Engine stuttering under load...
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From: Pasadena USA
Engine stuttering under load...
I have 93 F150 w/ speed density 302. It idles well and revs without 'missing'. Put the same motor under load and it stutters and is very low on power.
I have changed the plugs, wires, cap/rotor. I have also changed the fuel filter and Oxygen sensor. It shown no codes in KOEO or KOER mode.
It has 110K miles. I am thinking it may be the following, hall effect sensor in dist, ignition coil(?), TPS or EGR. Prior to this it would buck or stutter sometime when accelerating to pass. Part throttle acceleration especially problematic; if you kicked it down it would accelerate normally.
I will be checking the TPS & EGR function tomorrow, along with timing and a compression check (I'm getting desperate).
Any help would be appreciated.
Michael Means
I have changed the plugs, wires, cap/rotor. I have also changed the fuel filter and Oxygen sensor. It shown no codes in KOEO or KOER mode.
It has 110K miles. I am thinking it may be the following, hall effect sensor in dist, ignition coil(?), TPS or EGR. Prior to this it would buck or stutter sometime when accelerating to pass. Part throttle acceleration especially problematic; if you kicked it down it would accelerate normally.
I will be checking the TPS & EGR function tomorrow, along with timing and a compression check (I'm getting desperate).
Any help would be appreciated.
Michael Means
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Engine stuttering under load...
Yes i have the exact same problem with my 94 F-150 speed desity. its driving me nut, i cant figure out whats wrong with in. When you floor it, its fine, same as revving it, but 1500-2200rpm at gradual acceleration, it bucks and studders like crazy. If you find out whats wrong with your truck, let me know.
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Engine stuttering under load...
I have a 92 F150 with a 302 that was doing the same. I had everything new on the ignition but it still did it. I was messing around one day and was looking at the firing order, 8 fires right after 7 and they are tight next to each other. I split the wires up making sure 7 and 8 were far away ftom each other, that was all it was. 7 was too close to 8 causing a pre-ignition in 8, the knock sensor picked up a spark knock and retarded the timing causing my truck to fall flat on it's face. One other time it was acting similar it was the upper intake gasket, the one that goes between the intake manifold an the intake plenum. It would be fine until I put my foot in it, then it would start missing.
Hope this helps you, good luck.
Hope this helps you, good luck.
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From: Pasadena USA
Engine stuttering under load...
Ok, I will try seperating the 7&8 wires. I will also do a test on the uppper plenum for leaks. I will let you know how it went, probably Monday. My backup car, my 85 Capri RS decided to grenade the pinion gear. What a mess it broke the bearing retainer cap and the pinion nut sheared off in its threads. Looks like I'll be putting a whole rear end in the Capri. Hopefully I can get the truck to act right so I can get to the junkyard easier.
I will be running a compression check in the truck today as well. Will report back later or Monday.
Thanks Again,
Michael Means
I will be running a compression check in the truck today as well. Will report back later or Monday.
Thanks Again,
Michael Means
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From: MONTANA
Engine stuttering under load...
Just a thought.... Check the spark plugs. Make sure you have the correct plug part number for your engine/year. I had a guy switch out mine with new durring a tune up. The truck ran like crap after the tune up, took the guy 4 days to realize he grabed the wrong plugs from the shelf.... The truck idled fine but then under load, the engine would cut out.... Hope this helps.
Larry
1990 F-250 4x4 351 E4OD K&N etc.
Larry
1990 F-250 4x4 351 E4OD K&N etc.
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From: Pasadena USA
Engine stuttering under load...
[updated:LAST EDITED ON 25-Nov-01 AT 04:32 PM (EST)]My compression check showed 190 dry in all cylinders except #8. It had 60 dry and wet. I pulled the valve cover and did not find a broken spring loose rocker or any noticable defect except the exhaust spring did not seem to compress squarely. I guess I will have to pull the head and see if there is a burnt exhaust valve seat. I did notice some blowby exhaust gas in the valve cover vent tube that runs to the air intake box.
