Hello everyone. I've started working on a Bravada that I got for cheap, but has a lot of issues. Background info here: https://blazerforum.com/forum/new-me...bravada-59219/

So as I mentioned in the above post the Bravada has a pretty harsh stumble at idle and it smooths out when revved. When the engine is cold its smoother, but as it heats up it gets worse. When you go from Park to Drive and put a load on the engine it gets worse still. This is after the previous owner overheated it. It's throwing a cylinder 4 misfire code.

In an attempt to resolve I checked the easy things, distributor, cap, rotor, wires, plugs. All of them needed to be replaced, so I replaced them all. Still the stumble persists. PCV looks pretty good.

My next step will be to remove and clean the EGR valve and cavity, as I hear that can collect excessive carbon and cause an issue.

Vacuum pressure seems to be within tolerance.

Compression is all over the place. Cylinder 4 is around 100psi, Cylinder 5 is around 170 and the other 4 fall somewhere in-between 120 and 150.

Leak down test I get a pretty good amount of air going through the throttle body on #4. Which tells me bad valves. I don't believe I hear any air coming from the oil filler and I'm not noticing any excessive smoke from the car, so I'm hoping that's a sign the pistons are ok.

What do you think? What else can I do to check the pistons?

I'm thinking about having the heads redone. Almost 100k miles on the car this gives me a chance to do the head gasket anyways.

The next question I have for everyone, with 100k miles and the heads off, what else should I replace as a preventative measure? Water pump?

 

Cylinder 4 seems low and thats what is causing the misfire, so having the heads redone should bring that compression back up on number 4 as well as some of the other cylinders that are around 120, would be nice if they were all back up around the 150 range. I would also go ahead and replace the Lower Intake Manifold gasket, use the Felpro gasket and that should last you a long time.
Depending on what year your Brevada is, you might want to do the MPFI Spider upgrade and get rid of those poppet's. And of course do the normal, check your hoses, belt, etc.

 

It's a 2000 Bravada. It got a new lower intake manifold gasket about 3.5 years ago according to the records supplied by the previous owner. I would hope that it's not leaking again, but I'll definitely check it out. Do the 2000s benefit from MPFI Spider upgrade?

Thanks for the response!

 

I believe they started putting the MPFI in 2002, so your Brevada has the SCFI, a MPFI conversion will not benefit you as far as gas mileage etc, it will basically just take the headache later on in case you get leaky or stuck poppet's. Hopefully your lower intake gasket was replaced with Felpro, if you can find the records it may say what was put in

 

I was able to look up the gasket, it appears to be a AC Delco part #. So I might look at replacing that. Which parts store typically carries Felpro?

What is involved with the spider upgrade? I tried a quick search, but didn't find any instructions or pictures, do you have a link?

I've never worked on a 4.3 this extensively so it'll be a learning experience for me. Is this a good time to do the water pump? I kind of know where it is, but I'm not sure if this would be a good time to do it.

Anything else anyone can think of that goes wrong with these cars that would be lovely to do while I have it torn down and the heads off?

Thanks for all the advice so far.

Needs oil cooler lines too, is there 1 brand better than another? Can I do this anytime, or is this also easier to do with the tear down?

 

You can get the Felpro gaskets at most auto part stores, Napa, Carquest etc... I am not sure if the ac delco gaskets have been revised to be any better, someone can chime in if they are different than the crappy ones that the factory put in.

There is a how to thread I believe on how to replace the Lower intake gasket, the water pump is up to you, when you take the water pump off you can see of there is any side to side play, if there is then the bearing/bushings are going bad and it would be a good time to replace it.

The oil cooler lines can be done any time, but while your doing all the stuff you might as well do them too, you will have to loosen the motor mount on the drivers side and jack up on the motor a bit to give you enough clearance for the lines to slide out, makes it a little easier than cussin and all tryin to get them out, lol

 

With the handful of things I have done already, it doesn't seem like there will be a single job on this car that doesn't involve a healthy round of cussing.

 

Looking at water pumps today. Is MasterPro decent? It's at O'reilly's. It has a lifetime warranty. It also say that it's highly recommended that the fan clutch be replaced at the same time. I assume they are just talking about the cooling fan clutch?

Here are the parts:

Master Pro Select Water Pump CP5077 - New Water Pump | O'Reilly Auto Parts

Hayden 2786 - Severe Duty Fan Clutch | O'Reilly Auto Parts

Good idea? I figure with 100k miles on it. For $60 I might as well do the water pump, no sense of waiting until it's toast.

 

Anyone have the part # for the oil cooler lines?

Is there a transmission cooler on these too? Should I do those lines too? How about the Timing cover gasket? Are those even in the area and easier to do with the heads off?

As I said, literally, if it's in the area, I'll replace it. I don't care to be into it this far again. So I just assume take care of it all while it's torn down. What do you guys think?

 

If you wanna go ahead and do it,replace the timing cover gasket,since everything will be out of the way,heck even replace the timing chain too. Thats easy,just youtube chevy timing chain and watch a video.