I have a '95 Blazer that has had a misfire at idle for a couple years. Now, it's beyond that. If you let it set at idle for more than 3 minutes it acts like it's running a high lift cam. It hits so hard the vehicle shakes!

It drives perfectly fine. I think it's flooding out, due to when it begins it's "race car mode" you can give it throttle and it evens out for a little at idle.

There is a code for the IAC, but has been that way for a long time.

Here's what's strange. Fuel, timing, and compression are all up to par. I performed a leak down test as well, nothing. Pulled the intake twice (once to put a new dizzy in), no leaks noticeable. It has all new ignition components and a recent tune-up. AcDelco fuel pump two years ago. I'm starting to think it may be an egr issue, but never seen an EGR cause something so aggressive. It may also be a computer issue, but it'd be weird to only act up at idle wouldn't it? Injector is really loud as well, but has also been that way for a while.

I'm afraid for the engine. As it is my girlfriend's daily at the moment and she has no idea what to do if it were to get worse.. if it could aside from the engine blowing. Any help or ideas are appreciated.

 

plugs rotor cap should all be acdelco. wires also or at least better quality. sounds like and ignition/ elec issue. misfire of some sort

 

I used BWD wires, cap, rotor and NGK plugs. AcDelco and BWD are usually the same part. One company makes them and puts them in different boxes, and never had an issue with NGK's. Running the same setup on my 97. Ill post a video in a few on what its doing.

 

Well sir I must apologize to you. It has to be a misfire. I did another fuel pressure and leak down test today and all is perfect. Primes up to 60psi and only drops 5psi in 10 minutes. At idle and operating temp it runs 53psi steady, even when it begins to skip.

I'm going to change plugs and wires as the distributor is only 6000 miles old, and they have about 20k on them. I hooked my spark tester up, but it's difficult to catch a misfire with that, lol. Here is the video of what it's doing. It has been getting progressively worse over the past couple days. Ignore the turn down exhaust, lol.

https://www.youtube.com/watch?v=UePs...ature=youtu.be

 

I'd say for one you have an exhaust leak somewhere. I don't know if 95's have O2 sensors, but if they do an exhaust leak could cause O2 sensors to send readings that could cause an improper air fuel mix to the intake.

 

I saw the check engine light illuminated on the dash. You mentioned an IAC (Idle Air Control) code. Since the problem is during idle, I would investigate that code and circuit.

 

I didn't mean to put IAC. Lol, I don't know what I was thinking, it was a long day at work I presume. It's a code for the Air Charge sensor. It's been on for a couple years, the connector pushes itself out and every now and then I'll fix it just to get the light to go off.

The exhaust leak is where I had to temporarily put a 4" piece of flexpipe in. Ran out of welding wire, so I just clamped it. The exhaust before had holes all the way down, including one in the muffler. It does have 02 sensors as well.