92 Suburban - misses & ABS

[YooperInCO]

92 Suburban 350c.i. / 4wd.
It starts and idles fine, it runs fine all the time except when very, very, lightly on the gas it will "cycle" between normal engine RPM and very low engine rpm. It will be at normal RPM for 3 or 4 seconds, then bog down, almost like it wants to stall for 2 or 3 seconds and then bump back up to normal RPM.

It will do this in park, which should eliminate anything in the torque conv, transfer case and tranny right? While driving, you don't notice it until you back off the gas, and have very light gas petal pressure (like when cresting a hill), then it will act like you're trying to drive a manual transmission car in to high of a gear, bucking the vehicle some. As soon as I give it more gas, it quits.

Also, the ABS computer is not plugged in. I believe its the connection closest to the firewall that is unplugged. Is there any harm I could do to the vehicle by plugging it in? I have no idea why it was unplugged.

[MT-2500]

Originally Posted by YooperInCO

92 Suburban 350c.i. / 4wd.
It starts and idles fine, it runs fine all the time except when very, very, lightly on the gas it will "cycle" between normal engine RPM and very low engine rpm. It will be at normal RPM for 3 or 4 seconds, then bog down, almost like it wants to stall for 2 or 3 seconds and then bump back up to normal RPM.

It will do this in park, which should eliminate anything in the torque conv, transfer case and tranny right? While driving, you don't notice it until you back off the gas, and have very light gas petal pressure (like when cresting a hill), then it will act like you're trying to drive a manual transmission car in to high of a gear, bucking the vehicle some. As soon as I give it more gas, it quits.

Also, the ABS computer is not plugged in. I believe its the connection closest to the firewall that is unplugged. Is there any harm I could do to the vehicle by plugging it in? I have no idea why it was unplugged.

I would try a good tune up first.

ABS was proably unpluged because of brake lights on or a abs problem.
Abs on them was just for rear ABS brake control.
Plug in up and watch brake light.
If any check for abs codes.

[2000CAYukon]

Could be a bad EGR valve, EGR solenoid or vacuum leak. Testing the EGR valve and solenoid require a vacuum pump. You could try pulling off the vacuum line from the TBI to the EGR solenoid, plugging it at the TBI and taking it for a test drive. If the problem goes away, it is the EGR valve or solenoid. EGR valve should hold vacuum and move freely.

//2000CAYukon

[YooperInCO]

thanks!

I'll give it a try and let you all know what happens.