Rebuilt engine won't idle

[andrewjoelpeters]

Hi all,
Well, I started up my newly rebuilt engine today--exciting to say the least. I let it run at around 1900 rpm for 20 minutes or so to break in the cam, and everything (oil pressure, coolant temp, etc.) looked good. But when I released the throttle, it died after coming down to an idle. I set the timing to 7 BTDC at 1050 rpm--I couldn't go any lower or else the engine would die. It seems to be running well at about 1000 rpm or so. Any thoughts?

Also, how much smoke is okay for a rebuilt engine as it starts up? I've had a lot of smoke which I blame on the residual atf I used to help loosen some bolts on the front exhaust pipe, but I also saw a decent amount of light grey/white smoke from the tail pipe. It didn't smell like oil. I know I should expect some smoking, but this seems a little excessive.

Thanks for the help!

[dlb]

if it runs but won't idle properly, the engine is probably ok but there is something else you are missing. double check all the vacuum lines, check for vacuum leaks at the carb base and manifolds, double check the timing, etc.

i'm not sure about the smoke aspect of engine break-in so hopefully someone else can weigh in on that. white indicates burning coolant though, which makes me think head gasket. not likely it's blown already so just make sure the head is torqued down to spec.

[Petros]

New engines always smoke on start up, but the exhaust and all the parts that get hot. You have put motor oil all over everything during assembly, even in places where oil normally does not run, so yes smoke on first start is normal. and all of the parts that get hot (manifolds, exhaust pipe, etc) will also smoke as it burns off the oil and paint (or whatever) that was put on it during assembly.

After it is run for the first time and it gets good and warmed up, it should not smoke again. If it does, something is really wrong.

As far as Idle goes, check you have the cam timing correct, and check all of your vacuum lines and routing. sounds like a vac leak. these kind of annoying little problems come up on first start up, you just need to track them down and correct it.

Good luck.

[andrewjoelpeters]

Great, thanks for the guidance. I haven't started it again because I noticed a little fuel leaking from the fuel pump, but vacuum leak makes sense to me. I think there a are a couple of hoses that could use replacing. I also pulled the smog pump (wasn't being used--pulley was broken) so I wonder if I might be facing some complications from that.

If I get the fuel pump figured out today I'll give her another start and check again for smoke. I checked the head torque twice before install, so I have trouble believing that's an issue. Fingers crossed it's just that residual atf burning off...

[Petros]

removng the old smog pump should not cause any issues, just make sure you cap off all of the lines properly. that ionly effects the exhaust system and should not affect drivablity.

after you drive the car for 300 miles retorque the head bolts again, in proper sequence to full torque value, or it may fail later.

[andrewjoelpeters]

Yeah, my caps were a little bit skimpy because I couldn't find ones large enough. Got some better ones yesterday and clamped them with hose clamps. Looks way cleaner. I also checked the head bolts--they were all torqued to spec except for one. I'm not sure how that happened.

Started her up again yesterday, and tied off the throttle at around 1500 rpm while I looked around. Didn't see any smoke, so that feels good. I could hear an air leak (presumably) coming from somewhere beneath the front of the air filter. I'll do so more investigation soon.

[Highlander]

Check the wiring for the fuel cutoff circuits (Big Green connector) and make sure that you have them by the book for your car. I had the same issue with one of mine, someone had rebuilt the carb before I bought it and just plugged the wires in helter-skelter once I got those sorted out it idled at 850 rs perfectly (Until it was killed by an F-150! )