First I'd just like to say hi to everyone. New to these forums but not Chevy's and I'm actually posting on behalf of a friend. His Blazer is a '95 4.3L Vortec V6 with just under 160k miles.

The trouble he's having is that when he first starts the engine, it will fire and run for about half a second and then die, but if the gas is pumped it will stay running. If you immediately let off the gas it will die, but if you hold it steady at a higher idle and wait for the engine temp to rise just a few degrees, you can take your foot off the gas and it will idle just fine. I apologize but I didn't think to ask him if this is a constant problem or if it makes a difference whether or not the engine is warmed up. It's definitely an issue when the engine is cold tho.

I did some basic testing- there's power coming out of the coil [but I only measured 3 volts- is that normal?], he has spark and fuel. I tried checking the TPS but the position of the plug made it difficult to put my test leads on the pins and check resistance. Good connections and ground at the battery.

The fact that you can hold the engine at a higher idle and it keeps running sounds like a fuel pressure problem to me, but if that was the case I don't see it continuing to run after the engine warms up just a little bit.

I thought it could also be a relay problem, but the only relays I found under the hood were mounted on the passenger side [3 of them] but they weren't marked as to which relay was what. All I can tell you is that 2 of them were 5 pin and one was 4. I didn't know where else to check for relays either as I didn't see any panel boxes under the hood.

I was also curious if there's any way to pull engine codes w/out a scanner? On some past vehicles, I've been able to ground out the self test input plug and use the check engine light to count blinks and get codes that way. Is there any way to do that with a Blazer?

And if there's any of these answers I could have found in other threads, I'm sorry- I ran a search but maybe I just wasn't using the right keywords because I didn't find anything.

Thanks in advance for the help.

 

Sounds almost like your IAC valve has failed in the closed position. It is located near the throttle valve on the front of the engine. It should be on the opposite side as the TPS sensor. You could try removing the valve and cleaning the bore it goes into.

Another possibility is the EGR valve being stuck open. This is a somewhat common occurrence. This can also be removed and cleaned. You will need a new gasket and one with an integrated screen on the supply line should be available at pretty much any parts store.

As far as pulling the codes with out a scan tool, the only hope you have of that happening is if you have a 95 model truck with the truly OBD1 system. If it has the OBD2 connector under the dash, a scan tool is required to pull the codes. But for the OBD1.5 setups (OBD2 connector under the dash with the ECU in the dash as well), a special scan tool is required.

 

Thanks for the suggestions on the valves- I will check these things out and see if cleaning them does any good.

On pulling the codes- if it does have an OBD1 system, how do I go about checking the codes? Grounding the self test input? If so, where should I look for that plug at?

Thanks again.

 

Check out TroubleCodes.net for what you are looking for on an OBD1 system.

 

You just need the pinout for the OBD1,5 plug. It still has the wires for OBD1, so it's actually possible to still pull the codes with a jumper. I did it on my old 95 Blazer with OBD1.5

 

Thanks for the advice guys. I'll keep you updated.

 

You can get some codes, but not all codes from the OBD1.5 setup using the paper clip trick.

 

Well we haven't tried pulling codes yet, but I suggested to my friend that he try cleaning the battery connections. Reason being is my wife's jeep had acted up in the same manner a few months ago and that's what it took to get it straightened out. Well he was working on it and went to pull the positive terminal off, and the bolt for the side mount snapped off. Apparently there was a lot of corrosion build up on the terminal- I've never seen so much it's eaten thru the bolt, but it's still a problem none the less.

Anyway, he's going to buy a new battery and some post mount connectors for the cables and see what happens.

I'm probably still going to push him to pull any codes we can.

Thanks again guys and I'll continue to update you as I find out more.

 

Definitely not unheard of with the side mount terminals. When you replace the battery be sure to apply either anti-corrosion di-electric grease or, at least, petroleum jelly to the terminal.

 

Okay, so I finally have an update.

My dad had a spare battery he was willing to part with but it's a post mount. So my friend bought some post mount connections and we made the swap. The thing is, is that we had to move the neg. ground from it's original location to a bolt on the motor mount because the cable wasn't long enough to reach the post mount.

Now there's no power, at all- the dome lights won't even turn on. I know it's a good battery, because I charged it before I took it over to install it, and after the initial install we took it to the parts store just to double check it. So the battery is good.

The only two things I can figure is that the new ground location isn't good enough [and we did sand the connection points to make sure there's good contact], or in the process of switching out the battery a fusible link or possibly a relay shorted out. I just don't know where to look for it.

Thanks again for your help.