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Sixlitre 02-01-2001 08:01 PM

W.O.T. hesitation & stumbling
My 86 EFI 302

has developed an off the line stumble or hesitation. It only happens when you nail it from a standstill. If you take off lightly or even medium pedal, it's fine.

I'm running the same 89 octane ethanol (5-10%) I've always run. The tank is two years old. Today I stuck two bottles of Wynns injector cleaner in it, so I'll see what happens over the next few days.

It's a new longblock with only 8,000 miles on it, mind you I haven't changed the plugs since it was new two years ago.

Any ideas ? I was thinking either plugs or filthy injectors. Tell me it's something simple and cheap. Where are the fuel filters on an 86 EFI 302 ?

Any ideas appreciated


Steve83 02-01-2001 08:12 PM

Re: W.O.T. hesitation & stumbling
Sounds just like my plugs that had burned to a .14 gap, except my stumble was strictly between 1400 & 2100 RPM.

I would expect the filter to be in the frame rail under the driver's footwell. ???

83 Custom w/95 4.9L EFI, 78 NP435, 83 NP208, 83 D44IFS 3.07, 87 Ford 8.8ABS 3.08, Michelin LTX AT 31x10.50R15

muddybronco 02-01-2001 09:15 PM

Re: W.O.T. hesitation & stumbling
Man, I'd be afraid to floor it off the line in my truck. I know something would give, and it wouldn't be the bronco! .14 gap? that's pretty bad.'s a Jeep thing? My Bronco thing will run over your little Jeep thing.


Sixlitre 02-02-2001 10:57 PM

Re: W.O.T. hesitation & stumbling
The truck seems a little better today, though I didn't nail it completely off the line. I waited until it was in second gear and mashed it at about 15mpg and up. That didn't seem to phase it.

I was in Canadian Tire today and looked at the gas filter. It must fit inside a sealed housing right ? How do you relieve the fuel pressure and will the fuel pump re-prime the EFI ?


Steve83 02-02-2001 11:52 PM

Re: W.O.T. hesitation & stumbling
I'm not sure what your filter looks like, but I expect it's in a metal casing with a pencil-sized nipple at each end where the fuel lines attach. The whole case is replaced - not just the filter element, like on some carbs. To relieve the pressure, either trip the inertia switch (I'm not sure where it is on your truck, but look in front of the brake pedal) and crank the engine. It will stall when the pressure is drained. Alternatively, you could open the Schrader valve (like a tire valve) on the fuel rail - fuel will spray for a second, so be prepared. Yes, the pump will repressurize the lines, filter, and rail (after the inertia switch is reset) when you turn the ignition on.

83 Custom w/95 4.9L EFI, 78 NP435, 83 NP208, 83 D44IFS 3.07, 87 Ford 8.8ABS 3.08, Michelin LTX AT 31x10.50R15

Sixlitre 02-03-2001 06:10 PM

Re: W.O.T. hesitation & stumbling

Thanks for all the info. Truth is that it's been either too cold or too wet (melting under Bronco) for this weenie to crawl under and look at the fuel filter housing, though I did buy a filter today.

The other reason is the hesitation and stumbling "seems" to have disappeared (touch simulated dash wood). Either the two bottles of Wynns injector cleaner has worked it's magic, or the colder, dryer weather today took away the conditions that caused it. I was able to nail it from a standstill today and it got up and went with no hesitation.

Still, come the warmer weather I intend to treat it to new plugs and maybe an MSD stock style coil. I have a Jacobs extra thick cap and rotor on the Mopar and that made a world of difference, but with the wider terminal spacing on Fords, maybe it's not so critical.

Gotta fix the cruise too and then get the A/C recharged too. Maybe take a cruise into the states where they can recharge it a lot cheaper. I lost the charge when we stuck the new long block in two years ago in the Arctic, didn't miss it there.

Thanks again


**DONOTDELETE** 02-09-2001 08:45 AM

Re: W.O.T. hesitation & stumbling
Have you ever thought of converting your AC to 134a? I converted mine last summer in about 30 minutes. They sell convert kits these days for under $40, you can pick them up at wal-mart or places like that. You do not have to break open the system to do the convert. All you have to do is pump down your system and add the 134a oil and coolant. The oil is supposed to coat the seals so they are compatible with 134a. Not quite as cool as R-12 but 143a is about 3 dollars a can compared to 35-40 for R-12. So far my AC is still working good right now. I have not heard of any bad long term effects from this convert yet.

**DONOTDELETE** 02-09-2001 08:49 AM

Re: W.O.T. hesitation & stumbling
I havent heard of any long term effects either, but I don't think it gets near as cold as normal freon does. My freind Steve who does the conversion all the time says that if you put in the perfect amount, it does though. You just supposedly have to put in the perfect amount or it's gonna be warmer.

Steve83 02-09-2001 12:40 PM

Re: R-134a
Those cheapo conversions are not the right way to do it - that's why they don't get as cold. R-134a causes the mineral oil used with R-12 to congeal. The right way is to completely open the system, pour "flush" into all the parts, blow everything out with compressed air, pour PAG (PolyAlkaline Glycol) oil into the compressor, install a red capillary tube (it's sized to work with R-134a), replace the O-rings (~89 & earlier), put it all back together with a new accumulator/drier, pull a vacuum, do a leakup test, then charge it with R-134a to 23psi on the low side. It's also recommended to add a high pressure cutoff switch in the clutch circuit set to 475psi into the high side, but they're expensive. If you have access to an air compressor and gauges, and your own evacuator ($15 at Harbor Freight) to pull the vacuum, the whole thing only costs about $50-75.

83 Custom w/95 4.9L EFI, 78 NP435, 83 NP208, 83 D44IFS 3.07, 87 Ford 8.8ABS 3.08, Michelin LTX AT 31x10.50R15

Sixlitre 02-09-2001 07:28 PM

Re: R-134a
Thanks for the good A/C advice guys. I think I'll price both jobs by phone to places across the border and then drive down and get someone to do one of those procedures for me.

Years ago I used to change the seals and work on the Sanden units on my old big block and small block Mopars asn it was a piece of cake. That was when Canadians were "allowed" to do the work themselves and we could still buy those small freon cans to charge it up ourselves.

I don't think I want to be declaring any of the A/C equipment crossing the border, I'd rather have someone down there do it and "wash my hands" of being caught working on it.

But again, thanks for the advice


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