1986 Toyota pickup - sudden idle problems

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jasonamiller@gmail.com - 19 Jul 2006 03:26 GMT

I was performing the 90K mile maintenance on my 1986 Toyota pickup, and
decided to run some Sea Foam through it just to be sure everything was
clean. I poured about 1/4 of the can slowly into the carburetor of the
warmed up (and running) engine. It then coughed, backfired through the
carburetor, blew out smoke and died. It restarted, but since then it
won't idle at all, but will stay running very roughly if I give it lots
of gas.

I read somewhere else that Sea Foam can screw up the sparkplugs. So I
took all of them out and cleaned and inspected them. No change. The
engine will start but then die immediately unless I give it a lot of
gas and keep my foot on the pedal. As soon as I let my foot off of the
pedal, the engine sputters and dies.

Did the Sea Foam cause this? I'm very disgusted, because the engine
was running fine beforehand. Next time I'll leave well enough alone.

Jason

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Kevin - 19 Jul 2006 03:33 GMT

>I was performing the 90K mile maintenance on my 1986 Toyota pickup, and
> decided to run some Sea Foam through it just to be sure everything was
[quoted text clipped - 14 lines]
>
> Jason

Most likely the induction backfire blew off a vacuum line somewhere and you
now have a vacuum leak. It may have even blown back through the carb and
dislodged some crud or messed up a seal in the carb. It might have even
blown an intake gasket, but the point is that it really wasn't the SeaFoam
that did the damage, it was the backfire. There is a pretty good chance that
the problem is minor, although it may be hard to find the vacuum leak caused
by the backfire, but that is what I would be looking for if it was my truck.

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Kevin Mouton
Automotive Technology Instructor
"If women don't find you handsome, they should at least find you handy"
Red Green

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jasonamiller@gmail.com - 19 Jul 2006 03:44 GMT

Thanks for your reply. I thought it might be a vacuum problem, but I
couldn't find any vacuum lines obviously blown off. Any idea where I
can find schematics for the vacuum lines, so I know where to start?
I'll have to get someone to keep the truck running, so I can try to
listen for a leak. Is it most likely going to be right around the
carburetor?

If that doesn't work, is the next task to start dismantling the
carburetor to look for a problem?

Thanks,
Jason

> Most likely the induction backfire blew off a vacuum line somewhere and you
> now have a vacuum leak. It may have even blown back through the carb and
[quoted text clipped - 8 lines]
> "If women don't find you handsome, they should at least find you handy"
> Red Green

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Kevin - 19 Jul 2006 05:44 GMT

> Thanks for your reply. I thought it might be a vacuum problem, but I
> couldn't find any vacuum lines obviously blown off. Any idea where I
[quoted text clipped - 26 lines]
>> "If women don't find you handsome, they should at least find you handy"
>> Red Green

If you don't have a smoke machine the next best way to look for a vacuum
leak is by listening for it with a stethoscope. We have electronic
stethoscopes, but you can create a make shift one by holding a piece of
rubber tubing to your ear and probing for the hiss of a leak with the other
end. Be sure to check the power brake booster and A/C vacuum reservoir lines
and maybe even examine the EGR and PCV valve to make sure there is no leak
there.

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Kevin Mouton
Automotive Technology Instructor
"If women don't find you handsome, they should at least find you handy"
Red Green

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jasonamiller@gmail.com - 19 Jul 2006 16:46 GMT

I now know not to pour through the carburetor. That IS the method
described in the instructions on the can of Sea Foam. They say it's
also possible to use a vacuum line, but the carburetor is mentioned
first. Maybe they should change their directions.

My truck doesn't have power brakes or A/C. Any other recommendations?

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Paul Hovnanian P.E. - 20 Jul 2006 02:41 GMT

> I now know not to pour through the carburetor. That IS the method
> described in the instructions on the can of Sea Foam. They say it's
> also possible to use a vacuum line, but the carburetor is mentioned
> first. Maybe they should change their directions.
>
> My truck doesn't have power brakes or A/C. Any other recommendations?

As was previously mentioned, an EGR or PCV valve.

Its possible for a good backfire to jam or otherwise bugger up the
internals of things like PCV valves. This will cause a vacuum leak, but
not to the outside world. This will make detection more difficult, as
the leak will not be audible.

One way to diagnose such a problem is to locate each hose feeding into
the intake manifold and, with the engine idling*, pull it off. If the
engine lugs own or stalls, it probably wasn't part of the leaking
system. If the engine RPM remains constant, try plugging the port into
the manifold with your finger. If the RPMs pick up, that could be the
leakage path.

*if the idle is already rough, adjust the speed up first with the idle
speed setscrew rather than having somebody step on the throttle. This
technique depends on a consistent throttle/idle setting.

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corning_d3 - 19 Jul 2006 04:19 GMT

Pull the hose out of the brake booster and plug it while the engine is
running. Seafoam was meant to be pulled into the engine thru a small
vacuum line. Pouring petrol into the carb is a bad idea, unless you
hate your facial hair..

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