90renixxj

Hello, I was on here last summer try in to figure out what's wrong with my jeep. Winter is over here I go again.

1990 jeep cherokee (Pioneer)
W/1987 4.0L engine
Automatic aw4
Lifted 3 inches
33 inch tires
No muffler duals from the cat back 2.25
Replaced stock air filter box with cone filter(spectre)
4 off road lights on roof 2 in grille
Cb radio



Replaced:
Plugs
Wires
Coil
Cap
Rotor
Tps
Fuel filter
Fuel regulator
Refreshed all grounds
Upgraded ground cables
O2 sensor

Exhaust manifold is cracked at the #6 cylinder about an inch above the o2 sensor on the weld

Electric fan is basically bypassed with a wire at the sensor, so its on as soon as I start it and it stays on

If I turn my heat on or any of my aftermarket lights my voltage drops, probably need a bigger alternator

Now what it's doing:

Start ignition:
Takes about 2-3 seconds to fire

Engine starting:
Starts off just a tad rough for like a second, before regulator was put on it would run rough for like 5-10 seconds, clears up very quickly now

Idling:
Has a slight fluctuation in idle better now that I replaced the o2, but still there

Put it in drive:
Now if I try to take of normally it'll start missing and backfiring out of the exhaust, like some firecrackers or something,

Now if I just slightly depress the gas pedal I can get it to move quite nicely, until I get to about the top of the gear and it will do it again, I have to floor it to get through the crappyness until I'm up to my desired speed, it will cruise just fine until I let my foot of it will act all crazy again doing the same exact thing, sometimes it will go down a gear and then back up. It seems to be at the top of each gear it does this.

I can also get it to do the backfire misfire thing in park but it seems to only be a small portion of the throttle it does this.

I did get a new CPS I tried to slide the sensor part up the bar farther to the passenger side of the vehicle, I'm going to be replacing it with a regular one soon, could this be causing all my havoc? Possibly because of my cracked exhaust manifold?

Anyone that can steer me in the right direction that'd be great, I love this thing I need to get it running good

And could air in the cooling system of my RENIX cause this?

Crazy 8s

If the crack in the manifold is big enough it can result in more oxygen being detected at the o2 sensors, which would enrich the fuel ratio and could cause the issue you are describing.

90renixxj

That's what I thought, it seems to be running rich TAILPIPES ARE SOOTY REALLY BAD already have the new manifold and gasket, putting it on this weekend hopefully.

90renixxj

Its like 30 degrees in Michigan today so I was only out there for a minute, I tested the flat 3 wire connector at the tps, I put my DVM red lead on the middle wire B, and and put the black lead on the negative battery post, I got 1.6, I tested it in ohms lowest setting, DID I DO THAT RIGHT, if I did that's to high right?

Crazy 8s

You may be well-benefited from reading through Cruiser54's awesome RENIX tips. You will find a good methodology towards getting the TPS adjusted, and a whole lot more.

https://www.cherokeeforum.com/f51/cr...x-tips-153657/

cruiser54

Did you do my Tips 3,4,and 5?

Do those and then adjust your TPS per Tip 8.

Intake manifold bolts snug?

Look at this line also:

90renixxj

Yeah I've done 3,4,5. Today I did test the TPS I'm getting 4.78 for my reference voltage so I set the input to .81 I couldn't adjust it any further there was no more room left, it's tilted at an angle to me it doesn't seem right but I guess it could be.

Any input on this people?

90renixxj

And adjusting it didn't change one bit

cruiser54

Well, if 5 was okay, what was the ohms reading?

90renixxj

I don't remember the exact reading, I know it was really close to 0 ohms and I wiggled every wire harness I could especially by the valve cover, all the wires near the firewall, TPS wires pretty much everything I could reach, didn't fluctuate at all.

I'm starting to move towards the fuel pump I'm pulling it tomorrow to check the rubber line in there

cruiser54

Not a bad idea....

90renixxj

So I pulled the fuel pump out today, the rubber line is in ok shape kinda mushy still together tho, I'll replace the rubber line anyways tomorrow and there was no sock screen on the pump.

Is there a way to test the fuel pump to make sure it's good?

Not really sure what I'm gonna check next

cruiser54

Not without reinstalling it and checking pressure at the fuel rail.

DFlintstone

Some pump install FYI>>

Below is the inside of the tank. The black ring you see is the end of the cone that belongs on the end of the fuel return line on the pump assembly. That cone on the metal line holds the bottom of the whole deal in place. That there should be fished out, and installed on the metal fuel return line on the assembly. Then you seat the cone into the receptacle in the tank when installing it. The fuel return and pickup are located in a tray inside the tank, so return fuel is available to be picked up at the pump inlet, even when the tank is low or at an angle.

90renixxj

I got the screen out and took a crap ton of photos of the inside of the tank there isn't anything else in there that I could see