Ok, so I've always wanted a wrangler and I finally got one. It's a 93 2.5 5spd. It's not perfect but I always like a project! I already plan on swapping a 4.0 in it and have already bought one. I'm sure ill be asking tons of questions when I get around to doing that
But my post for today is about it running bad. It runs fine until its warmed up and then it starts bogging down and backfiring bad! I'm talking downshifting to 2nd on the highway to get it to move. Never overheated or got close to being hot. I've already changed the plugs, wires, dist cap, rotor, oil and filter, and air filter. It was pretty nasty underwood so I cleaned her up a bit.
o2's can fail within spec and never set off a cel. Even when they do fail out of spec the wont always set off a hard code. that keeps the light lite up. I periodically use the key trick to check for codes that wont set the light off.
If either of them or the MAP sensor were bad it would not run well, or at all, either cold or hot since they are vital for real time fuel/air/timing adjustments IIRC.
Hmm. He was saying he had a chevy do the same symptoms as my jeep and that is what it was. Said that they are made of plastic and that they crack...on e they get to operating temp they swell and oil gets inside and shorts them out causing them to run like crap.
Any thoughts on the muffler being clogged?
I feel like its more of a breathing issue than anything...
The cam sensor has nothing at all to do with what is normally called timing, which is nothing more than spark advance. Spark advance is read from the crank sensor not the cam sensor.
when the crank sensor goes kaput it shuts down the signal to send power to the coil and fuel pump from the ecm. this keeps the engine from flooding mostly. that is why i am saying it probably wont be the crank sensor.
before the peanut gallery chimes in here is what the cam sensor does....
This camshaft position sensor would just let the computer know what exactly is going on and whether the amount of air being let in is too much so then the MAF (Mass-Air Flow) sensor will have to restrict back on the amount of air let in by adjusting the throttle position sensor (TPS). The cam sensor also tells the computer at exactly what position the camshaft is. This allows the computer to know whether a particular piston in the engine is on the power stroke, intake stroke, or exhaust stroke.
not saying that the cam sensor can't be bad, i just don't want you being misinformed about it's function.
incidentally if the cam sensor is sending bad info you could be firing on the wrong stroke of the motor causing backfiring and loss of power.
as far as i know the water temp sensor has no bearing at all on ecm input on obd1. it is strictly an output reading of the water temp and nothing more.
now i do know that on some newer obd2 vehicles it will make the transmission shift later if the motor is not up to operating temp.
Well ****. I'm at a loss then. Don't want to start throwing parts at this thing and I REALLY don't want to spend too much on this motor as I'm gonna swap it ASAP. Just not ready yet.
i would start with the exhaust since it sounds to be all screwed anyhow.
it is possible that when the cat was tore out the cake may have already let loose into the muffler.
after that i would start checking sensors.
since it starts and runs i would rule out the crank sensor.
maf,iac, and tps would be the next place i look. i don't even know if that motor uses a maf i just put it there.
also... o2 sensor and make sure your not vapor-locking the fuel system anywhere. if the fuel lines are run in any weird place next to a heat source. also if the injectors are notorious for vapor-locking.
i don't remember what vehicle you have and i'm too lazy to look through the thread to find it. . . it would be a huge help for this problem or any future issues if you were to fill out your profile.
i would start with the exhaust since it sounds to be all screwed anyhow.
it is possible that when the cat was tore out the cake may have already let loose into the muffler.
after that i would start checking sensors.
since it starts and runs i would rule out the crank sensor.
maf,iac, and tps would be the next place i look. i don't even know if that motor uses a maf i just put it there.
also... o2 sensor and make sure your not vapor-locking the fuel system anywhere. if the fuel lines are run in any weird place next to a heat source. also if the injectors are notorious for vapor-locking.
i don't remember what vehicle you have and i'm too lazy to look through the thread to find it. . . it would be a huge help for this problem or any future issues if you were to fill out your profile.
Agreed! Cut the exhaust system before the muffler and spec the insides to see if is clogged, which I am doubting at this time. Then drive this Jeep if you can stand the noise and you won't get a ticket. If the exhaust is disco'd after the O2 sensor and it still bogs....it isn't a clogged exhaust system!
