First Impressions Diagnostic
Thread Starter
Member
Joined: Dec 2011
Posts: 120
Likes: 0
From: Montara, CA
Year: 99
Model: Cherokee
Engine: 4.0
First Impressions Diagnostic
Hey everyone! Thanks for putting together this great community! I am an long time car enthusiast but 1st time Jeep owner. I just bought my first jeep last weekend. It is a 99 Cherokee SE. I found it at a dealership and after doing the car fax, found it use to be a California gov. jeep. It looks to be in excellent condition.
After a week of driving it, some sounds and sensations have popped up. My first impressions are this, when I come to a stop on a hill, then go I can feel the driveline shift or settle. This also happens when I back out of my driveway onto a hill, then put it in drive. I am feeling this is the transmission mount. My question here, would this cause a deep driveline noise at highway speeds?
Second, the Jeep is hard to start in the morning. Unless I turn the key to accessory, then off and to accessory again waiting for the light to go out. Then it will start right up. I am thinking leaking injectors. Also, my gas mileage after 3 tanks is about 14 mpg. Seems low to me but I would like to hear your experiences with mpg and your rigs.
Third and most disturbing is a knocking sound just off idle. It does speed up with engine rpm but goes away when I start off. It also is not audible at idle. Only just off idle. I have searched the forum and have heard about the flex plate cracking and TC bolts coming loose. I have also heard the power steering pump can mimic a knocking sound when it starts to fail. When I got the jeep, it had a brand new belt on it and it does squeal in the morning when cold. Are their ways to diagnose this without removing the inspection plate or the belt?
Thank you all for a great community! I have plans for my jeep but I don't want to give my wife the impression it is not already a strong vehicle that will last by having to work on it heavily a week after I bought it!
After a week of driving it, some sounds and sensations have popped up. My first impressions are this, when I come to a stop on a hill, then go I can feel the driveline shift or settle. This also happens when I back out of my driveway onto a hill, then put it in drive. I am feeling this is the transmission mount. My question here, would this cause a deep driveline noise at highway speeds?
Second, the Jeep is hard to start in the morning. Unless I turn the key to accessory, then off and to accessory again waiting for the light to go out. Then it will start right up. I am thinking leaking injectors. Also, my gas mileage after 3 tanks is about 14 mpg. Seems low to me but I would like to hear your experiences with mpg and your rigs.
Third and most disturbing is a knocking sound just off idle. It does speed up with engine rpm but goes away when I start off. It also is not audible at idle. Only just off idle. I have searched the forum and have heard about the flex plate cracking and TC bolts coming loose. I have also heard the power steering pump can mimic a knocking sound when it starts to fail. When I got the jeep, it had a brand new belt on it and it does squeal in the morning when cold. Are their ways to diagnose this without removing the inspection plate or the belt?
Thank you all for a great community! I have plans for my jeep but I don't want to give my wife the impression it is not already a strong vehicle that will last by having to work on it heavily a week after I bought it!
Member
Joined: Dec 2011
Posts: 115
Likes: 1
Model: Cherokee
just worked on a 98 that had trouble starting,loss of power. had owner stop buying cosco gas fixed problem. when it does start what's the rpm? Over looked part is the temp sensor. tells the computor that the engine is cold, so it ups idle speed and runs richer till engine warms up.
::CF Moderator::
Joined: Aug 2011
Posts: 43,971
Likes: 1,578
From: Prescott, Az
Year: 1990
Model: Cherokee (XJ)
Engine: 4.0
As for the knocking noise, check and tighten your flexplat to torque converter bolts. Easy and requires removing the little quarter moon shaped inspection plate.
What brand of oil filter is on this Jeep?
What brand of oil filter is on this Jeep?
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CF Veteran
Joined: Nov 2010
Posts: 5,840
Likes: 117
From: In the middle of Minnesota!
Year: 1999
Model: Cherokee
Engine: 4.0
Let's get your 99 squared around. 99 is a very good year for the XJ! Nothing you mention sounds terribly concerning. I am very well versed with the 99 as I own one and have worked on a few in the 97-01 range.
