zogster

I've recently put my engine back together after replacing head gasket, belts, water pump and a few other bits, and it now seems to be idling too fast - but only when the engine's up to temperature. I replaced all the small vacuum lines as a first step to eliminating likely causes (I gather vacuum leaks in the old lines are a common source of idle problems), but that didn't seem to make a difference.

To be more specific... on starting the engine, it will idle at about 900rpm. But after a few minutes, when it's up to temperature, the idle rises to about 1,400rpm. i think the revs also don't drop off quite as quickly as the used to when I come off the throttle when changing gear.

Any suggestions for how to troubleshoot this?

(It's an '87 Turbo, RHD UK model, btw)

Kevin88951

I had a similar issue, but idle was around 1,000-1,200. I noticed the J-boot had a hose connection that was loose. After closer inspection the plastic tube which connects the hose to the J-boot needed to be replaced. I replaced the J-boot with a new one from Lindsey Racing. I decided to replace the plastic "Air Tube" with a medal tube I picked up at Home Depot that was the same size/length for @$4 in a durable coated brass. This resolved the high idle, but need to recheck the TPS/Idle setting.

zogster

Good tip, thanks Kevin - I did find that one of the connections on the j boot was a bit loose. I tightened it up and it seems to have improved things, though the idle can still wander a little while the engine's hot. It probably doesn't go quite as high as before, but I guess I just need to go through all the other vacuum lines as a first step to figuring it out.

Plus, there's another post-putting-it-back-together issue that I want to address more urgently, which is simply that the engine doesn't sound quite the same as it did before. Think I'll make a couple of recordings and post them here as I'm sure there'll be something in there that'll mean something to a more experienced former than me.

ehall

Yep. It sure sounds like a vac issue. I have the same problem. I know mine is a vac. issue. How does your car sound different?

zogster

Re. the sound - it was a bit boomier... traced it to the exhaust, and bolts that had shaken loose where one of the headers joins the rest of the exhaust. Which I think was a consequence of putting the lower balance shaft 180° out of phase when I did the re-assembly (or rather putting the sprocket back on 180° out of position...)

Douglas Adams might just appreciate the situation - a good example of the fundamental interconnectedness of all things, especially in the context of complicated engines.

Chris White

Always good to have a towel nearby when working on an engine. Peanuts help too.