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From: Peter Pearson on 6 Aug 2008 14:21
My 1982 pickup with the 22R engine (manual transmission,
California emissions controls) runs very raggedly under no
load or light load while warming up: stalls instantly at
stoplights, and while driving jerks as if I were tapping on
the accelerator.

My favorite two shops have failed to fix the problem, but I
think its idiosyncracies are so clear that someone who knows
old carburetted engines could probably diagnose it in a
minute. Here are the specifics:

* The engine starts easily.

* The Problem typically starts after 1 or 2 minutes
of driving. On very hot days, it starts sooner.

* The Problem disappears abruptly and completely after
about 15 minutes of driving.

* Aside from the instant stalling at stoplights, The
Problem is only noticeable when the accelerator is
depressed slightly. If the accelerator is depressed
more -- say enough to drive up a gentle grade at
60 MPH -- performance seems to be fine.

Does anybody see an obvious interpretation? (BTW: is this
the right place to ask?)

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From: doncee on 6 Aug 2008 17:56
>
> My favorite two shops have failed to fix the problem, but I
> think its idiosyncracies are so clear that someone who knows
> old carburetted engines could probably diagnose it in a
> minute. Here are the specifics:
>
> * The engine starts easily.
>
> * The Problem typically starts after 1 or 2 minutes
> of driving. On very hot days, it starts sooner.
>
> * The Problem disappears abruptly and completely after
> about 15 minutes of driving.
>
> * Aside from the instant stalling at stoplights, The
> Problem is only noticeable when the accelerator is
> depressed slightly. If the accelerator is depressed
> more -- say enough to drive up a gentle grade at
> 60 MPH -- performance seems to be fine.
>
> Does anybody see an obvious interpretation? (BTW: is this
> the right place to ask?)
>

Defintely sounds like carb problem. Probably choke coming off too
early. Haven't messed w\ carbs in long time but there is also a
device which is part of the carb, that adds an extra shot of fuel
during warmup. Can't think of the name of it but it may not be
functioning properly. Typically the rubber diaphram leaks or
cracks & makes it stop working. Either way my bet is carb
problem. Let us know what you find.
dc
From: Desertphile on 11 Aug 2008 09:52
On 6 Aug 2008 18:21:13 GMT, Peter Pearson
<ppearson(a)nowhere.invalid> wrote:

> My 1982 pickup with the 22R engine (manual transmission,
> California emissions controls) runs very raggedly under no
> load or light load while warming up: stalls instantly at
> stoplights, and while driving jerks as if I were tapping on
> the accelerator.
>
> My favorite two shops have failed to fix the problem, but I
> think its idiosyncracies are so clear that someone who knows
> old carburetted engines could probably diagnose it in a
> minute. Here are the specifics:
>
> * The engine starts easily.
>
> * The Problem typically starts after 1 or 2 minutes
> of driving. On very hot days, it starts sooner.
>
> * The Problem disappears abruptly and completely after
> about 15 minutes of driving.
>
> * Aside from the instant stalling at stoplights, The
> Problem is only noticeable when the accelerator is
> depressed slightly. If the accelerator is depressed
> more -- say enough to drive up a gentle grade at
> 60 MPH -- performance seems to be fine.
>
> Does anybody see an obvious interpretation? (BTW: is this
> the right place to ask?)

It sounds very much like a vacuum leak, perhaps in the air intake
hose. (But it two shops didn't notice a leak, surely it cannot
be.) The symptoms you described are exactly what my pickup had
when the underside of the air intake hose was worn through---
stalling or near stalling at stop lights, engine shuddering when
slowing accelerating.


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From: croy on 22 Aug 2008 09:33
On 8 Aug 2008 17:26:36 GMT, Peter Pearson
<ppearson(a)nowhere.invalid> wrote:


[snip]


>> Also check the EGR system. Stumbling on light acceleration is a
>> classic symptom of too much EGR. Disable the EGR by plugging the
>> vacuum hose going to the EGR valve and see if the symptoms change
>> dramatically. If so, you know it's the EGR system. If no change,
>> you're back to checking the vacuum lines and the carb. Good luck. Al


>Following the path of least resistance, I found a very accessible
>Vacuum Switching Valve that serves the EGR, disconnected all three
>quarter-inch hoses from the VSV, and clamped them off. The
>stumbling under light load disappeared. So, I'm going to pursue
>the EGR theory.


I saw this thread while lurking, and took interest. My 1988
22R pickup was taking longer to start on cold mornings and
had a pronounced stumble on drive-away during mid-warmup.

Curious to see if the EGR was adjustable, I thumbed thru the
shop manual. Apparently the EGR is not adjustable, but I
happened to notice that the valve mentioned by the OP has a
dry filter in the cap, and the manual recommended blowing it
out with compressed air. I did so, and couldn't believe the
transformation in this beast. It now starts quickly, the
stumble is reduced to the level of when the truck was new,
*and*, much to my amazement, the clutch chatter that had me
expecting a serious repair bill in the near future, seems to
have dissappeared as well. I have never spent a more
productive 20 minutes on a vehicle in my life!

So I give a big thanks to all who contributed to this
thread.

--
tbl
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