Hello, i have a 93 s10 blazer with a vortec 4.3 4X4, the problem is that it idles rough when the engine is warm sometimes stalling, it runs fine when its cold. it also have a hard time starting intermittenly, i would have to crank it four 4-5 times for 40 sec before it would start. i am not sure if the two problems are related but this is what i have done so far within the last year. new cap, rotor, plugs, plug wires, most vacuum hoses, ignition coil, fuel pressure regulator, and fuel filter. i have search for similar problems in this forum but have not had any luck. any help???

 

You should get yourself a fuel injection pressure tester guage, it will come in handy for knowing if your pump is shot or not. It will also tell you if you have a fuel leak internally. It threads on a little nipple behind the plenum where your fuel lines enter the intake manifold. Your pressure should be 55-60psi with the key on and not dropping off at all, then down to about 40 when starting and back up to 55-60 when running. I bought one of these for 50 bucks at the parts store and its a handy tool allright. You might also do well to take off that little VORTEC cover on top of the engine, and remove that little hockey puck looking thing have have a look inside the intake with a flashlight for puddles. It should just look oily black with NO puddles in the low spots. The puddles means trouble. If you see puddles then there is plenty of topics on here about the 'spider' injection system and all the how to's and what fors you will need to know. Theres also a great link from Gimpy for ordering this part for 180-300 bucks depending on what parts you want. The dealer is going to want over 800 bucks for it, so get the aftermarket if you need it.

Are you getting any trouble codes? (the Service Engine Soon light)

 

I will check the pressure, I was not aware that it had to be between a specific range (I notice the pressure valve before and pressed down on the nozzle and it shot out fuel, I assumed that is was good). It did have puddles before i replace the FPR, it is dry now. I did read a couple threads that suggests that a faulty EGR valve could cause rough idling, is it worth it to replace? the check engine light is not on.

 

You should pull out your EGR and take a look at its condition inside. maybe its all gummed up. If you have AC you are going to have to pull that upper plemum off to get it out though, it wont fit no matter how you turn it cause the AC bracket is in the way. If its full of crud, the cans of combustion chamber cleaner work wonders on breaking that stuff down so you can wash it out.

EGR valve is like 150 bucks... I wouldnt mess with it if it isnt throwing codes... Mine is so I think Im going to have to try a new one. If the moneys not a problem then go for it. I have 3 daughters so I hate spending money on cars cause no matter what they always need money for something, and its always a little more than what I got ... Makes me wonder what Im going to do when they are all teenagers, pull my hair out I guess and moonlight.

 

Fuel pressure was good, the parts store wanted 200-240 for th EGR valve, i dont have that kind of money to throw at my blazer. i got a local shop to diagnose the problem for cheap and they said it was the ignition control module, got the part for $40 at napa, just changed it and will see if this fix the problem.

 

Yeah EGR isnt cheap. Thats why I like the UPullIt yards.... EGR valves fit in pockets and dont cost anything... And you could get the same EGR off of Astro/Safari vans or S10 trucks of the same generation too. My CFI spider came from a safari van. Also, you never know what kind of goodies you will find there. I got a cold air intake for my toyota for 10 bucks with a K&N filter on it. I like to take a peek all the time for good speakers in the cars too. Ive gotten lots of good speakers there for 5 bucks a pair, sure beats 200 for a new pair and they play just fine.

 

Usually when the module goes bad it's just bad. Rarely are they intermittant but I'm not saying never.
When you said you cranked the engine to get it to start for 40 seconds or so that could indicate that your fuel pump relay is bad and the voltage is going to the backup through your oil pressure switch. When you first turn on the key can you hear the pump run for about 2 seconds and then shut off?
I hope the Ignition Module cures your problem. You can take them out yourself and get them tested at pretty much any auto parts store. They usually do it for free. In fact I've never been charged for it. They want to sell you the part if it's bad. You can't test then yourself. It takes a special voodoo machine. I guess your mechanic had a machine or he took it to the parts store. You should have them run the test a minimum of 3 times. (This for future reference)

 

the ignition control module did not fix my idle problem, im not sure what the local shop did to test to show that the ignition control module was bad, for what its worth they wanted to charge me $250 for parts and labor, i did it myself for $40. i will have to wait to see if the starting problem is still there, i can hear the fuel pump everytime i turn on the ignition so i dont think thats the problem. with the starting problem i had to crank it 4-5 times about 30-40 seconds. That problem does not happen all the time, maybe a couple times a week when the engine is still warm.

 

You can still take the old module to have it tested. If it's good, you have a spare.
What was your fuel pressure? You know you could have an intermittant pump. It should fire right up. Have you looked at your spark plugs. They usually tell a story.
As far as a rough idle, how's your PCV valve? These litt;e suckers have caused problems since they first put them on.
Did you say you are not throwing out any codes (besides 12)?

 

I have seen several ICM's throw intermittent faults. Heat is a definite factor to their reliability. If the heat doesn't escape properly, it can cause problems that will go away once the component temps drop a bit.

You definitely should have it tested though. And have them test it repeatedly (at least 10 times in quick succession).

If you haven't done so already, you really need to get a fuel pressure gauge on that thing. That is the only way to really rule out the fuel system.