1. For that clunk you feel when just starting out, it is most likely a dry slip joint. VERY common and often misdiagnosed. On older XJ's this joint was bathed in fluid, but not on 97 and newer. Here is a link on how to do it.
http://www.jeepforum.com/forum/f11/g...ite-up-357569/
2. For the extended crank time you are experiencing, the primary suspect is a leaking check valve in the fuel pump assembly. More on that below. Another VERY common problem with the 97-01 XJ. While you can piece meal parts in there, I generally recommend replacing the entire assembly as long as you have to take the gas tank down. If one part is failing, other failures may not be far behind. BOSCH is a very good brand of pump, whatever you do stay away from AIRTEX. Even with their low price point. Lots of issues with their fuel pumps.
3. You mention 14 mpg, but you don't mention what mix of city highway. Most 99's will get between 16-21 if the engine is running efficiently. What you can do is to freshen your tuneup hardware. New Champion copper plugs gapped to .035, new premium plug wires, distributor cap and rotor (brass contacts). Sometimes the oxygen sensors can get lazy before they actually will set a code and you can lose a bit of mileage that way too. Another good thing to do as a matter of course is to clean the idle air control and throttle body as they get carboned up over time and miles. More on that below too.
4. Follow cruiser54's advice on checking flexplate bolts.
5. The serpentine belt on the 4.0 needs to be pretty darn tight to stay quiet. Tighter than any other vehicle I've ever owned. Try tightening it just a smidgen. That is likely to resolve it.
Hope this helps. Enjoy your 99!
------------------------------------------------------
The check valve is located on top of the gas tank and is part of the fuel pump assembly on 95.5-2001 vintage 4.0 XJs. When the check valve starts to fail, it reduces fuel pressure to a point where an extended crank is needed to start the engine. It is a very common failure. I experienced it on my 99 at around 75K.
A good (and simple) way to troubleshoot this problem is called “the poor mans prime”
1. Turn key to ON position (do not crank the engine!)
2. The fuel pump will energize and run for a couple of seconds
3. Turn key to OFF position
4. Repeat above a two more times
5. NOW crank the engine over
If the engine starts quickly and cleanly after performing this procedure, you may have the check valve issue. If it starts and runs poorly for a few seconds, it could also be a leaky fuel injector resulting in the bleed down and the stumble upon startup is the engine clearing the excess fuel that has leaked into the cylinder because of the faulty injector.
Also be aware that a bad battery can give you this symptom. Sounds strange but it definitely does happen. Have battery load tested if you have any questions; your XJ does NOT like low available battery voltage. Be sure battery connections and posts are CLEAN.
Some troubleshooting tips for extended crank times:
Hook up fuel pressure gauge on the schrader valve on the fuel rail
Start engine and bring to normal operating temperature.
Observe test gauge. Normal operating pressure should be 49.2 psi (plus or minus 5 psi)
Shut engine off.
Pressure should not fall below 30 psi for five minutes.
If pressure falls below 30 psi, it must be determined if a fuel injector, the check valve within the
fuel pump module, or a fuel tube/line is leaking. An adaptor tool/hose included with the fuel pressure gauge can help you with this. Consult gauge manual for more information on this but here is basically how it works:
*Turn the engine off and immediately clamp the fuel line at the adaptor hose. Watch the pressure gauge and see how long it takes to lose pressure.
*If the pressure remains at 49 psi for an extended period of time then the problem is in the tank - possibly the check valve. If the pressure falls below 49 psi fairly rapidly then the problem is probably a leaky fuel injector.
You can limp a check valve problem along indefinitely if you wish as it doesn't mean the fuel pump itself is going bad. Normally, the check valve is replaced as an entire assembly as you have to drop the gas tank to access the assembly. Fuel pump assembly consists of fuel pump, regulator, check valve, filter. If you do replace the fuel pump assembly, purchase a high quality OEM style unit. Some cheap aftermarket assemblies don’t hold up and fail prematurely. I specifically seek out Bosch fuel pumps as they are the best in the business. Stay away from Airtex, as IMHO, they have a bigtime reliability problem.
