95 Blazer sometimes won't start

My blazer sometimes won't start after running for awhile and sitting parked. It started doing the not starting thing first, now it will run but cuts out between 2 to 3000rpm and will suddenly just croak will driving and won't start back up. I have fuel (replaced filter) got spark (pulled wire and got the snap in the arm to prove it)! I replaced the ignition coil, and even tried a little injector cleaner (why not). It will start up again after sitting for a couple hours but just croaks after it warms up good, HELP! Its gotta be an ignition problem, I would think? I'm new here, so let me know if I am too awfully confusing!

search for CPI injector

It runs fine at idle, if its the CPI don't they usually run rough?

I just changed the cap and rotor as the spark was orange, now good blue spark, same problem. Can you tell me where the egr is on this thing?

If it was the EGR, the engine would barely idle.

Remove the top vortec plate and the IMTV valve underneath it and look down into the plenum and look for washed spots where fuel has washed the normal black deposits away.

It looks kinda damp in there. There doesn't appear to be any washed spots though.

So everything was thick with black deposits?

It appeared to all look evenly coated to me. This thing is frustrating! What about the fuel pressure regultor?

That is on the CPI injector, it was the item you actually peered down onto when you looked inside the plenum.

Grab yourself another upper plenum gasket and remove the upper plenum cover and thoroughly inspect the whole plenum area for leakage.

I think you were right! I removed the upper intake and the whole passenger bank in the lower plenum was washed, the driver side was fine. I believe it is the fuel pressure regulator as it is on the passenger side and is notorious for going bad. I will try a new regulator and get back to ya. Thanks and nice Blazer you have there, mine is also a black LT 4x4. I just got it 4 months ago and have quite a few plans for it. Also my 4 wheel drive isn't working, its electronic. If I put it in 4 wheel drive it doesn't go in and when I go back to 2 HI it just flashes back to 4HI and a loud clicking noise comes from up front when I move. I put on a new vacumn actuator but again, same problem. The only way to get back into 2HI without the clicking is to unhook actuator and jerk the cable. It has vacumn to the actuator any ideas?

don't replace the regulator, you replace the whole injector.

Also, your encoder motor for your transfer case is shot probably or you have a vacuum leak in the line going to the actuator.

My blazer sometimes won't start after running for awhile and sitting parked. It started doing the not starting thing first, now it will run but cuts out between 2 to 3000rpm and will suddenly just croak will driving and won't start back up. I have fuel (replaced filter) got spark (pulled wire and got the snap in the arm to prove it)! I replaced the ignition coil, and even tried a little injector cleaner (why not). It will start up again after sitting for a couple hours but just croaks after it warms up good, HELP! Its gotta be an ignition problem, I would think? I'm new here, so let me know if I am too awfully confusing!
i had a problem like that a few months back mine was the egr

Replaced the CPI, same problem. Am ready to take it out behind the barn and shoot it!!! lol Any ideas?

You replaced the whole injector?

Yes, went ahead and replaced the whole cpi and nut kit. Also changed the egr, still have the same problem. Do you think maybe it is the sending unit?

Did you use a new upper plenum and EGR gasket when you replaced the CPI and EGR valve?

All new gaskets installed, I followed all factory torque specs.

check your fuel pressure with the key on and the engine off.

Ok, replaced the cpi, the nut kit, put on a new coil, icm, cap and rotor, new plugs and rotor, replaced the sending unit, the fuel pump is good, changed the egr, and still have the same problem, truck runs fine when it is cold and hasn't ran for awhile but once it warms up it starts cutting out around 2-3 rpm and then it will die and not want to start back up. Sometimes it won't start if you shut it off until it sits for a few hours. Oh yeah changed the plug wires too. HELP!!!!!!!!!!!!

Will a stuck thermostat cause this? I remember when i bought it the guy said it was leaking and he fixed it before I picked it up. Maybe he got silicone happy. I have noticed some fluctuations in the temp. quage, but it never has got really hot. However the first time it did this dying and not starting it sat for like 4 hours and the motor still felt warm when I got there to work on it.

I'm thinking your cat is completely plugged from the fuel leaking from the old CPI injector.

Do you hear any rattling from under the truck?

No rattling, I already thought of the cat and cleaned it. I bought a new thermostat and temp sensor, will give them a whirl and see what happens.

I don't know, I put in new stat and temp sensor and no change, truck warmed up started its bogging and cutting out and but I could get it started back up 9 out of 10 tries......If I give her throttle real slow it revs fine, if I hit the pedal it bogs and cuts out. Maybe cat is still plugged? If it was the cat wouldn't it do this when it was cold and not warmed up though? It starts all this when the blazer starts to get warmed up and gets worse the hotter it gets or if it is really hot outside.

No rattling, I already thought of the cat and cleaned it. I bought a new thermostat and temp sensor, will give them a whirl and see what happens.

How can you clean a cat convertor?

How can you clean a cat convertor?

By backwashing it with liquified dog... (listens to the crickets chirp)

Yeah, that line caught my attention too a day back and I just could not bring myself to say anything. At least, not anything immediately constructive. You CAN'T clean a catalyst - only replace. At least, that is true about automobiles. Industrial catalysts can be cleaned by chemical processing, but these are the cats that control smog and acid emissions from factory smokestacks... different world altogether.

Its a technical process that involves a ratchet, hammer and a 3foot chunk of exhaust pipe slightly smaller than the inlet and outlet on the cat........ BY the way, the cat looked clean to me, was NOT at all carboned up, I would say it was replaced not too long ago. Which brings me back to the d@*n cpi, maybe the one I got is defective or something. I have noticed when this started my oil pressure is lower at idle, like around 30, but goes up on acceleration to where it always has, but it used to idle about 40-50. I think it is getting a little gas in it and thinning. Will a bad cpi start fine after the blazer has sat for awhile, then run fine till it warms up and then make it bog, not want to rev over 2,000 rpm, sometimes die and then be hard to start until the vehicle has sat several hours? Cold starting and running not a problem just starts its crap after it warms up. I have always done all my own mechanical work and have never had a problem as baffling as this. My 99 xtreme never gave me this s#*t! Thanxs for trying to help all!

By the way BlazerLT I know some give you a hard time about always saying the cpi, but from what I have heard from other owners and even dealer mechanics, this is the most common problem on w code 4.3's.

By the way BlazerLT I know some give you a hard time about always saying the cpi, but from what I have heard from other owners and even dealer mechanics, this is the most common problem on w code 4.3's.

Yea, people think I go on and on about the same thing.

I know the problems with each year and I tell them most common problems.

If anyone has a problem with that I could care less. I am only trying to help. They just see the fact that I help almost everyone and when it comes to the same W engine, we already know the problem in most cases. If someone has a problem with me cutting to the chase and telling them where to look, meh, let them go and spend 1000s trying to fix it if they know better.

Also, you do know you have a pre and post cat O2 sensor so you can't remove everything in the cat and expect it to run properly.

Its fixed! The first cpi I put on was no good, leaking like a faucet. Went and got a new one and no problems now. Blazer running better than when I bought it! Thanks Lt

No problem, no go and get your oil changed ASAP and get a new set of plugs in that engine.

DON'T KEEP ON DRIVING WITH GAS SATURATED OIL!!!!