Maybe replacing the seals on intake and exhaust valve would be easier than pulling the head? And can I run a comprssion check in the one cylinder by just pulling its plug or do I have to do all?
Thanks Again,
Michael Means
Maybe replacing the seals on intake and exhaust valve would be easier than pulling the head? And can I run a comprssion check in the one cylinder by just pulling its plug or do I have to do all?
Thanks Again,
Michael Means
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Engine stuttering under load...
Did you try a bit of oil in the #8 cylinder and test again? I have heard that the #8 can start acting up because of the way the pcv valve is plumbed into the plenum. It goes in right at the back of the plenum in line with the #8 intake runner. I had an itermittent miss that I cured by re-routing that PCV line to the vacuum tree in the middle if the plenum. I read somewhere in this forum that the air and gasses from the PCV can screw up the #8 rings and even the piston! A lean problem maybe? A bit of a design fault for sure but one that is easily fixed if caught in time. I had 28000km on my 5.0 when I altered mine and have had no problems since.
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From: Pasadena USA
Engine stuttering under load...
Yup, I tried the oil in the cylinder, cycled a couple of revolutions then put the checker on. Stayed at 60 in the cylinder. This is the first I have heard of the #8 going lean, but I have experienced some light pinging under load. This weekend coming up I will pull the head and see what I have. I'm praying for a toasted head gasket, but the way my luck is running it will be a holed piston or broken ring/land.
My backup car 85 RS Capri decided to grenade its ring gear, one axle bearing cap and the pinion shaft bolt snapped in half when I went to remove it. Luckily my wife has been so kind as to let me user her 93 Mustang GT to get to work; she's sort of a kept woman
.
It keeps getting better...
Michael Means
And I will move that EGR vacuum source to the manifold tree.
My backup car 85 RS Capri decided to grenade its ring gear, one axle bearing cap and the pinion shaft bolt snapped in half when I went to remove it. Luckily my wife has been so kind as to let me user her 93 Mustang GT to get to work; she's sort of a kept woman
.It keeps getting better...
Michael Means
And I will move that EGR vacuum source to the manifold tree.
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From: Pasadena USA
Engine stuttering under load...
Here is an update on my truck's 5.0. I did a compression test last week and all cylinders showed 190 except #8 which showed 60 dry and 60 wet.
I pulled the head and saw no scoring in the cylinder, no cracks that I could see. The piston was not holed or no broken top ring land.
The valves in that cylinder looked just like the others. I could see no evidence of improper seating. I will break the valves and springs down tomorrow to make sure.
I did find the fire ring on the head gasked to be seperated on the lower portion near the alignment dowel. The bolt there goes through the water jacket and there is a water passage very close. The antifreeze that I drained had a darkish color to it. It did not look rusty, but almost like it had been colored by exhaust. I could not smell any fuel or exhaust in it but the truck has sat for three weeks now. I did run it last week to operating temp prior to the comression test.
So, I guess my question is, could this firering and head gasket material seperation be the source of my low compression if the valves and thier seats check out fine?
Oh, and can the upper to lower intake gasket be reused if it came off clean?
Michael Means
I pulled the head and saw no scoring in the cylinder, no cracks that I could see. The piston was not holed or no broken top ring land.
The valves in that cylinder looked just like the others. I could see no evidence of improper seating. I will break the valves and springs down tomorrow to make sure.
I did find the fire ring on the head gasked to be seperated on the lower portion near the alignment dowel. The bolt there goes through the water jacket and there is a water passage very close. The antifreeze that I drained had a darkish color to it. It did not look rusty, but almost like it had been colored by exhaust. I could not smell any fuel or exhaust in it but the truck has sat for three weeks now. I did run it last week to operating temp prior to the comression test.
So, I guess my question is, could this firering and head gasket material seperation be the source of my low compression if the valves and thier seats check out fine?
Oh, and can the upper to lower intake gasket be reused if it came off clean?
Michael Means
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