1999 Chevy Blazer 4.3

[black86glhs]

Have a friend with this truck. Engine was just rebuilt. Starts and runs fine. Light throttle is good, but anything over 1/4 throttle and it is gutless. Does not miss, hesitate or stutter in any way. No codes. Drives exactly the same with the exhaust cracked open before the cat as it does with no exhaust leaks. Feels like a 2.2/2.5 with the timing belt off a tooth. No power all the way to 5500RPM.
There is the back story. My guess is one of 2 things. Either the distributor timing is off or the cam timing is off. Even though there is no timing adjustment at the distributor like a normal small block, it is possible to be off a tooth when installing, I think?
Also, verified map and maf are working and no vacuum leaks.
Anyone got any ideas or thoughts........other than sell it or buy a Dodge....LOL.

Thanks.

[bradp]

Fuel pressure....water in the fuel tank...just for $hits and giggles unplug the MAF and see how it runs.

[black86glhs]

Fuel pressure good, +60 psi. Fuel is also good. Not sure if he unplugged the MAF yet. I'll check on that. MAF was changing on the scanner, but worth looking at. Thanks.

[turbovanman²]

Yes, you can still get the dizzy installed wrong, I bet he's a tooth out. Set at TDC, there is an arrow on the dizzy which you align the rotor.

[black86glhs]

Yes, you can still get the dizzy installed wrong, I bet he's a tooth out. Set at TDC, there is an arrow on the dizzy which you align the rotor.Ok, that is what I thought. He said he will check it. Thanks.

[black86glhs]

He is going to perform a compression test next. The timing marks lined up. It just doesn't make any power. No misfires or cutting out, just no nuts to it.

[bradp]

He is going to perform a compression test next. The timing marks lined up. It just doesn't make any power. No misfires or cutting out, just no nuts to it.

Did the rockers get over-tightened?

[turbovanman²]

That sucks, hmmmmmmm, wonder if he got the timing chain on wrong?

Brad, rockers aren't adjustable, IIRC.

[black86glhs]

Did the rockers get over-tightened?I tried to get him to usee the 2001+ heads but his rebuilder told him they weren't the right ones for his. They will bolt up and work fine, but head followed the guys advice. The guy who built it is more into diesels, so he didn't know. So he might have them torqued down.


That sucks, hmmmmmmm, wonder if he got the timing chain on wrong?

Brad, rockers aren't adjustable, IIRC.That is what we were thinking. Like said above, I'm not sure if he did it or if the machine shop did it. I'll check with him later. This is going to be something really stupid, I can tell already...lol. Thanks guys.

[turbovanman²]

What heads is he running? The Vortec heads are all the same from 96+, there is no different head for 2001+ engines?

[black86glhs]

What heads is he running? The Vortec heads are all the same from 96+, there is no different head for 2001+ engines?The heads and valvetrain changed around 2000-2001. Believe me, I have already been thru this.:nod:

[turbovanman²]

The heads and valvetrain changed around 2000-2001. Believe me, I have already been thru this.

From all I've seen, nope. What changes?

Not sure what you were working on but part number is the same on the head from 96-2005. I've worked on lots and never noticed a thing. The earlier ones had head changes and valve train changes, some were adjustable, some weren't etc.

http://www.gmpartsdepartment.com/partlocator/index.cfm?action=getLocatorKeySearch&siteid=214533&chapter=DP1002&catalogid=1&year=1998&make=11&model=S15%20jimmy


1998 GMC S15 jimmy



Description Year MSRP Price Core Price Your Price
cylinder head, s-series - 2.2l - 2.2L 1998 $796.93 $0.00 $641.53
Engine - cylinder head & valves - cylinder head
View Illustration
cylinder head, s-series - 4.3l w/balance shaft - 4.3L W/BALANCE SHAFT 96-05 $672.13 $0.00 $440.58
Engine - cylinder head & valves - cylinder head
View Illustration

[Orangetona]

Possible EGR problem? I know 4.3Ls had some EGR issues. Or a weak coil.

[black86glhs]

From all I've seen, nope. What changes?

Not sure what you were working on but part number is the same on the head from 96-2005. I've worked on lots and never noticed a thing. The earlier ones had head changes and valve train changes, some were adjustable, some weren't etc.

http://www.gmpartsdepartment.com/partlocator/index.cfm?action=getLocatorKeySearch&siteid=214533&chapter=DP1002&catalogid=1&year=1998&make=11&model=S15%20jimmy
Ok....I'll say this slower.....I.....have ....already.....been......thru.......this. The Valve train was different. Also, the intake ports were a little different. I can't find the article I read back when I was finding cyl heads for this truck. The previous owner cracked both of them. Like I said, they will work as long as you swap the valve train over.

[bradp]

Possible EGR problem? I know 4.3Ls had some EGR issues. Or a weak coil.

Weak coil sounds like a possibility.

[black86glhs]

He swapped the coil, ign module, crank sensor(previous issue), MAF and TPS over to his 96 and it ran flawlessly.

