Hello all! I recently purchased a 1999 Blazer with a 4.3 vortec and 295,000km. I also found out recently (the hard way) that it needed more than a little work... I have done so much that I've probably forgotten half of it but here's a list of my labour of love so far:
Distributor, cap, rotor, wires, plugs.
Brand new catalytic converter.
Vacuum lines all around.
Used Spider and brand new fuel pressure regulator.
O2 sensor.
Intake plenum and about 5 gaskets for the spider.
Used cylinder head to replace the last one with cracks all through it.
Fuel pump assembly.
Full compliment of engine gaskets (head, intake, exhaust, EGR).
Brake lines, pads and e-brake cable.
Transmission pan gasket and filter
Probably more but that's all I can come up with right now.

So here's my problem: I got it running well enough but it still feels gutless. When I start it up it idles fine but when I try to drive it, the engine refuses to turn faster than about 800rpm and I have to feather the throttle until finally it wakes up but once it does, it's usually good until it cools off and restarts again. When I drive, it has a sound coming from the engine that is reminiscent of a really bad intake leak and changes pitch with engine speed, and there is a noticeable lack of power between closed and half throttle. Even at full throttle it just does not seem to want to really accelerate, it just does it because it has to.
The only codes that come up (now that I've fixed the laundry-list of problems) are lean mixture-both sides-and bank 1 sensor 1 malfunction. I have replaced all of the suspect parts and now am completely certain that there are no intake leaks. I've done the carb cleaner/propane test on everything from the 4x4 vacuum actuator to the manifold gaskets to the brake booster and I cannot find this problem at all. I even pulled my EGR tube off and inspected it for leaks because I was out of ideas.

I have hooked up a vacuum gauge and at my elevation I have roughly 17 inches Hg at idle (which is fairly good for approx 3000 ft) and with the gauge hooked up to the cabin system and a couple good throttle bumps, it holds almost 24 long after the engine stops so I know my heater actuators are still in good shape.

Please can anybody give me even a nudge in the proper direction? I am on the quest for quiet and no CEL but there sure are rocks in my path. Anything will help greatly since I have lots of experience turning wrenches, I just need to know which nuts to work on.

Thanks folks and I look forward to hearing from you soon!

 

Could also be a clogged cat

 

Cat is brand new. And I just replaced the MAF today.

 

double check the flow of exghaust your old cat could have came apart and plugged the muffler partially off - been there done that

 

Ok so I removed the new cat and put on the old converter pipe after I gutted it (it was fine, yet another money waster) to see if it changed anything. Nope. Except for now it backfires out the tailpipe on deceleration from highway speeds. I did, however, find out that my emissions systems lines to the evap canister were all rotted away; as soon as I touched them they crumbled to pieces. I fixed them and now my lean codes are gone. My new fuel pump doesn't seem like it is holding pressure too well after I shut it off anymore because I've had to bleed the fuel system numerous times to work under the intake plenum and it doesn't spray out of the service port, it dribbles. That and the gauge reads low fuel when I still have about 15-20 litres still in the tank. I'm wondering if that has anything to do with the fact that every time I open the gas cap there's massive amounts of vacuum within the tank.

Also, when I checked the compression before I started working on everything, bank 2 had zero in 2 holes (that's why I replaced the passenger side cylinder head because it was cracked to sh**) but the other side had 145-110-140 and I figured it was alright. Should I suspect the other head as well? I mean, could I have a leaking valve seat and that's why I have the hissing noise? I took the exhaust manifold off and magnafluxed it (I do metal inspections for a living) and came up with no cracks anywhere, and the exhaust system has no plugs according to my vacuum gauge.

I get a definite decrease in vacuum at highway speeds and the only thing I can think of is that I should have checked the other head while I had it apart. Can anybody maybe tell me if I'm on the right track at least? I don't want to rip the motor apart YET AGAIN if there is something else that could be the problem...

Thanks folks!

 

IMO - if you have massive vacuum when you open the filler cap at tank i think you have a prob in the evap system - as far as i know the tank should pressure up to a extent and the evap system removes the excess pressure - even if it's not the evap system in my thinking with the tank under massive vacuum the fuel pump can't pump fuel - about like tipping a pop bottle up and sucking on it without letting air in - suck as hard as you can you still will not get any pop -

 

Do another compression test on all the cylinders.

Report the numbers.

 

So I fixed the vacuum lroblem in the gas tank-the air valve thing above the frame rail was plugged and full of mud. I cleaned it out and reinstalled it and now I have THAT sorted out. So with no more vacuum issue, the truck still runs the same. I plan on doing a compression test tomorrow as well as the oil test if I find anything out of whack. I did, however, go to the wrecker (it was half-off weekend) and pull an exhaust manifold without the EGR fitting and the matching intake manifold that has no valve. It also came with a spider assembly that is a bit different than the one I have-instead of poppet nozzles, there are wires going to where they sit in the manifold.... I'm guessing it is an updated style with the injectors right close to the valves rather than inside the spider itself. Not sure if it will work, mine is a 99 and I pulled it from an 03... Here in Alberta there are no strict emissions laws so I'm not worried about that stuff, but I'm curious as to why there was no EGR system on the other vehicle. Whether or not there are laws, I would think the EGR was necessary for proper fuel delivery and such. Maybe I'm wrong; maybe it's a better system that has proven results for emissions? Could it be completely aftermarket? It all has the GM stamps on it....

Either way, it only cost me 60 bucks for all that, so even if it doesn't work for my truck I can sell it on ebay or something.

I have the day off tomorrow so I'll be checking and posting the compression when the engine is cold and when it is hot. I don't know if it will make any difference, but it certainly won't hurt. I've had the plugs out so many times I could do it in my sleep.....

Once again, thanks for the replies and I'll be here tomorrow!

 

50% sale on Memorial Weekend, was that a Pick n Pull Toolkit member??? Damn those checkout lines were long this weekend. Haha.

I know this is a PITA. I went through something similar last year. I tested a bunch of the electricals before I went to fuel pump concerns. I did do a fuel pressure test and it read good.

Anyway, I don't trust aftermarket electrical parts. I've had a lot of issues with all makes and I just go OEM for electrical parts. Those electrical signals vary sometimes and that can cause these little problems. If I don't buy new, I buy a few at a salvage yard and have them tested at O'reillys or Autozone. That MAF needs to be tested even though its new, check the ICM too. The ICM was my problem and it did some of what you're complaining about. The first ICM I bought was new and it was bad so that's another reason I don't like aftermarket electrical parts. Those are easy parts to test and change out. Once you have eliminated those issues, then you can take off the plenum and change those injectors. Thats a PITA too but not as bad as a fuel pump. Check your electricals, then check your fuel. It is getting fuel or it wouldnt run at all.

 

That is a factory fuel injection system. In 2003 GM updated from the poppet style to a true multi port system. It plugs right in and works better. From the compression test in post #5 your #3 cylinder looks too low. My factory service manual doesn't give psi numbers. But all cylinders should be within 10% of each other.