OK, now that I have put over 3k miles on the Blazer since I got it going, I have noticed one annoying problem.

1995 S10 Blazer 2WD
4.3 (W) CPI
4L60E

So, while the truck is warming up I notice that the RPM's will fluctuate a little (50-100 RPM) nothing to crazy.
If I drive conservatively the truck does ok, at cruising speeds it is ok too.

What I have noticed is that if I get on it hard (Shifting out above 3500RPM) from a dead stop or at speed, when I slow down to stop or drop below 1500 RPMS the idle is bouncing/surging between 450-1300RPM, I have to keep my foot on the brake and gas at the same time to keep it from stalling.

It has only stalled a couple times while it is acting up. I have also noticed that if I put it in park it will idle ok, but it sounds like it has a big lopy cam in it and the fuel smell is pretty stout. If I put the trans in neutral and revv it up a couple of times that will sometimes fix the issue, but this last time it did not.

Some times when it is cold out and I put the truck in gear after it has warmed up for about 10 minutes it will sound like it is going to start surging, but most of the time it will calm down and idle normal, I would say 98% of the time it is fine.

I have installed new plugs (Delco Rapid Fire), wires (Taylor Spiral), dist. cap (Mallory), new rotor (Delco), fuel pump (Delco), FPR (Doorman), EGR Valve (Delco) and I cleaned the TB and the IAC...tested the TPS (nice steady sweep).

I have looked for vacuum leaks too and have not found any. It will not surge if I drive easily but, if I have to really get up and go that is when I have the issue.

Oh, and fuel pressure is KOEO 59-60psi(Key on engine off) and right at 58psi when running.

SES light has come on twice, but the odd thing is that if you shut the truck off and let it sit for a little while the SES light is gone and the problem is too. And no I do not have a code to give (I know it would help) but, each time this has happened I have been out at work and there is no one around that can pull the codes for me.

Thanks for reading and any input you might have.

 

I don't know a whole mess about these trucks, but I feel like I might have been having similar issues lately with my '93. Sitting in park, she was up and down all over the place, a lot of the times she'd stall right out. I was driving back east from Louisiana recently and I was noticing that the RPMs were ALL over the place. I was getting 9mpg and it took forever just to get her up to speed.

My dad and I opened everything up this week and there was gas all up in the spider assembly, it was soaked. Replaced it yesterday, and now she's idles steady and gets up to speed better than ever. It'll take a few days to see if the gas mileage has improved, but it's looking up. Don't know if this helps at all! Best of luck.

 

Well, I've had the same issue before. But mine was a vacuum leak combined with the previous owner turning up the idle using the idle adjustment.

So this is basically what I checked for when mine was doing the same thing:

1) Vacuum Leak
2) IAC Valve
3) Throttle Body Butterfly (to make sure it doesn't have carbon stuck on it)
4) Throttle cable (to make sure it isn't faulty)
5) Check the idle adjustment screw to make sure it is where it is supposed to be at.

Hopefully this helps!

 

Thanks for the input. The idle on the Blazer is at 650RPM, as for the Throttle Body and IACV they are both clean.

If I unplug the IAC Valve it still does it...so, I think that might rule it out as being the culprit. Is there any other test that can be done on the IAC??

Oh, and I changed the Nut Kit too before I installed the engine.

 

Ok, I finally was able to get a video of the check engine light flashes....caution this is a long and dry video.

I counted the flashes and then started to get confused and gave up on some of it...I did not catch it on video but at one point it flashed 5 times really fast then 13-14 times really fast.

As you can tell the truck is idling like it has a huge cam in it but, it is all stock....funny thing is when I shut it off and restart the truck it reset and there is no problem.

It does this every once in a while.

Any input is welcome.

Thanks.

Check Engine Light Flashes - YouTube

 

1995 S10 Blazer 2WD
4.3 (W) CPI
4L60E


The above specs are the same as the '95 I now have - it also had the same issues You've described (and more) . There were a combination of things to correct in my case . The IAC valve , even clean does not mean it works . There are two sets of windings that are pulsed by the engine management to control pintle movement - a good strong IAC will have an audible click noise when the key is turned to run ,right before start . Do You hear a click ? Also , when the EGR was replaced , did You use a new gasket with the screen ? Carbon will prevent the valve from fully seating so the "new" EGR won't close . The last thing was the MAP sensor mounted on the top of the intake manifold - it mounts with an oring type seal directly ported into the plenum - checked ?

 

Thanks for the input "onebadsuv" so this weekend I put some seafoam in the old engine (thru the brake booster line) and changed out the IAC and new plugs (rapid fire) and delco wires.

When I was pouring in the seafoam it started to smoke so I finished and shut off the truck....man that thing "dieseled" for about 15 seconds I tried turning the ignition back on...but it finally died.

In the process of the dieseling it spit out a thick black ozze back out of the booster line....all over my master cylinder.

I let it set for about 20 minutes and then ran it until it quit smoking. This morning I was taking my kiddo to school and it shut down on me 4 or 5 different times.

It had a noticeable miss and it would bog down and diesel before it would die...while driving. So, I popped the hood and noticed arching from the coil...found a small piece of wire hanging out of the boot that connects the coil to the distributor. Clipped the wire and put some tape around the boot and all ok for now.

The shutting down issue was resolved by disconnecting the IAC and now it runs really good....but the odd thing is....No check engine light!!!

Wonder if my ECU is bad and it does not know that it is sick. LOL Any input folks??

Thanks