Throttle surge at 1500 RPM
 

Here's a new issue... The throttle on my 2002 Blazer has been surging intermittently. I can generally make it happen around 50mph / 1500rpm.

While holding the pedal steady on a level road at that speed / RPM, the engine RPM will jump higher and drop back down by itself. I only need to go slightly faster or slower to make it smooth out. Did a lot of driving this week, and performance, gas mileage, etc. has been otherwise normal. SES light is not lit.

I'm thinking there might be a dead spot in the TPS. Any other ideas?

Muchas gracias!

Sounds like the torque converter is unlocking then locking up again. 45-50mph is the speed for this to occur. It really won't hurt anything.

I have the same problem with a 98´Blazer :(

I try to avoid this speed range, but this is not a solution :(

If it is very pronounced and the RPMs will stabilize to the high side if you lightly tap the brake pedal while maintaining constant pressure on the accelerator, you may be experiencing a phenomenon called torque converter shudder. You can search for "torque+converter+shudder" or "tcc+shudder" on the forum to hear what others have experienced and what steps others have mentioned to alleviate the concern.

Thanks! Good to know it will be OK for a while. I don't have a garage, it's a bit cold to be working on it in the driveway... Was out driving yesterday, but holiday traffic etc. would not let me get it up to speed long enough to test response to the brake pedal. I did read up on how the trans uses input from the brake pedal switch to affect lock-up.

Might be time to service the trans. Had a GM rebuild installed maybe 60-70k ago...

Did various types of driving in the past few days. Was able to hold it at 45-50 mph on several occasions. Wanted to try tapping brake pedal. Problem has not recurred. Seems strange, but I'll take it...

Start by verifying transmission fluid level. The torque converter will start locking/unlocking like that when the trans gets about 1qt. low. Besides that TPS/MAP/MAF are used for shifting so those could be other variables that can affect converter issues.