EGT skyrocketing

[heptofite]

on my 2.9, cylinder 6 showed an EGT of over 700 degrees, and cylinder 3 showed an EGT of 650, as read by my IR thermometer.

smoke was rolling off the manifolds, and oil pressure dropped, and there was a crapload of valve noise.

the fastest i'd gone before that was about 70mph, so what could have caused the exhaust temps to get that high?

and, am i correct to operate on the assumption that the heat caused the loss in oil pressure, and not a loss of oil pressure caused the heat? because once the engine cooled off the oil pressure came back.

 

[Hopman]

Would an overly rich or lean fuel mix cause it? Maybe it's a bad injector or two. But I could be wrong.

 

[adsm08]

and, am i correct to operate on the assumption that the heat caused the loss in oil pressure, and not a loss of oil pressure caused the heat? because once the engine cooled off the oil pressure came back.

Well, it could go either way, but since it came back after cooling down I'd guess the heat caused the pressure loss.

Would an overly rich or lean fuel mix cause it? Maybe it's a bad injector or two. But I could be wrong.

Possible. Lean makes it run hot, rich makes it run cool. I'd guess that since its a batch-fire system that it'd be somewhat lean on all cylinders. If the temps rise X, X+Y, X+Z across the cylinders going back, then a bad pair of injectors could do it.

 

[mentalbreakdown00]

I agree with him, a cooler cyl is richer on gas inversed for a diesel

 

[feellnfroggy]

If its running rich, he could have cylinder wall wash. which would thin ou thte oil film and possibly heat up his cylinders if it was too extreme, but lean sounds better. Also if his cat is getting clogged it could be 'backing up' his system?

 

[mentalbreakdown00]

It would get low on power and can easily be checked by vacuum gauge, I would be he ran lean for a moment breaking down the oil.

 

[heptofite]

If its running rich, he could have cylinder wall wash. which would thin ou thte oil film and possibly heat up his cylinders if it was too extreme, but lean sounds better. Also if his cat is getting clogged it could be 'backing up' his system?

there isn't a cat on the truck ATM.

 

[scotts90ranger]

timing in check? not enough spark advance and the heat from combustion moves into the exhaust, too much and the engine gets too hot.

700 isn't too hot on the manifolds, when the actual exhaust temp gets in the 1500* range is when you need to worry about burning valves, at work we look at exhaust manifolds with the IR guns all the time to look for dead cylinders and they can get in the 500* range at idle with no load.

 

[heptofite]

timing in check? not enough spark advance and the heat from combustion moves into the exhaust, too much and the engine gets too hot.

700 isn't too hot on the manifolds, when the actual exhaust temp gets in the 1500* range is when you need to worry about burning valves, at work we look at exhaust manifolds with the IR guns all the time to look for dead cylinders and they can get in the 500* range at idle with no load.

my front cylinders were in the 250-300 range, i say 700+ on the rear, because it doesn't go higher than that on my IR gun.

thing is, there was a shitload of smoke rolling off the manifold when i popped the hood.

 

[mentalbreakdown00]

then check your rear cylinders for timing, high compression, and a/f ratio

 

[heptofite]

then check your rear cylinders for timing, high compression, and a/f ratio

and how might i go about doing that?

 

[crusin93]

I'm with adsm08 on this one. Number 3 and number 6 are lean. Pull the plugs and compare to verify the lean condition. I would look to an electrical malfunction because of the vicinity of the two "shared" lean cylinders. Also, while your there, check the resistance accross both injectors. It's not likely but possible that both injectors are sticking.