So for some background information I recently bought an 08 Chevy Tahoe with 201k miles for $1900 bucks. The seller let me hook up my tool and was up front about the check engine light and the P0121 code. After purchasing it, one of the first things we did was clean the throttle body. After finishing that, the heater core hose snapped at the firewall and sprayed antifreeze everywhere. A day later we replaced the hose and started the truck up. The p0121 code was gone but the truck still had issues idling and had another code. The idling issues were a bit to be expected after seeing the state of the throttle body but we next went to work on the p0449 code and replacing the snapped evap solenoid above the spare tire that sits under the truck on the backside. After replacing that, we finally were code free and rid of the check engine light, but still had major idling and surging RPM issues. At times after starting up the truck they would soar and maintain over 2k. We tried to manual reset, I even bought the idle relearn 977-002 tool. The tool wouldn’t work due to starting the truck with it plugged in the rpm would stay over 2k. We replaced the throttle body all together which also didn’t solve the problem.
Finally I took it to a shop and for $25 bucks he plugged in his fancy expensive tool and was able to do and idle reset/relearn. This made a tremendous difference of no longer having 900-1200 rpm in park or staying at or above 2k while driving. However, there has been one fundamental issue that has not improved since I first drove it after the first TB cleaning.. the first acceleration from over 10 mph the rpm will surge and feel like driving in quick sand but after waiting a few seconds with it over 2500, it’ll almost “relax” drop all the way sub 1k and drive perfectly. That is until it’s time to slow down for a turn or having to stop and drop below say 15mph. At which point the next acceleration will do the same thing. Surge/struggle, drop down to where it should be and relax, drive amazing. Rinse,repeat, everytime. The shop said the transmission is slipping and the fluid was a bit low and smelled burnt. We added some and I’m going to get a fluid and filter change here soon but was curious if anyone has had similar issues or suggestions on the problem. For context, when I test drove it he mentioned a similar problem although it wasn’t occurring on first acceleration it was more like from 2nd to 3rd or the 35-50mph range. Also a side note that’s interesting and unique - 2 separate times since owning this truck has it started itself completely with no keys or anyone’s the truck. This last time the doors were still locked and both times putting the keys in the ignition to try and turn it off did not work, only pressing on the brakes a few times did. I did see something about this brings known issue if a aftermarket alarm or remote start is installed, which the previous owner did install an aftermarket alarm. Any help or suggestions would be appreciated.
Finally I took it to a shop and for $25 bucks he plugged in his fancy expensive tool and was able to do and idle reset/relearn. This made a tremendous difference of no longer having 900-1200 rpm in park or staying at or above 2k while driving. However, there has been one fundamental issue that has not improved since I first drove it after the first TB cleaning.. the first acceleration from over 10 mph the rpm will surge and feel like driving in quick sand but after waiting a few seconds with it over 2500, it’ll almost “relax” drop all the way sub 1k and drive perfectly. That is until it’s time to slow down for a turn or having to stop and drop below say 15mph. At which point the next acceleration will do the same thing. Surge/struggle, drop down to where it should be and relax, drive amazing. Rinse,repeat, everytime. The shop said the transmission is slipping and the fluid was a bit low and smelled burnt. We added some and I’m going to get a fluid and filter change here soon but was curious if anyone has had similar issues or suggestions on the problem. For context, when I test drove it he mentioned a similar problem although it wasn’t occurring on first acceleration it was more like from 2nd to 3rd or the 35-50mph range. Also a side note that’s interesting and unique - 2 separate times since owning this truck has it started itself completely with no keys or anyone’s the truck. This last time the doors were still locked and both times putting the keys in the ignition to try and turn it off did not work, only pressing on the brakes a few times did. I did see something about this brings known issue if a aftermarket alarm or remote start is installed, which the previous owner did install an aftermarket alarm. Any help or suggestions would be appreciated.
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