Hiccups

Dango · 07-19-2013, 12:04 PM

My '94, 5.8, 351 is missing at idle and in drive- particularly at 25-30 and then again at 60mph. It was running fine until I parked it in the sand at Pismo Beach. Did a little 4-wheeling but nothing major.

It's been in the shop for 4-days now and they cannot find the problem. Timing was adjusted, new plugs, plug wires, gas and air filters, etc. They stuck a new fuel pump on and then took it off as that was not the cause. They've had it on the diagnosis machine and eliminated all of the codes that have popped up. It's got a fresh tank with 91 octane. Today they're going to do a compression test on the cylinders and valves but I highly doubt that could be the problem.

Are we missing something here? Looking for any suggestions...

Thanks.

lndshark · 07-19-2013, 12:56 PM

My gut says ignition module or ignition coil. Any vacuum leaks at the intake manifold or throttle body?

Dango · 07-19-2013, 01:23 PM

No vacuum leaks and he's checked the coil. Don't know about the ignition module. I'll call him right now and ask.

Thank you.

Dango · 07-19-2013, 03:24 PM

Yep. Ignition module, throttle body and mass air flow sensor have all been checked as well. I'm still looking for an answer as I have to drive it 2200 miles by next weekend (my mechanic is closed this Sat and Sun).

carringb · 07-19-2013, 10:14 PM

Clean the crankshaft position sensor. Probably has crud on it. Check the wiring while your at it. But speed sensors faulting at certain frequencies is usually metal contamination.