89 Blazer Surge/Miss/Shudder

[ZJumper]

Hello everyone. I recently picked up a 1989 Chevy Blazer 350 TBI, 700R4 with 94K miles that is bone stock down to the stereo. It starts great and idles fine. Under hard acceleration it accelerates with no problems, but when cruising at very light to light throttle in 3rd or in OD it has a very light stumble, miss, shudder, shake that I can't really pinpoint. I don't know squat about the TBI system on these rigs as I've been a q-jet carb and efi guy my whole life.

I've looked around at all the vacuum lines/PCV valve etc. Where should I start looking next? Is there a TPS on the TBI system, and if so where? Any ideas on where to look to fix my rig would be much appreciated. Thanks.

 

[4x4k20]

i would check the tbi gasket to see ifs its leaking first

 

[ZJumper]

Today, I checked the fuel filter...it was almost plugged solid, so I changed it out. It's still doing the surge/miss but not as bad.

I just checked the gasket you're talking about it and it looks to be ok...maybe I should change it just to be safe? Any other ideas? TIA

 

[blazerguy 90]

If your blazer is all stock I would recomend that you remove the TBI and clean it real good, and replace the base gasket, there is a TPS sensor on the TBI, its on the right side and has a 3 wire plug thats plugged into it. also remove the IAS (I think thats what its called) its the round looking sensor behind the TPS sensor with a 4 wire plug going to it, clean it real good as well as the area that it screws into. the TBI is a very simple fuel injection system to work on, once you get into it a little you will find that out. also remove the EGR valve and make sure its working properly and make sure its not plugged up with carbon, if it is clean it out real good with carb cleaner. I have a 90 Chevy Blazer and I had to do all of these things on mine when I got it, also check all of the vacuum lines, when I got my blazer all of the vacuum lines were shot.

Larry.