Low rpm, moderate load missing/stumbling

[crazypete]

What is low rpm, medium-high load missing a sign of? The transgo kit engages OD too soon sometimes and I have to pull the car up a hill at 1400 rpms. I'll get this sorta missing sensation, a jumpy intermittent sensation in the power like 1 cylinder is not firing ocassionally but it completely goes away from 1700 rpms on up. It will cruise just fine at low rpm and low load but it cannot take any moderate throttle or it will start missing like that. It completely goes away with rpm every time, usually completely gone by 1700-1800.

Is this my lack of vacuum spark advance? A lean condition? I am running 54 primary jets and no other complaints, good power, no overheating. I run 19 degrees initial but it was doing it back at 10 as well. There is no vacuum advance possible.

Is this spark, fuel or what? The car is a champ otherwise and I'd like to fix this before my FTI cam arrives.

Thanks guys

Pete

 

[crazypete]

Rumpity bump! This is an easy one I think...maybe

 

[powertrax91]

i had a similar problem... it turned out to be a lack of fuel (cloged Filter)...

 

[crazypete]

So it's a lean miss? I thought that 54 primaries seemed a bit on the small side of things. Car ran so good otherwise and I sort of wanted to keep the smaller jets with gas prices the way they are....

 

[90mustangGT]

You say the #1 isn't getting spark occasionally. That needs to be delt with first. Of course check to be sure the spark plugs and wires are good and the plug is gapped properly as well as not fowled. Then I would look towards either a weak coil or the module, and pickup in the distributer. The pickup acts much like a crank sensor, when mine started going out, I had a similar issue.

 

[crazypete]

No it just feels like an occasional misfire but it's at low rpm/high load only. Distributor is quite old but the plugs and ignition is almost new. Wires are older but a crossfire would be continuous and not rpm based.

Anytime this is happening, I can put in the gas and stumble up past 1700 and it clears right out and I can roar out to 4k no problems, smooth as glass.

 

[89CopCoupe]

i had a similar problem... it turned out to be a lack of fuel (cloged Filter)...

... are you running a mechanical pump? ... Maybe the diaphram is weak.

 

[crazypete]

Actually, the mech pump is about 3 years old now so it could be it. I would think the motor would shut off if the FP didnt supply enough gas. The bowls would get sucked dry and the motor would die.

Well, I have the replacement FP sitting in the shop but I didnt want to mess with it till I took the timing cover off to do the cam. Chicken and egg.

....mmm, that made me hungry

I'm gonna try wicked upjetting it this afternoon and go for a spin to see what happens.