This 2.3 has got me stumped.

[Off Road SHO]

Well dang, it's not the valves. I borrowed a leak down hose tool and pressurized number 3 cylinder and I don't hear any air coming from the intake or exhaust, but I hear a LOT coming up through the oil drain back holes in the head. I either have a hole in that piston or the rings are totally shot.

I might not have gotten enough oil into the cylinder when I did the first compression test (in hopes of determining if the lack of compression was from valves or rings). I just pumped a good 4 or 5 squirts of Marvel Mystery Oil and will let it sit over night, just in case it's a stuck ring or two. I don't have a borescope to look down into the cylinder.

Another odd thing I found was a spark plug with two longitudinal splits in the upper porcelin insulator. Unfortunately, I don't know which cylinder I pulled it out of, or if it didn't crack after I pulled them out.

If this ends up being a bad piston/cylinder/rings, I am not going to mess with it; the truck is just not worth it.

Tom

 

[Bryan22]

don't give up hope! I lost a motor in my 94 at 250,000 miles, found one for a steal. Got home and compression was 90 110 30 60. I was pretty well furious but decided to take a gamble. I ran a quart of atf in the oil for about 100 miles drained it, and it's be going strong for 60,000 miles now.

Even though one cylinder is at 90, i wouldn't bet on that being the sole reason for it not running. so before you toss the truck I'd find out what made it die and don't get too discouraged about low compression on one cylinder.

 

[Off Road SHO]

Finally got some oil into #3 and it brought the compression up to 155 cold. I don't think I actually got any oil into it on the first try. Now I'm wondering if the spark plug that had the split insulator was in cylinder 3 and wasn't firing correctly if at all. Maybe that allowed unburnt fuel to wash down the cylinder and caused some scoring.

Anyway, I got a new valve cover gasket and new plugs. I'll start re-assembling it tomorrow and see if it runs any better.

Tom

 

[kimcrwbr1]

You may be alright do you know how old the wires are. If you plan on keeping it now would be the time if your not sure get some good low resistance wires. Take it on the road for a good beat at freeway speeds and while it is still hot pull the plug wires one at a time and see if the engine reacts the same on all four cylinders. If #3 is burning run it till it pukes. Shop around for a engine to either rebuild or plug and play if you feel that one is on the way out. If you know what your doing you can swap it in a day or two if you have all the parts together

 

[Off Road SHO]

Update. I put 4 new spark plugs in, gapped to .043. The plug wires look brand new. Cranked it over and it fired right up and idles 90% better than it did before. This is my take on what was/is wrong: I think the cracked plug was mis-firing or firing erractically or not at all, with the injector still firing the unburnt gas was washing down the cylinder wall of number 3, thereby giving me the 90 psi reading in that cylinder. When I finally got some MMO in there and let it sit for 2 days, a new compression test showed about 155.

I drove it around the block (4 miles) and it seems to run okay but not great. Brought it back in the shop and checked the valve timing. When the bottom pulley has it's notch at TC on that plastic cover, a line connecting the cam sprocket's dimple and it's center of hold down bolt, points right at the center pointer. So I guess the valve timing is okay.

I'm still only getting 15 inches of vacuum, so I guess I will re-check the ignition timing. It's sitting at 20-21 at idle on a warm engine right now.

Thanks for all the advice guys.

Tom

 

[Off Road SHO]

Reset the ignition timing, it wasn't far off, but still only getting 20-21 degrees BTDC when we plug the SPOUT back in. And still only 15-16 inches of vacuum. I think I'll get the smoke machine back out and see if I have a vacuum leak I might have missed on the first go round.

Tom

 

[Off Road SHO]

Update, Still stalling out. Tried isolating the Brake vacuum booster out of the equation and still dies out. Disconnected the PCV and plugged the intake side and it seems to idle much better. Hmmmm.... could this be introducing too much un-metered air?

Tom

 

[Off Road SHO]

Seems to idle so much better with the PCV disconnected; maybe it was getting so much blow-by from the number 3 cylinder that it was causing too much positive pressure in the intake and causing the MAP sensor problems? Heck I don't know.

