Bad Idle/Hesitation/Gas Milage in my 98 Jeep Grand Cherokee Laredo - JeepForum.com
 
LinkBack Thread Tools
post #1 of 13 Old 07-15-2017, 05:12 PM Thread Starter
KingDanza
Registered User
 
Join Date: Jul 2017
Location: Louisville
Posts: 5
Bad Idle/Hesitation/Gas Milage in my 98 Jeep Grand Cherokee Laredo

Sorry if this is in the wrong section, or if my descriptions of my problems are bad. I'm no where near mechanically inclined and I'm doing my best here. My 98 Jeep Grand Cherokee Laredo 4.0 (6 cylinder) is having some idling issues, hesitation issues, acceleration issues, high fuel consumption, bad exhaust and power issues. The error code is P0171 which is System Lean In Bank 1. I've changed the MAP sensor, Crankshaft Position Sensor, Spark Plugs, Spark Plug Wires, Distributor Cap, Rotor Button, PCV Valve, CCV Valve, O2 Sensors, Catalytic Convertor, Exhaust System, Throttle Body has been cleaned, Fuel Injectors have been cleaned (with cleaner), cleaned the Idle Air Control Valve, and checked the PCM board to see if it was loose and it wasn't. I'm all out of ideas, does anyone know what the issue could be or know someone that may? Comment and let me know. I'm losing my mind over this ****.

KingDanza is offline  
Sponsored Links
Advertisement
 
post #2 of 13 Old 07-16-2017, 12:28 PM Thread Starter
KingDanza
Registered User
 
Join Date: Jul 2017
Location: Louisville
Posts: 5
Bump guys, the thread just got moved. This is my only means of transportation so any help would be greatly appreciated.
KingDanza is offline  
post #3 of 13 Old 07-16-2017, 12:55 PM
RedRiverT
Registered User
1997 ZJ 
 
Join Date: Nov 2014
Posts: 357
From your description of your issues, when I read "high fuel consumption" I immediately thought I would suspect a leaking fuel injector letting fuel flow constantly, but then I read where you have the Lean code, so that doesn't add up. Check your fuel pressure.

You've changed everything except the camshaft position sensor (I forget what its true name is). It is in the distributor and PCM uses its signal to trigger the injectors.

Oh yeah, check the wiring to the O2 sensors to see if it has rubbed through against anything. Now that I thought of it, that makes the most sense. The PCM is interpreting Lean and thus has richened it up repeatedly, resulting in way too rich and high consumption.
RedRiverT is offline  
 
post #4 of 13 Old 07-16-2017, 01:06 PM
poor93
Registered User
1993 ZJ 
 
Join Date: Jan 2016
Location: Bakersfield
Posts: 31
Garage
Running lean can be a vacuum leak somewhere. The high fuel usage could be a fuel leak under the car..... Replace the fuel filter for ****s and giggles to see if that help with the lean. I make only 200 miles to a tank but thats do to the 76cc combustion chambers and fuel tank leak.
poor93 is offline  
post #5 of 13 Old 07-16-2017, 01:34 PM
RedRiverT
Registered User
1997 ZJ 
 
Join Date: Nov 2014
Posts: 357
On the 98 (if it is the same as 96-97) the fuel filter is in the same housing as the pressure regulator and is on top of the fuel pump module, so you have to drop the tank to replace it. And decent ones are $80+ so you're probably better off to go ahead and replace the entire pump module. There's lots of ****s but no giggles about replacing the fuel filter. Of course, I may be wrong and they may have gone back to the separate filter on 98s. The more I think about the more I think I remember reading that a few years ago when I was messing with mine.
RedRiverT is offline  
post #6 of 13 Old 07-16-2017, 04:04 PM
kg6mov
Hears the voices
 
kg6mov's Avatar
1996 ZJ 
 
Join Date: Nov 2012
Location: Cupertino
Posts: 13,815
Did you use all mopar sensors?

Did you clean the grounds?

What tests have you done, or did you just throw parts at it?


To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.


To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.

1984 F250, 460 BB, T19, work truck/future tow pig
1987 Mercedes 300D Turbo, the diesel daily, 30mpg in style

Quote:
Originally Posted by Texas ZJ1 View Post
I heard someone yell "mall crawler" from the back porch. I'll go see who said that. Be right back.
kg6mov is offline  
post #7 of 13 Old 07-16-2017, 05:07 PM Thread Starter
KingDanza
Registered User
 
Join Date: Jul 2017
Location: Louisville
Posts: 5
Quote:
Originally Posted by RedRiverT View Post
From your description of your issues, when I read "high fuel consumption" I immediately thought I would suspect a leaking fuel injector letting fuel flow constantly, but then I read where you have the Lean code, so that doesn't add up. Check your fuel pressure.

