Advice needed on rough running engine episode

dcdoug · #1 (**permalink**) 08-31-2012, 11:41 AM

Engine - 427FE, Holley 3255-1, ignition coil (no box)

Last night within a mile of leaving work, before the engine was really even hot, my engine started running rough, wouldn't hold a good idle, backfiring on deceleration, etc. (It ran fine on the way to work) Since I was in traffic, I didn't find out if it would idle without dying since I was worried about being able to restart it so I kept the revs up when stopped. Ran better above 3,000 RPM, but still felt like it was misfiring. After driving for about 30 minutes, the problem totally went away and stayed away for the last 10 minutes of the drive.

I don't think the engine was hot enough to suffer from percolation (which does happen to me at times) since it started so early in my drive.

What do you think? Did some little piece of junk get into an air bleed, get hung up on a needle valve? Coil going bad? (seems unlikely since it ran fine later when engine was hot)

Other thoughts of things to look at if it happens again?

jhv48 · #2 (**permalink**) 08-31-2012, 12:34 PM

Perhaps a drop or two of water worked it's way through your carb, or a piece of dirt momentarily plugged a jet. If it runs fine now, cross your fingers and keep on driving.

patrickt · #3 (**permalink**) 08-31-2012, 01:17 PM

It's either dirt in the carb or an intermittent electrical problem. The fact that it ran OK at upper RPMs tells me it's probably just dirt.

Dwight · #4 (**permalink**) 08-31-2012, 01:40 PM

Pour a can of Sea Foam into the gas tank.

Dwight

JLip · #5 (**permalink**) 08-31-2012, 07:21 PM

Mine was doing the same thing with only 3000 miles on the engine. My buddy came over and said because of the MSD throwing so much spark it was probably the distributor cap and rotor. I wouldn't of believed it until he pulled the cap. DAMN!! There was quite a bit of built up on the contacts. He hit it with a little sand paper and it ran like a top. I replaced the cap and rotor and cant believe the difference. Hmmmm......... He told me that he replaces his every season along with the oil.

dcdoug · #6 (**permalink**) 08-31-2012, 08:45 PM

I was due to replace cap and rotor, so I did, but after inspection, I doubt that's what it was. I'll test it tomorrow as I go to cars and coffee.

patrickt · #7 (**permalink**) 09-01-2012, 07:59 AM

Quote:

Originally Posted by dcdoug

I was due to replace cap and rotor, so I did, but after inspection, I doubt that's what it was. I'll test it tomorrow as I go to cars and coffee.

Make sure your distributor weights are not sticking in that old POS distributor... then as it heats up good, they unstick. Now, if you only had a little remote camera that could wirelessly let you watch your weights from within your car, as you drove it, you could monitor the whole process while you zoomed on down the road. Then, if it misbehaved, you could look down at the monitor and see where the weights were. Yeah, that's the ticket....

You could even watch the monitor with one eye while you nailed it to WOT on the Beltway, with the other eye on the road making sure you stay in your lane.

davecobra · #8 (**permalink**) 09-01-2012, 08:54 AM

It could be a little ethanol buildup in the airbleeds of the carb, take a little carb cleaner and shoot down the air bleeds on the primarys and secondarys, then drive it. I have seen this fix more rough running engines than anything else.
David

razerwire · #9 (**permalink**) 09-01-2012, 10:02 AM

I thought my transmission was going out because at idle a lot of noise was coming from it. Car has a Tex Racing 4 speed with straight cut gears. The engine was also running real rough. Car has 42 gal fuel cell with foam and a rubber bladder inside and I have been afraid to add sea foam or stabil to gas as I would refill the tank. Some of the gas could have been 6 years old so I drained the tank and filled with 91 octane. Engine now runs better at idle ,900 rpm, and noise is gone coming from transmission. More gas problems to come because of junk gas.

dcdoug · #10 (**permalink**) 09-01-2012, 10:52 AM

Quote:

Originally Posted by patrickt

Make sure your distributor weights are not sticking in that old POS distributor...

Uh, that would be vintage.

I rebuilt the distributor a year ago and am pretty sure it's fine (advance weights were sticking before I did though).

dcdoug · #11 (**permalink**) 09-01-2012, 11:01 AM

As it turns out, I am down to about a 1/8-1/4 tank (I rarely let it get that low given the inaccuracy of the fuel level gauge) and I think it just sucked up a bit of crap from the bottom of the tank which temporarily fouled the carb. Ran great this AM, which isn't surprising given it ran fine at the end of my drive home on Thurs. So I guess all is good for now. Thanks for the suggestions!

I may put some Seafoam in when I refill for good measure.