okay here it goes, I did all of this yesterday but received no help. I have a 1994 Jeep Grand Cherokee that isn't running very well. The tranny went out during winter and I put a new one inabout 2 weeks ago. While installing we accidentally mashed the CPS in the back of the motor. (we found that out after the truck would not start). So I changes the CPS (pain in the neck) and the truck starts but ran very rough. So I figured that cranking on it a bunch may have fouled the plugs, so I bought a new set, and the truck will idle good now, but when you rev it up it cuts out and sounds horrible, it back fires and just isnt drivable at all.

When I changed the plugs I remembered that cylinder #2 spark plug wire was really hard to remove, so I thought maybe I broke the wire. SO last night I swapped it with one on my truck, but it was not the problem. I removed the plug and it had been firing and it was no dirtier then cylinder #4.

So I thought of other things I could have screwed up, (I think it has to be something I did, because before the tranny went out, the thing ran like a champ, (it ran better then my truck and it has 201,000 miles and my truck has 83,000 miles.

I remembered that to get to the CPS aside from EGR crap that I removed, I also undid #6 and #8 cylinders fuel injector wires. I wrote down what color wires, went with which one, but I reversed them just to make sure, and the truck runs horrible wont rev up hardly at all. So I know I had that right. So I began to think, the wires are very old and hard so I think it might be possible that the copper in one of them broke when I removed it, so my question is how do you test for something like this. Could I run a jumper wire off of another injector that fires at the same time or something, I thought of jumping off the battery but then it would flood out because it would constantly spray. Maybe I could check the voltage on the wires, what should it be.

My dad said that the injectors may have clogged up after sitting for a couple of months. I dont think that it would happen, but what do you think.

 

Try to determine if it is a fuel or electrical problem.

It sounds to me like you may have a couple of spark plug wires reversed. If not, make sure the wires are routed properly. If certian wires are touching (don't remember which), the spark will jump from one wire to the next and cause a mis-fire.

In my experience fuel system problems get worse with rpm, regardless of engine load. Ignition problems get worse with engine load, regardless of rpm.

Hope you get it figured out.

 

Could be clogged up injectors or could be the wiring harness or the clips that connect to the injectors themselves.

Have a read of my replies to granpa49s thread below. Suggest you follow my suggestions to see if this is what your issue is. Could be a cheap fix for your problem if thats the case

https://dodgeforum.com/m_1251115/tm.htm

 

Being that the CPS is right next to the distributor, make sure that you didn't accidently knock one or two wires offthe cap, or even got them switched at the cap.

A second thing to check is the wiring to your Camshaft Position Sensor. This sensor sits inside your distributor and has a wire that runs out of the distributor. The wire very easily could have been damaged/crimped off during the transmission install as it is in the same back of engine area where you were working. The wiring should run from the distributor to the connector and then cleanly to the drivers side of the engine compartment. I had an intermittent issue awhile back and found that my camshaft position sensor wire had been nicked during installation of my new engine. Replaced the sensor and my truck came back to life. This would cause your fuel injectors to have issues.

 

my earlier post where i thought that the wire could has been broken, no longer applies. I went out side and undid the fuel injectors in question while idling. The motor ran much worse, which means that they work. Some of the injectors clips are broken on in so INDY thanks for the comment, those MSDs look like they would work very well, definately in my not so distant future. Heck for 15 bucks, probably put some on my truck and it runs fine.

As for the spark plug wires, That is not possible, I never undid them from the distributor, and when I changed the plugs I did not reverse anything. I am really starting to believe my dad that maybe the injectors are just clogged. I just cant think of how that happened. It seems like if it was running good when the tranny broke, that it should be running good now. As for the CPS wiring. It would not start at all if it was broke (believe me lol).

I wonder if removing wires while the truck is reved up to its max 3,000, I can remove the wires from the injectors and see which one does nothing. At least I will have it narrowed to which cylinder is the problem.

 

ok, went out side and tried a few things. First while idling I removed the injectors one at a time, all made the motor miss, now remember that the truck runs fine idling, so that means all injectors flow good at idle, and also that all of my injectors have good contact with their wires. As for the next thing i reved up the motor a bit around 1800, which is when the motor starts to miss, and removed the wires again one at the time. Still all of the injectors made the motor miss worse, none of them stuck out worse then any other. I suppose that they all could be stopped up equally, which to me sounds like a fuel filter, but it was changed probably less then 20,000 miles ago.

And also I triple checked the plug wires, they areall plugged in to the distributor, and all go to the right plug.

Again thanks for the help guys

 

Have you hooked up a vaccum gauge to the engine? A vacuum leak is easy to create on an engine with 200,000 miles. Hoses become brittle and crack if pushed or pulled accidentally.

Have you checked your fuel pressure? That might tell you if your filter is partially plugged.

 

well, I think I have good news, I figured that my dad was probably right, so we pulled the injectors this afternoon, and I haven't even cleaned them yet, but I can tell that those things are clogged up horribly. I went to town and got some cleaner, gunna blow through them tomorrow, and I also bought a new fuel filter. Unlike our rams, Jeep actually put a fuel filter in the line, and not the tank (what a great idea lol...) any way I will update tomorrow. But I definately think this is going to fix my problem