You've changed everything except the camshaft position sensor (I forget what its true name is). It is in the distributor and PCM uses its signal to trigger the injectors.

Oh yeah, check the wiring to the O2 sensors to see if it has rubbed through against anything. Now that I thought of it, that makes the most sense. The PCM is interpreting Lean and thus has richened it up repeatedly, resulting in way too rich and high consumption.
I'll check the O2 sensors, any way to diagnose a bad camshaft position sensor?

Quote:
Originally Posted by poor93 View Post
Running lean can be a vacuum leak somewhere. The high fuel usage could be a fuel leak under the car..... Replace the fuel filter for ****s and giggles to see if that help with the lean. I make only 200 miles to a tank but thats do to the 76cc combustion chambers and fuel tank leak.
The filter is in the tank, not going to be easy.

Quote:
Originally Posted by kg6mov View Post
Did you use all mopar sensors?

Did you clean the grounds?

What tests have you done, or did you just throw parts at it?
No I didn't use all Mopar. I just got what Autozone had in stock. I honestly just threw parts at it a little at a time. I'm no where near mechanically inclined. Anything that I have done is done by friends. I don't make much money at my job currently so I really can't afford to take it to get it tested for all kinds of stuff. It's also my only means of transportation to work so if it goes down, I'll be in bad shape. Not that any of that really matters but I'm just trying to be as transparent as possible and give you all the information I know about it.
KingDanza is offline  
post #8 of 13 Old 07-16-2017, 05:16 PM
kg6mov
Hears the voices
 
kg6mov's Avatar
1996 ZJ 
 
Join Date: Nov 2012
Location: Cupertino
Posts: 13,815
Yeah, we've seen a lot of bad results with non mopar sensors unfortunately. Specifically Crank and Cam position sensors. 02 sensors should be Mopar (made by NGK) or NGK (made by, well), bosch has proven to be unreliable out of the box.

The dirty dozen has a few good tests in it and a lot of good information that will at least help you with jeep speak immersion so we can help easier: http://www.jeepforum.com/forum/f13/1...talls-1407423/

Read through that and clean the grounds, if you can I would get the big three sensors swapped for the good stuff as a baseline.


To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.


To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.

1984 F250, 460 BB, T19, work truck/future tow pig
1987 Mercedes 300D Turbo, the diesel daily, 30mpg in style

Quote:
Originally Posted by Texas ZJ1 View Post
I heard someone yell "mall crawler" from the back porch. I'll go see who said that. Be right back.
kg6mov is offline  
post #9 of 13 Old 07-16-2017, 05:23 PM
Uniblurb
Web Wheeler
 
Uniblurb's Avatar
1996 ZJ 
 
Join Date: Jan 2012
Location: Central
Posts: 8,627
Correct RedRiver in the fuel filter w/regulator is in a 'can' on top of the fuel pump module on the 97-98 although the 96 falls within the 93-96 and has an inline filter in front of the fuel tank.

Real poor design on the 97-98 and don't think I'd trust about any filter/regulator. Agree, you may as well replace the whole module with a Bosch 67649 module for the 97-98 if the pumps bad. Rockauto carries it for $171 plus shipping which is the best deal around.

http://www.rockauto.com/en/moreinfo....315963&jsn=403

But just like anything else do some testing before replacing it. Spec is 49psi +/-5psi while it shouldn't drop below 24psi after 10-20 min after shutdown or the check valve on the pump is bad. Edit: many parts stores like Advance and Autozone have loaner fuel pressure testers for the Chysler/Jeep fuel rail connection.

Hopefully you installed a Mopar crank sensor since there's just too many problems with aftermarket ones. Edit: there's a crank sensor resistance test in my signature you may want to use on your new Autozone crank sensor. If it shows resistance between B&C it's bad. Get one of your friends to test it with a multimeter set to low ohms if you don't have one.

Believe I'd make sure all the grounds are good/clean and clean the PCM ground is critical. Real good 'dirty dozen' thread in my signature and look at the "Grounds" section for a photo link of the PCM ground on one of the coil bracket studs.

Have you checked for a cracked header/exhaust manifold? They're known to crack at the tube welds on the 4.0. On first start up with hood up listen to the driver's side engine closely. If you hear an exhaust leak then it quiets down as it warms up typically the welds can be cracked.

What happens is the cracks at the welds will also draw air in then the o2 sensor reads a lean condition with too much oxygen. In turn the PCM will dump unneeded fuel in and you end up with poor mileage and eventually a clogged cat.

Agree, you should probably check for any vacuum leaks too and good luck.

