I have a 1989 Toyota pickup truck, 22R 4 cylinder with a 2 barrel carb. and manual transmission. It currently has about 215k miles on it. At 160k the engine was torn down and looked really good so no major changes were made. The problem I?m having is the engine idles really hard, sometimes it shakes pretty violently. I checked the vacuum lines, ignition timing, air filter, pcv valve, thermostatic air cleaner, and sprayed the carb with cleaner. I took off the old egr valve (which was clogged with carbon) and replaced it. I then set the idle speed to the specified 700 rpm. The problem is the engine still bounces around and the engine speed goes up and down between 600 ? 800 rpm, sometimes jumping as much as 60 rpm at a time. When the engine first starts up it runs ok, but once the fast idle cam disengages it runs rough and lopes. When I accelerate it runs ok and does so even for a few seconds after I let off the gas but then it runs rough and lopes. Does anyone have any idea what the problem is?

 

Have you checked for vac leaks? Visual inspection isn't going to get it for vac leaks.

Clean / rebuild the carb?

 

thanks for the response...

I checked the vacuum lines with a stethascope, I didnt think I heard any hissing, I read that you can check for leaks with a soap/water mixture and see if there are any bubbles, this didnt make sense to me as I thought that kind of trouble shooting was only applicable for air escaping out of something like a tire, not being sucked into something like vacuum lines, am I wrong?

Also I put on a rebuilt carb just a few years ago

 

Never used soap and water.. I generally use carb cleaner.. Spray it on the base of the carb, the manifold, anywhere you suspect leaks... If the engine changes running RPM, you've hit a leak.

 

Check the Carb. Sounds like a stuck float.
Possible dirty fuel filter
Leak around Carb. sucking air

 

yeah check the carb. Choke could also be stuck