Date: Sun, 03 Nov 2002 12:59:47 +0000
From: Grunff <>
Subject: Re: Jerkiness under engine deceleration (again)

Matt Gibson wrote: > A few months back, I posted about having a slight back-and-forth jerkiness > under mild engine deceleration, at fairly low revs, evident most in second > and third gear. I got a few suggestions here and from other places, e.g. > engine mounts, clutch, etc. but none of them seemed to be the problem. I > now seem to have found out what's wrong, so I thought it was worth posting. > > The car's a 1988 900T16S, by the way. > > I finally took the car for an interim service last week, and asked the > dealer (a main dealer I'd never used before) to try to find out what was > wrong. > > Apparently, it's a worn throttle damper, and a new one will cost me about > fifty quid, including fitting. Hopefully I'll get it done this week. Now, > it sounds perfectly plausible given the symptoms that something called a > "throttle damper" being broken would be the cause, but what the heck _is_ > it? Nobody else had ever mentioned it, and it's not in the Haynes manual > anywhere that I can see. Anyone got any ideas what this thing looks like, > where it is, etc? LOL! They're taking you for a ride *big* time. The throttle damper, AKA dashpot, is a small flying-saucer shaped device with a plunger. As the throttle closes, it pushes the plunger in, the plunger slows down the closing of the throttle because it is oil damped. Take a look for yourself - it's on the throttle housing (near where the air filter is). Open the throttle with your finger, then release it. It should go in gently, it's motion being resisted by the dashpot. The symptoms you describe, hesitation under acceleration, can not, in any way, be attributed to a failed throttle damper. The job of the damper is to stop the engine cutting out when you suddenly release the throttle, especially under high boost, when the throttle plate is slammed shut by the force of the turbo induce air flow. -- Grunff

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