Since it runs good cold it is wiring (or sensors) when it goes into closed loop mode.
Ok. I'm gonna take it in tomorrow morning for a new exhaust from manifold back. Thinking I'm gonna leave the cat off. Any thoughts?? Hopefully this will take care of my problem...if not, then on to the next clue...
Ok. It's not the exhaust. It did have the original muffler on there so I went ahead and put a flow on it. It's a heck of a lot louder and seems to have a little more power as it should. But the problem is still there. I threw a new coil on it as that was the only thing besides the dist that I haven't changed in the ignition system. Still not any better. Any ideas where I should go next??
Have you checked mechanical time yet. Yes the sensors can be tested. THe procedure is in the FSM. I just saw a link to it earlier this morning but forgot to save it. I am sure someone posting in here has it though.
You have had some high temps lately haven't you? I forgot if you mentioned it or not but are you still running the clutch fan? Does the engine temps get kind of high on these runs you are making? Is it worse at slow speeds faster than at highway speeds?
Popping back through the throttle body and general lack of power could also be vapor lock from excessive heat in the engine compartment.
Wrap your fuel lines in the engine compartment with insulation and aluminum foil to see if that makes a difference.
Yes...checked timing and it's steady at 8 degrees.
It's not getting hot at all. Generally runs at 180. It only happens at highway speeds and only after more than 10 miles. Air filter is brand new and clean. Gonna change the fuel filter but don't really think that is the issue...hopefully I'm wrong...
Under the hood it gets hotter than normal in the hot weather though and that is where your fuel system is. Pop the hood so the safety catch has it and drive it. See if that stops it from running like crap. BE CAREFUL if you do that add a safety strap of some sort.
In 1987 I bought a brand new Chevrolet El Camino SS. For the first two years that I bought it I had to change the fuel filter on it every 2,500 miles or so. It would bog, and or begin to stall while running down the road. Did that until I had about 20k on it. It never backfired though.
And no, the stealership had no idea what the problem was. They got one shot at fixing it and then I never brought it back to them.
Vapor lock in MPFI. I have never heard of a vehicle doing that. Are you sure there isnt carbon build up in the cylinders. When that gets hot it could be causing it to fire at the wrong times just from heat build up in the carbon deposits.
If that fuel is too hot when it hits those injectors I think vapor lock is a distinct possibility even for MPFI. Or at least he would run real lean since the hot fuel has much less density.
But if he is getting pre-ignition from hot carbon spots the OP can just dribble water down the throttle body while revving the engine and the steam made will boil off the carbon deposits pronto....just like a cracked head gasket would do to the plugs valves top of the piston etc. maybe that is that he should try next.
But his symptoms seem to be heat related. What do you think is the problem if it isn't carbon build up?
Maybe the coil/ignition module is getting too hot? The OP does live in Texas.
No I'm not sure. But I really don't want to do too much as I'm a lout to start tearing down my 4.0 and send it off to the machine shop. Hopefully have that in in a few months.
I apoligize if this has been answered already I am on my phone and don't remember all the posts. Jave you checked the crank sensor? Also the cam sensor it can cause the ignition timing to becone erratic and fire the plugs at the wrong time. Is the dizzy tight? Is there any play at the rotor. Again I apologize if these have been answered already?
Ok broke out the iPad so I could read easier. I think you should try the water trick. Don't use sea foam if your not worried about the engine long term. The more I think about the more it sounds like the pick up sensor in the dizzy or the ignition coil. Both of those sensor will work on the 4.0 so you can use them as spares if you like
No...everything is tight as far as the dizzy and the rotor and cap. Already replaced them with no change. Yes it happens at night too. Coming back from the movies the girls were cold...it was fairly cool out that night and it did it just the same. I mentioned the cam and crank sensors in this thread and no one thought that was relevant. Is there a way to check them or are they cheap as I don't want to really throw parts at this thing. No one has ever had this problem before??
I'll try the water thing when I get home this evening.
I already tried the I coil and it didn't change anything. So I put the old one back on and am going to go get my $50 back. Where is the pick up sensor located and how much if a pain is that to change?
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