[Orangetona]

Sounds like its time for a dodge :) lol

[black86glhs]

Sounds like its time for a dodge :) lolYeah, I'm starting to think the same. lol

[turbovanman²]

Ok....I'll say this slower.....I.....have ....already.....been......thru.......this. The Valve train was different. Also, the intake ports were a little different. I can't find the article I read back when I was finding cyl heads for this truck. The previous owner cracked both of them. Like I said, they will work as long as you swap the valve train over.

WHAT!!!!!!!!!!!

And I'll say again, I've worked on both and NEVER noticed any difference. I'll phone my friend at GM to get part numbers.

Your thinking of the the 3100 or 3.8's, they changed valve train etc. :p


Ok, so technically, we are both right, damn GM.

The part number for the heads is the same for both years, BUT the valve train lists differently for the 98 vs 01, AND to make it worse, if you order a head from GM, even though the part number is the same, you have to order or use the 01 valve train.

So I sorta apologize, :thumb:

[black86glhs]

Considering I'm the one who took the heads of the 2001 and compared them to the 1999 heads, I know what I was looking at. The studs changed along with roller rockers. I also read some change to the intake port, but can't verify that.
I had not seen it before either. But found out the hard way. Now I have a set of 2001 heads in the garage and no 4.3 to install them on.

[turbovanman²]

I'll take them, you ship them and I'll buy you a beer or 2, :lol:

[RoadWarrior222]

Fuel pressure good, +60 psi. Fuel is also good.
I might figure it's dropping under load = fugged pump, fugged filter, line restriction crimp or blockage, fugged regulator, fugged fuel rail... especially check where anyone might have dented rails being clumsy with the block or head or something.

Edit: one could imagine that some lean fuel problem caused the cracked heads in the first place.

[black86glhs]

I might figure it's dropping under load = fugged pump, fugged filter, line restriction crimp or blockage, fugged regulator, fugged fuel rail... especially check where anyone might have dented rails being clumsy with the block or head or something.

Edit: one could imagine that some lean fuel problem caused the cracked heads in the first place.She ran it hot. Block and heads were sent to his brother in law and rebuilt. One of the shop guys did the work as he works in the office. New pump, regulator, filter. He is going to check out the rockers and make sure they did screw that up. next will be a compression check and then pull the front of the engine and see if the cam timing is fubar.

[black86glhs]

Everything checked out fine including the rocker arms and push rod length.
He just did a compression test on his 96 4.3 S-10 with 180,000 miles and it had 130 psi almost across the board. The 99 blazer we are talking about showed 105 psi......What in the hell would cause this in all 6 cylinders but let it idle like normal and not cause it to misfire? The long term and short term fuel trims are trying to pull fuel. They show -17.8.
Swapping injectors from the other truck did nothing to improve it. Same with MAF and distributor swap.
Anyone have any ideas? Thanks.

[88_pacifica]

Everything checked out fine including the rocker arms and push rod length.
He just did a compression test on his 96 4.3 S-10 with 180,000 miles and it had 130 psi almost across the board. The 99 blazer we are talking about showed 105 psi......What in the hell would cause this in all 6 cylinders but let it idle like normal and not cause it to misfire? The long term and short term fuel trims are trying to pull fuel. They show -17.8.
Swapping injectors from the other truck did nothing to improve it. Same with MAF and distributor swap.
Anyone have any ideas? Thanks.

Quick question... Are they the original pistons? Maybe they are the wrong ones(deck height) and the compression is off. Also, you might want to make sure that the rings were sealing all the way around. I have actually seen ALL of the pistons in a motor once that had blowby and not due to install error. He used Chromemoly's and they never fully seated. Did you do a hone on the block? It seems weird that everything else would match up and it not have a misfire unless maybe the computer is pulling a buttload of timing due to 'masked knock' issues. Do you have the ability to run a datalogger of some sort and look for knock retard?

[black86glhs]

The machine shop did the work on it and put it all together. We both are wondering about the rings and pistons. He says it does not have blow by, but I have not verified it myself. He is good about spotting stuff, but he could be missing something. Supposed to be the original pistons. He is gonna call the guy and get more info on what they did. Otherwise, we are pulling it and tearing it down to see what happened. Would like to find something more concrete than a hunch before pulling it. S-10's are a ----- to pull a motor on. Maybe I should take my borescope over.....hmmmm.

[turbovanman²]

What does the cam retard say?

[black86glhs]

I'll have to check with him on that.

[black86glhs]

It has been a little while since he looked at the parameters, but we know it was very similar to his 96 4.3 parameter wise. No knock retard. Timing was showing advanced and would change as it was revved up and down. In other words, it didn't show timing as retarded due to knock or timing being incorrect. Timing marks were verified on the timing gears and distributor to be spot on.
We are both wondering about the rings not seating. We have no idea what rings were used. If they are Moly rings, it makes sense. He has a call into his B-I-L to see what he says about the parts used. Thanks guys.

[RoadWarrior222]

Just had a thunk.... totally weakass valve springs, either the originals that completely lost temper when overheated, or the wrong replacements.

