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Author Topic: truck missing  (Read 5003 times)

Offline tarheelboy

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Re: truck missing
« Reply #15 on: December 06, 2013, 08:50:53 pm »
I'm still thinking it's more likely a fuel issue.  Fuel issues are very prone to showing up based on load/demand.  Spark issues are generally very easy to spot at specific revs regardless of load.  But, doesn't hurt to cover all the bases while diagnosing, did you replace the cap and rotor along with those wires and plugs?

Yep...hook up a pressure gauge to the fuel point under the hood and drive around. See if the pressure drops off. How I found my problem.
may be a dumb question but if the pressure gauge is under the hood how will I see it while I drive around?
LOL...true...get long enough rubber hose so you can see gauge while driving.
Well yea...that makes sense. I probably should have thought of that.
So if I hook up a pressure gauge and give it gas, if the pressure drops I should look at the fuel system?
'89 W100
318
3 inch lift

Offline Smitty

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Re: truck missing
« Reply #16 on: December 06, 2013, 09:05:28 pm »
If I remember correctly, you should see a certain amount of fuel pressure. If it drops below the minimum pressure you have a bad pump. I had a Bronco II years ago. Under acceleration it would bog/miss etc. Mechanic hooked up a gauge on the fuel rail and did a test drive. Saw low pressure at the rail. Replaced the pump...all fixed. Could also check fuel filter...clogged up? 
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Offline tarheelboy

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Re: truck missing
« Reply #17 on: December 06, 2013, 09:09:46 pm »
My first thought was the fuel filter but my experience is with clogged filters the vehicle would miss most all the time. What confuses me with the issue I am having is it only misses upon initial acceleration unless I give very light gas(to the point of people honking cuz I am going so slow) once it gets going I can stand on the pedal if I want to and it doesn't miss at all.
'89 W100
318
3 inch lift

Offline Jims1dodge

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Re: truck missing
« Reply #18 on: December 07, 2013, 01:09:00 am »
What about timing.  It may not be advancing initially and then catches.  On the real old vacuum advance distributors when that line leaked it acted this way. 
Just a thought
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Offline noplugs

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Re: truck missing
« Reply #19 on: December 07, 2013, 01:12:55 am »
Ok, I had an issue with my Focus but maybe this will help.
It had sputtering acceleration unless I really floored it and it would run rough during wet weather.
Turns out that the ignition coil maintains ground through the mounting screws. When i took to coil off I discovered that two of the three mounts were broken and not making good ground contact. Replaced it with a new coil and it runs like a top now.
Might want to check any mount points and ensure everything is grounded real well.
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Offline tarheelboy

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Re: truck missing
« Reply #20 on: December 07, 2013, 06:32:30 pm »
I am checking everything at this point. I ran it yesterday and removed one plug wire at a time and each one roughened the idle so no dead cylinder. I removed each plug and looked at the electrode. Normal gray/brown deposits so no fouling. One of the plugs had wet oil on the threads and I noticed that the valve cover was leaking oil directly above that plug. I am assuming the oil wouldn't get past the threads and cause any problems but am going to change the gasket anyway. Moving on to vac hoses now. How do you check a hose for a vac leak? If I put a finger on one end ant it has suction would that eliminate that hose as leaking?
'89 W100
318
3 inch lift

Offline tarheelboy

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Re: truck missing
« Reply #21 on: December 07, 2013, 06:59:40 pm »
I just read something interesting while pricing fuel pumps. (just in case) Has anyone had issues or heard of low fuel hesitation? My truck never ever has more than 1/4 of a tank of gas in it. I googled low fuel hesitation and found some posts from people describing the exact symptoms I have been experiencing. Any thoughts on that?
'89 W100
318
3 inch lift

Offline Buford445

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Re: truck missing
« Reply #22 on: December 07, 2013, 10:05:18 pm »
Fill it updrive it and see if it helps  :whistling:


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Offline Tom Courtright

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Re: truck missing
« Reply #23 on: December 08, 2013, 04:04:19 pm »
When the fuel gets low like that any dirt in the tank can congregate on the filter,... and you lose lubrication in the pump itself because it uses the fuel itself to stay lubed and cool

it aint low till it scars asphalt

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Offline tarheelboy

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Re: truck missing
« Reply #24 on: December 15, 2013, 08:03:32 pm »
Ok so I could not find any obvious vacuum hoses leaking. I sprayed carb cleaner at the junction where the intake manifold marries up to the engine. No change in idle. I also sprayed the junction where the throttle body? marries up to the intake manifold and the idle dropped. Is this normal or a problem?
'89 W100
318
3 inch lift

Offline tarheelboy

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Re: truck missing
« Reply #25 on: January 14, 2014, 07:32:53 pm »
Well, took off the throttle body and there was no gasket left. Changed it and the fuel filter. The fuel that dumped out of the filter was black so I figure my fuel hoses are breaking down. Also my hard fuel lies are leaking everywhere now that I changed the filter. Everywhere there is a clamp...rusted through. I must have shifted things while banging around under there. So now I am going to run all new fuel hose and see what happens.
'89 W100
318
3 inch lift

Offline tarheelboy

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Re: truck missing
« Reply #26 on: March 10, 2014, 03:24:19 pm »
Well I am still having issues with the hesitation/missing issue. Just to recap symptoms and repairs so far:

Hesitates under normal acceleration
Extremely light acceleration it is fine. I can accelerate as hard as I want to once she gets moving.
During idle, in park, engine begins to idle rough after about 15 minutes. Idle gets worse and worse until the truck cuts off and a plume of white smoke shoots from the throttle body.
Hesitates and backfires when heavy gas applied while in park. Truck will cut off when this happens.

things I have fixed:

plugs and wires, ran great for 2 months. then...
new fuel filter
replaced bad throttle body gasket

I feel like I have eliminated a spark issue. Fuel and air are about all that is left. Does it still sound like a fuel delivery issue? I haven't checked the fuel pressure. I don't have a gauge and I don't know how. Going to try that next. Any other suggestions would be great.
Thanks.
'89 W100
318
3 inch lift

 

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