Help: 90 Fox Weird Hiccup (misfire?)


New Member
Apr 24, 2017
hey all, here's issue at hand and can't figure out, car is a 1990 302 gt40 iron head get 40 intake, got 24lbs injectors and massair, Car has a gremlin, at times will start up fine no problems, other times you start it and it dances around the idle dropping from 400-1200 rpm, here's my big issue, come into 3rd gear and put my foot into the things ass and it's a rocket, after the top of pull I throw into higher gear and " cruise" then intermittently will either run fine or developed this "misfire / stumble / I have no idea ,sometimes even here like a pop noise " it has like 1/4 of the power it usually does until I put my foot in the things ass again and it will clear up, then you can just be driving normal and no rhyme or reason it will start doing it again until you matte the gas pedal to clear it up, I'm lost, I did. Cap rotar wires plugs (yes there gapped) o2 sensors brand new mass air n injectors someone hopefully will have answer or similar problem that they have fixed,currently I scanned car with the snap on brick scanner and codes were 44,32,33, There is no longer a smog pump or canister, the heads were blocked off and doesn't sound like there are any vacuume leaks, timing is at 12 deg , sounds electrical to me only because when you fully floor it prob goes away. Then again I'm unsure and Any help would be greatly appreciated Thank you all
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Wasn't a pretty sight...and I've got big hands
SN Certified Technician
Mar 2, 2015
Have you tried cleaning and tightening up the pins in the salt and pepper shakers at the back of the intake ?

Check the distributor pick should be tight ( it shouldn't wiggle ) its below the rotor button and reads the gaps in the metal piece below the rotor button. It also shouldn't look powdered....or soft.

A weak bad ignition coil can also cause similar issues...but usually result in car cutting off or not starting until cooling down.

I hate to tell you this....but it could be a lot of things. Check vacuum with a vacuum gauge....check spark with a spark tester.

These cars have also been known to develop vacuum leaks into the lifter valley under the intake. If an intake gasket has slipped you won't be able to tell without pulling the intake.

Do you have catalytic converters ? When was the last time you replaced the fuel filter ?

I'd start with the salt and pepper shakers...been there...done that. Report back with what you find out. Wish I could pin point it for you.