96 4.0 ZJ Laredo, 2004 4.7L WJ Limited, 96 4.0 XJ (son's)


To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.


To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
&
To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
.
Uniblurb is offline  
post #10 of 13 Old 07-16-2017, 11:30 PM
RedRiverT
Registered User
1997 ZJ 
 
Join Date: Nov 2014
Posts: 357
Ah, 96. I was pretty sure I remembered that I got hosed by one year with the stupid filter on my 97. I didn't think about the cracked header being one of the common issues.

To the OP, my exhaust manifold / header cracked down at the bottom where the pipes come together. I think that is the common location. I could see the crack from underneath, and could hear it as Uniblurb decribed. If you find a crack, you can patch it, or perhaps more accurately stated, "cover the hole" with fine steel wool or that fiberglass muffler wrap held tightly with wire. This should greatly restrict if not completely stop any air from getting into the exhaust and screwing with the O2 sensor.

I can't quickly find a test for the camshaft position sensor (aka "pickup coil"). I think I remember one, maybe in the "Stalling" thread in the signature below Uniblurb's post. It seems like it is a simple ON/OFF signal and you simply connect a meter to it and turn the engine over to see if you get a regular interval pulse ON as the distributor turns. It might be in this thread:
http://www.jeepforum.com/forum/f13/c...-them-1432264/
RedRiverT is offline  
post #11 of 13 Old 07-17-2017, 06:58 PM Thread Starter
KingDanza
Registered User
 
Join Date: Jul 2017
Location: Louisville
Posts: 5
Quote:
Originally Posted by kg6mov View Post
Yeah, we've seen a lot of bad results with non mopar sensors unfortunately. Specifically Crank and Cam position sensors. 02 sensors should be Mopar (made by NGK) or NGK (made by, well), bosch has proven to be unreliable out of the box.

The dirty dozen has a few good tests in it and a lot of good information that will at least help you with jeep speak immersion so we can help easier:

Read through that and clean the grounds, if you can I would get the big three sensors swapped for the good stuff as a baseline.
Pretty sure the O2 sensors I have are Bosch since they were honestly the cheapest. I'll read through that article, thanks for the suggestions.

Quote:
Originally Posted by Uniblurb View Post
Correct RedRiver in the fuel filter w/regulator is in a 'can' on top of the fuel pump module on the 97-98 although the 96 falls within the 93-96 and has an inline filter in front of the fuel tank.

Real poor design on the 97-98 and don't think I'd trust about any filter/regulator. Agree, you may as well replace the whole module with a Bosch 67649 module for the 97-98 if the pumps bad. Rockauto carries it for $171 plus shipping which is the best deal around.



But just like anything else do some testing before replacing it. Spec is 49psi +/-5psi while it shouldn't drop below 24psi after 10-20 min after shutdown or the check valve on the pump is bad. Edit: many parts stores like Advance and Autozone have loaner fuel pressure testers for the Chysler/Jeep fuel rail connection.

Hopefully you installed a Mopar crank sensor since there's just too many problems with aftermarket ones. Edit: there's a crank sensor resistance test in my signature you may want to use on your new Autozone crank sensor. If it shows resistance between B&C it's bad. Get one of your friends to test it with a multimeter set to low ohms if you don't have one.

Believe I'd make sure all the grounds are good/clean and clean the PCM ground is critical. Real good 'dirty dozen' thread in my signature and look at the "Grounds" section for a photo link of the PCM ground on one of the coil bracket studs.

Have you checked for a cracked header/exhaust manifold? They're known to crack at the tube welds on the 4.0. On first start up with hood up listen to the driver's side engine closely. If you hear an exhaust leak then it quiets down as it warms up typically the welds can be cracked.

What happens is the cracks at the welds will also draw air in then the o2 sensor reads a lean condition with too much oxygen. In turn the PCM will dump unneeded fuel in and you end up with poor mileage and eventually a clogged cat.

Agree, you should probably check for any vacuum leaks too and good luck.
I was told that the exhaust header is cracked when I have my exhaust replaced. But of course I have no idea what that even meant, so I just let it slide. Is there a way to weld the crack or use some sort of epoxy to hold it or am I pretty much screwed? I'll check my fuel pressure too or have my boy do it for me since I literally have no idea. I just relay everything I get suggested to him basically. Thanks for the heads up though brother, sorry I don't have much information to give you.

Quote:
Originally Posted by RedRiverT View Post
Ah, 96. I was pretty sure I remembered that I got hosed by one year with the stupid filter on my 97. I didn't think about the cracked header being one of the common issues.