---------------------------------------------------------------------------------------
The Idle Air Control (IAC) is mounted on the back of the throttle body. The valve controls the idle speed of the engine by controlling the amount of air flowing through the air control passage. It consists of a stepper motor that moves a pintle shaped plunger in and out of the air control passage. When the valve plunger is moved in, the air control passage flows more air which raises the idle speed. When the valve plunger is moved out, the air control passage flows less air which lowers the idle speed. Over time and miles, the IAC can get carboned up which can have an adverse affect on idle quality. Cleaning the IAC may restore proper function and is an easy procedure to perform and good preventive maintenance so it is never a bad idea.
CLEANING THE JEEP 4.0 IDLE AIR CONTROL
Remove the air filter cover, associated hoses and the rubber boot that goes from the air filter cover to the throttle body. Remove the IAC with a torx driver (2 bolts; one can be kind of hard to get to)
“Gently” wiggle out the IAC from the throttle body. Gasket on the IAC can be re-used if it is not damaged
Clean the IAC with a spray can of throttle body cleaner; inexpensive and available at any place that sells auto parts. Throttle body cleaner is recommended rather than carburetor cleaner as it is less harsh, safe for throttle body coatings and is best for this task. Use cleaner, a rag and a toothbrush and or Q-Tips. Be gentle; don’t twist or pull on the pintle that protrudes from the IAC as it is fragile and you could damage it.
Thoroughly spray clean and flush where the IAC seats in the throttle body with the same spray cleaner
It is also a good idea to clean the entire throttle body itself, the butterfly valve inside of the throttle body and all associated linkage as long as you have things disassembled
Reinstall IAC and check idle quality
1. For that clunk you feel when just starting out, it is most likely a dry slip joint. VERY common and often misdiagnosed. On older XJ's this joint was bathed in fluid, but not on 97 and newer. Here is a link on how to do it.
http://www.jeepforum.com/forum/f11/g...ite-up-357569/
2. For the extended crank time you are experiencing, the primary suspect is a leaking check valve in the fuel pump assembly. More on that below. Another VERY common problem with the 97-01 XJ. While you can piece meal parts in there, I generally recommend replacing the entire assembly as long as you have to take the gas tank down. If one part is failing, other failures may not be far behind. BOSCH is a very good brand of pump, whatever you do stay away from AIRTEX. Even with their low price point. Lots of issues with their fuel pumps.
3. You mention 14 mpg, but you don't mention what mix of city highway. Most 99's will get between 16-21 if the engine is running efficiently. What you can do is to freshen your tuneup hardware. New Champion copper plugs gapped to .035, new premium plug wires, distributor cap and rotor (brass contacts). Sometimes the oxygen sensors can get lazy before they actually will set a code and you can lose a bit of mileage that way too. Another good thing to do as a matter of course is to clean the idle air control and throttle body as they get carboned up over time and miles. More on that below too.
4. Follow cruiser54's advice on checking flexplate bolts.
5. The serpentine belt on the 4.0 needs to be pretty darn tight to stay quiet. Tighter than any other vehicle I've ever owned. Try tightening it just a smidgen. That is likely to resolve it.
Hope this helps. Enjoy your 99!
------------------------------------------------------
The check valve is located on top of the gas tank and is part of the fuel pump assembly on 95.5-2001 vintage 4.0 XJs. When the check valve starts to fail, it reduces fuel pressure to a point where an extended crank is needed to start the engine. It is a very common failure. I experienced it on my 99 at around 75K.
A good (and simple) way to troubleshoot this problem is called “the poor mans prime”
1. Turn key to ON position (do not crank the engine!)
2. The fuel pump will energize and run for a couple of seconds
3. Turn key to OFF position
4. Repeat above a two more times
5. NOW crank the engine over
If the engine starts quickly and cleanly after performing this procedure, you may have the check valve issue. If it starts and runs poorly for a few seconds, it could also be a leaky fuel injector resulting in the bleed down and the stumble upon startup is the engine clearing the excess fuel that has leaked into the cylinder because of the faulty injector.
