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Discussion Starter #1
Hi got some good imformation last time I posted a dilemma wondering if someone can help again.Had to get my top welded the other night and while I took the 1990 spider new motronics out drove for about 25 miles got to the welding shop idled the car I noticed in nuetral the engine going from 6rpms to about 10rpms not yet sure if it does it all the time but would like to get a jump on it before it's a problem.Can anyone tell me what to look for Sal Thanks.:eek:
 

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I'd start by checking for air leaks... Your Spider has a Bosch Motronic fuel management system, which I am not really familiar with. Nonetheless, there is an excellent write-up for the series 3 Bosch L-Jetronic (Spiders up to 1990). While the fuel management is not identical, the process and approach is certainly very applicable. You can find that write-up on the Hi Performance Store web site. They also have a Motronic write-up under development.

Best regards,
 

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im really familiar with your exact year

there is a small amount of normalcy to a very subtle oscillation of the idle-rpm when the car has first warmed up. i mean EVERYONE i know with motronic has that issue.

when its doing its dance (should be pretty inconsistent) give the throttle a strong blip to 3k rpm or 4k and it should be gone when the rpms come back down. if it does, your fine. if not than you need to check the IDLE-AIR ACTUATOR. its off the hard-airtube on top of your engine, left-side, and resembles a small silver cylinder with a J-shaped hose coming off your hardtube. (pretty much the closest BOSCH thing to your water-reservoir).
when engine-mounts go bad, allowing the engine to twist a bit, this hose can take a bit of stretching and create small splits. i have had to replace mine before. also , when you remove the unit, (removing the small C-bracket the holds it to the Air-Intake-Plenum there is a black, thick bushing that keeps it snug in the plenum. make sure that bushing is sound and soft and air-tight.

another thing that can possibly cause your issue is the VVT plug at the end of the left-side valve-cover. closest to the fans. make sure that wires there are happy and snug. this will also take some damage when an engine twists and can cause very subtle changes in engine speed.
 

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Discussion Starter #5
Thanks Guido for your time I will check those things out as soon as I get A chance to start her again.
 
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