Missing Cylinder?

It's a 4.0/AW4.

It seems to idle rough, and the second you start to rev it up it goes BUP BUP BUP BWAAAP (studders and then takes off).

When you're driving it, if you touch the gas pedal like an egg shell it goes okay, but pretty much dies on hills. If you mat the pedal, the exhaust starts to almost shake and then it'll backfire.

I checked fuel pressure, it's holding 50 pounds when running but the check valve is shot in the tank. Bleeds down pressure when you kill it. I disconnect the fuel line from the tank, and the rail, blew that out, blew out the fuel rail, swapped sensors on throttle body with known good ones and nothing.

Jeep was running fine about two weeks ago. He decided to wash the engine off with that degreaser stuff and it seemed to start acting up after that.

He said he cleaned some grounds off but that was about it. Here's a video of it. If you listen carefully you can hear it sounding really bad.

https://m.youtube.com/watch?v=rgDkw6ncTDM

It's throwing a code but I can't find my code reader. Obviously I need to get them read but any suggestions?

The Trouble Codes will focus your diagnostics. Too much water on the Throttle Position Sensor (TPS) can kill it. TPS testing is suggested. O2 sensors can cause similar symptoms. O2 sensor testing and O2 wire harness/wire plug inspection is suggested.

x2 on tps

Tim_MN said:

The Trouble Codes will focus your diagnostics. Too much water on the Throttle Position Sensor (TPS) can kill it. TPS testing is suggested. O2 sensors can cause similar symptoms. O2 sensor testing and O2 wire harness/wire plug inspection is suggested.

Click to expand...

TPS has been swapped out with a good one to no avail.

There is no rear 02 sensor on this jeep, but I thought only the front one had to do with controlling the engine?

If it is the 02 causing that why would it run fine before and then start acting up?

hows the spark plugs? and what year? but best bet is to check the codes.

"second you start to rev it up it goes BUP BUP BUP BWAAAP (studders and then takes off). "

"When you're driving it, if you touch the gas pedal like an egg shell it goes okay, but pretty much dies on hills. If you mat the pedal, the exhaust starts to almost shake and then it'll backfire. "

In my experience this is likely to be a bad vacuum signal to the MAP sensor assuming the MAP sensor and its wiring is OK. I have disconnected and fiddled with just about every other Jeeps sensor and never had those symptoms until I disconnected the MAP sensor wiring or vacuum line. The Vacuum line is a common source of leaks that can cause this.

Did he leave a ground wire broken or disconnected, or damaged?

Sorry guys, i totally forgot to mention, it's a 1997.

Code reader should be here tomorrow so that should help me out a little bit.

So go through and check all my vacuum lines to make sure they're not leaking? Would a leaky PCV valve (the two on top of the valve cover) leaking cause something like this?

Also isn't the only vacuum line going to the map sensor that little maybe 1/2" long one that goes from the sensor itself to the side of the throttle body?

I would imagine if he saw a broken ground wire he would of fixed it/repaired it properly.