missfire at idle on new engine

whats my problem iam lost

More info is needed. What motor?? what are the specifics?? what kind of ignition?? what cam, compression, carb??

Does it have a good dedicated engine-to-chassis ground wire/strap?

q uote="BBFTorino"]More info is needed. What motor?? what are the specifics?? what kind of ignition?? what cam, compression, carb??[/quote motor 637 ford msd dis and a 7al2 box lunati solid lifter compression is 13.5 carb is 1050 pro systems

DILLIGASDAVE wrote:Does it have a good dedicated engine-to-chassis ground wire/strap?

yes it has three grounds

Did you check the "rotor phasing"?

Check pickup /crank trigger wiring polarity. Also check the trigger magnet polarity at the crank trigger wheel. One or more may be installed  incorrectly from the factory.

FErocious68XL wrote:Check pickup /crank trigger wiring polarity. Also check the trigger magnet polarity at the crank trigger wheel. One or more may be installed  incorrectly from the factory.

does not have a crank trigger

Check pickup trigger wire polarity.

Always the same cylinder that misfires? If so, swap that wire with another cylinder and see iff the misfire goes with the wire. If not, swap plugs and check again. Also look for clean terminals inside the dist. cap ...and any signs of dirt, scratches, etc., in the cap.

maverick wrote:Always the same cylinder that misfires? If so, swap that wire with another cylinder and see iff the misfire goes with the wire. If not, swap plugs and check again. Also look for clean terminals inside the dist. cap ...and any signs of dirt, scratches, etc., in the cap.

new cap roter andwires and plugs

Compression test??
Re-check valve lash??
Have the MSD box re-checked.

tzford wrote:

maverick wrote:Always the same cylinder that misfires? If so, swap that wire with another cylinder and see iff the misfire goes with the wire. If not, swap plugs and check again. Also look for clean terminals inside the dist. cap ...and any signs of dirt, scratches, etc., in the cap.

new cap roter andwires and plugs

I didn't ask how old they are. I was merely suggesting that a FREE and SIMPLE TEST might RULE THEM OUT as a possible source of you aggrivation.

Lord knows, none of us has ever found a new part to be defective. Carry on.

BBFTorino wrote:Compression test??
Re-check valve lash??
Have the MSD box re-checked.

msd box checked twice by msd ben over valve lash 5 times ;compression test fine

Plug wires run to close to each other. 7&8.the problem. Most of the time

Check your firing order again to make sure you don't have 2 wires crossed. It happens.

cletus66 wrote:Check your firing order again to make sure you don't have 2 wires crossed.  It happens.  

checked fireing order a number of times

IF the miss is only at idle, and...
IF the miss is always the same cylinder, and...
IF all electrical components for that cylinder are working properly, (not just assumed because they're new) and...
IF the spark plug is not contaminated with oil, then...
...chech for a vacuum leak somewhere along that intake runner, anywhere from carb base to the flange at the cylinder head.

If the plug shows oil contamination, look for a leak under the manifold (from lifter valley into the intake port).

Personally, I'd use one of those cheap spark testers plugged into the spark plug wire to test while running. If the running spark is good, proceed with above.