Also be aware that a bad battery can give you this symptom. Sounds strange but it definitely does happen. Have battery load tested if you have any questions; your XJ does NOT like low available battery voltage. Be sure battery connections and posts are CLEAN.
Some troubleshooting tips for extended crank times:
Hook up fuel pressure gauge on the schrader valve on the fuel rail
Start engine and bring to normal operating temperature.
Observe test gauge. Normal operating pressure should be 49.2 psi (plus or minus 5 psi)
Shut engine off.
Pressure should not fall below 30 psi for five minutes.
If pressure falls below 30 psi, it must be determined if a fuel injector, the check valve within the
fuel pump module, or a fuel tube/line is leaking. An adaptor tool/hose included with the fuel pressure gauge can help you with this. Consult gauge manual for more information on this but here is basically how it works:
*Turn the engine off and immediately clamp the fuel line at the adaptor hose. Watch the pressure gauge and see how long it takes to lose pressure.
*If the pressure remains at 49 psi for an extended period of time then the problem is in the tank - possibly the check valve. If the pressure falls below 49 psi fairly rapidly then the problem is probably a leaky fuel injector.
You can limp a check valve problem along indefinitely if you wish as it doesn't mean the fuel pump itself is going bad. Normally, the check valve is replaced as an entire assembly as you have to drop the gas tank to access the assembly. Fuel pump assembly consists of fuel pump, regulator, check valve, filter. If you do replace the fuel pump assembly, purchase a high quality OEM style unit. Some cheap aftermarket assemblies don’t hold up and fail prematurely. I specifically seek out Bosch fuel pumps as they are the best in the business. Stay away from Airtex, as IMHO, they have a bigtime reliability problem.
---------------------------------------------------------------------------------------
The Idle Air Control (IAC) is mounted on the back of the throttle body. The valve controls the idle speed of the engine by controlling the amount of air flowing through the air control passage. It consists of a stepper motor that moves a pintle shaped plunger in and out of the air control passage. When the valve plunger is moved in, the air control passage flows more air which raises the idle speed. When the valve plunger is moved out, the air control passage flows less air which lowers the idle speed. Over time and miles, the IAC can get carboned up which can have an adverse affect on idle quality. Cleaning the IAC may restore proper function and is an easy procedure to perform and good preventive maintenance so it is never a bad idea.
CLEANING THE JEEP 4.0 IDLE AIR CONTROL
Remove the air filter cover, associated hoses and the rubber boot that goes from the air filter cover to the throttle body. Remove the IAC with a torx driver (2 bolts; one can be kind of hard to get to)
“Gently” wiggle out the IAC from the throttle body. Gasket on the IAC can be re-used if it is not damaged
Clean the IAC with a spray can of throttle body cleaner; inexpensive and available at any place that sells auto parts. Throttle body cleaner is recommended rather than carburetor cleaner as it is less harsh, safe for throttle body coatings and is best for this task. Use cleaner, a rag and a toothbrush and or Q-Tips. Be gentle; don’t twist or pull on the pintle that protrudes from the IAC as it is fragile and you could damage it.
Thoroughly spray clean and flush where the IAC seats in the throttle body with the same spray cleaner
It is also a good idea to clean the entire throttle body itself, the butterfly valve inside of the throttle body and all associated linkage as long as you have things disassembled
Reinstall IAC and check idle quality
Last edited by tjwalker; Dec 23, 2011 at 08:41 AM.
CF Veteran
Joined: Jan 2011
Posts: 1,894
Likes: 4
From: Las Vegas
Year: 1999
Model: Cherokee
Engine: 4.0
Hey everyone! Thanks for putting together this great community! I am an long time car enthusiast but 1st time Jeep owner. I just bought my first jeep last weekend. It is a 99 Cherokee SE. I found it at a dealership and after doing the car fax, found it use to be a California gov. jeep. It looks to be in excellent condition.
