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Any quick fixes for a rusty stuck heat manifold riser valve? I want to spray it with solvent and hit it with a wood handle but thought I would ask about it first...  

giving it a spray with wd40... and carefully working the shaft more and more and more until it moves a quarter turn freely... is how most people unstick them...

i normally disconnect the vacuum control while doing this...


warning..  you might really want to check the vacuum hoses and actuator..

without vacuum applied to the heat riser valve.. it will remain closed... blocking the flow and diverting it across the intake manifold .....

i looked for heat riser valves for a 90 buick...   which model do you have.  from what i saw... 88 was the last year for heat riser valves.. at least in the applications i looked at..


there is a ported vacuum switch on the intake manifold. this valve switches vacuum on at a low coolant temp... usually around 110F  below that the vacuum is blocked to the heat riser actuator..     the vacuum hoses that connect to this vacuum switch for some reason get a lot of fuel vapor exposure.. and get really soft and leak..   this causes the heat riser valve to stay closed...

try not to spray WD 40 on the oxygen sensor...  

Thanks, I'll give it a try when weather gets warmer. I have a 1990 Buick Estate wagon with a 305 V8. Seems like it is affecting my MPG and maybe will affect my EPA inspection this July. It just barely passed Ohio inspection 2 years ago.  

what's interesting..  that exact model does not show a heat riser valve..

it does show an EFE grid that is in the carb mounting gasket...

what is the 10th digit of the vin number????  the 8th digit should be a" Y "  

the VIN is 1G4BR84Y7LA406364. I noticed that that vacuum line is a metal tube rather than a rubber line from the vacuum port.