to doing that.

 

It doesn't appear to have made any difference, except I've now got Error code 42 but thats probably my soldering.

 

Still confused now, only other thought is that the spark plugs are a bit over 120k miles now, and they were last changed at 60k, could this have any effect?

 

For less than £10, for a set of Bosch ones it definitely worth a check. Probably the first thing i'd of tried really..

[Rob]

Changed spark plugs, still no difference, except it now idles at 1000rpm instead of 1100rpm.

The only time it worked properly was when I put scooters spare throttle body on, then it worked for a day or two before reverting to high idle.

[TLicense]

Rob,

 

The ECU takes input from mainly two things to achieve a given idle. Throttle position and coolant temp. It then sends a signal to the idle control solenoid that moves to the position demanded by the ECU and let's the required amount of air into the plenum to achieve the given idle. That's all there is.

So one of 5 things is going wrong here.

1. The ECU is knackered and giving out the wrong signals for a given input.

2. The correct throttle position isn't being sent to the ECU.

3. The correct coolant temperature isn't being sent to the ECU.

4. The idle solenoid isn't moving to the correct position.

5. You've got another air path into the plenum with the throttle position shut.

 

You had it working with a known good throttle body, which to me rules out 1,3 and 4 as they don't have anything to do with the throttle body.

 

So it's either the throttle isn't fully closing when you're off throttle, or the throttle position sensor isn't relaying the correct throttle position to the ECU. That's all it can be, as nothing else happens within a throttle body.

 

Have you got or can you get hold of a workshop manual? It explains in there the correct values you should get from the TPS sensor and also the correct gapping for the throttle when closed.

 

If not I'll see if I can find 5 minutes when I get home to post them up.

[Scooter]

Rob during all these on off changes which of the gaskets did you change/renew

[Rob]

TLicense, it worked for a day with a known working TB then went back to idking high. I've already checked all the resistences across the IAC and the TPS, and set the TPS according to the manual.

 

Scooter, I didn't split your TB apart from the Y-plenum, so there was no need to change that gasket, even though I bought 4 spares just in case.

Originally it was idling at 1800 but dropped to 1100-1200 after I dismantled it all and replaced the TB gasket. Today it was idling at 1000 after the sparky change.

I could get some new vacuum hosing and replace the lot just to be sure.

The butterfly that divides the 6-plenum, that should be open by default?

[Scooter]

I could get some new vacuum hosing and replace the lot just to be sure.

 

can't hurt

 

...hope its that simple......

[pistonbroke]

Just seen this and thought I'd give you my thoughts. My TT used to have a slight erratic idle, nothing like what you're getting but still erratic, would idle at 1000 for a while after enthusiastic driving then settle to 600 eventually.

 

I replaced a load of the vacuum hoses with samco blue stuff and its made my idleing a lot more stable.

 

[Rob]

As if by magic, I've just replaced all vacuum hoses with blue silicon,

 

and

 

and

 

 

and it's made no difference.

 

I still can't get away from the fact that if I turn car on and let it sit on the drive, it'll eventually settle at 700rpm and there's no play in the throttle, it's firmly shut, if i rev to +2500 and hold it there for a while, it'll fall back to 700rpm and no play in throttle.

If I go for a drive, It'll settle at 1000rpm, and then I can push the throttle shut and it'll go back to 700rpm.

(and it did this with scooters TB on as well)

[Rob]

I haven't yet changed the pipes from the big power steering banjo into the head and the front side of the main plenum, they're a bigger diameter and they didn't have any at my local shop MotorSports, who incidentally told me Michael Lane dyno'd at 700+ three weeks ago.

[Dr_Doom]

Have you done the error code 42 fix?... the wiring going to the odometer?..

[Rob]

I reinstalled the TRL speed cut device so that negated the need to check for dry solder joints on the odo PCB.

[Dr_Doom]

For how long it takes to do, try it anyway. You've tried everything else... When i was having idling problems & the car used to cut out when driving, this cured it. I'd tried everything else first though

[Rob]

Thanks for the pic, but that re-wiring has already happened by way of me installing, (or rather re-installing) the Speed cut box'o'tricks.

 

When I removed one of the little short vacuum hoses from the underside of the main plenum there was a hiss of air. Should there have been any vacuum present in a non-running engine?

[Chris Wilson]

Yes, it's the vac supply for the variable length induction system.

[Rob]

Thanks Chris. (sounded a bit The Day Today there)

 

Variable length? where, who, when? Do you mean the secondary butterfly thing between the two halfs of the plenum?

[Chris Wilson]

Thanks Chris. (sounded a bit The Day Today there)

 

Variable length? where, who, when? Do you mean the secondary butterfly thing between the two halfs of the plenum?

 

yes the butterfly varies the length and volume of the plenum to pull up mid range tiorque or add top end power as required.

[Rob]

Chris, any thoughts on the throttle butterfly, should there be any "closable" play in it after driving?

[Rob]

WIth the arrival of chilly mornings, it's now back to idling at 1400rpm, after I've driven to work, some 1/2 hour drive along dual carriageway.

 

I've never changed the multi-layer metal gasket between the plenum and the Y-piece, could this be leaking, more so in the cold weather when things are more contracted?

 

When I was taking it all apart in the summer, this gasket was in many "leafs" at the top and stuck together at the bottom, is this normal, the manual says this is a non-replace part when the two bits of teh intake are dismantled.

[Chris Wilson]

When did it last have a new thermostat in it?

[Rob]

NevAh evAr.

 

You also mentioned the temp sender earlier, where is this located please?

[Rob]

Chrrrriiiiisssss, why you no never answer this question? que? que?

[Chris Wilson]

It's in the top radiator to head neck, the one with 2 wires to it, the sensor with a single wire, next to it, is for the temp gauge. You can test them if you have a workshop manual, the figures are in there.