[88_pacifica]

Just had a thunk.... totally weakass valve springs, either the originals that completely lost temper when overheated, or the wrong replacements.

That's true. I missed that one.... valve float could be an issue, but he should still have 'ok' compression though.

[black86glhs]

Yeah, but it would miss and spit if that was the case. It can be run all the way to redline, it just take 60 seconds to wind it out.......and that is just first gear!!! But never misses or sputters.

[Vigo]

I had a 4.3 blazer driving me crazy after i changed the motor (yes it is a -----) and i eventually found this:
http://i279.photobucket.com/albums/kk124/Vigo327/DSC02838Large.jpg
http://i279.photobucket.com/albums/kk124/Vigo327/DSC02836Large-1.jpg

Once it had any load on it the spark would go into the wrong wire, and fire into the other cylinder's exhaust stroke, so you never felt the bucking, just 2 cylinders going dead like a light switch.

[turbovanman²]

Rings not seating would result in tons of blowby and oil smoke so that can't be it.

Based on what you've told us, Its possible they used the wrong pistons, the cranking compression should be 160-170 psi.

Barring that, I'd say wrong timing chain if possible or the wrong cam installed. Something has lowered the compression and that I bet it whats causing his lack of power.

[Vigo]

I agree the compression is way low for one of those.

If the cam were a tooth or two off you'd have terrible compression and be down on power. If you've got a compression tester hose you can put the crank at cyl #1 TDC and blow air into #1 to make sure the valves arent open when the crank says it should be TDC. Since he has two of the same truck he should be able to compare when the valve opens relative to where the crank pulley is at based on the noise of the air, just turn crank slowly until a valve opens and make note of where the pulley is via marks, etc. That would tell him if the cam timing is different without pulling both valve covers or pulling the front off the motor in the 99.

[turbovanman²]

Good idea, but use very low air pressure, if you use high pressure, say anything over 20 psi, the piston can be forced down very quickly and shitt gets trapped. Ask me how I know, :(

[black86glhs]

Thanks for all the ideas. I'm going to go by there and try putting air in the cylinders. See if we can hear air in the exhaust or the intake. Otherwise, we are going to be pulling it and seeing what we can do about the rings or see if we find something wrong.
I'm going to search around some more but it looks like it will get disassembled. This will be interesting to find what is wrong.

[RoadWarrior222]

With that motor, it seems like they would have to have been extremely creative to get the wrong stroke crank or wrong rods in there, but you never know.

[Big_P]

No codes, right?

[black86glhs]

No. We had O2 codes, but they are gone after changing them out. Like I said, it is the weirdest thing. Runs like an old Bronco II with the 2.3 L4.....LOL.

[RoadWarrior222]

Extreme core shift mismatch at the intake or exhaust mani?????

[turbovanman²]

With that motor, it seems like they would have to have been extremely creative to get the wrong stroke crank or wrong rods in there, but you never know.

There are a few piston combo's, so if you didn't match up the old pistons to the new ones, its possible to put deeper dish in vs maybe the stocker has a slight dish.

[RoadWarrior222]

Yeah, like SiTy pistons... but even then it should still be high 8 point something compression, maybe like driving a 2.8 Jimmy, not like a diesel Chevette or something.

---------- Post added at 06:17 PM ---------- Previous post was at 06:12 PM ----------

Hey do these things have either an octane plug for mountain gas, or a test plug that could have got knocked out, broken or lost when working on it?

Either of those will retard the timing, well one retards it a bit, the other zeroes it.

[turbovanman²]

Yeah, like SiTy pistons... but even then it should still be high 8 point something compression, maybe like driving a 2.8 Jimmy, not like a diesel Chevette or something.

---------- Post added at 06:17 PM ---------- Previous post was at 06:12 PM ----------

Hey do these things have either an octane plug for mountain gas, or a test plug that could have got knocked out, broken or lost when working on it?

Either of those will retard the timing, well one retards it a bit, the other zeroes it.

Like TBI pistons, Vortec, etc.

No octane plug.

[Vigo]

Good idea, but use very low air pressure, if you use high pressure, say anything over 20 psi, the piston can be forced down very quickly and shitt gets trapped. Ask me how I know,

Good catch! i forgot :wow1:

[black86glhs]

An update with good news! Both of the trucks we have owned(he has one and I used to), had just a simple y-pipe. He was doing some research and found that this blazer has some type of resonator or pre-cat built into the y-pipe. He pulled the y-pipe off and proceeded to lay 2 black patches down his driveway!!!:partywoot:
He is going to cut the top off of the thicker section, clean it out and weld the pipe back together.
Now if he would come up with another block for my car I could send to the machine shop, all would be right in the world.:thumb:

[turbovanman²]

Good news, :nod:

[black86glhs]

I hate it when they make small changes to vehicles and the aftermarket doesn't see it or they figure it is the same as all the other years.:mad:
Thankfully, it wasn't his daily driver and it could be driven around town at lower speeds. This thing is clean, though and already has a rebuilt 4L60E. Full leather interior in great shape. So it was worth it, especially considering his 96 S-10 will probably not make it past the winter.:thumb: