So I changed my crankshaft position sensors (brand new AC Delco) and it didn’t do anything at all to fix the problem.
I was trying to figure out if there was any detail which I hadn’t posted yet. When I am driving and I cancel the cruise control with the lever, I hear somewhat of a “thunk” sound. Also, when I see the RPMs on the way down, once they get to 500 or below, if I hit the accelerator to try to “catch” it, it will hesitate for a moment with no change in the RPMs, then “wake up” with a jerk like I hit the gas hard from a stop.
Last Friday, I found an old post on a forum somewhere about someone having the same issue. They mentioned that they had cleaned the EGR valve, so I figured with two bolts and a connector being all that needs to come off to remove it, I might as well try.
I held the valve in basically the same position that it is installed (meaning I didn’t turn it upside down) and sprayed in the opening with throttle body cleaner (not carb cleaner). I then used a “pipe cleaner” to clean the inside, and I also worked the plunger up and down after I sprayed it.
I had a few “false alarms” in the past thinking it was fixed, so I wanted to wait until I was sure before posting. I now have to lose the habit of constantly glancing at the tach to see if it’s about to stall.
Thank you to everyone who posted here to help me. It would be interesting to know why cleaning the EGR valve fixed it.
Thanks for posting the update, and glad you finally got it solved! A faulty EGR – in its normal failure mode of allowing too much exhaust gas to pass into the intake manifold or allowing exhaust gas to pass when it shouldn’t be letting any through – that usually produces stalling-like (or hesitation) symptoms on acceleration, which you said you didn’t have. But if the valve sticks slighly open and never fully closes, that could produce the symptom you noted. That isn’t as common of a failure mode, but as you have found it, it does happen. Usually the ECM would detect it as an EGR failure, or at least complain about the air/fuel mixture beingout of whack, but for some reason your car’s ECM wasn’t able to figure it out in your case.
...allowing exhaust gas to pass when it shouldn't be letting any through...
I have that problem myself sometimes :).
But seriously, the car didn’t have any issues at all as long as my foot was on the accelerator.
I should have cleaned the EGR valve first, but you know what they say about hindsight. At least I only spent about $135.00 in unnecessary repairs. I should be happy I didn’t spend a couple thousand like some have before finding the issue.
Thank heavens. Very interesting. Now I wonder if thats what was wrong with my Riviera before I junked it. I know I looked at it but don’t think I ever took it off because it looked so rusted on that thought I would create more problems. You woulda thunk that there’d be a trouble code or something that would have been set. Who cares if it worked. Congrats. Now you’ve earned your star so you can post to help others here.