22r - carburetor - cool engine and hesitation

Hi all..
I have a 1988 Toyota pickup, 140,000 miles, 22R engine. It is carbureted and well maintained...
However here is the problem. Whenever it is cold or cool out, the
engine hesitates or stutters a bit until it warms up. During the summer or when its warm, the problem is diminished significantly to the point where only I can tell there is a problem. If its really hot out there is virtually no problem at all...
I have checked nearly every carb / vacuum related valve, the AAP valve, the choke, most vacuum switches, you name it. I recently tuned the engine up, checked the timing, new fuel pump, new fuel filter, new air filter and so on with no real improvement. The compression is right on the money and so is the engine vacuum. The engine power is also rock solid.
I am at a total loss. Although this problem is minor, I would really like to solve this situation. Could it be the mixture?
The problem is obviously related to the temperature. Are there any switches, sensors or devices that rely on temperature to operate? I am debating a carburetor rebuild but figure I should ask about my options first.
Cheers and TIA
Tom
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tom wrote:

How about the AAP diaphram, you mentioned the valve. This bugger is hard to get too, easier to just take the whole carb off then you have easy access to it. While the carb is off spray it down with carb cleaner good, then for good measure get some silicone vacuum lines and replace the vac hoses on the carb and the rest of them in the truck while you're at it.
I had the same symptoms you described, hesitation when cold. A new AAP diaphram fixed it.
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Hey...
Yeah, I should have mentioned, I replaced ALL the vacuum lines...every last one....I tested the AAP diaphram, it works just fine...Back to the drawing board...
thanks though!
Tomv
On Mon, 21 Jun 2004 14:33:36 -0400, The Patriot

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wrote: | | > | >
How did you check the choke? I had the same symptoms on my '87 22R when I bought it a few years ago. The choke appeared to work but was not closing enough on cool mornings here in the TX panhandle. I played with the adjustment until it choked when the engine was cold and still opened up with warm up.
--
Jarhead
| >tom wrote:
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Hey...
"How did you check the choke?"
Visually...I took the air cleaner off, and it operated to specifications (it was completely closed, then slowly opened as the engine warmed...) I also did the vacuume test where you apply vacuume that opens the choke a bit, and that checked out ok also...
I dont think its the choke because even when it is warm, there is the slightest hint of hesitation (its one of those things where only I can tell, thats how slight it is...)
The only thing left that I can think of is the heater under the manifold that operates from the thermo sensors, but I doubt its that either..Im convinced more than ever that is must be the carb....(yes, a tuneup was done very recently :-D
In a way I wish it was the AAP, my saga would be over at least!
Cheers
Tom
wrote:

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just a suggestion, float level reduced from wear?? makes it go lean. but I assume you checked the glass window on the carb. lean could be scum in the carb too. sounds like your on the right track. Also, base gasket on carb leaking slightly could cause lean mix. cold air=more lean also so that sounds right. good luck, I have a slightly similar problem, but mine is 22R-EFI. Slighty noticeable hesitation at low rpms, runs good when cold, hesitates slightly when letting off to shift gears when hot.??? EGR??? EPS??? Not unusable, just slightly annoying.

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