My Blazer started idling hi and rough, like a plug was fouling, I took it to the shop & they said a plug wire was arching on the block and it was good to go. I picked it up and about 3 minutes into driving it did the same thing and stalled in the road . took it back to the shop & they called me saying no codes came up, this is where it started to get expensive. I replaced plugs & wires , EGR Valve , ignition control module , fuel injectors , now it doesn't stall but idles rough , the worst in drive when I come to a stop & reverse. I love my Blazer but I can't afford to replace every part under the hood. ( if anyone can help me it will be greatly appreciated )

 

There are two different ways to address a vague problem like a rough or a high idle. One is to stab at the long list of things that can cause problems like this until you stumble across the issue or you can systematically go through a testing process until you find the problem and then replace or repair that part(s). If you don’t get lucky the first approach can get expensive. The systematic diagnostic approach is tedious for some people and requires more test equipment and a problem solving mindset.

im one of the diagnostic and testing guys here. I’ll give you a starting list of things to test/evaluate and I’ll be glad to help you if you want to go this route. If not no problem.

1) Still no codes?

2) what are the fuel trims at idle and 2500 rpms?

3) Have you looked at a misfire counter?

4) Do you have the ability to look at live data to check the sensor values to see if they make sense?

5) Can you look at CMP retard?

6) Has anyone done a compression test?

7) Have you looked for vacuum leaks?

8) Have you done the LIM repair yet?

9) Has any work been done on the fuel injection spider?

10) Do you know your fuel pressure readings?


Theres more but this can get you started. There are so many things that can cause a rough idle that you have to narrow it down. Here are some possibilities:

Fuel pressure
Bad injectors
Bad fuel
Spark
Spark timing
Vacuum leaks
Bad sensor (tps, ECT, map, MAF, O2 ...)
Low compression (valves, rings, head gaskets, ...)
EGR
IAC
...


George

 

Scratch 9), I see that you had your injectors replaced.


George

 

First suspicion, air leak or leaky vapor return from charcoal cannister (or bad cannister.)
The 95 FI system relies on an air solenoid to trim the idle air, and also fuel vapor return from the tank for correct mixture.
That = "too lean" and will lead to misfire.

Also your mechanic screwed you several times. Its illegal to replace parts that dont solve a problem under Consumer Protection laws of all 50 States.
They are clueless and are "shotgunning' the problem (blindly replacing parts) which is ILLEGAL.

 

If this is true then you will see it in the fuel trims.

George