Carburated 1984 toyota 22R. Rough Idle and rare but occasional stall, COLD engine only. When I say cold engine only, I mean it's like an ON/OFF switch between just below normal operating temperature, and normal operating temperature. When the temp gauge needle hits horizontal, the idle speed returns to normal, the afterfire during deceleration stops, and the nasty carbon filled exhaust is not puking black anymore.

I believe something is making it run rich. I check the choke and it is fine, when the engine is half warm the choke is wide open. I'd suspect the EGR valve but the only thing stopping me from ripping it out is the fact that the problem goes away when the engine is warm. EGR would cause rough idle all the time would it not? I was so sure it was the BVSV's (thermal switch that controls vacuum) that control the EGR system and AAP, but they seem to be fine. I have the 84 factory service manual so it's pretty well explained; but the trouble shooting guide only gets you so far.

Any ideas carb and emissions experts?

Cheers.

 

Check the aap (aux accelerator pump) on the carburator, pull the vacuum hose off and see if there is gas in the vacuum hose, if there is replace the aap diaphragm and that will fix your problem. I just went through this same problem on my 84 4Runner.

 

BINGO! Ya know I ruled that out cause I was sure I just put a new one in, must have been the previous carb...or Neihoff's quality is down. Anyways, guess all I needed was someone to tell me...cause as soon as you said it, it made perfect sense, cause the AAP only operates when the engine is cold. As soon as the engine is warm, the BVSV closes, and the extra gas is no longer getting sucked through vacuum line.

Just happened to have the diapragm laying around, plopped 'er in and she runs like a top. I wish you could just get a diapragm kit cause that's the second carb kit in a year and all I used was the diapragms.

 

is it hard to install the aap? im not really familiar with carbs but mine is havin the same prob...just wondering if it was difficult.

 

No its not hard, its just 3 screws to remove the cover. I did mine with out removing the carb and it took about 15 minutes.

 

Aap did not fix mine so i swapped the accelerator pump on the opposite side

 

When do you check the Check the aap (aux accelerator pump)? After your done running it and its warmed up or while its cold?