Holy smokes guys, I just got done replacing the water pump and filled up with coolant again, go to start the engine, and bam. It was a weird start, I could feel something was off, and it was idling very poorly from the start (about 1000 rpm cold start). Soon after when the idle went down to normal (550 rpm) it was struggling like mad, very weak. By weak I mean I would give it some gas and it would rev up fine then once off the throttle the rpm would dip very low, almost stall (200 rpm). With AC on idle rpm dropped to 400, I also got it to stall with the AC on and just giving it some gas! What's VERY weird is after I got it to stall I started it up again and all the above symptoms were gone, it was still a rough idle but the normal idle it has had. I've been having weird things with my idle lately, sometimes I will come to a stop at a red light and the idle will just jump all around like mad, usually with the AC or heat on but it has happened once without too. Guys should I honestly just try a new IAC valve? I have had idle problems ever since replacing that valve, but I can't ever seem to prove it's causing the idle issues.

 

Given all the diagnosis we have tried, i would agree with that possibility. Keep in mind that you might have to readjust the throttle stop again to get reasonable IAC counts.

 

Thanks, Les, it's just so weird I can't get that to happen again now! You should have seen when I made to stall by just giving it gas with the AC on, I had a big smile on my face because things were finally happening and I thought it must be the IAC valve acting up finally. But I took it on a 1.5 hour drive today monitoring IAC counts the whole time and they looked normal, everything went normal. Almost makes me think something electrical could be going on causing an intermittent problem like that! I'm not even sure anymore after thinking about what I want to do here, in my line of thought the IAC valve either mechanically works as intended or doesn't work at all (you could still have gunk in the TB and it's clogged up = poor performance). I'm just having a hard time believing the IAC valve is intermittently failing as I explained in the previous thread, but I still feel like it's an IAC-related problem. I was reading up yesterday about bench testing the IAC valve using a multimeter, there was also something about manually actuating it on the bench with battery power, any tips on doing this for our IAC valves would be very appreciated!

 

I'm quite sure IAC uses a stepper motor. Probably pretty difficult to control on the bench. You may want to read up on them before trying it. Good luck! Keep us posted!

 

Thanks Les, I'm back here with some more stuff! So a few days after replacing the water pump, I was leaking more coolant. The rad failed! So it took three more days to replace that as I needed to wait for the thread sealer to dry around the oil cooler adapter. So three days pass and I replace the rad and am ready to start again. Start it up and I can tell it's again not right, and sure enough, it's doing this same thing where it wants to die when I let off the pedal, can't compensate for me turning the AC on, and I got it to stall out with turning the steering wheel while I had the AC on and I revved it a small bit. Here's the thing! So while it was doing this I waited for the rpm to come down to normal (600 rpm) and IAC counts were way high, at 128 on idle with the AC off and just idling. That's why it's running like crap! The counts are usually at 60 for the same rpm... So I made the truck stall out and turned it on again, it did the same thing once more and I was able to stall it again, then I turned it over again and boom IAC counts back down to 60 and it runs normally again I could not get it to stall or even dip in rpm. So what could be happening here that my IAC is at 128 counts when it should be only at 60?

 

It seems IAC is intermittently not controlling. I believe you are reading the actual position not the commanded position, but I'm not 100% on that. Personally I would go ahead and replace the IAC (but one from a completely different source just in case the first manufacturer somehow got the application wrong). Good luck!!

 

Thanks Les, so I think it's safe to say I have identified a problem with the IAC valve. If it wasn't so expensive I would go ahead and get a new genuine one but I really want to be sure here. It's just such a tough call, as I was saying before I was having idle problems ever since replacing my IAC valve and putting in this one. What led me to replace the IAC valve was last summer one day I tried to go to work and my truck just out of the blue would not start, it would only start if I was holding down the gas pedal and it would only stay running if I was on the gas pedal, as soon as I let off it would die. So this led me to think my IAC valve was stuck closed and decided to get a new one, the thing is I came home from work that night (found a different ride) and the blazer started normally and I took it for a drive. I still replaced the IAC valve the day after that and it did have some caked-up carbon on it so I was thinking it was plausible it was stuck, then freed up later when I was able to drive it. Since replacing the IAC valve it has had a rough idle, even through a whole engine rebuild the rough idle persists! I still have the old IAC valve which I believe is the original one, I have cleaned it up the best I can, do you think it's worth it to try and switch them out and see what happens?

 

Absolutely try the old one!! If it still runs the same it's not the IAC valve!!

 

Thanks Les, I will try that out here in the next few days. Holy smokes guys, my blazer just keeps on giving this time of year!! Waterpump to the rad, I thought I had the cooling system done up for the winter time and good to go. I went out just a bit ago to do a little weekly inspection of everything to make sure it all looks good and saw more coolant in the same spot on the frame as when the rad was leaking! So of course I opened the hood and boom take your pick, coolant on the inner part of the hood, coolant all over the rad. Since it was leaking close to the upper rad hose I didn't want to condemn the new rad right away so I started it up and had a look, let it run for a few minutes, and no leaks. Turn it off and boom leaked right out of the upper rad hose!! Guys I really thought I had seen all the leaks I needed for this year, honestly might just be better to park it up and try again next year LOL. But in all seriousness, I checked the hose clamp and it's tight, it's already making an indent in the hose so I don't really want to tighten the clamp more and possibly damage the hose. What would you guys suggest to make this hose stop leaking for good?

 

New hose or cut it back some. About all you can do. The neck is same size as before, right?