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Hi Everyone

 

I recently stripped my inlet manifold to paint plenum backplate etc.

I did not separate the throttle bodies from linkage or adjust linkage....i kept it all intact.

I put it all back together with new gaskets, checked surfaces for high points etc as i am a fairly competant home mechanic and i am used to stopping air leaks, fitting gaskets etc.

While i had it apart i had my injectors cleaned by a reputable company and checked these by use of an injector pulsation tool before i put them back in.

I also fitted all new vac lines and tested vac fittings and lines using a vacuum pump. I also tested map sensor readings with a vac pump and all is fine there.

 

Now when i start her up she has high idle revs and to cure this the minimum air rate screw has to be turned so far out that it no longer makes proper contact with the throttle stop (throttle butterflies fully closed) before i can get the counts off zero to about 15.

 

There are no restrictions causing the butterflies to stick slightly open either.

 

I am very careful when it comes to air leaks so i am surprised that this has happened but this must be an air leak.... right?

 

I have sprayed over the manifold with brake cleaner but can find nothing!

 

So my question is......before i restrip and regasket and check for manifold cracks is there something i could be missing as i am pulling out what hair i have left!

 

Could anything else cause this????

 

If you think like myself that it has to be a vacuum leak let me know too!

 

Many thanks for any replies in advance.

 

Pete

 

 

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Now when i start her up she has high idle revs and to cure this the minimum air rate screw has to be turned so far out that it no longer makes proper contact with the throttle stop (throttle butterflies fully closed) before i can get the counts off zero to about 15.

 

 

Pete, are you following the manual for adjusting the air rate screw? Normally it's a factory setting.

 

Normally, idle is controlled by the IAC. Perhaps you have an issue here? Have you tried a reset through Freescan? Any fault codes showing?

 

Has the throttle jacking capsule been deactivated and the quadrant secured on your car? This can interfere with idle (although, you'd probably notice this if the butterflies are open).

 

Cheers

Ian.

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Hi Ian

Thanks for your reply. I have reset the IAC valve and i have even swapped the IAC with another and unfortunately have the same issue.

Yes following the manual for adjusting IAC counts but i am presuming that the IACV  going straight down to 0 counts indicates that there is air getting in somewhere else beyond the butterflies causing the IACV to fully close.

No fault codes apart from code 35 for idle 200rpm over desired idle..... unless i adjust the minimum air rate screw right back which causes the IAC counts to go to about 15.


Throttle jack and ebpv removed before i got the car. Electrics for them are still there and vacuum hoses have to these have been blocked off.

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Throttle jack and ebpv removed before i got the car. Electrics for them are still there and vacuum hoses have to these have been blocked off.

 

 

Just to confirm...  The throttle jacking capsule and triangular quadrant have been removed completely?

 

http://www.lotusespritworld.com/EGuides/ETechnical/EBPV.html

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The ECU will command a fast idle of about 1500 rpm on a cold engine, even without the throttle jack. 

 

Though the IAC counts should come down to 20-40 when the engine is fully warmed up to 80C coolant temp.

The IAC take a Loooooooong time to stabilize, so if you are making fast adjustments, you will totally miss the correct range.   If you played with the minimum air rate bleed screw and opened the butterflies too much, then the IAC might be going to 0 to try an compensate for too much air due to that adjustment. 

 

The other alternative is that you have the throttle cable too tight.  It should be adjusted so that the TPS voltage is between .45-.65V when the throttle is closed.  Also you do need a little slack for when the engine grows with heat. It should still have a small bit of slack with a warm engine, with TPS Voltage .45-.65V and go to 100% at full throttle (engine off of course).

 

The rubber hose from the IAC to behind the butterflies is probable really dried out and hard now, and could be leaking (min shattered when I tried to remove it).

 

Also there is the check valve from the charcoal canister and another from the crank case breather.  Are those in good shape?

Travis

Vulcan Grey 89SE

My Lotus Photo and Projects Album

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Hi Travis

Thanks for your reply.

TPS is 0.60 volts. The throttle cable is slack and i have checked one way valves on purge line from charcoal cannister and and crankcase hose with vaccum pump and they are in good shape.

When car is up to proper operating temp i can only get the iac to raise to about 15 counts and then there is no adjustment left (it makes no difference as butterflies have come to the end of their travel).

Its looking more and more like re-stripping down i think.

Would you agree?

Pete

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