misfiring

[ibit]

My 1994 extended cab pickup suddenly started misfiring, sound rough
will not run over 40 mph at best, engine stalls. I put new plugs, fuel filter and injector cleaner in fuel. It is no better. Any suggestions what this might be and what to do? Thanks.

[yobug_e]

Try new plug wires, and check the distributor cap and rotor. If damaged... replace.

[eduardo]

hey ibit, you could possibly have a bad intake manifold gasket! do you hear an excessive amount of hissing when you're standing over the idling engine? another highly possible problem could be a broken down ignition coil! with a bad manifold gasket the engine will run like crap right when you start it but with a bad coil it usually runs fine for a while and when you start going down the road your engine will start jerkin & spittin & sputterin until it ultimatly dies! but if you let it sit and cool for about 15 mins it'll start right back up and do the same thing all over again! a bad calyllitic converter also behaves almost exactly like a bad coil but when your engine dies if you get out and look at the converter it'll look, sound & smell like it's about to melt down! a bad coil will also feel alot hotter than normal. i'm not too sure how your fuel pump is rigged? being a '94 i'm sure it's electric. if it's anything like a ford it may have a high pressure pump on the frame rail and then a low pressure one in the tank. if the high pressure pump was bad i doubt the truck would even start but it would start if only the low pressure was bad and it would run like crap! it could also be a fouled oxygen sensor! injector cleaner is uaually pretty useless so i guess worst case scinario might be bad injectors altogether!? i should mention that the bad intake manifold gasket is definatly the most unlikely! good luck!

[eduardo]

ibit, if it turns out to be the catyllitic converter if at all possible try and remove it and just beat out the honey comb material inside so it all just breaks up and falls out! then just reinstall it as a straight pipe. converters only reduce your vehicles performance and they're extremely expensive to get replaced especially in areas where emissions testing is mandatory! but then again if you do live in an area where testing is done then you might not have much choice other than getting it replaced. good luck!