Thread: 429 misfire!

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hi guys i have a 69 tbird with a 429 thunderjet engine with c6 trans. ive spent he last few years getting her back on the road - i live over the pond in england so its been a long wait- well i just got her onthe road last week but shes started missfiring but only when idling or very low revs. its ok when im driving but when im stationary or going very slow the car feels lumpy etc. have checked all the plugs,leads, distributer cap and rotary arm etc - theyre ok.

any ideas???

as far as i know it runs on leaded petrol but i have to put unleaded in and then use an additive - could this be why???

checked that - no change!
ive put some fuel system cleaner in with the petrol thinking the carb might be dirty but thats not worked - ive checked for breather pipes etc everything seems normal ........ strange.

put it in drive and hold the brake and give it a little gas .. put the plug wires under a load and see if they break down .. giving you a low speed lugging miss ... look at the motor run at nite in the dark and see if voltage is jumping around

ive had a few mates look at it earlier today and they think its more of a spluttering , i start the car and its fine for a min or two then the revs seem to lower and it seems to want to stall, its also like it when i put it into gear and give it no gas - just letting it creep or if im stood at a junction in drive with the break on - splutter splutter splutter! ive also noticed that it takes a lot more to get the car to start as before when it would fire up straight away it now takes ages!

hmmmmmmmm

Hey Chris. check make sure your vacuum advance is working ok. Check the ends of your plug wires make sure their ok. Good luck. I almost forgot, dirty fuel filter has caused same problems your having.

And if he hasn't found the problem in 6 weeks. Time for a new approach.

Dang, your right nitro. Guess I better smoke another bud.

Check for water in the gas, drain the carburetor float bowls and refill them with fresh fuel through the flow bowl vent tubes and see if it starts easily then.

Check for a clogged fuel filter.

Check the idle mixture screw settings on the carburetor baseplate.

11-30-2007.........

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