help required

[mikesmith]

hi people, can anyone help? My Esprit has decided to invent its own random cruise control. Start the car from cold, no probs, warm up in driveway, no probs, drive it around at a legal pace, no probs, but if the red mist should decend and you give it some beans then it decides to idle at 3000 rpm. On the road you dont have to touch the throttle to maintain 50mph Come to rest and it drops to 2500rpm. It does eventualy come down but its no happy. The back ground to this that the engine has been out and had, new timing belts, alternator, air con pump, all turbo hoses, two dump valves, plugs, and anything else that was about to brake. The first thing that goes through the mind is what have i left off/connected wrong, but i've been over everything i can think of and have found no probs. It seems strange to me that it only occurs when you give it some helmet? No fault codes present. Does a proper lotus diagnostic computer go into the system any deeper than the EOBD that I can get into. Any advice would be great and probably stop me reaching for a box of matches.

[gt1]

Have you checked for obvious mechanical things ? Throttle linkage all fine and returning correctly ? Air leaks on the plenum and surrounding areas ? If the throttle butterflys are shut then no amount of clever ecu based info will make the engine speed increase...

A sniff of ether is a really good diagnostic tool for air leaks.

[peter_england99]

The Lotus Tech 1 scanner certainly has additional functions that my basic OBD-II scanner doesn't have.

In regards to the problem:

- Could the ECU still be 'learning' your idle settings?

- What throttle position is being reported when you have the high idle? Is it 0? if not you could have a sticking throttle.

Hope you find the problem before you get the matches involved.

Regards,

Peter.

[Günter]

use some brake cleaner and spray it from throttle body end , and from the opposite site (belt side) under the plenum. But do care not to spray on the hot turbos or anything exhaust related parts. If your engine speed rises it surges the cleaner trout an leak.

[superdavelotus]

I would have thought it was your air idle control valve clogged up or faulty?

Or you could have tightened the throttle cable too tight and when you floor it, your pedal is actually pulling too much cable and linkage is being stressed? Not sure if you can do this on the V8 or not but you certainly need to check that you have got your throttle cable and linkages right.

Dave

[mikesmith]

Thanks for the advice, its a bit of a pain , odd that it only does it after driven hard ish, you first notice it when changing gear, revs up instead of down then when you stop youve got the high idle. Throttle linkages all cleaned and adjustment checked, butterfly on the stop, throttle body and inlet manifolds all got new gaskets, idle speed unit cleaned out . Im going to put it on the gas analiser and check high CO/ HCs when playing up ( poss dribbly secondary injector ??? ) With reguards the ECU learning, this i did think about. Is there a set way to drive to let the ECU learn? it has been disconnected for the past three months. Throttle position switch has good readings with no drop outs. That light at the end of the tunnel never seems to get any closer.