missfire at idle on new engine

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missfire at idle on new engine

Post  tzford on January 6th 2017, 5:51 pm

whats my problem iam lost

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Re: missfire at idle on new engine

Post  BBFTorino on January 7th 2017, 12:18 am

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

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Re: missfire at idle on new engine

Post  DILLIGASDAVE on January 7th 2017, 3:08 am

Does it have a good dedicated engine-to-chassis ground wire/strap?
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Re: missfire at idle on new engine

Post  tzford on January 7th 2017, 10:01 am

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

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Re: missfire at idle on new engine

Post  tzford on January 7th 2017, 10:02 am

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

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Re: missfire at idle on new engine

Post  FalconEh on January 7th 2017, 2:09 pm

Did you check the "rotor phasing"?
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Re: missfire at idle on new engine

Post  FErocious68XL on January 7th 2017, 2:59 pm

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.

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Re: missfire at idle on new engine

Post  tzford on January 7th 2017, 3:09 pm

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

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Re: missfire at idle on new engine

Post  FErocious68XL on January 7th 2017, 3:18 pm

Check pickup trigger wire polarity.

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Re: missfire at idle on new engine

Post  maverick on January 7th 2017, 7:09 pm

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.
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Re: missfire at idle on new engine

Post  tzford on January 7th 2017, 9:49 pm

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

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Re: missfire at idle on new engine

Post  BBFTorino on January 7th 2017, 9:56 pm

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

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Re: missfire at idle on new engine

Post  maverick on January 7th 2017, 10:02 pm

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. Rolling Eyes
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Re: missfire at idle on new engine

Post  tzford on January 7th 2017, 10:18 pm

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

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Re: missfire at idle on new engine

Post  DanH on January 7th 2017, 11:07 pm

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

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Re: missfire at idle on new engine

Post  cletus66 on January 8th 2017, 1:06 pm

Check your firing order again to make sure you don't have 2 wires crossed. It happens.
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Re: missfire at idle on new engine

Post  tzford on January 8th 2017, 2:13 pm

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

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Re: missfire at idle on new engine

Post  maverick on January 8th 2017, 2:34 pm

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.
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