[Machinist_Dan]

First post but lots of reading and I thank everyone for their contributions. Vehicle is a 1987 P/U 2wd M/T 22R (carburetor-Aisan #35291) 330K miles but about 7K on motor. Having a couple of problems, rough idle, truck bucking going down the road and the fuel will not stay in the bowl of the carb overnight. Rebuilt carb in Jan. and truck was running good. Started loosing fuel in bowl about month later but was still getting 23mpg so didn’t think much of it. Kept a check on oil for fuel smell but I got none. Then about 3 weeks ago the truck all the sudden started going dead when you would push in clutch after running down interstate or driving at the same speed for a couple of miles. Things I have done:droped fuel tank-clean as a pin inside, changed fuel filter, new fuel pump, added clear inline filter between pump and carb, rebuilt carb(second time), check timing, re-torque intake, head, and exhaust, checked valve clearance, compression check (178- 183psi), checked plugs and gap, new dist cap, checked air gap of signal rotor and pickup, checked all vacuum hoses, new air filter, changed oil, cleaned inside EGR vacuum modulator(above EGR valve) this seamed to help the going dead part when pushing in clutch. Checked the Emission Control Mod (gray box inside truck) with no broken solder joints also changed out with one from junk yard –no change. Removed the fuel cut solenoid tested ok and cleaned. Choke plate works great (passenger side) but the plate on the driver side remains almost closed all the time. And when you give it gas it tries to close (this seams odd to me or is this how it works). Now my problem is when going down the road it bucks when holding the accelerator in the same place as to maintain speed. It does not hesitate on acceleration. The fuel level (when idling) in the bowl is in the middle of the sight window. Rough idle-it will stay at about 800rpm if you rev it up it only comes down to 950-1100 and stays for a minute or five and all the sudden drop to 680-850 it varies. When idling at 750 I see no drops of fuel falling inside carb but if it is idled high I see them. Plus sometimes the idle will surge up and down.

Sorry for the long post, just wanted to give as much info as I could.

 

[chuck landry]

Been awhile since i dealt with the carb models, but what i do know, the float bowl cannot drain, per say. Been there. But the lowest point of the bowl passages into , can't recall official term, the enrichment diaphragm. Under the float bowl, front of carb at bottom.. Triangular shape with a vacuum hose connecting. To check if its bad, engine off after running for a minute or two, pull off rubber hose, point it down and touch the opening of hose. Should not be wet from fuel. This valve goes bad and sucks raw fuel into intake manifold from the bowl.. Common toyota carb problem. If its bad, its replaceable externally, suggest factory part only. Let us know.

 

[Machinist_Dan]

I think you are describing the aux acc pump. There was a new diaphragm that came with the rebuild kit that I got from NAPA this weekend. I will double check this afternoon when I get home but I don't believe there is a leak there. I will also pull the top of carb off and see where the level is.

 

[Machinist_Dan]

Checked the vacuum line running to the aux acc pump and no fuel. the fuel level inside the bowl is droping about 1/2"-5/8" and the level is no where near any jet or hole. Someone suggested that I was getting evaporation due to hot motor and carb. So I cranked it up for about 30 seconds to get the fuel into the bowl and shut it off. I will check in the morning.:headbang:

 

[ed h]

Dan I'm having exact problem. What did u ever figure out?

 

[Machinist_Dan]

the bucking part..I only notice it at low speeds25-30mph like driving thru neighborhoods. I never got it fixed just leared to deal with it. This is just my to and from work truck for gas mileage so just decided not to put that much money in it. I will tell you that I did replace the carb with a new rebuilt one and it did not help so if you dont have any major problems with yours dont wate your money.

 

[Matt22r]

Had the same problem with my 87 p/u 4x4 mt 22r. In the rebuild kit did you replace your needle and seat? When I replaced mine I had the same problem. Took me weeks to figure out that my float was out of adjustment. I can't remember the specs off hand but when I go to school tomorrow(I go to UTI so I can print off any and all diagrams that the dealerships use) ill take a picture of the specs for the float level. Oh and also it would be a good idea to check your electronic choke, it could be malfunctioning( just an idea). One more thing, about your carb...the drivers side plate will only move when your putting a load on the truck, ie out driving it.


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