After a week of driving it, some sounds and sensations have popped up. My first impressions are this, when I come to a stop on a hill, then go I can feel the driveline shift or settle. This also happens when I back out of my driveway onto a hill, then put it in drive. I am feeling this is the transmission mount. My question here, would this cause a deep driveline noise at highway speeds?
Second, the Jeep is hard to start in the morning. Unless I turn the key to accessory, then off and to accessory again waiting for the light to go out. Then it will start right up. I am thinking leaking injectors. Also, my gas mileage after 3 tanks is about 14 mpg. Seems low to me but I would like to hear your experiences with mpg and your rigs.
Third and most disturbing is a knocking sound just off idle. It does speed up with engine rpm but goes away when I start off. It also is not audible at idle. Only just off idle. I have searched the forum and have heard about the flex plate cracking and TC bolts coming loose. I have also heard the power steering pump can mimic a knocking sound when it starts to fail. When I got the jeep, it had a brand new belt on it and it does squeal in the morning when cold. Are their ways to diagnose this without removing the inspection plate or the belt?
Thank you all for a great community! I have plans for my jeep but I don't want to give my wife the impression it is not already a strong vehicle that will last by having to work on it heavily a week after I bought it!
After a week of driving it, some sounds and sensations have popped up. My first impressions are this, when I come to a stop on a hill, then go I can feel the driveline shift or settle. This also happens when I back out of my driveway onto a hill, then put it in drive. I am feeling this is the transmission mount. My question here, would this cause a deep driveline noise at highway speeds?
Second, the Jeep is hard to start in the morning. Unless I turn the key to accessory, then off and to accessory again waiting for the light to go out. Then it will start right up. I am thinking leaking injectors. Also, my gas mileage after 3 tanks is about 14 mpg. Seems low to me but I would like to hear your experiences with mpg and your rigs.
Third and most disturbing is a knocking sound just off idle. It does speed up with engine rpm but goes away when I start off. It also is not audible at idle. Only just off idle. I have searched the forum and have heard about the flex plate cracking and TC bolts coming loose. I have also heard the power steering pump can mimic a knocking sound when it starts to fail. When I got the jeep, it had a brand new belt on it and it does squeal in the morning when cold. Are their ways to diagnose this without removing the inspection plate or the belt?
Thank you all for a great community! I have plans for my jeep but I don't want to give my wife the impression it is not already a strong vehicle that will last by having to work on it heavily a week after I bought it!
If that doesn't help, read this.
GL and welcome.
Thread Starter
Member
Joined: Dec 2011
Posts: 120
Likes: 0
From: Montara, CA
Year: 99
Model: Cherokee
Engine: 4.0
Wow! I have never been on a forum where the answers are so fast and so thorough! Thank you!
I will be going through the Jeep this weekend as I have a day off for Christmas. The mounts are first on my list. One thing about the fuel injectors, it does sputter after I get it started in the morning. Like it is running on 3 or 4 cyl, then it clears up and runs fine with a very smooth idle which leads me to believe the injectors are dirty. I saw a deal on the 4 hole injectors for something like $140 on here so I might go ahead with those.
While I am replacing the mounts, I will open the inspection plates and check the TC bolts. Hopefully, that is all the knock is.
Thanks for the wealth of information! I will follow all these steps! I really love this jeep and the community and I can't wait to start building this thing.
I will be going through the Jeep this weekend as I have a day off for Christmas. The mounts are first on my list. One thing about the fuel injectors, it does sputter after I get it started in the morning. Like it is running on 3 or 4 cyl, then it clears up and runs fine with a very smooth idle which leads me to believe the injectors are dirty. I saw a deal on the 4 hole injectors for something like $140 on here so I might go ahead with those.
While I am replacing the mounts, I will open the inspection plates and check the TC bolts. Hopefully, that is all the knock is.
