I've searched and couldn't find anything to help me, so hopefully someone will have an idea of what's going on. I've got an 02 4.3 Blazer, and a few hours ago as I was driving home the fuel pressure started spiking to 80psi when accelerating. As soon as I let off the gas the oil pressure returns to normal. It's not throwing a code, but it's now continuously spiking to 80 when I hit the gas and dropping when I let off. Clog? Sensor? Anyone have any idea?

 

The first thing I would recommend is to check the oil pressure with a mechanical gauge. It is possible that the sending unit is faulty or that the wiring is grounding out. 80psi is the max value on your gauge, is it not?

 

Has anything been done to the car lately? Oil change? Anything?

 

I'm coming up due for an oil change soon, and gauge maxes at 80. I was having trouble with an overheating issue last week while driving that I got taken care of just a few days ago, had air in the lines. I never let it go past 235 degrees.

Shortly after posting the spiking stopped, and the temp returned to normal (20psi idle, 40-42psi max under high rpm). I drove it around this evening with no spikes, but when I started the truck up just a few minutes ago I had a lifter tick that lasted a couple minutes before it quieted down and went away. I'm leaning towards cleaning the push rods out. I'm wondering if the overheating caused it to get partially blocked with sludge thus causing the oil pressure to spike today. I haven't had a previous lifter tick issue, so I want to think it's connected. Sound like a possibility?

 

Could be. Depends on how bad it overheated. It could have cooked the oil in one of the galleys or caused a restriction in flow.

Try this. About 100 miles before your next oil change, dump in 1/3 of a can of Seafoam into the oil and run it. You can use the other 2/3 of the can through the throttle body (disconnect the MAF sensor electrical connection & remove the intake hat on the throttle body then start the motor and slowly pour it in). In the crankcase, it will clean up any deposits. Down the throttle body, it will clean up the intake, valves, & cylinders. If it's badly carbon'd up, you'll get quite a smoke show out of it so if you have neighbors close by, you might not want to put it in the throttle body.

 

I tried the Seafoam, and it took it about 5 miles of easy driving (no more than 2,000 rpms) for it unstick. Didn't fog out the neighborhood, but definitely blew smoke when I poured it in the throttle body. Drove it about 60 miles, and the lifter dropped again, but the oil pressure never spiked again.

I was already planning a tune up this weekend, so I decided to go ahead and replace the lifters, too. When I busted into it, the lifter was dropped and there was play in one of the rocker arms on the #5 cylinder. Haven't got the push rods out yet, so I don't know if they're clogged up. I figure after 175k miles I might as well go ahead and replace all the lifters at once. Besides I already had an oil leak on the front of my intake manifold that needed fixing, so perfect time to do that. Looks like I went from an overheating problem to a top end rebuild in a week's time. Go figure.