Now we're chasing a dang oil leak from we thought the front crank seal. Replaced that and still a leak, a big leak. After removing the black plastic rear timing cover, we found that the auxillary shaft's seal was the actual culprit.

Boy are we getting good at tearing down this engine.

Tom

 

[kimcrwbr1]

The best way I have found to isolate a vacuum leak is with a piece of vacuum hose. 2 or three feet lond and put one end up to your ear with the other end search around all the gaskets fittings hoses. you will hear a hissing when you get close to a leak. just be careful of moving parts. My pesky leak was on the carb base. I got some gasket material pulled the carb and glued a piece of 180 grit to a piece of plywood and slowly resurfaced the base of the carb. It made a huge difference it sounds like your gettin close, have you tried unplugging the knock sensor maybe it is telling the computer to retard the timing see if it makes a difference unplugged and watch the timing as you plug it back in. I am not sure where it is but it should be screwed into the block with two wires out of it. The PCV is probably the most neglected tune up item the book says if it rattles it is good that is wrong just replace it with spark plugs there is no way to clean a PCV and they cost as much as a cup of espresso.

 

[dmassey]

well if it will keep running if you open the throttle a little bit then the IAC is a possibility, i'd try to supply it some fuel when it dies to see if you're losing fuel. i don't remember the low pressure pump specs but that seems really low

Before it dies. does it stumble? If it does you may have a bad IAC. A way to test it is as soon as it starts, unplug the IAC and it should stumble and possibly die - sooner than it does now. If the idle doesn't change (get worse) you may well have a bad IAC. If the idle does get worse with the IAC unplgged, the IAC is probably okay.

 

[Off Road SHO]

If we plug the PCV so that all the blow-by is not being forced into the intake, it ides just fine. As soon as we connect it up it stumbles and dies. So we will leave it plugged for now. The other crank vent that comes out of the oil fill cap and goes into the intake is also blowing so much it is carrying oil with it. I will have to catch can it.

I think that all the blow-by is pressurizing the intake a little and therefor causing the MAP sensor to read higher. I think that will then cause the PCM to give more gas. Don't know for sure, just guessing at this point.


Tom

 

[kimcrwbr1]

If we plug the PCV so that all the blow-by is not being forced into the intake, it ides just fine. As soon as we connect it up it stumbles and dies. So we will leave it plugged for now. The other crank vent that comes out of the oil fill cap and goes into the intake is also blowing so much it is carrying oil with it. I will have to catch can it.

I think that all the blow-by is pressurizing the intake a little and therefor causing the MAP sensor to read higher. I think that will then cause the PCM to give more gas. Don't know for sure, just guessing at this point.


Tom

Do you have a new pcv your noy forcing anything it is supposed to pull from the crankcase. put the new PCV in and start it if it dont run you have other vacuum issues also get a vacuum guage. Take a piece of vacuum hose and put one end up to your ear and search around with the other when it is running around all the untake gaskets and fittings. you should be getting fro 17 to 21 inches in hg at an idle on the vacuum guage.

 

[Off Road SHO]

I'll get a new PCV today, but what can I do about the blow-by coming out of the oil filler cap line?

Tom

 

[kimcrwbr1]

see if the pcv works first it pulls the gasses out of the crankcase, positive crankcase ventilation is what PCV stands for. If you still have blowby with a new PCV then yea it is more than likely rings didn`t you say the head has been recently rebuilt the valve guide seals should be good. Blowby is from bad rings a hole in the piston or valve seals. If you dont know how old the PCV is just put in a new one and change it with plugs as regular preventative maint. Also change/clean the breather filter so your pulling filtered ambient air in the engine to keep the crankcase clean.

 

[Off Road SHO]

Dang, this things got so much blow-by that I don't think I'll be able to attach the breather cap to the intake and that will fail me at our emissions testing. Idles and runs fine with the PCV open and the breather open.

Tom