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Poor performance from 5.0 litre engine
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NaymzJaymz
User
Mar 16, 2013, 2:19 PM
Post #1 of 5
(1439 views)
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Poor performance from 5.0 litre engine
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Hello, the vehicle in question is a 1991 Ford Bronco with a 5.0 litre engine. Mileage is 209,000, which is obviously a lot, but it's had regular oil changes. A few years back I foolishly overheated it, but it ran fine and easily passed the smog test twice before being parked for the past year. I've started it several times, but this latest time the engine sounds like one of the cylinders isn't firing, giving me a "thuddy" idle and similar performance with increased throttle. I've done a compression test with results of between 170-160psi on all eight cylinders. Will a tune up likely clear things up, or would it likely be something worse with an engine this old? The parts I'll replace will be the distributor cap, rotor, spark plugs, plug wires, and ignition coil. Should I replace any other parts(other than the engine)? I will replace all these parts at the same time. Let me say that I realize that this is a naive sounding question that might make an experinced mechanic laugh, and I'm not looking to be chastised for what I haven't done yet. Isn't that the point of a forum like this? I'm just a working man trying to save a few bucks by getting a few more miles out of this loyal old Bronco. The compression seems to indicate a solid old engine, and there is no check engine light on. Thank you for your help.
(This post was edited by NaymzJaymz on Mar 16, 2013, 2:25 PM)
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Discretesignals
Ultimate Carjunky
/ Moderator
Mar 16, 2013, 3:55 PM
Post #2 of 5
(1405 views)
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Re: Poor performance from 5.0 litre engine
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If it hasn't had a tune up, it is probably time. Replacing the wires, plugs, cap, rotor, and coil would be something an experienced tech would recommend if all those things have a lot of age and mileage on them. When you do your tune up try to route plug wires 7 and 8 as far away from each other as possible in your wire holders. Those two wires like to cross fire.
When you remove the spark plugs inspect the ends. See how the plug color looks and take note of any abnormal conditions. There are plug condition charts strewn all over the internet.
Start with that and see how it runs.
Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.
(This post was edited by Discretesignals on Mar 16, 2013, 4:04 PM)
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NaymzJaymz
User
Mar 17, 2013, 11:34 AM
Post #3 of 5
(1376 views)
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Re: Poor performance from 5.0 litre engine
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Thank you, sir, for your answer. As I said, it is sort of a naive sounding question, but I'm learning. Can you or any other contributor think of another tune up oriented part, other than the ones I mentioned, that I should replace? A friend who is an experienced mechanic once told me that there could have been some lifter damage during the overheat that happened a few years ago. Wouldn't that problem have reared its head before now? If I can't get this thing running better with a thorough tune up, perhaps I will rebuild the engine. I've always wanted to rebuild a motor, and a 302 Ford would be a good project. Very common engine and relatively easy to remove from a vehicle like this. Thank you!
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nickwarner
Veteran
/ Moderator
Mar 17, 2013, 7:00 PM
Post #4 of 5
(1357 views)
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Re: Poor performance from 5.0 litre engine
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Your compression is good. Rebuild it and it will still run like crap because you haven't solved the issue that made it run bad. I'd be looking at your vacuum hoses. They are all old, and they are cheap. Change them all. But a few feet of the normal sizes at the parts store when you go get your tune-up stuff. Use a razor to cut one line at a time along the side to make it break off of what it holds to, and then cut a new piece to replace it.
It is an easy one to pull. Its an easy one to rebuild. But you won't gain a thing unless you get to the root of this driveability issue. You'll just throw away a lot of money.
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Mar 20, 2013, 3:45 PM
Post #5 of 5
(1326 views)
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Re: Poor performance from 5.0 litre engine
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With Nick on this. Vacuum anything even hose to brake booster and PCV grommet still available and way down back usually run OK if bad but smell of burning oil off engine if so.
These engines are generally not troublesome but anything stupid can happen. Compression should mean this can run well again,
T
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