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MrP

Help guys: high idle on V8

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Hi chaps my cars been laid up for a while just went for a quick drive accelerated up a straight stopped at the traffic lights and the revs wont drop below 2500 rpm, ive left the car disconnected come back to it the next day and started it again and idle is still 2500 rpm!!!!

Ive pulled up a fault code which is - P0507 idle control system RPM higher than expected

When putting my hand close to the exhausts the gasses are red hot obviously id expect them to be warm but these seem to be very very hot, also whilst looking into the engine bay the left n/s turbo manifold is GLOWING red and the right is not, im thinking possibly the cat has collapsed would these syptoms occur if it had, I dont dare drive it incase I do some damage am I being paranoid or rightfully cautious really could do with some help!!!!! :)

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Upgrade today to remove Google ads and support TLF.

Ok I can see that the revs could be IAC valve (is this a lotus only part) but what about the high heat coming from the exhausts and the glowing red N/S turbo manifold is that normal?

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Hi Matt,

Is the airflow from both exhaust roughly equal? If one is much stronger than the other then there could be a blockage in the exhaust (possible caused by a collapsing cat).

I doubt very much that the IAC is a Lotus only part. But as it's under the manifold I can't get at the valve to check what is written on it. I'd guess it's a GM part.

I recently had an IAC valve problem with it stuck low (i.e. low idle). Lotus South West kindly connected the 'Tech 1' scanner that allows you to manually increase and decrease the opening of the valve. This freed up my IAC, and hopefully will not stick again soon.

Regards,

Peter.

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Hi Peter, yes it does seem to be equal from both exhaust, I have a standard exhaust and wasnt sure if the pipes run through each other inside the box or wether they are completely separate? I take it having one turbo manifold glowing like the sunset isnt right?

About the IAC what do I need to do, take it off and send them it in the post and they will have a play

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I will head out to the shop tonight and check that part for you if you like (assuming somebody else doesn't get the part number first)... the intake plenum on Aerobats v8 isn't bolted down, so i can check that iac fairly easily.


Modifying esprit's.. now that's fun..

PS... I AM NOT A CERTIFIED MECHANIC.. I Have chosen to help those in need, in the past and must not be construed as being a certified technician.

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Hi Matt,

I've never had the standard exhaust, so can't comment if the two exit pipes are linked together inside the silencer box. I know the with the 'sports' exhaust that the exhaust pipes are not connected. My straight pipes, obviously are also not connected. Maybe someone else could shed some light on the standard exhaust layout.

I'd not be happy with one turbo significantly hotter than the other. Both engine banks and turbos should be running at roughly the same loads, and hence have similar temperatures.

In regards to the IAC, South West Lotus Centre didn't need to take the valve out. The 'Tech 1' scanner is the official Lotus service tool that plugs into the car's OBDII socket. Once connected, you can increase and decrease the valve opening. So by manually opening and closing the valve they managed to free it up. Whether in my case the valve stays unstuck for long is another issue. I.e. I think in the next year I'll end up having to get a new one.

Regards,

Peter.

Edited by peter_england99

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standart box is linked toghether..

exhaust gas goes from each side into an chamber (one RH, one LH) in those chambers is some steel wool and the pipes are open ended an perforated.

there is an blade inside the third [the middle] chamber on which the gases are gone reflected, than they can pass the perforated connecting pipe that is the outled left and right.

Oh, and yes -IAC valve is an standard bosch /GM part in my eyes !!


*********************************************************************

to name the things if I see them, that's what I call integrity..

*********************************************************************

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Hi

I got a new IAC valve off ebay not too long ago just in case i ever need it.

As Gunter says it is Bosch with a number on it.

0 280 140 516

Hope that helps.

I am located in Norfolk and of course if any use to you, you would be welcome to borrow the new IAC to see if that helps.(But to be realistic i would not post it)

Mark

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IAC valve is a constant headache for me. High heat can cause them to stick closed or open. I would find that taps with a mallet on my plenum would slowly unstick the IAC and return it to normal. Not practical at stoplights. Likely time for a replacement. Alternately, you could have a significant intake leak on that bank which would explain the high idle and the lean mixture (hot exhaust). Spraying a bit of carb cleaner at the edges of the plenum while it is idling high is a good test to find a bad gasket. This is a long-shot. Just the only thing that would tie the two symptoms together. More likely is the failed cat. High engine bay temps may have shortened the life of the IAC but it is time for a new one anyway. When you have the plenum off you can inspect the gaskets.

The cat issue should be easy to confirm. The difference in heat for the collapsed cat will be obvious to your hand from a few inches. I believe the exhausts are linked, so you wont be able to tell much from the relative flow out of the pipes.

Pretty much I am agreeing with what the others have said.

Regards,


Rod

98 Esprit V8

Dynamic Racing Turbos

Water Injection

Factory Red ECU

3 bar MAP piggyback

Straight-through exhaust

TurboXS BOVs

Blitz I-color boost control + Wide-band AFR

Porsche/Getrag G50/52 Transmission (...coming soon someday)

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Great advice thanks, il get a new IAC valve ordered (thanks for the number guys im sure that will help) and whilst im waiting try what youve suggested tap the plenum etc and take off the back box that way I can check the heat coming from both cats il get back to you once ive done these and let you know, watch this space cheers chaps.

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maybe some of the others would giggle now, but what is if you regulate manually -just to verify that iac functionality is not working. The iac should be an external bypass valve, with an simple piston or disk mechanic system inside -it does nothing else than regulate the diameter of airflow that can pass by the throttle. So if you just put an normal hose attached to the ports and squeeze it manually by hand, you should be able to vary the idle...

Edited by G

*********************************************************************

to name the things if I see them, that's what I call integrity..

*********************************************************************

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Ok chaps I have fitted a new IAC valve and the idle is now fixed but still have a problem with the left bank running hot I have taken off the back box and the gases are hotter from the left hand side also taken off both Cats and felt directly from the turbos and the left side is still a bit hotter. I also swapped the cats over (yes this is possible) and is still running hot on the LH bank.

Whilst having the plenum off I looked at the gaskets and they look fine, with the Cats off I pulled the wastegate lever and it seems to move easy enough and the door opens with no problems is there anything else I should be doing or checking?

Here are my figures from the OBD might be of help, do these look like they should?

PS check light is on for O2 Bank 1 Sensor 2

cant seem to upload pics as yet

Edited by MrP

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Hi Mat,

It would be interesting to see what your O2 sensors, short & long term trim are doing. If you were running lean the temperature would rise.

Regards,

Peter.

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Heres some data pics I tried to add last night

otherdata.jpgfueltrim.jpgo2.jpg

Edited by MrP

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