Help!!!427 misfire 2000 - 3000 rpm - Ford Forums - Mustang Forum, Ford Trucks, Ford Focus and Ford Cars

priobe · 12-09-2007, 08:05

Hello all,

I have been trying to figure out a misfire problem or possible misfire. Here is the problem.

When I drive the car and get to 2000 - 3000 rpm I get a ticking sound as if the motor is detonating. I am running weber IDA 48 and never recall hearing this sound ever. I have tried changing the following items

spark plugs
spark plug wires
msd 6al
jetting the carb to run rich
changing advance springs for heavier springs in the distributor
added additional ground leads to motor and MSD

If I ease into the gas very gently I do not hear the noise if I drive normal the noise is there. But as soon I get out of the 2000 -3000 range the noise is gone.

Please help with suggestions

Butchart · 12-10-2007, 18:43

Surprised no one has tried to help. Here's a shot in the dark. Seems like you may have a high voltage leak somewhere, check for cracked dist. cap. Make sure high tension wires are not touching anything. I assume you are running electronic ignition, if not, try replacing the condenser in the distributor. I don't know what this MSD 6al term is. Try running the motor at night under slight load or rev it up a bit and with hood up, see if you can see arcing somewhere around the high tension wires and the dist. cap. Worth a try.

priobe · 12-11-2007, 07:52

butchart,

Thank you for responding. I have replaced the cap, rotor wires, MSD 6 AL, installed a video camer underhood at night to see if there are any voltage leaks, with no luck.

The MSD 6 al is a Multiple Spark Discharge which sends multiple sparks to fully burn the gases in the combustion chamber. Basically it is an amplifier.

I would like to know if the mixture is too rich if this would casue a misfire?

Butchart · 12-11-2007, 17:04

I do know too rich of a mixture can fowl up spark plugs and send out black exhaust out of the tail pipes. Pull a plug and see if its black with carbon deposits, that would eventually cause misfire. What year is the motor from.
Check sparkplug gap, should be 32-36 thou. With that MSD system one would think it would fire with no problem. One more item, got all the sparkpug wires in their correct places on the dist. Its so easy to screw up on that sometimes.

ford4v429 · 12-11-2007, 20:31

I'd suggest richening it up and see if it clears...back in '83 I put a 69 396 BBC in my '81 D150(but I'm a Ford guy really :) and the new 750 holley I had on it would rattle at cruise only- easing up it was ok, but normal driving right about 2500 rpm it would rattle...never did mess with the carb- got horrid mileage, put the original quadrajet back on and quiet as a churchmouse. After swapping the carb I thought jeez- guess it was running way lean at light cruise, luckily the motor wasnt hurt, drove it daily @ 17mpg up till '93 when I bought a new F150...I didnt mess with it, but someone told me rejetting wouldnt help it was the wrong power valve switching from idle to power circuits...I dont know but guess holley has different power valves depending on what kind of vacuum you pull...I had a very mild cam on a fairly big motor so it pulled a very strong vacuum at light throttle, which I was told causes power valve to shut, returning to idle bleed circuits...I dont know, the only carbs ive really messed with are tiny little model heli carbs, and a few quadrajets ive had over the years...

an easier way to check might be to get it up to temperature, when its rattling, to make sure its not humidity/octane/fullmoon whatever related, and back the timing off about 5 degrees to see if it quits rattling- if it does she's runnin lean. the funny thing with mine was it would detonate with cheep gas/too much timing, but it was a totally different sound than the soft rattle at cruise I got- but same cause...if you cant find an ignition issue, might be worth a shot?

cjperformance · 12-14-2007, 02:00

are you using one or more webers? air bleed size in them can cause this problem even when using very large jets. drop your air bleed size and this will make the main jet circuit more responsive. i need to know more info on your set up but webers are real easy to tune and will give masive performance when sized and tuned correctly. can you tell me, cam specs, comp ratio, exhaust system specs, intake manifold type, how many webers, auto or manual, if auto i need convertor stall speed, ram tube length/diameter and type of air cleaners if fitted. thanx.