Bucking Cruiser (1 Viewer)

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May 28, 2008
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Sorry for the lame title, but I don't really know what to call it. I have a stock 1982 FJ40 with all the emission stuff on it and passes Cal smog check. The truck runs great expect when I transition from off gas pedel to on gas pedal. It hicupps/bucks once. It's been doing it for about 6 months now and it's bugging me. It also does it when I'm in a very slow deceleration, it will buck and almost feel like someone tapped the gas pedal??? I originally thought it was the carb but I rebuilt it and same. Replaced sparkplugs, cap and rotor and wires, still same. Could it be a faulty smog pump? The smog pump goes to the air injection rail and there is a checkvalve inline... Could it be that? Any ideas would be great..
 
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Bucking is a symptom I usually associate with fuel starvation or fuel delivery problems, but your description isn't entirely consistent. Fuel delivery problems are worst when the engine is under high load, like going up hill in 4th gear with the pedal to the metal.

A transition from closed throttle to open bucking is more likely a plugged transition slot, which is part of the idle circuit. Does your idle solenoid work?
 
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I had a similar problem and fought it forever. Turns out that my EGR was sticking (not sure if it was open or closed). The truck would "buck" under acceleration. It was mild, yet incredibly annoying. I ended up pulling a vacuum line from the EGR and plugged it with a wood screw and the truck runs like a dream now. If Pin_Head is not correct, it may be worth doing as I have and plugging that vacuum line. I can snap a pic of the vacuum line in question and send it to you if that helps. Good luck!
 

FineWynsFJ40

Eff-Jay-Farty
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I would say try the EGR idea that jjhancock suggested, and I'm going to say fuel filter. Also, check your fuel tank to make sure no rust flakes might be occasionally blocking the flow. That's all I have. When mine bucked, it was because there was diesel mixed in with the gasoline, but that's another story for another time.

Brian
 
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Pin_Head, I believe my idle soleniod works fine.. Idles smooth as silk, then I unplug the soleniod and cruiser dies... Is that all I should check or should I start checking all those vacuum soleniods on the drivers side fender well?

JJhancock... Yes please post or send me a picture of your fix of the vacuum line..If the EGR was the problem, why not just replace the EGR?? But your correct, not a huge problem just VERY annoying.
 
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Help

Anybody else out there that had similar problems with good advice??? Let me know..
 
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Stupid EGR!

The reason I didn't just replace the EGR is really just that I was tired of futzing around with this ultra annoying problem, and I had a fix that was free. I had Jim C. rebuild my carb (wise move btw), replaced every vacuum line under the hood, new fuel filter, adjusted timing, and probably a bunch of other stuff that I can't remember as it's been a couple years now. Bottom line, I was so happy when I plugged the vac line in the attached photos that I didn't want to "cross the streams" by trying to replace the damn thing. Pics:







 

FJ40Jim

The Cruiser Whisperer
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If a person in Califonika were to use a BB inside that hose and then reinstall the hose, it would turn off the EGR system while still looking completely stock. Wouldn't that be a shame...
 
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I know that the smog police aren't as tough here in Colorado as I have heard they are in California, but I passed my emissions check with flying colors even with the vac line in the above pics plugged exactly as in the pics above. The emissions people didn't say a word. The fact that I passed makes me think that the EGR does next to nothing with respect to emissions, but I'd be interested to hear from anyone, especially the almighty Jim C, what kind of difference a properly functioning EGR actually makes.
 
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No difference.

Thanks for the great pics JJHANCOCK. Tried your sugestion and still the same. At very slight throttle and off throttle to on throttle the car feels like someone turned off the key for a split second. I'm still wondering if it could be something with the smog pump and air injection valve or maybe the vacuum advance???? Any other suggestions?
 

1911

chupacabra
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I had a similar symptom when the wire broke off the end of my fuel cut vacuum switch (on the DS fender, bolted to the big air injection manifold/valve); you might check that and the solenoid on the carb for correct operation.
 
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Unfortunately they test the EGR function as part of smog test.
They no longer do an EGR function test in the Peoples Republic of California. They used to, but not for the last 6-8 years. All it needs to do is pass a visual test, gas cap seal and tailpipe tests.

Thanks for the great pics JJHANCOCK. Tried your sugestion and still the same. At very slight throttle and off throttle to on throttle the car feels like someone turned off the key for a split second. I'm still wondering if it could be something with the smog pump and air injection valve or maybe the vacuum advance???? Any other suggestions?
Not likely anything to do with the air pump or vacuum advance.

More likely a problem with the control of the idle cut off valve by the manifold pressure and the "smog" computer. Try grounding the green wire of the idle fuel cut off and see if the problem goes away.
 
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A bad accelerator pump can cause problems when the throttle is advanced, because there is not enough fuel for the engine. This is especially bad during the transition from idle until the main jet(s) kick in. Often called an off-idle flat spot. This can be caused by defective parts, a clogged or partially clogged passage, or excessive heat boiling the fuel out (Holley carbs are notorious for this).

With the air cleaner off, and the engine hot and off, manually operate the throttle on the carb while looking down the carb bore. You should see a healthy stream of fuel. If not, there's your problem. If the fuel stream is good, then something else is at fault.
 
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Well, I've been playing with all the vacuum lines and the numerous vacuum switches on the fender well. I disconnected all the vacuum switches and Cruiser still runs fine but off/on accerelerater transition still bucks. The accelerator pump pumps fine and no change when EGR is disconnected. I'm wondering what governs the idle solenoid. Is it managed by the ECU box inside the cab by the clutch pedal. When does the solenoid turn on and off. When idling I unplug it and the car dies. Does it turn off on deceleration?
I haven't hot wired the solenoid yet, but plan to tonight to see if that makes any difference.
 

FJ40Jim

The Cruiser Whisperer
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ICS power comes from the ignition switch.
ICS ground is through the emission computer.
Logic inputs include VSS, RPM and vac switch.

Try connecting the ground side of the ICS to ground.
 
Joined
May 28, 2008
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OK, the ICS is not the problem. Jumped it to a constant ground and no change...

SO I had the truck idling with the air cleaner off and playing with the thottle and had it rev'ing at about 1500 rpms. It would surge from 1500 to 2000 rpms and would not stay constant. If I was over 23-2400 rpms it would stay constant. It idles perfect too. So I thought it might be a sticky vacuum advance in the distributor, so I disconnected the vac hose and the idle dropped a couple 100 rpms but when I rev'ed back to 1500 and held there the surging stopped???? So I took it for a drive hoping the hiccup/buck would be gone.....still there.

So I believe it's carburation. At very slight throttle it's either starving or flooding with gas. But when you give it more gas it runs fine. I know motorcycle carbs pretty well and on them there's:
  • the air/fuel - afffects idle
  • the pilot jet - affects just off idle
  • the needle height and taper - middle range
  • main jet - 3/4 to open throttle
So if it was a motorcycle I'd change the pilot jet and maybe adjust the needle. What should I do on this stock 2 barrel Cruiser carb??? HELP:bang:
 

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