pedenspeed

Well I have been researching all night long, and I think I have some new places to start checking, but I thought I would get some more opinions from the Guru's. Basically what happens is this, if I put my foot in the pedal, the engine chokes out immediatly. If on the other hand I start out slow, I can accelerate until RPM's reach 2200 before the engine starts choking out. Since I have starting trying to diagnose the problem, it has actually gotten worse, to where now I can do over 10 miles an hour. First thoughts were a plugged Cat, so I cut the exhaust just before the cat and removed it. There was no change, and so now I have no cat, but straight pipe to the muffler instead. I checked the Fuel pressure, and it is at 31PSI, but no idea if it changes when vacuum line is removed (just found the procedures on diagnosing that during my research tonight) so I will check that out today. Thought it was possibly the MAP, so I replaced it. No change, but through my research, I now have the procedures on troubleshooting all the sensors, so I will be checking the rest of the sensors today. I have checked compression on all cylinders, and all seem good, atleast less that 10% variance between cylinders. Did a complete tune up (because of emissions failure) last August. Cap and rotor, spark plugs, and wires, changed oil and filter, fuel filter, air filter. Tried fixing all vacuum leaks that I could find, which I still have minor ones, and will continue plugging away on them, however, i dont believe this to be my issue. As I said, I now have some new ammo under my belt after researching all the great info on this site, but does anyone have any other areas that I might check, other than all the sensors, and fuel regulator? All your info and ideas are greatly appreciated, and I will let ya know what I find, when and if I find anything.

always89

Sounds to me like your drawing in air somewhere. I would take a can of starter fluid and spray it on the intake gasket, the intake itself, different places. When the engine rev's, theres a hole, crack, or bad seal.

93XJLI

change your MAP sensor

spietrzak_pee*pee

i kinda have the same issue but it doesnt do it until i hit a certain part on my pedal or 70 mph. i unplugged my map sensor and it went away i looked it up and said the ecm might be bad. but yea id chek out for air cause im still finding little air leaks. as for the 31 psi i believe it should be 39 to 50 thats what it says in the haynes book. its annoying with mine.

laidoff

This sounds a lot like a problem I was having with my jeep. Mine end up being the intake gasket. I used a product call "Copper Spray-A-Gasket" it was prob. the best thing I could have done when putting the intake on. Do make sure to follow the directions on the can and make sure to seat the intake while the "Spray-A-Gasket" is still tacky

pedenspeed

already changed map but that was only sensor i have tried so far. also checked for intake leaks with starting fluid already. none reared its ugly head. possibly an intake gasket but most likely would have shown up during the compression and leakdown test. however could b under a load between cyclindersor when its warm. will run all the diagnosttics on the sensors hopefully today. this is so mind boggling.

pedenspeed

ok using the information from this forum posting:

https://www.cherokeeforum.com/f51/he...ix-links-1397/

I checked the air temp sensor and it checks good, I checked the coolant temp sensor and it also checks good. Next it was time for the TPS, which is not easy to probe I might add this is where the tables turned. Supply voltage terminal A to D was 4.11 volts but when I probed B to D, it returned a value of Neg .805 volts and no matter what position it was in ( I even pulled the sensor off the throttle body and moved the lever) it never moved off of -.805 volts. So what do you all think, am I doing something wrong or is this a bad sensor?

EDIT: Ok conflicting information on how to test the TPS, this article http://www.lunghd.com/Tech_Articles/...iagnostics.htm says test A to B and B to C, so I will test this again and see if the results change, which I am sure they will.

pedenspeed

Ok, have been off the project for quite some time, but got back to it today. So after putting the TPS back on and testing it the right way, all seems good with the TPS. I got .8 volts at closed, and voltage increases as I move the lever. question there though, does it need to be EXACT .8 volts, I have .843 should i adjust it closer to .8 or will i be fine? Now on to more info though, I decided to change the fuel filter, I am starting to believe maybe this is fuel related. Drove the jeep up to the nearest auto store, purchased a filter, drove back home. On the way to the store, couldnt get more than 2200 to 2300 RPMs, on the way back it was down closer to 1500 rpm. Got home, pulled the old filter, gas looked fine. Installed new filter. Turned ignition key on and let the pump fill up the fuel rail, and then tried to start the jeep. Almost thought it wouldnt start, cranked and cranked and cranked, finally it came to life. Took it for a drive, stomped on the accelerator and thru rocks and dirt everywhere (gravel road). Seems to run fine for the most part, but I am not sure its fixed. Gonna hit the highway with it and see how she does here in a few hours so will keep you posted.

PingPong

Think you have a fuel issue problem. The fuel psi shoudl be between 40-50psi at idle. Sounds like you are starving the motor of fuel. If changing the fuel filter fixed it great.. if not change the fuel pump

fishtaconc

Renix, OBDI were 31PSI @ Idle 39 PSI @ WOT, OBII is constant 49PSI

pedenspeed

well fuel filter did not do the trick. Next I went and found a fuel regulator out of the local parts yard. That didnt fix it either, so I guess its onto the fuel pump. Prolly get to that tomorrow, this has got to be one of the most frustrating problems I have ever seen. Hopefully the fuel pump does the trick.

pedenspeed

Woohoo, problem solved. So in the pooring down rain today I went to the local junk yard again, and pulled out the last fuel pump in the entire yard. Took it home and installed it, and low and behold the beast lives once again. Thanks for the help all, this is about the 4th pump I have put in in about 8 years, starting to think I need to drop the tank and have it boiled or something. Just glad to have a rig back on the road, now on to the next project

PingPong

PPl fail to realise that running fuel tank low on fuel causes the pump to run hot and shortens its life. always keep at least a 1/4 tank or more fuel in it