DingoGoneWild

Ok so I have had an ongoing problem:

Engine Shakes. Gets up to 3000 rpms wont go any further, needle bobs up and down... run for a little longer trying to gain speed past 50 and it clears out. Runs fine.

I have had the injection system cleaned 3 times in the last 3 years. Just had a valve and head job done two months ago. Problem started back up... Same old bull.

What should I do?????? Please help.

MonacaYankee

You should add the info about misfires like you did in your other post.

First thing. What check engine light codes are you getting?

I had a bad upstream o2 sensor make my jeep run rough after first accelerating when it's cold. It would backfire and sputter in second gear. It would sound like a shotgun if I tried to floor it to get it to quit. Does not sound as serious as yours.

Clean the throttle body and check for vacuum leaks. Check the throttle position sensor and manifold absolute pressure sensor.

I have heard of plugged up catalytic converters making Cherokees run rough like you described. Disconnect the exhaust at the header and run it on open headers and see if it does the same thing. Plugged cat will glow red hot so you would probably know if it's the cat or not without running open headers but it sure is fun and loud.

DingoGoneWild

Do you think a faulty vacuum could cause this? Because I hit a deer a while back and the vacuum is no longer sealed properly. The one behind the bumper

MonacaYankee

You talking about the cylinder with the vacuum connection on the top? That's the vacuum ball. It's only to provide a boost to vacuum operated components at full throttl and even out the boost (heat blend doors an example). It would not cause the jeep to run rough.

DingoGoneWild

I dont know what other post you are talking about.

MonacaYankee

This one.

salad

Any codes stored in the computer? Check engine light doesn't need to be on for a pending code.

DingoGoneWild

Check engine light is on. I need to get it to a mechanic to get the codes checked out

MonacaYankee

Sounds like a good way to lose more money like you already said that any mechanic you have gone to has not fixed anything.. Just take it to advance,autozone, napa, oreilly etc... They will read the codes for you for free. Or buy a scanner, very very nice tool to have.

DingoGoneWild

Well I live in the woods. Its either take it to a mechanic 10-20 miles away or drive 80 to napa or O'reilly

DingoGoneWild

Alright, well I am headed to town on friday. Ill let you guys know what I find.

DingoGoneWild

Went to O'reillys and got the codes.
P0306 Cylinder 6 misfire
P0303 Cylinder 3 misfire
P0455 Evaporative Emissions System Leak, Gross Leak/No Flow
P0203 Injector Circuit Open Cylinder 3

Any suggestions on what the main problem might be?

Ianf406

For the p0306/p0303 most common are going to be:
Faulty spark plug or wire
Faulty coil
Faulty oxygen sensor
Faulty fuel injector

P0455 shoudnt cause your problem but things to check:
A loose or improperly affixed gas cap
A non-conforming gas cap (i.e. not factory/original brand)
Other leak or damaged piece in EVAP system

The P0203 is usally caused by a bad injector.

I bet you need new injectors or something is messed up with your harness I have a set of 784s for sale in Missoula. Could always swing by and see if they help. Ide check the voltage at the injector pigtail. First making sure you are indeed getting power there.

DingoGoneWild

Ill have to get my old receipts and figure out what I have already replaced before I do anything to it.

salad

Check out the injector wiring harness. Rubbing against the fuel rail can cause shorts that will contribute to three of those codes. Pay special attention to where it jumps from the firewall to the engine. Peel back the tape and loom covering and inspect the wires themselves.

The EVAP leak is likely a coincidence