Bucking at 60 mph sometimes different speeds

jeffpinto · Mar 22, 2015

87 2.0 carb 5 speed
New fuel pump cleaned carb
New plugs wires cap rotor and ignition coil
The truck bucks at 60 sometimes 65 and if I push the clutch in and try to rev it when it bucks it sounds as if the motor died but I still have power to lights/radio/etc if I floor it when it bucks with the clutch in it take a couple seconds until it will ecru ally rev up
I'm leaning towards maybe clogged cat/ ignition control module/ carb issue
Any help would be great because after it bucks sometimes it will only let me go 50 mph thanks guys

Mark_88 · Mar 22, 2015

Howdy Jeff,

What carb does it have...1 or 2 bbl?

I'm thinking it could be something with fuel flow because I've been through just about every situation with my 2.3 carbed (was a 2.0 with a 2bbl carb) and bucking was almost always fuel flow.

It could be that your carb has a float bowl that is sticking and not allowing enough fuel after sustained highway speeds. The bucking is actually a crudely intelligent way of releasing the float bowl...

If your carb doesn't have a float bowl then it could be the fuel pump is lagging behind on supply and you may need to adjust the fuel supply line...it would be burning way too rich and you should be able to smell it. Adjusting the float bowl is fairly easy and it sounds like you may be knowledgeable enough to do this on your own...just be careful pulling the top end off that the needle doesn't drop out...it will only do that if the float has become detached...

Sudden dying at highway speeds on mine turned out to be float bowl issues and flooding. I was using an electric 4.5 psi pump to replace the manual one and the float would be in the high position so the fuel was just flowing over the top of the carb and it would eventually flood...if your truck doesn't die out on you then it's likely an adjustment issue.

A plugged cat will just bog down and it will feel like there is no power at all...and may plug to the point where it stalls out the engine and will not start due to excessive backpressure...but you can check that if you want to drop the exhaust system...but a simple test is to put your hand on the tailpipe (only do this when the system is fairly cool) and completely cover it...hold it for a few seconds and then pull your hand away...you should hear a POP and feel the pressure on your hand...

The above will not work if there are leaks in the exhaust though...

Andy D · Mar 24, 2015

A clogged cat in a carbed car will glow red hot . Also it can be seen with a vacuum gauge. I would eliminate a few cheaper and easier things first. What is the state of the ignition? How is the coil? I've found that the best coil check is a known good one..You replaced it all. no joy.. Borrow or rent a compression gauge. Watch a few videos about it if you have never done it before. There may be an exhaust valve getting burned. Any vacuum leaks? Clogged fuel filter? Maybe do a volume test on the fuel pump. Throwing parts at a trouble until it goes away can get expensive and sometimes create additional troubles. A little diagnosis can save lots of money and time. Also, you are the proud owner of a 28 yr old Ford. It is a freaken marvel that it runs at all. It was never intended to be around so long.

Bucking at 60 mph sometimes different speeds

jeffpinto

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Mark_88

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Andy D

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