Jeep Cherokee Talk banner

1 - 20 of 22 Posts

·
Registered
Joined
·
7 Posts
Discussion Starter #1
New plugs and coils, injectors, 4 oxygen sensors, throttle position sensor, map sensor, fuel pump, and fuel filter. All brand new. My jeep will start up usually the first time. But will not when it gets warmed up. If I leave my jeep idling it starts to bog down after a few minutes. And then will not start again without starting fluid. What else is there to do?
 

·
Super Moderator
Joined
·
10,415 Posts
Ok First, what year? What engine? How many miles? Does the fuel pump cycle when you turn on the key?
Are the parts, cheap parts store parts or dealer/mopar?
 

·
Super Moderator
Joined
·
10,415 Posts
Usually you're ok with the parts store as long as they are name brand and just not the cheapest. You may be suffering from "heat soak" basically, the fuel in the fuel rail gets so hot that the fuel starts to boil. You should have a Schrader valve in the fuel rail. Put a gauge on it and see what the fuel pressure is minimum 40 psi for our 4.0's.
 

·
Super Moderator
Joined
·
10,415 Posts
Then you need to check your wiring to the fuel pump. They have a ground wire that is attached to the chassis near the connector. Make sure it is in good shape and the connection to the body is clean Ana making good contact.
 

·
Registered
Joined
·
6,997 Posts
Gluck, usually heatsoak doesn't hit until you shut off and restart. At idle there should be enough constant fuel to keep it running clean. At least on my 2001.
Some questions we need to verify for kicks: what plugs and what did you gap them to? Injectors: stock or 4hole design? Were they new or used/tested/rebuilt?
Is the jeep getting especially hot in these situations? Or just the usual 210?
 

·
Super Moderator
Joined
·
10,415 Posts
I thought heat soak could happen while idling. Mine is a 96, and I have been on trails using very little throttle, and after a while, it will sputter then shut off. Sometimes it will start and other times it just cranks, after it sits for a few minutes. It will usually start but spit and sputter and I have to throttle the hell out of it until it smooths out. Then it runs fine. I wrapped the fuel rail with header wrap and it seemed to eliminate the problem. I thought it just might be a leaky injector (4 hole). I dunno.
 

·
Registered
Joined
·
6,997 Posts
Can't say I've seen that before.
 

·
Administrator
Joined
·
6,426 Posts
Supes is partly correct. Under almost all incidents of heatsoak it only occurs after the fuel pump is turned off. With the pump on, any loss of pressure due to preatomization of fuel is counteracted by the pump constantly trying to force new fuel up the path.

There are of course incidents where any number of other things can happen allowing the system to vaporlock, but generally it does only occur when the engine is off.
 

·
Registered
Joined
·
7 Posts
Discussion Starter #11
Wrapped the fuel rail and injectors. Still doing the same thing. They are brand new one hole injectors just like what came out of it. I let it idle and it shut off after about 15 or 20 mins. Any other ideas?
 

·
Super Moderator
Joined
·
10,415 Posts
Do you have an obd II scanner? I have a blue tooth scanner that plugs into the obd II port. Then I use an app on my phone called Torque Pro. Since it wireless, I can walk around the vehicle while I check things. For the $35.00 investment, it's definitely worth it. I can see live data from the engine/exhaust sensors. I check the O2 sensors, tps, short term and long term fuel trims, engine temps,vacuum, and RPM's. There are others that I can't think of. I just look through the list to see what you can monitor. Not all ECM's give complete data through the OBD II port on cheep scanners. Also, have you check the manifold and exhaust for leaks? O2 sensor wiring? I have seen the wires get melted.
And in the Fwiw column, check your wiring that goes between the firewall and rocker cover, the wire loom and insulation can get chafed by one of the valve cover bolts and the wires can short out.
 

·
Registered
Joined
·
7 Posts
Discussion Starter #13
I believe I'll just burn the piece of crap. I'm 900 into it and still no change. This jeep is crap. But thanks just the same
 

·
Super Moderator
Joined
·
10,415 Posts
No need to get violent. But I would think some diagnostics as to what the sensors are doing should be first.
I worked on a Chevy blazer, (s10) before it came to me it spent 6 months sitting in a field cause it wouldn't run. The owner changed 3 fuel pumps and still couldn't fix the random shutdowns. He was convinced he was buying from a bad batch of fuel pumps. I checked the ground wire to the fuel pump and it was just about rusted in 2. I pulled it off with very little effort. I cleaned the frame and put a new connector on the wire. Drained the old gas, filled it with fresh. Cycled the key a few times to prime the fuel pump and it started right up, ran good. He was planning on selling it to preserve his sanity, but my repair fixed the problem. He was still driving it a year later. Sorry to blabber. I just hate to see you give up on it. I know they can be frustrating as hell. But I believe your issue can be solved. 👍
 

·
Registered
Joined
·
7 Posts
Discussion Starter #15
Would a loose ground wire not effect it more consistently? It only gives me starting issues after it warms up.
 

·
Super Moderator
Joined
·
10,415 Posts
Anything electrical will draw more amps as it heats up, if the ground is weak, it may not be able to carry the amps it needs. Electricity is like water, it follows the path of least resistance. I used to work on DOT plow trucks, trucks that used salt on the roads. Salt is like our worst enemy. It loves copper wires. And wreaks major havoc on grounds. I've had backup alarms going off when you used the turn signal. It was always the grounds.
 

·
Registered
Joined
·
6,997 Posts
Lets take a step back. You listed the parts you replaced, and we took your word for that and that it was done right. Maybe it wasn't? So now I'll start the redundant questions that question your work. Sorry, happens to all of us. Leave out a detail and that could be the difference. Its not personal, I promise.

Did you disconnect the battery cables and touch them together after installing all those parts? O2 sensors affect the mixture the pcm is trying to calculate. You need to reset that after the sensor installation. It takes another 50 startup cycles to relearn its patterns.

Then go back and double-check the part numbers for the O2 sensors. Ralph77 and I just went through all that when I replaced mine this spring. There are too dang many part numbers for those buggers.
 

·
Registered
Joined
·
7 Posts
Discussion Starter #18
Replaced the coil pack bc it was showing multiple misfired. Now it's worse. It tries to bog down every time I push the gas!!!! I'm over 1000 in New parts the wrong direction. And I do admit that a mechanic I am not sir. By no means. Just thought I couldn't afford a shop. Maybe could have saved me some money.
 

·
Registered
Joined
·
2,474 Posts
Stop throwing money at the problem! You need to start with the basics first before you do that, otherwise you're just taking shots in the dark. Ive had my fair share of electrical gremlins with other vehicles, and they suck to try to figure out, but this doesn't sound electrical to me yet.

Did you ever do a fuel pressure test? Test it when the engines cold, and after it warms up and acts up on you.

I'd look into doing a compression test on your cylinders also, cold engine and hot.

A leak down test wouldn't be a bad idea either if you can get the tool to do one.

Make sure you get spark to each cylinder, again test while the engines cold and hot. I'd pull the fuel pump relay while doing this so you're not wiping your cylinders either.

Then of course the last item would be timing, which would be more difficult as your engine is electronically controlled. I cant help ya much on that one cause I've never had to chekc into that issue on a newer jeep before,, but with a good Google search ya can find how to check that though. Aside from that, if you've heard of a noid light you can get a set to test your fuel injectors to ensure that they get their signal to fire when they're supposed to.
 
1 - 20 of 22 Posts
Top