My Jeep Grand Cherokee has 286,000 miles on it,I think I need to clean the injecter it is L6/4.0L I priced the injectors at $94.00ea Is there a way that I can Clean them.

Check fuel pressure, may have clogged fuel filter.

This what I think is happening. Your engine is running rich because the ECM thinks it has too much air and so injects more fuel. When you now introduce air, by taking th e vacuum line off, the fuel mixture is now more balanced. Have you cleaned your MAF sensor? Also make sure your engine coolant is full.

need injection cleaning,bad injector,bad gas.thank you

WOW ! Thats a lot of miles. I just reccomend keeping on top of your oil changes and tune ups. Sounds like you have done a great job so far.

What is the misfire code?

If it is a specific cylinder try swapping the injector with another cylinder. If the misfire follows the injector to the other cylinder than you know the injector is bad. If it doesn't follow than I would be checking compression on that cylinder.

I’m happy to assist further over the phone at https://www.6ya.com/expert/jeremy_d728a59f986299fa

who installed the CSM, sounds like it was installed incorrectly?

Also, are your battery connections tight?

If you haven't changed the plugs or had the fuel system cleaned, now would be a good time to do it. The number 1 culprit for rough idles is dirty injectors or plugs. You can try an injector cleaner in a can (or bottle) for under $10 and see if it helps, and then work from there. If there isn't any improvement then if you are able to, check the plugs for any gunky buildup and if you find a bad plug, make sure you replace them all (or have them replaced) at the same time.

The best i find is the Lucas fuel injector cleaner, for the price and quantity you get I find it to be fail safe. Just follow the instructions and if you like, do some research on the Lucas fuel injector cleaner on line. They run for around $10.00 and i get almost a year out of it. Good luck and hope this helps.

it could be that one of the injectors is bleeding off pressure not allowing enough fuel pressure to start. the 5.9 and 6.7 cummins need at least 2000 psi to start

My Answer:

Poor gas mileage can be a result of many many things.

First of all you need to find out what is the factory normal gas mileage for your model year Jeep SUV. It should have said on your window sticker if you bought it brand new. If you are a 2nd or 3rd owner then a Jeep dealer would have info. Google search will tell you as well, and only takes a couple minutes to find.

I did a quick Google search and for a 2003 Jeep Grand Cherokee with a (4.7L V8 engine) the average mileage is roughly 14 mpg.

Not sure what engine you have as to options, etc?

How you drive will greatly change that number up or down depending on a number of driving and driver variables.

A few being -

Driving habits?

Tire pressures?

Engine tuned up?

Lube & oil/filter changes (every 5,000-7,500 miles? Air filter changes (every 10,000-15,000 miles)? Read your auto manual for exact recommended intervals.

How many people in the SUV on average?

Are you towing anything?

Type gas you are burning - BRAND? (See injectors below)

Area you are driving in (hills and valleys verses flat out,
etc)

Jeeps in general don't have a good track record for great mileage, and rough engine idling is always a clue that your fuel injectors are dirty. Typical on all Jeeps with port fuel injection systems! On Jeeps with dirty fuel injectors your mileage will go way down accordingly. If your not putting at least a 12 oz bottle of say Walmart brand Super Tech Fuel Injector Cleaner (~ $1 each) in your gas tank religiously every logged 1000 miles, or every 2 tank fill ups, then you are just inviting dirty fuel injectors and POOR fuel economy!

My 1993 Ford XPLR with a 4L V-6 engine (and ~ 160,000 flawless driven miles) gets roughly 22 miles per gallon on the highway with cruise control on, and about 17 around town on average. I religiously put a 12 oz bottle of the above injector cleaner in my gas tank every 1000 miles!! Of course I do all my own tune-ups, general repairs, and suspension maintenance (shocks, O2 sensors, trans oil changes, lube & oil/filter changes, code reading and clearing, etc) myself and it shows! I don't trust repair shops except for say Tires and Balancing at SEARS.

Hope that helps ease your mind about gas mileage as it relates to your Jeep there.

Frank