'96 Saturn SL high revs

I have a '96 Saturn SL with a 1.9 SOHC. I recently removed the engine and transmission to change the clutch. I also changed the timing chain guides, the valve cover gasket, the timing chain gasket, oil pan gasket, front and rear crank seals and motor mounts. After I put it back in, it revs to 3500-4000 rpms and is very rich (so rich it smokes). I replaced the throttle position sensor since it had a crack at the plug and to see if that was the problem. I have looked at everything again and nothing is jumping out at me. Any ideas?

You may have gotten the timing chain a tooth off or two.

I didn’t move the timing chain. I held it in place and removed/replaced the chain guides one at a time (I had an assistant). If it did move, how would that make the motor rev? I would think that it would run rough not rev which is why I didn’t consider that. Is there something that I am not understanding though?
Thanks for the input.

I would be looking for a vacuum leak. A vac leak will cause a high idle and a lack of vacuum at the MAP sensor will cause it to run rich. These things were also notorious for failing coolant temp sensors.

I’m with pete peters. Is it just revving steady at 3500-4000? Start by just inspecting the throttle body and cable for binding. Check the operation of the idle air control valve. Double check all of the input ports. There should be a schematic of the vacuum system under the hood that can help you track everything down.

Yes it goes straight to 3500-4000 rpms and stays there. The longest I have let it run is a few minutes to avoid any damage. Also, no check engine light yet.
I will check the vacuum system.

These guys specialize in Saturn S series cars.


OK, so I have replaced the TPS, engine coolant temp sensor, the canister purge valve, and the PCV. All because they had some physical damage so I figured what the hey, except the PCV but it was cheap and easy. I cleaned the throttle body.
If I cover the TB while it is running, it gets mildly better but the revs are still above 3000. I sprayed brake cleaner around the manifold looking for a leak but know change.
I am lost. A reminder-I removed the engine and transmission to do the clutch (we just purchased this car). I also installed many gaskets/seals while it was out (see original posting). It ran very smooth and normal, it was impressive how smooth it was which is why I bought this one. So, is there anything that I could have hooked up backwards/wrong that would cause this?
Any other ideas?
Thanks for all the help so far and all to come

Also, It runs REALLY RICH

OK so I’m thinking all along "where is a large enough opening to cause this high idle?“
After dropping a pair of pliers behind the engine, I found a hose laying behind the steering rack and cross member. I traced it back to the brake booster, which of course is vacuum operated. The next question, “Where is the fitting for it?” How about a 1/2” opening in the intake? Would that cause this? If you not sure…it does.
When starting this project, I told my nephew that we would leave something behind the motor unplugged…I was right!
Thanks for all of the input everyone. Hope I can return the favor.

Whenever I get into pulling lots of connectors and hoses and stuff I keep a roll of very brightly tape around. I wrap a little around each thing with a big tab handing off as a flag. The bonus is that you can also label if needed. It makes it much harder to miss stuff.

I’m actually surprised that this didn’t keep the engine the from running. More often if its a leak that large the air leak has to be metered or the PCM won’t deliver the fuel for it. But this thing probably has a MAP sensor - so that probably does it.

In any case, many thanks for the follow-up report, and so glad you got it straightened out.