I posted this on the "engine and transmission" forum yesterday but have had no response so I thought I would try it as a general question here to see if I have better luck. I am just looking for some place to start.

My son-in-law has a 97 Blazer with the 4.3 and 4 wheel drive. The motor will start and idles smoothly, but as soon as it is put in gear, it dies. I actually sounds like it is under heavy load as it will start to ping before stalling. We checked the motor for codes and there are none.
Does this sound like a motor problem or is it possible that it is the transmission? I have no experience with Blazers, being primarily a Ford man myself so I don't know if this is something that is common in these vehicles.
Any ideas?

 

Hello MAScott,

There is a lot of help here for you, but you might want to post some more info
Like how many miles you have on the vehicle, and what you have done to
the vehicle for maintenance or major work. With some more background info
I am sure somebody will pitch in with something to get you started.

Mark K

 

Thanks for the reply Mark. I guess at this stage, I'm just looking for some direction as to what to look for. The Blazer has about 160,000 Km(100,000 miles) on it and, as far as I know has had only normal maintenance done to it. My Son in Law tells me that he was driving it home when it started to slow down, requiring more and more throttle until it was barely moving. He managed to get it to his mother's and into her yard. I had a chance to look at it briefly last week and took the codes (none) but wasn't able to spend more than a few moments on it.
The truck is about an hours drive from me and I am expecting to go there later this weekend. I want to jack it up, put it on jackstands and try it with no load to see if that makes a difference. I am really looking for some advice as to what to do next, especially if it acts the same without a load.(or even if it does make a difference.)
The motor runs smoothly at idle and will rev up in neutral. It only stalls when it is dropped in gear and the accelerator pushed. I am leaning towards the problem being transmission related but I'm just guessing at this stage.

 

There are a lot of things that might cause this. I'm not your best source, but transmission problems, fuel problems, and vacuum leaks are all high on my list of guesses. Pinging sounds like lean air-fuel ratio, so I'm thinking fuel.

My first question is whether it might have low pressure at the fuel rail (which would suggest a plugged fuel filter or a failing fuel pump). If you're up to it, follow the fuel system diagnosis instructions at https://blazerforum.com/forum/tech-articles-diy-29/96-fuel-system-diagnosis-23038/

The other thing that will probably be useful to know for anyone who comes to help later is whether you can detect a vacuum leak. Search the forums for ways to check vacuum pressure or test for vacuum leaks.

 

Man, that fuel pressure test thread is getting a lot of links lately!

If that checks out ok, then there are other things that you can run through. Clean the EGR valve, throttle body (including IAC valve), and MAF sensor (all of which are covered in great detail in other threads). Maybe check the intensity of the spark.

Can you keep the engine running by giving it some throttle?

Now for the administrative duties... Please read through the rules of the forum. Just because you have not gotten any responses in the original thread does not mean that you should create another thread in another area. This is defined as Double Posting and is prohibited by the rules of the forum.

I mean... Come on... You barely waited 24 hours before jumping ship and posting another thread. You MUST have patience. No one is getting paid to respond in any case.

*Merging the two threads together*

 

OK, first of all, I want to appologize for breaking the forum rules and double posting. I guess I was just anxious to get some direction before going there to look at it. I realize no one is paid to give advise and am very thankful for the help I have received to date.
I want to thank mgkyle for the link. When I checked it, however, I realized that I have neither the tools or expertise to do such a diagnosis. I did check around the manifold and injector with a propane tank and could find no indication of a vacuum leak.
I tried the truck out today, started the engine and tried accellerating it both in neutral and in drive with the back wheels off the ground. The engine would idle and rev quickly to about 2800 - 3000 revs, then appeared to load up. It would not exceed 3000 rpm no matter how hard the pedal was pressed, actually "loading up" more until it stalled. The rear wheels turned when in gear which seems to rule out transmission or locking brakes as a contributing factor.
The noise, which I had indicated was "ping," appears to be much lower in the engine and seems more likely to be bearing noise or piston slap. It is not severe and only happens when the engine is fully "loaded up."
I'm beginning to believe this may be a problem beyond my limited abilities but would appreciate any further suggestions before it is turned over to a pro.

 

Starting to sound like a clogged catalytic converter. Pull the O2 sensor directly ahead of the catalytic converter (B1S2 on a 1997) and see how it runs. It'll be loud, but this will tell you if the catalytic converter is restricting exhaust flow.

 

Thanks. We'll try that.

 

swartlkk, thank you so much. We removed the O2 sensor as you suggested and the engine ran beautifully (though noisily) so it appears your diagnosis of a clogged catalytic converter was right on the money.
Now he just has to replace it and he is good to go. Thanks again.