Bucking Pickup!

Hello;
    I have an 89 Isuzu Pickup 2.3L 2bbl 5 speed 135000 miles. The truck wants to bog and stall when starting off and then bucks at partial throttle. It seems to clear up under heavy throttle and then starts over when I come to a stop. The weird thing is that sometimes it will clear up and run fine for a while! Have replaced dist.cap, plugs, coil, wires, rotor, fuel filter, and recently installed a rebuilt carb. Is this a fuel delivery problem? electrical? Massive vacuum leak? All help appreciated!
JW

JW wrote:
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My guess would be a vacuum leak. If it clears up at heavy throttle that would tend to point away from the fuel problem although I had a sticking float that had similar symptoms.
Since you recently replace the carb you might look at the base of the carb as well as any vacuum hoses for leaks.

It may be a long shot, but I had a similar problem with my Ford van. It turned out that the catalytic converter was plugged. This can affect a number of things, including vacuum, compression, etc.

I have a 88 pickup that does the same thing. I have re-built the carb, replaced the fuel oil pump, re-placed fuel oil filters and all of the hoses. What is the best way to check for vacuum leak around the base of the carb? Could I spray some starting fluid around it and if the engine speeds up there is a leak?
Steve

"News3" wrote: > I have a 88 pickup that does the same thing. I have re-built > the carb, > replaced the fuel oil pump, re-placed fuel oil filters and all > of the hoses. > What is the best way to check for vacuum leak around the base > of the carb? > Could I spray some starting fluid around it and if the engine > speeds up > there is a leak? > > Steve
Hi, I have a 94 Isuzu Pickup and it has that exact problem. You could try this url for info....http://www.misterfixit.com/izuzzu.htm I tried multiple mechanics and haven’t had any success. Most of the time it doesn’t happen when I bring it in to them. It’s been a few months since your original post, have you found a solution? Well if you do, let me know. Any help is greatly appreciated.

"user1793" wrote:
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Hello JW, :o
I too have an 89 ISUZU with the same problem that you have reported. Mine has about 160,000 on it.
Did you ever find out what was causing the problem?
I am reluctant to replace any parts until I have a good indication that, that will fix the problem since I just traveled down that road with a weird electrical problem.
Any advice you can give me will be greatly appreciated.
God Bless KW

Nope! Still working on it !!!
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"user1793" wrote: > Nope! Still working on it !!! > > On 5 Apr 2005 02:01:06 -0400, 49er
> wrote: > > >"user1793" wrote: >  >>Hello; >  >> >   >>    I have an 89 Isuzu Pickup 2.3L 2bbl 5 speed > 135000 miles. The >  >>truck wants to bog and stall when starting off and > then bucks at >  >>partial throttle. It seems to clear up under heavy > throttle and then >  >>starts over when I come to a stop. The weird thing is > that sometimes >  >>it will clear up and run fine for a while! Have > replaced dist.cap, >  >>plugs, coil, wires, rotor, fuel filter, and recently > installed a >  >>rebuilt carb. Is this a fuel delivery problem? > electrical? Massive >  >>vacuum leak? All help appreciated! >  >> >  >>JW > > > >Hello JW, :o > > > >I too have an 89 ISUZU with the same problem that you have > reported. > >Mine has about 160,000 on it. > > > >Did you ever find out what was causing the problem? > > > >I am reluctant to replace any parts until I have a good > indication > >that, that will fix the problem since I just traveled down > that road > >with a weird electrical problem. > > > >Any advice you can give me will be greatly appreciated. > > > >God Bless > >KW
Thanks for the speedy reply. :)
Check this out.
Of all places, I got a tip from my Barber. He thinks it may be a clogged catalytic converter.
He says he experienced problems similar to ours and that’s what caused it.
Needless to say, I’ll be checking mine out this weekend!

    Thanks for the tip!!! I'll check out mine to! Also might be a good idea to make sure the muffler is not rotting out inside and causing a blockage. But if U unbolt the exhaust at the converter this will take care of both. Good luck!!!
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Hello,
I was having a similar problem with my 95 2.3L Pickup, 185k miles. I had just replaced the head gasket and after a few months I had the truck stumbling or hesitating. This would occur when I would be shifting from 1st to 2nd on the five speed at first and then later developed into a number of other situations included downshifting while taking an off ramp or a slow climb while on the highway. Sometimes parked on the side of the road because the truck could not continue due of excessive bucking I would rev the engine and it made a sound like it may backfire. It felt as if the gas was being cut off but it would continue to run. I have no tach so I cannot say what the rpms were doing exactly.
It would come and go. Since it did not happen all the time I decided to watch for any patterns that might appear. The nearest thing I could figure is that it only occurred in warmer weather (above freezing). This turned out to be a red herring.
Recently it had gotten so bad that it was nearly un-drivable. I figured at this point that it was bad enough and happening consistently enough so a mechanic might see it in person. I went to an Isuzu dealer because I felt that they may have seen this sort of thing before. After three hours of diagnosis ($250) they tell me that it had been traced back to a bad ground connection on the engine and that the ignition and fuel system were ok. When I looked around the engine compartment I could see that they replaced a few nuts connecting a pair of grounds to the engine. They claimed there are four grounds connected to the engine and I have not had time to see if they changed any hardware on the rest. Apparently when the engine was revved the ground connection was intermittent.
It has only been a few days but it seems to be running a whole lot better. Its running smoother and the problem has not occurred so far. I am cautiously optimistic this was the problem given that when it first started it would occur every couple of months.
It seems the link posted by mpd7 got it right for my truck. I wish I had seen it earlier.

"lebeaua" wrote: > Hello, > > I was having a similar problem with my 95 2.3L Pickup, 185k > miles. I > had just replaced the head gasket and after a few months I had > the > truck stumbling or hesitating. This would occur when I would > be > shifting from 1st to 2nd on the five speed at first and then > later > developed into a number of other situations included > downshifting while > taking an off ramp or a slow climb while on the highway. > Sometimes > parked on the side of the road because the truck could not > continue due > of excessive bucking I would rev the engine and it made a > sound like it > may backfire. It felt as if the gas was being cut off but it > would > continue to run. I have no tach so I cannot say what the rpms > were > doing exactly. > > It would come and go. Since it did not happen all the time I > decided to > watch for any patterns that might appear. The nearest thing I > could > figure is that it only occurred in warmer weather (above > freezing). > This turned out to be a red herring. > > Recently it had gotten so bad that it was nearly un-drivable. > I figured > at this point that it was bad enough and happening > consistently enough > so a mechanic might see it in person. I went to an Isuzu > dealer because > I felt that they may have seen this sort of thing before. > After three > hours of diagnosis ($250) they tell me that it had been traced > back to > a bad ground connection on the engine and that the ignition > and fuel > system were ok. When I looked around the engine compartment I > could see > that they replaced a few nuts connecting a pair of grounds to > the > engine. They claimed there are four grounds connected to the > engine and > I have not had time to see if they changed any hardware on the > rest. > Apparently when the engine was revved the ground connection > was > intermittent. > > It has only been a few days but it seems to be running a whole > lot > better. Its running smoother and the problem has not occurred > so far. I > am cautiously optimistic this was the problem given that when > it first > started it would occur every couple of months. > > It seems the link posted by mpd7 got it right for my truck. I > wish I > had seen it earlier.
Thank you. My problem turned out to be a clogged PCV valve. I took a chance and replaced it because it was a cheap part and easy to do. To my surprise, all my troubles went away. :)