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Hello all. New to the forum. I have a 91 F-150 5.8 4x4. Truck was running fine. A/c was working. No issues. I go for a drive and I had to engage 4x4. For whatever reason after using the 4x4 for like 5 minutes. The truck started running really crappy like it was running on 5 or 6 Cylinders. The engine is shaking everywhere like I have busted motor mounts(I checked and they are fine) Long story short I barely made it home. I bought the truck used, so I figured I it was missing because of bad wires or plugs. I bought new plugs, wires, coil, distributor rotor and cap. After replacing those items, the truck ran just the same. And now the a/c does not come on the clutch doesn’t engage. And it dies with the a/c load. Please help. Thank you
Logistics Pro
Joined: Dec 2003
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From: Foothills of NC
Put a vacuum gauge on a full vacuum port and see what you have. Should be 15+ according to what your elevation is.
Could very well be a timing chain problem, and low vacuum is a sure sign of a jumped chain.
Could very well be a timing chain problem, and low vacuum is a sure sign of a jumped chain.
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Thank you. Never used a vacuum gauge. Can I get one at any auto parts store? Also can you give an example of a full vaccum port? Thank you
Cargo Master
Joined: Mar 2010
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From: Laramie, WY
The brake booster vac line works for checking manifold vacuum. Most auto parts stores should have gauges, either to buy or rent. Not a bad idea to check fuel pressure while you're there renting tools.
Have you pulled codes? An Innova 3145 works well for doing so, but a paper clip can be used to count flashes too.
Have you pulled codes? An Innova 3145 works well for doing so, but a paper clip can be used to count flashes too.
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The brake booster vac line works for checking manifold vacuum. Most auto parts stores should have gauges, either to buy or rent. Not a bad idea to check fuel pressure while you're there renting tools.
Have you pulled codes? An Innova 3145 works well for doing so, but a paper clip can be used to count flashes too.
Have you pulled codes? An Innova 3145 works well for doing so, but a paper clip can be used to count flashes too.
Lead Driver
Joined: Oct 2016
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From: Houston/Sugar Land
Thank you. Will I get an accurate reading checking the manifold vaccum if the engine isn’t runnng properly? I didn’t pull codes because I don’t have a reader. I’m going to get one tho. Do I plug it into the diagnostic tester on the drivers side under the hood? Thank you
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Thank you. I will definitely get a Haynes manual as well.
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FTE Chapter Leader
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From: Central Mississippi
Welcome to FTE. You've joined the ranks of many here who buy a perfectly fine running truck with a hidden flaw that rears it's head after purchase.
Lots of folk here that'll help.
My contribution at no cost & minimal work expended is pull the shutter-wheel under the rotor & brush, vac, spray with electrical cleaner, blow/w compressed air, etc. the magnetic PIP sensor.
Lots of crap can build up & dirty the signal that everything EFI/ignition is based off of.\\Welcome again & good luck.
Lots of folk here that'll help.
My contribution at no cost & minimal work expended is pull the shutter-wheel under the rotor & brush, vac, spray with electrical cleaner, blow/w compressed air, etc. the magnetic PIP sensor.
Lots of crap can build up & dirty the signal that everything EFI/ignition is based off of.\\Welcome again & good luck.
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Lead Driver
Joined: Oct 2016
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From: Houston/Sugar Land
Welcome to FTE. You've joined the ranks of many here who buy a perfectly fine running truck with a hidden flaw that rears it's head after purchase.
Lots of folk here that'll help.
My contribution at no cost & minimal work expended is pull the shutter-wheel under the rotor & brush, vac, spray with electrical cleaner, blow/w compressed air, etc. the magnetic PIP sensor.
Lots of crap can build up & dirty the signal that everything EFI/ignition is based off of.\\Welcome again & good luck.
Lots of folk here that'll help.
My contribution at no cost & minimal work expended is pull the shutter-wheel under the rotor & brush, vac, spray with electrical cleaner, blow/w compressed air, etc. the magnetic PIP sensor.
Lots of crap can build up & dirty the signal that everything EFI/ignition is based off of.\\Welcome again & good luck.
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New User
Joined: Jul 2021
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Welcome to FTE. You've joined the ranks of many here who buy a perfectly fine running truck with a hidden flaw that rears it's head after purchase.
Lots of folk here that'll help.
My contribution at no cost & minimal work expended is pull the shutter-wheel under the rotor & brush, vac, spray with electrical cleaner, blow/w compressed air, etc. the magnetic PIP sensor.
Lots of crap can build up & dirty the signal that everything EFI/ignition is based off of.\\Welcome again & good luck.
Lots of folk here that'll help.
My contribution at no cost & minimal work expended is pull the shutter-wheel under the rotor & brush, vac, spray with electrical cleaner, blow/w compressed air, etc. the magnetic PIP sensor.
Lots of crap can build up & dirty the signal that everything EFI/ignition is based off of.\\Welcome again & good luck.
FTE Chapter Leader
Joined: May 2006
Posts: 12,322
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From: Central Mississippi
The shutter-wheel is under the rotor. Remove 2 screws. PIP lives under.
PIP replacement requires pulling dist & removing gear on shaft.
It's solid state so USUALLY it either works or not. Sometimes you get a code for its failing, but not always.
PIP replacement requires pulling dist & removing gear on shaft.
It's solid state so USUALLY it either works or not. Sometimes you get a code for its failing, but not always.
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The truck was running great until I went four-wheeling and I was hitting some huge boulders… And it did start running really bad right after that. I noticed that the shield that covers the catalytic converter was bent really bad. Didn’t notice a hole or anything. Tapped it with a hammer and I couldn’t hear anything loose? Is it possible that hitting the converter/exhaust caused a blockage and that is the problem? Thank you
After further reading,i took out the O2 sensor from the front of the converter, and it ran much better and had better vaccum(15-16) at idle. But once I checked it at higher rpms, it got lower than when the sensor was in(9-10). When I floored it it went down to almost zero. But the engine stills shakes really bad. Checked the motor mounts and they are good. Also if I turn the a/c on the truck won’t staying running without reving up the engine.
Test at over 2000 rpms. Based on what I read this could indicated a clogged converter or exhaust
Test at idle. I’m at 4800 ft. It fluctuated from 13-15
Last edited by Redbone68; Jul 13, 2021 at 12:23 PM. Reason: New info
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New User
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The brake booster vac line works for checking manifold vacuum. Most auto parts stores should have gauges, either to buy or rent. Not a bad idea to check fuel pressure while you're there renting tools.
Have you pulled codes? An Innova 3145 works well for doing so, but a paper clip can be used to count flashes too.
Have you pulled codes? An Innova 3145 works well for doing so, but a paper clip can be used to count flashes too.
The truck was running great until I went four-wheeling and I was hitting some huge boulders… And it did start running really bad right after that. I noticed that the shield that covers the catalytic converter was bent really bad. Didn’t notice a hole or anything. Tapped it with a hammer and I couldn’t hear anything loose? Is it possible that hitting the converter/exhaust caused a blockage and that is the problem? Thank you
After further reading,i took out the O2 sensor from the front of the converter, and it ran much better and had better vaccum(15-16) at idle. But once I checked it at higher rpms, it got lower than when the sensor was in(9-10). When I floored it it went down to almost zero.
Last edited by Redbone68; Jul 13, 2021 at 12:20 PM. Reason: New info
Logistics Pro
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Is it possible that hitting the converter/exhaust caused a blockage and that is the problem? Thank you
I would think maybe you damaged the O2 sensor.
I think it is mounted right in the center of the exhaust y-pipe, right in front of the catalytic converter.