Backfires and stutters
#1
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Year: 1993
Model: Cherokee
Engine: I6
Backfires and stutters
I finally got the 1990 Cherokee I6 to run after replacing the CPS, fuel filter, pump, distributor, cam sensor, etc...But now it backfires. It's not consistent either. It idles fine around 900rpms, but when I put some gas to it quickly it backfires sometimes, if i gradually do it it wont backfire as much. It back fires in the manifold it sounds like, although while testing I was once able to get it to backfire out of the exhaust.
While I was trying to get her to run I replaced the injectors with the Neon 703's. Maybe they're too much for my engine?
I fixed any vacuum leaks that I can tell. I don't think it's timing otherwise I would believe that the idle would be crap.
I pushed the TPS lever down with a screwdriver while it was idling and noticed it ran a little rough.
Any ideas?
While I was trying to get her to run I replaced the injectors with the Neon 703's. Maybe they're too much for my engine?
I fixed any vacuum leaks that I can tell. I don't think it's timing otherwise I would believe that the idle would be crap.
I pushed the TPS lever down with a screwdriver while it was idling and noticed it ran a little rough.
Any ideas?
#3
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Year: 1993
Model: Cherokee
Engine: I6
I thought I did, I moved the balancer to 0 on the timing marks, set the distributor to 5 o clock, when it sat it was at 4 like it says in the FSM. I had heard that if the distributor gear is off even a tooth the engine wouldn't start.
#4
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Year: 1998
Model: Cherokee
Engine: 4.0
My XJ still backfires so I know what your going through. I have replaced every part possible but the MAP sensor. That's my next move at least. I will let you know what happens.
Mike
Mike
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Year: 1993
Model: Cherokee
Engine: I6
I brought the balancer to 0 and instead of taking the valve cover off I just took spark plug 1 out and looked when I saw the piston. (the page says that if the balancer is on 0 and the valves are open to turn it another 360, which doesn't make sense to me. Every time the tick mark hit 0 I could see the piston coming up
Anyway, the H.O. distributor has its cam sensor wires almost right under the 1st plug, whereas on the non-
H.O. the wires come out under the 5th plug. Anyway, according to everything I've read, if you're looking at the engine from the pass side the rotor should be pointing at 5'oclock with the trailing edge of the rotor just touching the 1st plug on the distrib. That's where I am and I have no start at all now. I've now reindexed this ****ing thing a half dozen times and the 7th time just turned the shade of my blue face a little darker.
#7
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Year: 1993
Model: Cherokee
Engine: I6
I re-re-indexed it again and it starts again. I've indexed every conceivable way and this way, according to the FSM is the only way and it starts again, but it's still back firing.
Idles fine. Still just stutters and backfires between the 1200-2100 rpm range. If I floor it, it's fine. When sitting at park and I very slowly bring the rpms up it will usually not back fire, but not when it's in drive, it back fires everytime.
Think I've ruled out a misindexed distrib. Square 1 anyone?
Idles fine. Still just stutters and backfires between the 1200-2100 rpm range. If I floor it, it's fine. When sitting at park and I very slowly bring the rpms up it will usually not back fire, but not when it's in drive, it back fires everytime.
Think I've ruled out a misindexed distrib. Square 1 anyone?
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#8
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Year: 2001
Model: Cherokee
Engine: 4 liter
Is your advance working?
On engines with a distributor there must be a device to advance the spark. Since you said it idles fine ,that maybe your issue.
#9
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Year: 1993
Model: Cherokee
Engine: I6
The ECM does the advancing and retarding, theres no manual way to do it on a I6 4L engine. At least from everything I read.
BTW, put new plugs in, didn't help. Went with champions RC12Y's or whatever, they're the copper plus ones.
BTW, put new plugs in, didn't help. Went with champions RC12Y's or whatever, they're the copper plus ones.
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Year: 1998
Model: Cherokee
Engine: 4.0
Here is an interesting article on engines that backfire.
http://www.2carpros.com/how_does_it_work/backfire.htm
Mike
http://www.2carpros.com/how_does_it_work/backfire.htm
Mike
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Year: 1993
Model: Cherokee
Engine: I6
I was worried about the injector order and found the wiring diagram. They're fortunately/unfortunately right. (wish it was that easy) Also, the distributor is setup as 1-5-3-6-2-4 as it is stamped on the throttle body. Again, wish it was that easy.
I'm really beginning to think these injectors are too much for my old engine. I think I'll step away from it today for the Cherokees and my healths. So sick of this crap.
I read that article from 2carpros too. I'll probably read it again tonight and take some notes so I can take steps tomorrow.
Just for grins, I think I'll disconnect the O2 sensor to see if anything changes.
I'm really beginning to think these injectors are too much for my old engine. I think I'll step away from it today for the Cherokees and my healths. So sick of this crap.
I read that article from 2carpros too. I'll probably read it again tonight and take some notes so I can take steps tomorrow.
Just for grins, I think I'll disconnect the O2 sensor to see if anything changes.
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Year: 1999
Model: Cherokee (XJ)
Engine: 4.0 I6
put your thumb over the spark plug hole and turn the crank with a beaker bar. when the air in the cylinder is pushing against your thumb, trying to blow it off the hole, you are on the compression stroke. this is where you need to be when you set your distributor and crank together.
also, since we have a distributor, there should be an a timing advance control in the distributor. it is either mechanical in the form of some springs with wieghts (fly wieghts) or vacuum controlled. i don't remember seeing a vacuum line hooked to the distributor though
also, since we have a distributor, there should be an a timing advance control in the distributor. it is either mechanical in the form of some springs with wieghts (fly wieghts) or vacuum controlled. i don't remember seeing a vacuum line hooked to the distributor though
#14
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Year: 1993
Model: Cherokee
Engine: I6
put your thumb over the spark plug hole and turn the crank with a beaker bar. when the air in the cylinder is pushing against your thumb, trying to blow it off the hole, you are on the compression stroke. this is where you need to be when you set your distributor and crank together.
also, since we have a distributor, there should be an a timing advance control in the distributor. it is either mechanical in the form of some springs with wieghts (fly wieghts) or vacuum controlled. i don't remember seeing a vacuum line hooked to the distributor though
also, since we have a distributor, there should be an a timing advance control in the distributor. it is either mechanical in the form of some springs with wieghts (fly wieghts) or vacuum controlled. i don't remember seeing a vacuum line hooked to the distributor though
I sincerely believe there is no manual timing advance on our distributor. I know there is no vacuum connection and the distributor only has the camsensor/pickup coil in it.