I have a 88 blazer full size w/ 350 and throttle body. The truck sputters and misses under load but only after being driven for at least 5 - 10 minutes. It starts fine and always idles fine. Doesn't miss revving in park but will do it in drive and brake applied. There are no codes.

Here's what I have done so far...

Cap and rotor
fuel filter
Clean and gap plugs and inspect for damage. replaced one and one was quite oil-fouled.
Replaced one plug wire that had got hot and swelled.
checked for vacuum leaks
Replaced muffler [no catalytic converter]
Fixed pos battery cable that had contacted exhaust and was 1/2 eaten thru and shorting-- giving me an intermittent check engine light. That has stopped.
Timing
Checked EGR- idle decreases when pushed, moves when revved

I have read other posts on this topic and fuel pressure test is recommended. I have a gauge but there is nowhere to hook it up on fuel injection. It only has the tank mounted fuel pump and the manual says you can't work on it or check it and need special tools. How can I get an idea if this is possibly the problem.

I also still need to check for play in the dist. gear.

I'm new here and if anyone has any advice it would be greatly appreciated. Thanks!

I just removed the O2 sensor and it is really dirty. Manual says no solvents so how to clean?

This would seem to be a possibility for my problem as it functions on a loop until it reaches 600 degrees.

EDIT>>>> Replaced O2 sensor and still no help.

 

New fuel pressure regulator and water temp gauge and still not fixed.

I'm getting tired of throwing money at the problem. Remove and inspect the distributor is next I guess.

Would be nice to get any response to my post. It would be greatly appreciated.

 

You need a TBI adapter to test fuel pressure on your engine.

While you are checking the distributor, check the pickup coil.

 

Well, I fixed my problem and have the truck tuned up and running fantastic. Turns out my problem was a little 3-way check valve in the vacuum hose that was broken. One of the first things I had checked was vacuum hoses and somehow had neglected to see the broken T fitting as it had fallen down behind the distributor. One side of fitting led to the back of the throttle return control and another led to a barb on the back of the intake manifold.The third hose went thru the firewall to ? [cruise control?] That line had another T w/ line to transmission? All of that was open because of the broken valve.

Could have had it fixed if I'd been more thorough the first time. You live and learn.


Any way, the truck is fixed and I wanted to post the results. I read a lot of threads about similar problems and most of those posts just end mid-problem with no final chapter. Didn't want this thread to go out like that. Some help there from previous posts and I like the way links come up for similar threads.

I didn't get much response to my posts from the regular members tho.....You must get an endless parade of new members who post the same vague questions over and over and then leave when their ride runs again and no thanks. Probably should have posted this in the main.

Well, thanks for the help.

I probably knew better than to double post as if I didn't know where the edit button was and the thread needed bumping. Thanks to the mod who fixed it and replied.

Actual recent pics of my truck:













Which stripeing package should I go with? I can't decide...

 

Glad you got it all fixed up and that it was something easy! Vacuum controls a lot in the newer K5's and can really cause some whacky things to happen.