Yesterday i noticed my truck wont rev above 3k rpm. I read online clogged cat, but i replaced mine back in july. And in september rthe tps, iac, plugs wires, dist cap and rotor, coil (due to failure). All within the last 30k miles.

the symptoms are it starts and idles fine, but wont rev in any gear including park and neutral. Then it sputters and runs rough for a minute before returning to normal, no cel either. Maybe a failing fuel pump?

 

Can you check fuel pressure?

 

I just did, its at 50. 50 on turnover and when running.

first key on went to 20, second got it to 43 or so then at crank stays up at 50.

whats interesting, is that the truck ran smooth, idled well, and sounded normal up until i tried to force it past 3k rpm the last time... Now it has a knocking, idles rough if at all and wont idle without gassing it about 50%. It had a loid vacum sound coming from the tb, where the hole the iac goes at is. Not the hole with the blades . The knocking sound is coming from the pan, so im going to pull it and look at the main bearings/rods. Plugs look good except 2 have gas on them.

 

Well, im going to check dist cap and rotor first but then the pan. Should have also noted the mileage is 260k.

 

Still have a cat on there? Bet its clogging.....

 

So this is what i discovered.
My radiator and cap has a oily residue on it. I last changed the radiator fluid when i replaced the radiator about a year ago. It had around 210k miles then so ive driven it 50k miles since replacement and when i did replace the radiator the fluid was nice and green, like it should be. I owned the truck 4 years and drove it 80k miles on that fluid/radiator but needed to replace it because it was cracked.

The bottom of the pan has a thick sludge, whitish in color but the majority of the oil is black as sin as usual. Its not a lot, and not mixed with the oil. No sign of abnormal oil when it was drained.

I pulled the pan, and checked all the rods for bad bearings but saw no signs and nothing different from when i replaced the rear main seal a year ago. A little side to side play but thats it. While i was down there i also checked out the other areas i could see, the came and rollers, cylinder walls, cylinders, etc. and though its hard to see and i couldn't see everything well, i didn't find anything unusual. All of the videos iv'e watched for bad bearings the engine runs and has a steady tick or loud knock, which is not the case here. The sound i heard was random clacking, which i have heard the motor do before when not running right and sputtering on or misfiring. Just not as much as now.

While i was underneath i noticed a drip of radiator fluid running down from the above water pump, not a lot, and it hasn't really dripped off the motor either, but its leaking.

After this i put the pan/starter back on and I ran compression tests on all cylinders and found that cylinders 5 & 7 have low compression at around 40-70 psi. On the picture, for cylinder #5 you can see multiple results because i tested cylinder #5 a few times. 5 & 7 were the last two i checked, and #5 was the first cylinder way low and came up first with 40, then 50 & 70. I had difficulty getting the gauge in the hole because of the brake booster so i reinserted it each time to ensure it was sealed. The #7 i tested once at 40 with many cranks and it never got above 40. Cylinder 2 shows a low initial result because i just didn't crank enough to build up and got a 60 reading, came back and it was still low but pretty close to the rest.

So, my conclusion is that the head gasket is blown between 5 & 7 and that the radiator fluid has not leaked significantly into the engine, but maybe seeped in a little bit, gotten into the radiator, and that when i tried to rev the engine on the driveway above 3k i fully blew it out.

Any takers on another diagnosis?

 

I think a cylinder leak-down test is in order....... see where your compression is going.

Oil in the radiator may be from the trans cooler..... as pressurized engine oil doesn't come anywhere near cooling jackets.

In any event, you have three cylinders below minimum spec. (100 psi) Need to find out why.

 

Did leak down after head gasket change. Exhaust ports on 5/7 leaked. Passenger head cracked between #8 valves but dont think was causing much of an issue. Replaced heads.

got it together, fires up idles well. Wouldnt even run before.

same problem. Wont rev up past 2500, gets shaky and doesnt rev then misfires. I have front 02 out and still no rev.

 

Still possibly a plugged Cat. Could also be a bad cam sensor. It controls timing of the fuel injectors.

 

Clogged cat. Melted down ans in a million pieces/dust.