Originally Posted by fantic238

this thread is for all those who would like to ask something tech related and don't want to start a new thread or hijack someone elses, and for all those tech related questions you happen to ask in the big off topic threads. Me and some of the older members will answer every kind of question as long as it is tech and polite.
P.s. For the newbs: Stupid questions don't exist, there are only stupid answers. Feel free to ask whatever you want. "what is a jeep?" is a good question....

Edit: If your question is very common (eg: Lift) please do a research first and if you don't find the answer come back here, 75% of the questions can be answered within a 5/10 min browse using the "search" button on the black banner menu.
For any lift & tire questions go here first: https://www.cherokeeforum.com/f2/all...go-here-10579/

Originally Posted by Anthony S.

I'm getting weak heat/air flow on my 01 GCL. I've replaced the blend doors,sealed up the hole that I cut.and now I'm getting codes 52 and 56! easy fix? or sale my baby???

Originally Posted by Anthony S.

how do i post a question!!!

Originally Posted by Basslicks

*sigh*

1992 XJ 4.0
TB is clean
AIC is clean
TPS is new
MAP is new
Coil is new
Wires are less than a year old.
Distributor, cap, and rotor is new and converted to the HO style
Recently replaced the valve stem seals... plugs are still pretty cruddy from all the oil intrusion.
Brand new MOPAR FPR - holds pressure to the rail looooong after the jeep is turned off.
Cleaned the injectors probably about a year and a half ago.
Has a stant 195* t-stat, the factory fan setup in place, and the shrouds are all still there as well. Cooling system has been given the Amway flush recently.

So here's the problem: I can go out to it after it's been sitting overnight or for at least 30-60 minutes, start it up, it will idle and run fine and I can drive it anywhere I want. If I'm in a lot of stop and go traffic, drive-through lines, or it sits and idles a lot, it starts to run HORRIBLE. Starts missing, then backfiring, then no power, then won't even rev, then eventually dies. After a few starting cycles, I can get it to run again by blipping the throttle through the RPM ranges and then tromping on it until it pretty much redlines. It's acting similar to heat-soak, which I know is a late-model HO thing and not an early model HO thing. So this leads me to believe that maybe the crack going all the way around the manifold at above the collector might be heating things up and making the sensors fail. Or maybe heat-soak?

To sum up, anyone know if a cracked-through exhaust manifold will cause the motor to backfire, run like crap, and just not drive in general?

My suspicion is the manifold, but I wanna know for sure before I pull the trigger on it and it's not the problem.

Originally Posted by TFitzPat87

Hi Gents, now that it's been cold here in the good ole mitten I'm back to using the heat and defroster. What I'm curious about is... should the electric fan effect oil pressure? Whenever the defrost is on and I come to a stop, and the fan starts to cycle, the oil pressure rises. When it turns on, it bumps up about 5 psi, and when its off it drops back down. Is this normal or should I be looking for something? It doesn't effect rpm, so I find it weird that oil pressure would change. I'm not super worried about it, but if it's particularly normal, I'd like to correct whatever the problem might be.

Originally Posted by Basslicks

That sounds like an electrical issue. I would start be doing a ground refresh and then check all of your connections... remove all of them, spray them with electrical cleaner and then put some dielectric grease on the connections. Not sure how it's happening, but it sounds like when your fan kicks on, it's effecting the connection to the sender.

Originally Posted by TFitzPat87

Thanks Bass Licks! That actually makes some sense because my oil pressure gauge is kind of funny. It's not bouncing all over the place, but it's not consistent. I'll be cruising around and it'll be just below 50psi, then look down a couple seconds later and it's just over 40psi. Look back again a minute later and it's back up to around 50psi. (Sender is fairly new, and a mopar replacement)

By the way, my apologies on my spelling (affect, effect). 2 hours of sleep isn't cutting it today. Plus wouldn't it actually be the compressor cycling?

Originally Posted by rcguymike

The symptoms sound really similar to what my XJ was just doing. I had a cracked manifold, fixed that and it ran better, but not perfect. Ended up being the wiring to the MAP sensor near the back of the head had worn through and was occasionally shorting out. I had all the symptoms you have. I just got done travelling with work and winter was close so I ended up having the dealer fix both, was ~$400 to fix crack(new intake gasket, no rusted bolts to deal with etc), and ~$150 they found and fixed wring along with replacing the connector for the MAP sensor. If that's your problem you could fix both problems in an afternoon with a welder and less than $100 in parts. Also reset your computer as the fuel trims get really out of wack with either of those problems.

Originally Posted by Basslicks

The compressor kicking on would make change it for a second, but once the motor caught back up, it should go back to where it was.

Originally Posted by TFitzPat87

When the compressor or fan (whichever it is) kicks on, the oil pressure goes up with it until it kicks back off. Then after a couple seconds, the oil pressure will drop back down. It cycles quite frequently too. I don't remember this on my old XJ. When I'm moving, it never kicks on, but once I come to a stop, it seems like its on and off every 10 seconds. I just start doing some connection refreshing and see what happens. The problem now is weather (cold, rain, snow). Mmmmm... gotta love the dirty glove!

Originally Posted by TFitzPat87

Hi Gents, now that it's been cold here in the good ole mitten I'm back to using the heat and defroster. What I'm curious about is... should the electric fan effect oil pressure? Whenever the defrost is on and I come to a stop, and the fan starts to cycle, the oil pressure rises. When it turns on, it bumps up about 5 psi, and when its off it drops back down. Is this normal or should I be looking for something? It doesn't effect rpm, so I find it weird that oil pressure would change. I'm not super worried about it, but if it's particularly normal, I'd like to correct whatever the problem might be.

Originally Posted by Basslicks

*sigh*

1992 XJ 4.0
TB is clean
AIC is clean
TPS is new
MAP is new
Coil is new
Wires are less than a year old.
Distributor, cap, and rotor is new and converted to the HO style
Recently replaced the valve stem seals... plugs are still pretty cruddy from all the oil intrusion.
Brand new MOPAR FPR - holds pressure to the rail looooong after the jeep is turned off.
Cleaned the injectors probably about a year and a half ago.
Has a stant 195* t-stat, the factory fan setup in place, and the shrouds are all still there as well. Cooling system has been given the Amway flush recently.

So here's the problem: I can go out to it after it's been sitting overnight or for at least 30-60 minutes, start it up, it will idle and run fine and I can drive it anywhere I want. If I'm in a lot of stop and go traffic, drive-through lines, or it sits and idles a lot, it starts to run HORRIBLE. Starts missing, then backfiring, then no power, then won't even rev, then eventually dies. After a few starting cycles, I can get it to run again by blipping the throttle through the RPM ranges and then tromping on it until it pretty much redlines. It's acting similar to heat-soak, which I know is a late-model HO thing and not an early model HO thing. So this leads me to believe that maybe the crack going all the way around the manifold at above the collector might be heating things up and making the sensors fail. Or maybe heat-soak?

To sum up, anyone know if a cracked-through exhaust manifold will cause the motor to backfire, run like crap, and just not drive in general?

My suspicion is the manifold, but I wanna know for sure before I pull the trigger on it and it's not the problem.

Originally Posted by cruiser54

I'm not convinced it's the manifold.

How does a manifold under exhaust pressure bring air in to screw with an oxygen sensor?

Originally Posted by rcguymike

Depending upon the crack and location I think a Venturi effect would cause it to draw air in.

Originally Posted by cruiser54

whatever......