To the OP, my exhaust manifold / header cracked down at the bottom where the pipes come together. I think that is the common location. I could see the crack from underneath, and could hear it as Uniblurb decribed. If you find a crack, you can patch it, or perhaps more accurately stated, "cover the hole" with fine steel wool or that fiberglass muffler wrap held tightly with wire. This should greatly restrict if not completely stop any air from getting into the exhaust and screwing with the O2 sensor.

I can't quickly find a test for the camshaft position sensor (aka "pickup coil"). I think I remember one, maybe in the "Stalling" thread in the signature below Uniblurb's post. It seems like it is a simple ON/OFF signal and you simply connect a meter to it and turn the engine over to see if you get a regular interval pulse ON as the distributor turns. It might be in this thread:
My header is cracked as I stated to the last fella I replied to. I'll check out that thread right now though and see if there is anything I can do to fix it without it costing me $600+.
KingDanza is offline  
post #12 of 13 Old 07-18-2017, 12:29 PM
Uniblurb
Web Wheeler
 
Uniblurb's Avatar
1996 ZJ 
 
Join Date: Jan 2012
Location: Central
Posts: 8,627
Quote:
Originally Posted by KingDanza View Post
Pretty sure the O2 sensors I have are Bosch since they were honestly the cheapest. I'll read through that article, thanks for the suggestions.
Not sure where you did your shopping and may have been the local parts store. Actually online the OE NTK oxygen sensors are less expensive than the Bosch ones by a few bucks. I'd get those Bosch o2 sensors out of there since they don't work well on these ZJ's. And you may want to try unplugging the upstream/front o2 sensor and see if runs better w/o it as a test.

The NTK 23121 upstream sensor for your 98 4.0 sells for $34 plus shipping on Rockauto. It's $38 on Amazon w/free shipping but that's with a prime account as far as the shipping goes.

The NTK 23088 downstream sensor in the back of the cat sells for $33 on Rockauto plus shipping or $38 on Amazon w/prime.


Quote:
Originally Posted by KingDanza View Post
I was told that the exhaust header is cracked when I have my exhaust replaced. But of course I have no idea what that even meant, so I just let it slide. Is there a way to weld the crack or use some sort of epoxy to hold it or am I pretty much screwed? I'll check my fuel pressure too or have my boy do it for me since I literally have no idea. I just relay everything I get suggested to him basically. Thanks for the heads up though brother, sorry I don't have much information to give you.
Yeah, not good to have a cracked header since it heats everything up in the engine compartment and creates havoc with lots of things. Any type of patch would just be temporary and even when it's re-welded the metal next to the welds is weakened while it can crack again. Plus at least the intake manifold has to be removed so labor wise you might as well install a new header.

Some of us installed the below Dorman 674-196 header/exhaust manifold including myself on my 96 4.0. Actually the price has been dropping and it's $137 on Amazon if you have prime. You'd have to check the shipping costs on Rockauto where it's $112 plus shipping.

Note on the below photo where there are metal bellows built in so the welds may not crack when the metal expands.

https://www.amazon.com/Dorman-674-19.../dp/B000C17GUY

Rather than the thin gasket which comes with it I'd go for the heavier Felpro MS94790 which is around $12.

I should mention having a cracked header won't necessarily cause the problems you're having. I ran my cracked header for about a year and never had misses.

I'd still be checking that new off-brand crank sensor resistance and the fuel pressure. When I installed 2 brand new crank sensors from Advance they were just as bad as my bad OE one which drove me nuts! And don't bypass cleaning that PCM ground since it's so important. Good luck!

96 4.0 ZJ Laredo, 2004 4.7L WJ Limited, 96 4.0 XJ (son's)


To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.


To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
&
To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
.
Uniblurb is offline  
post #13 of 13 Old 07-29-2017, 05:25 PM Thread Starter
KingDanza
Registered User
 
Join Date: Jul 2017
Location: Louisville
Posts: 5
Okay guys is there any way it could be a fuel pump/filter failing/clog? The reason I ask is because when I give it heavy gas it starts to act a little better and the problem seems to be getting worse as the days pass. I'm currently saving money to have some cash to fix whatever the problem may be. I've looked up the P0171 code and there are just a few things left that I haven't changed that could be causing the problem, and the pump/filter was one that I seen. Take it easy on me if this is a stupid question.
KingDanza is offline  
Reply

Quick Reply
Message:
Options

Register Now



In order to be able to post messages on the JeepForum.com forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.

Password:


Confirm Password:
Email Address
Please enter a valid e-mail address for yourself.



Email Address:
OR

Log-in









Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.




Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page



Posting Rules  
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are On
Refbacks are On

 
For the best viewing experience please update your browser to Google Chrome