Idle Problems in my 'Burban

Old 03-29-02, 10:12 PM
Thread Starter
Join Date: Mar 2002
Location: Louisiana
Posts: 416
Upvotes: 0
Received 0 Upvotes on 0 Posts
Unhappy Idle Problems in my 'Burban

'89 Suburban, 5.7L (350) Auto, TBI

OK guys, sit down this is a long one...
Just put an AutoZone Series II engine in my Old Raggedy Suburban. 1989, 233,000 miles on last engine. Went in smoothly, started right up, runs great on the highway, idles terribly.
So I...
Re-checked the timing (pulled wire, set @ TDC, reconnected wire), readjusted the valves (backed off till tapping, tightened till tapping stopped plus 1/4 turn), looked for loose wiring, vacuum hoses, etc..(manifold vacuum steady @ 19"). Still has poor idle to the point where it sometimes kills engine. Next day, driving after tinkering with it, and the ignition killed for a split second. The reason I noticed it was because my "fasten seat belt" light came on and my radar detector restarted just like when you first turn on the key. Since then this has happened 2 or 3 more times.
Same day, getting on the interstate to go to work my check engine light comes on with a hard signal. I read it at work and it came up a 43. Since the engine was under load at the time the code appeared, I'm thinking it's the knock sensor screwing up my timing. Changed sensor, no difference in idle quality. Have since changed the EGR Valve, and Idle Air Motor (TBI). No difference.
Idle is poor on cold engine start, seems to improve a little as engine warms then gets poor as reaches operating temp.
Any other ideas on what's wrong before I give up and take it to the dealer???

Also, it appears that the previous owner had emptied the catalyitc converter. The plug on the bottom looks all bent up and the old engine was smoking through the exhaust pipe. On this new engine, I have 150 miles on it now and am seeing sporadic smoking at an idle. Should chromemoly rings be seated by now, or should I go have a talk with the AutoZone man????

Any help will be appreciated!
Old 03-30-02, 06:44 AM
Visiting Guest
Posts: n/a
Check the Basics on the engine. Run a compression check and change the oil one more time to make sure you flushed out any assembly lube or other problems.

Sounds like it's running rich or has other troubles. Did you change all the tuneup parts when you did the swap?

Additionally, have you checked for alternator output/loose grounds? A bad alternator will cause wacky things to happen to a modern engine.

Another thing to consider if it is temperature related is a bad coolant temperature sensor. It will fool the computer when bad. It's probably the orignal and quite lazy at this point.

What I would do:

1) Check the alternator output. See my post "The Basics"
2) Check the compression versus the spec.
3) Double check for anything missing, loose or bad.
4) Change the O2 sensor and the coolant temperature. Both are maintenance, not failure items.
5) Change the oil one more time.
6) It IS the right engine for the truck, is it not?
7) After doing that, go back to Autozone and talk to them if there is no improvement.
Old 04-08-02, 10:42 PM
Thread Starter
Join Date: Mar 2002
Location: Louisiana
Posts: 416
Upvotes: 0
Received 0 Upvotes on 0 Posts

After many hours under the hood, hitting my head on walls, using questionable language... finally took it to a shop. (Which hurt my pride)

After a week they found out that there was a corroded terminal on the ignition switch which was causing voltage variations to the computer power supply. Nothing to do with the new engine, just happened to act up a the same time. Changed ignition switch, runs like a sewing machine.

I guess we learn something new everyday!

Thread Tools
Search this Thread
Ask a Question
Question Title: