miss at idle and under load
Thread Starter
Intermediate
Joined: Nov 2003
Posts: 36
Likes: 0
From: brampton
miss at idle and under load
Hey guys...I have a freshly rebuilt to stock l98...engine has a miss at idle and under load..I can feel a stumble in the engine and also hear it out the tailpipe. Could this be valves to tight...Should I try a compression test to see which cylinder has the over adjusted valve...Thought it might have been the iac but it does this not only at idle..any ideas would be appreciated as its driving me crazy... :chevy
Team Owner
Joined: Mar 2001
Posts: 54,124
Likes: 30
From: Cincinnati, Oh USA
Re: miss at idle and under load (86 silver bullit)
The most likely cause is a plug not firing reliably. First check the plug wires one at a time with an ohmeter, they should measure about 5000 ohms per foot. When it is dark out, start the engine and look for sparks occurring on one or more plug wires. Plug wires get pinholes in them and spark through the pin hole to ground and that plug doesn't fire. Pull the cap and look at the condition inside the cap. It should be dry and no carbon tracks. Look at the rotor and particularly for burn marks in the little well under the center of the rotor, it may have sparked through the rotor causing occassional sparking and thus missing. Look at the condition of the carbon button too.
Thread Starter
Intermediate
Joined: Nov 2003
Posts: 36
Likes: 0
From: brampton
Re: miss at idle and under load (jfb)
Everything is new..wires rotor cap plugs...I am going to pull the plugs to see there conditiond..if everything looks o.k...can it be a tight valve. A few people have told me just to run it as its a fresh motor..it might go away, but this is the second one I have done, but this one the valves were adjusted buy the shop..the other one I did the adjustment on my own and didn,t have this issue..
Team Owner
Joined: Mar 2001
Posts: 54,124
Likes: 30
From: Cincinnati, Oh USA
Re: miss at idle and under load (86 silver bullit)
The last set of new wires installed on my 87 had one go bad the day after installation. A misadjusted lifter would have to be so bad that you would hear loud knocking or it would be backfiring through the MAF. Since you have to remove the plug wire to check the plugs, get your ohmeter out and check the resistance of the plug wires too! Its easier than removing a spark plug!
