Mechanical interference when starting - won't idle for long
Thread Starter
Racer
Joined: May 2003
Posts: 348
Likes: 1
From: Hermosa Beach, CA
LS1 stumbling and backfiring all of a sudden
I've got a weird problem that just developed. The engine was sitting for a couple of weeks from the last time it was running (nothing happened at that time) and when I went to start it turned over and stopped abruptly with a loud clank like it hit something when turning over. I was trying to track down what it was so turned it over again and it started up and ran for a couple of seconds before sputtering out. I tried hitting the throttle to keep it going but that didn't do anything. (Threw code P0654). The combination of these things makes me think the crank position sensor has come loose and is hitting the reluctor wheel but I've never heard of anything like this. Before I go on a wild goose chase, has anyone experienced something like this? Thanks in advance.
Last edited by cresus; Apr 29, 2009 at 09:55 AM.
Melting Slicks
Joined: Jun 2008
Posts: 2,283
Likes: 16
From: Katy Tx
There was a thread on here recently where a head gasket was bad and leaked down while sitting - put water in a cylinder which stopped the motor when cranking (his was so bad it sheared the starter off the block) -- might be worth pulling the plugs and cranking it to see.
Thread Starter
Racer
Joined: May 2003
Posts: 348
Likes: 1
From: Hermosa Beach, CA
Turns out it was backfiring and kicking the engine backwards against the starter that made me think it was hitting something. I got it to run and stay running but it's running so rough. I logged it to see if I could figure out what was going wrong but haven't been able to yet. I forgot to turn off the air pump so it just looks very lean and then very rich. Timing is very erratic. I disconnected the MAF and it seemed to get slightly better but definitely didn't fix the problem. When I try and give it any throttle the engine tries to die but will then roughly accelerate to a higher rpm. Very hard to get to rev though. Lots of stumbling/backfiring involved. Any ideas what could cause this sort of behavior on a stock engine? I put headers on it and it was running fine a few weeks ago but then all of a sudden this happened. P0654 is gone now (I think that may have been related to disconnecting my instrument cluster). No other codes getting thrown.
