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Now the 87 Blazer is acting up

ktmoutfront

ktmoutfront

We live in the stupidest times.
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Bone stock. 45k on new GM engine. 102k on truck.
This does not happen during cold idle.

If I hold the throttle just off idle, it sounds like a big block on alcohol. Durring exceleration and deceleration it is fine. Running at fwy speeds it is fine. But if I run it just a crack open, it lopes. Has never died. No black smoke that can be seen. If I open it up a hair more or completely back off, it goes away.

I changed the TPS and checked the timing. TPS was no change and timing is right on.
 
When I tore down my engine the other night. I noticed the bolt torque to disassemble seemed weak. The EGR port of the gasket was blown. Oil leaks at the back of the manifold also. I tried the propane torch to find vaccuum leaks and found nothing. My engine had way more symptoms and problems but I realized something while troubleshooting. Don't overlook the simple mechanical failures. Bolt torque being the a problem when we run them how we do
 
ktmoutfront said:
Bone stock. 45k on new GM engine. 102k on truck.
This does not happen during cold idle.

If I hold the throttle just off idle, it sounds like a big block on alcohol. Durring exceleration and deceleration it is fine. Running at fwy speeds it is fine. But if I run it just a crack open, it lopes. Has never died. No black smoke that can be seen. If I open it up a hair more or completely back off, it goes away.

I changed the TPS and checked the timing. TPS was no change and timing is right on.
Click to expand...



did you check for codes?

sounds like an EGR sh*ting the bed..
 
yeah, that's exactly the conditions the last one I had going bad did.... surprised it didn't throw a code tho... our systems LOVE to throw EGr codes at the drop of a hat...
 
Do you have a scan tool or? Check IAC counts when fully warmed up and even driven. Then check IAC counts at idle in gear and park. Under 40 is acceptable on a stock engine. 20 is better.

When the throttle shaft/blades wear on these TBI units the blades close.

When idling look down throttle bore and see if fuel is puddling at bottom.

If puddling or IAC counts are high turn min air screw in 1/4-1/2 turn.

Use your timing light to look at injector spray pattern. It should be cylindrical and same on both sides with very few drips, check idle and off idle when issue occurs.

I still don't like any brake fluid for vacuum leak tests and even starter fluid has changed over the years for EPA compliance... ie... does not work like the lod days. Try a propane torch and spray at throttle shaft bushings when cracked open/problem occurs. This is where they wear. Any shaft play at this point?

For anyone with EGR codes that keep popping up and no EGR issues? Do you now have dual or free flowing exhaust? It makes the EGR test harder to pass. I've found the test in the chip and can adjust it so the high and low are more in line with new exhaust and will pass test. This is a fix, not a dis-able test.
 
Spray looks good all the way through the rpm range. Checked tbi shafts already. Will mess with it more on Monday.
 
x3 on EGR.

Sounds like the same thing my truck was doing. I unplugged the EGR and it went away instantly.
 
I finally was able to look into this. Pulled the EGR valve. Was black, but no build up. Moved freely and worked with light vacuum. Replaced it based on you guys saying it was bad, even thoigh it looked good and worked.

Obviously did not work correctly, because the new one solved the problem. 30 minutes total time.

Thanks for the input.
 
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