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'86 BII XLT 4X4 - stumble


voodoochylde

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A few weeks ago, the truck died on me while waiting in traffic for road work. Finally got it to restart, tried again to drive home, and it died again...and again...and again. Diagnosed as a TFI Ignition Control Module. Replaced with one from Autozone. Truck refused to start after that. Checked for fuel pressure on the rail and came back at 32PSI. Seemed OK so I started chasing spark. Whaddya know? Number 4 and number 6 cylinder - no spark at all.

I went ahead and Seafoamed the intake for good measure. Dad hanged rotor button, distributor cap, spark plug wires, and motorcraft spark plugs (properly gapped to .044") for me as I had no time to put into it. I checked his work and told him I thought he had the spark plug wires out by 180 degrees, he disagreed, and I hadn't messed with it until now.

Got in it yesterday...wouldn't start so I moved the plug wires around and BOOM she starts just like she should! I hopped in to test drive after letting it warm up. Took it to the bottom of the hill, put it in 1st gear, nailed the throttle and was amazed that it actually *did* have power! UNTIL it stumbled on me bigger than heck. For about 1 - 2 solid seconds it acted like it was receiving no fuel at all. I let off the throttle and it eventually came back to normal.

I am now thinking it's the fuel filter. FPR vacuum line has no fuel on the vacuum side but I don't know how old it is. Fuel sending unit does not work so I also somewhat suspect the in-tank pump.

Any other suggestions? I plan on changing the fuel filter beside the starter for now but I am open to checking other things.
 


eclipse2001gt

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When you change the fuel filter watch your fuel pump since you don't know when a filter was changed. Could lead to a weak fuel pump that has been working with a clogged filter.
 

kimcrwbr1

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Keep an eye on the fuel pressure maybe it was just a air bubble in the system. Does it still stumble and how much fuel was in the tank.
 

voodoochylde

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It only had about a third of a tank - determined by the "Thump the tank and listen" method as my gauge does not work. I intend to fill it all the way up next week. Changed the filter, got soaked in gasoline (yes, I am slow LOL) and it absolutely refused to start. Didn't have time to mess with it today.

Got in today, hit the key and she started right up! Fuel level is VERY low right now but it starts and runs when I turn the key. Didn't drive it any as I don't have any gas to put in it.

I intend to replace the FPR next week along with the fill-up. Still smells a bit rich at idle and the idle hunts a bit. It also hesitates if I goose the throttle hard - if I suddenly floor it, it acts like it loses fuel pressure but then begins to climb the tachometer as it should.

I suspect the FPR but it could also be the canister-style fuel filter. Forgot to buy a new one so it's also on my "To Do" list.

Christ I'm tired of not having this thing running. I'm hoping to work the bugs out by winter so I can save some miles on my Impreza!

Thanks for the responses guys!
 

kimcrwbr1

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For the stumble start with the idle air control on the throttle body take it off and clean it and put a new gasket on it if you can find one first is best before you take it apart and clean the air charge temp sensor not sure where it is on your engine but use electrical cleaner not a harsh solvent. if you clean or change a sensor you need to reset the computer disconnect the battery while your cleaning them to set the new values run it for about 20 minutes and see if it settles down. A good tune up if you havent done so for winter is a good idea including plug wires and PCV if you dont know how old they are.
 

Shran

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Check your fuel pressure again with the engine running... should be around 30psi at idle and up to 40 when you open the throttle. If it is not in that range then you probably have a fuel pump or regulator issue. Be sure that both pumps are working too, you have one on the frame and another in the tank. It can run fine sometimes with just the high pressure frame mounted one, but will usually display at least some weird symptoms.
 

voodoochylde

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Rainelle, WV
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1986
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Ford
Engine Size
2.9l
Transmission
Automatic
kimcrwbr1, I already cleaned the IAC with MAF Sensor Cleaner (just because I know it doesn't contain harsh solvents which could damage other sensors). The IAC solenoid's plunger functions smoothly and. I reused the old gasket as it looked brand new. I already did a full tuneup. That includes distributor cap, rotor button, spark plug wires, spark plugs (motorcraft and yes, I checked gap before install), PCV valve, and front fuel filter. The only thing I can think of that I still need to do is oil change w/motorcraft filter, air filter (the old one still looks brand new but I'd like to change it anyway), and the cartridge style fuel filter. Maybe a full tank of gas with 1/3 to 1/2 can of seafoam just to help clean the fuel system up.

Shran, I agree regarding the fuel pressure. I meant to check it but ran out of time/daylight. I'll hit it again next week. Hopefully she'll straighten up as I'd like to have a winter truck!
 

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