Engine Running Rough

[likearock78]

Hey guys, quick question. I had a 1981 GMC half ton with the 350 4bbl, I removed the engine (ran excellent) and put it into a 1978 Malibu. Went to start it and it runs, but really rough and backfires. I didn't remove the distributor or anything like that. Just dropped it in and flashed it up. Any suggestions?

[txab]

Perhaps the distributor got moved. Did you remove any plug wires? If so check for proper firing order.

[likearock78]

Yeah we tried moving it around till it ran better but no help and the wires are all on right.

[grampadirt]

If you haven't already I'd remove the dist. cap and make sure all's well in there.Make sure the rotor is OK and look for any debris that may have come loose when pulling/installing the engine.Also look for any cracked/broken wires to eliminate any arcing.Run the engine at night,easier to see any arcing anywhere...maybe,just by coincidence the ignition module took a sh*t at that same moment

[likearock78]

All is good under the cap. Ill check for broken wires, I know some were melted but I taped them up and fixed them good but doesn't hurt to double check. How do I test the ignition module?

[grampadirt]

All is good under the cap. Ill check for broken wires, I know some were melted but I taped them up and fixed them good but doesn't hurt to double check. How do I test the ignition module?[/quote]

 

 

My Haynes manual says ''special equipment'' is needed to do that.It also says to remove and take it to an auto parts store or dealer service dept. to have it checked.That seems like a PITA but what else is there to check? Plugs,OK.Wires OK.Cap OK.Rotor OK.Firing order OK.Timing OK. There isn't much else.If it backfires it's gotta be electrical...it just sounds like firing order or timing.?

[likearock78]

OK hmm plugs and wires are all on right. I can double check the timing again. What part do I remove and have to take in?

[grampadirt]

OK hmm plugs and wires are all on right. I can double check the timing again. What part do I remove and have to take in?

 

 

The ignition module.It's the rectangular looking thing in the lower right cornes with the numbers on it...

[likearock78]

Oh right OK. I'll look into that. I'm thinking maybe the timing chain jumped somehow maybe also could cause that?

[grampadirt]

It's possible,but stretching is more likely.But that would occur over time,not quickly.I think you should do a compression check.That will tell alot about the engine

 

edit:is there any way you could take a little vid of the thing running? Even a decent P&S camera can do OK vids

[likearock78]

Hmm ya not sure. I could try to get a video yes.

 

edit:is there any way you could take a little vid of the thing running? Even a decent P&S camera can do OK vids

 

[2007VictoryRed]

BackFire means your Off Time. Do You Have a Timing light? If So Take the #1 Spark Pulg Off, Remove The Distributor Cap But keep all the spark plug wires In tack and lay the cap off to the side. (That will lose the spark to the engine so it will not start on you) Get a 1 Inch shocket (I belive) and a ratchet and turn the engine by hand, Untill top dead center on pistion number 1, for Checking for top dead center get a flat blade screw driver and put it in the spark plug hole and fill around for the pistion is at its top. Then remove the distributor get a Long flat blade screw driver and Put it in the hole were the distributor sits and turn the gear in side of the engine that is conntected to the cam shaft, Then Put the distributorp back in and check to see if the rotor points to pistions #1 spark plug wire on the distributor cap, take the distributor out agine untill its right. Put everything back togther After everything is right there. Find out whats the proper timing for that engine. Start the engine, losen the distributor hold down bolt, Not to much but enough to move the distributor. then Plug The vaccum (spelling) advance, With a flat blade screw driver. The vaccum advance is the silver looking thing looks like a cone thats on the the side of the distributor, there should be a rubber hose that gose int he the carberator remove the side that gose into the carberator, Plug with the screw driver. get the timing light and point it on the harmonic blancer. Move the timing by moving the distributor. move it untill is right. Put all back and the adj. the jets on the carb. Should fix problem.

[grampadirt]

If you do this be sure it's on #1 compression stroke....

[likearock78]

OK I will try all of this. Might take me a bit, but please keep checking back and I will keep you guys updated on whats happening. Thanks for the help too.

[grampadirt]

 

,just for sh*ts & giggles dbl. check the firing order