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Discussion Starter · #1 ·
I am about at the end of ideas. I have a 91 S10 Blazer 4.3 4x4. It has developed a misfire/rough idle and now occasionally stalls.

Misfire seems to only be noticable at idle to 1/4 throttle.

Stall happens in reverse usually at low speeds or at a complete stop with my foot on the brakes.

Whats been replaced within the last 6 months:

-Cat removed & Flowmaster exhaust installed
-Map
-TBI rebuild
-O2
-TPS
-EGR
-All vaccuum lines have been ziptied into place
-Plugs
-Wires
-Cap
-Rotor

There are a few other odds and ends that are not coming to mind. All parts have been replaced with new. All TBI attached sensors have been replaced.

I am sucking oil into the TBI on occassion or so it appears.

Any ideas on where to go next?
 

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Discussion Starter · #3 ·
Compression seems normal if not good considering (315,000 Miles). Lots of performance when I get on it. Vacuum is a must check.

Thanks!
 

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Mine used to stall while braking or stopped but a new IAC fixed that... you can clean it but i hooped mine so a replacement was in order
 

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Discussion Starter · #5 ·
Vacuum is good or seems to be. AFR is odd to say the least..

Idle after warm start is around 12

While driving ranges from 10 to 16
and under normal acceleration is consistent at 14

When breaking drops WAY low.

IAC was replaced new in August. I will update the orginal post too. I may have damaged it due to improper install however.

Thanks for the ideas guys!
 

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You could have a leaky brake booster, after you shut the truck pump the brakes a few times if your booster is good the brakes should become extremely hard after a couple pumps once all residual vacuum is used up. If booster is bad it will remain easy to pump brakes. Also if you pump your brakes while truck is running if you can make your truck stall just by pumping brakes its a good sign your booster is pooped. My 96 jimmy had that problem. It also wanted to stall right after i let of the brakes and was about to take off.
 

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Replace the PCV valve.

I replaced the plugs in my van, it ran good for 2 days, was missing for some time untill I pulled the Bosch POS's out and put in some NGK's, hasnt been missing since.......
 

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Vacuum is good or seems to be. AFR is odd to say the least..

Idle after warm start is around 12

While driving ranges from 10 to 16
and under normal acceleration is consistent at 14

When breaking drops WAY low.

IAC was replaced new in August. I will update the orginal post too. I may have damaged it due to improper install however.

Thanks for the ideas guys!
Your vacuum readings are low. You should be at least 16 to 22 HG at idle.
I would check the brake booster, and PCV like mentioned

Vacuum Testing
http://www.aa1car.com/library/vacleak.htm
 
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