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stalling when let go of gas pedal!

awesomefullness

awesomefullness

New member
hello all. i recently swapped my engine in my 1997 gp, for the same L36 out of a buick. however, whenever i have the engine under a load and let go of the gas, the rpm's will drop to about 5-600 and then bounce back up to 1k or so, unless i let off the gas very slowly it seems to not stall as often...
at first i thought it was a vaccuum leak, i double checked everything and found no issues. when i swapped the engine, i used the whole upper intake and throttle body assembly off my old engine because i was too lazy to swap throttle cables :th_laugh-lol3:
after the swap it always threw a MAP sensor high value code, and today after it stalled a few times, it threw a throttle position sensor code... why would these only be happening now and no problems with these sensors on my old engine, especially since the sensors and throttle body are from the old engine?
also...the new engine had a small pool of oil sitting in the lower intake manifold...could that have something to do with it? and can these sensors cause it to stall? please help!
 


The pool of oil is likely from not using a sealant on the LIM bolts if that was swapped over. If not it's common enough and when you do LIM gaskets, use a pipe sealant with ptfe. This shouldn't effect the idle.

Since you have the codes, address the sensors that are being brought up. It's possible the engine ground didn't get cleaned and connected as well as it should (lower front trans bolt is the location). Another possibility is that the TB was moved around and either wiring got biffed around or stuff got knocked around. Either way, I'd try swapping the TPS and hoping for the best. If that doesn't fix it, start checking for loose or pulled wiring.
 
LIM was not swapped over by me. i believe its a leak through the pcv valve, as the engine was standing on its side when i picked it up -.-
 
Give the PCV valve a check and make sure you have 2 o-rings, one actually on the PCV itself, and the large one that sits in the lip of the UIM that is covered by the cap that holds the MAP sensor. Been there, done that lol..

Jay
 
The puddle of oil is normal in ALL L36\L26 LIMs, since it is the same exact part. Oil gets pulled from the PCV because the CAM produces great vac. Sounds like a bad IAC solenoid, wich does not always give a code when bad. Good luck.
 


hello all. sorry for the late reply. problem was actually the MAP sensor, the clip which holds it was broken on one side, and the MAP sensor was falling apart as well. All is good, ordered a new clip and put it all back together, no problems or codes since.
 
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