Engine I.D. & running problem

I have been reading through this site for some time now and have a couple of questions. My biggest question is I just purchased a 95 Jimmy 4.3 from a friend. It is a 'W' code but the engine was replaced with a 97 4.3. That is all I know so how do I tell for sure what engine I have to be able to buy parts? Were all 97s 'W' code?

The problem is the truck starts but idles horribly, kind of loping and not drivable, I think, I haven't really tried to drive it yet. My friend had the truck for 4 years and always took care of it, the engine change was before they got it. It always ran great and this happened, the EGR, Fuel pump & filter, and a few sensors were replaced before he gave up. It has also developed a coolant leak in the front of the engine on the passenger side. The hoses look good and dry and there is not much room to get a good look at where it is, it only leaks when running.

Also, when running I can hear a major hissing sound at the front of the intake and when I take the hose off the front it is very loud.

So as to the second part of my question I have read through the technical pages and it seems reasonable the intake gasket might be shot, this might explain the leak/noise? As for the running issue if it's not that the likely culprit would be the spider. The leak could actually be a water pump leak, just haven't looked hard enough yet. Is a hissing sound normal at the front with the intake hose off?

Once I take it apart I'll have more of a clue and will be able to check the spider and such but really would like to know when I buy parts what engine to buy them for.

Thank you,
HFK

Did it run right when the engine was first replaced or has all of the bad running problem came up later?
How much of the 97 engine was used like the upper intake and computer sensors? MAF sensor?
The engine itself should be about the same.
But the there is only 4-5 different PCM/VCM setups starting in 95 or even 94 1/2 years?

Is it setting any codes or is the check engine light on?
How is the fuel pressure?
You need to find that coolant leak.
Any coolant in the engine oil?
If it is the intake gasket that could be one of your problems.

When my friend bought the truck she was told that the engine had been replaced with a 97 so I have no idea what was changed/replaced/swapped. I was hoping there was a way to visually i.d. the engine or a casting number somewhere.

She has had the truck for over four years and has never had any major problems and it always ran fine until about a month ago. I was told the coolant leak just started about a week ago well after the running issues happened but maybe it just got noticable and leaked slightly before. They took it to advanced but couldn't get the code reader to work on it. The light is on and I'm gonna go and look for the connector to see if I can try getting any codes from it.

I am still curious about the loud sucking sound at the front of the intake, is this normal on these?

Thank you for your help, like I said I'm getting ready to start checking things and hopefully can come up with some more information.

It depends on where it is.
Spray the area with some carb cleaner an see if it makes a difference in engine running.
Some 95 were a change over years.
Some OBD11 and some OBD1.
To get codes on it you you may need a engine capable scanner.
is the diagnostic connector OBD1 or OBD11?
Is the PCM/VCM behind glove box or under the coolant tank on right front fender?

My connector under the dash has 16 pins. The procedure for getting codes I saw was a 12 pin ALDL so I would assume I have OBD11, correct? If so it looks like I getting a scanner.

My connector under the dash has 16 pins. The procedure for getting codes I saw was a 12 pin ALDL so I would assume I have OBD11, correct? If so it looks like I getting a scanner.
It still can go either way.
Where is your PCM/VCM?
It mat say on unde rhood sticker if OBD1 or OBD11

I undid the panel under the glove box and it has attached to it what I would assume to be PCM/VCM, looks like a computer box to me. Of course not one sticker in the engine compartment says a thing about OBD.

I undid the panel under the glove box and it has attached to it what I would assume to be PCM/VCM, looks like a computer box to me. Of course not one sticker in the engine compartment says a thing about OBD.

The PCM behind glove bod will usually be silver colored and about the size of a small radio.
But I have not saw any attached to the under neath cover.
If it has a VCM it will be under the coolant tank on right front fender well.
But on a 95 with a 16 pin OBD11 or OBD1 type 12 pin type connector it will usually need a engine capable scanner to get codes or read engine data.
96 up were full OBD11 and only require a OBD11 scanner or code reader tyo get codes.

MT-2500, Thank you for all your help so far. I have an ODBI with an ODBII connector, aren't 95 vehicles fun? I'm sure that is why when my buddy took it to Advanced they couldn't get the codes, they didn't know about this.

I should have everything I need by the end of the week to get the truck talking to me so I can get an good idea what direction to head in. I'll update my progress to try and help others.