Thanks for the wealth of information! I will follow all these steps! I really love this jeep and the community and I can't wait to start building this thing.
CF Veteran
Joined: Aug 2010
Posts: 1,150
Likes: 1
From: Nashville, TN
Year: 1997, 1993
Model: Cherokee
Engine: 4.0L
Wow! I have never been on a forum where the answers are so fast and so thorough! Thank you!
I will be going through the Jeep this weekend as I have a day off for Christmas. The mounts are first on my list. One thing about the fuel injectors, it does sputter after I get it started in the morning. Like it is running on 3 or 4 cyl, then it clears up and runs fine with a very smooth idle which leads me to believe the injectors are dirty. I saw a deal on the 4 hole injectors for something like $140 on here so I might go ahead with those.
While I am replacing the mounts, I will open the inspection plates and check the TC bolts. Hopefully, that is all the knock is.
Thanks for the wealth of information! I will follow all these steps! I really love this jeep and the community and I can't wait to start building this thing.
I will be going through the Jeep this weekend as I have a day off for Christmas. The mounts are first on my list. One thing about the fuel injectors, it does sputter after I get it started in the morning. Like it is running on 3 or 4 cyl, then it clears up and runs fine with a very smooth idle which leads me to believe the injectors are dirty. I saw a deal on the 4 hole injectors for something like $140 on here so I might go ahead with those.
While I am replacing the mounts, I will open the inspection plates and check the TC bolts. Hopefully, that is all the knock is.
Thanks for the wealth of information! I will follow all these steps! I really love this jeep and the community and I can't wait to start building this thing.
cruiser54 asked about the brand of oil filter on it, the reason being that fram filters suck and can kill the engine due to a cardboard valve in the can which can unseat and block oil flow to the engine (and cause some engine noise).
Go with a Wix, Napa Gold (made by wix) Purolator, Mopar, Mobil 1 or Motorcraft (yes that's a ford filter) oil filters and you can spend hours reading about which oil to put in the engine but you will find a strong following for 15W-40 Rotella which is actually a diesel oil. You will find that the Rotella quiets down some of the lifter tick that pretty much all 4.0's make.
Oh if the dealer did a tune up pull the spark plugs and check to see what plugs they are. Your 99 should have champion copper spark plugs in it. No platinum, no iridium, no 2,3,4 prong expensive plugs. Cheap champion coppers make the 99 and earlier 4.0's run the best. Trust me, I've tried many different plugs over the years and always go back to the basic champions.
Good Luck!
Thread Starter
Member
Joined: Dec 2011
Posts: 120
Likes: 0
From: Montara, CA
Year: 99
Model: Cherokee
Engine: 4.0
Ok, I got my oil changed at OilStop. I asked for 15/40 oil and made sure the filter is not a Fram. It is a Warner oil filter. When they finished, the knock was much louder. It was embarrassingly loud since I was driving my father around. I went to Kragen and bought a quart of Duralube and put half in. That did not seem to help but this morning, when I started the jeep, I noticed it ran much smoother and the valvetrain noise was much quieter. The knock got quieter as well. I could barely hear it most of the day. When I got home, I put it in drive with my foot on the break and gave it some gas. The knock was more audible. this leads me to believe it is either piston slap or a rod bearing and not the flex plate. I am going to check that this weekend though when I replace my transmission mount.
My question now is how long have you gone with a knock? Should my jeep fund be geared towards replacing the engine before the lift\tires or have you had good luck just keeping it lubed with an additive and driving it with a knock?
My question now is how long have you gone with a knock? Should my jeep fund be geared towards replacing the engine before the lift\tires or have you had good luck just keeping it lubed with an additive and driving it with a knock?
Thread Starter
Member
Joined: Dec 2011
Posts: 120
Likes: 0
From: Montara, CA
Year: 99
Model: Cherokee
Engine: 4.0
Just checked my torque converter bolts and they are all tight. The knock only happens when the engine is warm and I can not hear it at idle or on the highway. Only under load and just off idle.