grand cherokee laredo question

[travman151]

I have a 98 jeep grand Cherokee Laredo and it has a small problem stalling, its not the the time but its every once in a while, any ideas??? im new to the jeep world, I purchased my first jeep less than a week ago. I love it

[greg92jeepxj]

Welcome to Jeepz.com '98 grand , was supposed to inherit one from my dad . Said no and should taken it as its long gone now. My younger brother turned it over on the street at 40+ and my other brother stripped it what was still good . I was supposed to get the rear disc set up for my '92 XJ but they flat bedded it too soon. Well any way , it was a real nice jeep , power everything ! No wonder you love it ! These rough idle , hesitation , hard start / no start and stalling are starting to grow in numbers around here. Sounds like the former owner either did not maintain well enough or did all the basic maintenance and couldn't find the problem. I have some questions for you ; to your knowledge , was it tuned up and fuel filter changed ? At the minimum , change fuel filter if it wasn't and note any change in behavior . The jeep , not yours . Lol.
don't know your level of skills maintenance and repair wise but if you want to take this on your self , we can advise you . Fuel pump pressure should be checked , fuel pressure regulator vacuum line on and off . Record readings . Cylinder balance test to find if one or more cylinder is a problem. This is easy , you just need the adapters that plug onto the spark plugs and plug high tension wire (spark plug wire ) back on . With engine running , use a 12v test light clamped to ground and touch each adapter for a second . The rpm should drop while grounded . If there is no change in rpm , that cylinder is a problem. That's my way since I have the adapters (somewhere) but you can just pull a wire off a plug and note change the same way. If you find a bad cylinder , check the spark plug for damage I.e. cracked porcelain . Check plug wire for damage like cuts or loose or broken connectors. Check distributor for cracks and carbon tracking inside cap. Check rotor for burned tip and worn tip. Take off air cleaner snorkel to throttle body and see if Venturi is dirty , especially around idle air valve inlet . Idle air control motor should be removed and cleaned along with chamber the control motor attaches to. If real dirty , the housing that the idle motor attaches to should be removed from throttle body , housing and throttle body chamber cleaned thoroughly with throttle body spray cleaner.
Look for any leaks around where fuel injectors attach to intake and to fuel rail. If found , o-rings should be changed on all injectors , top and bottom. Pull spark plugs out to see if saturated with raw fuel . Note exact condition of spark plug ; fuel saturated , carbonated, electrode damage , inner porcelain damage and/or color and condition(contaminated) . A compression check with all plugs removed and throttle valve (accelerator linkage) wide open should be performed to determine condition of engine. Record all results after each procedure. This is a good start diagnostic wise , but if unable to perform yourself , at least you will know what a mechanic should be doing for you and at least know what to expect from their service. Hope this helps. Let us know how things go when you can . Best of luck , greg

[travman151]

thank you greg, i knock alot about mechanics just new to the jeep world, ive owned many vehicles since i was 16, this tho is my first jeep and i love it..monday morning on my day off i will do what the post said and ill post later monday night the results of all the test, thank you so much for the tips... :) happy jeepin..

[greg92jeepxj]

Your most welcome brother . If you got a body on your jeep , good engine , trans , etc. , any error can be broken down systematically. I know , I make it sound so easy , but this is how I approach every problem . If I can keep my cool and keep the big picture in sight , I may just find the cause . I'm still learning , but you can't learn to swim from a book . We got to get our hands dirty . The trick is , not bloody. Research , apply , accomplish. Repeat . That is what I try to do every job I take on . If I got my head on straight , I usually get something done right. Whenever I advise someone how to diagnose or proceed , it is like I am doing it myself. The advise I have given so far is the start of process of elimination in terms of what is good and what isn't . With any luck , the cause will be found before more extensive diagnostics are applied. That is always the hope . We do our own work for many reasons . Save money , labor of love, and just the fact that no one will care more about your car than you. Hope you find the cause soonest , but if not found , we will know the status of the items checked and figure what's next. Good luck brother and will be in touch . Greg

[MudderChuck]

Which engine? If it is the 4.0 the IAC is worth a look. They usually screw up worse when cold. Two reason for intermittent problems with the IAC, on eis something in the charging system isn't right, battery, alternator, grounds. The IAC sees to need every bit if voltage it can get to work right and may often be the first indicator of a charging problem. Also gum tends to build up in the IAC, the piston and the seats, they can get sticky.

The IAC can be a tricky one to troubleshoot, it may not trip any trouble codes, especially if it is just dirt that is causing the issues.

[greg92jeepxj]

Good call MudderChuck . I just today heard the complaint of a fellow employee stating that the reason for their a/c and I.p. cluster glitches was due to inadequate alternator output . Once again, I am reminded of PROPER DIAGNOSTICS of which I usually preach but am now the victim of malpractice upon advising a new member. Thank you for your accurate and most welcome advice and feel free to subscribe this thread as we may read more post from this member as typically assistance may further be needed. As always , all are welcome without invite to participate in the assistance of a member in distress . Thank you again MudderChuck , greg

[greg92jeepxj]

Which engine? If it is the 4.0 the IAC is worth a look. They usually screw up worse when cold. Two reason for intermittent problems with the IAC, on eis something in the charging system isn't right, battery, alternator, grounds. The IAC sees to need every bit if voltage it can get to work right and may often be the first indicator of a charging problem. Also gum tends to build up in the IAC, the piston and the seats, they can get sticky.

The IAC can be a tricky one to troubleshoot, it may not trip any trouble codes, especially if it is just dirt that is causing the issues.

P.S. - I had better check my alt. too as I have been seeing similar signs now that a/c season is well upon us. I returned an alternator when I swapped a starter on my 4.0 earlier this year believing the output was adequate . While charging , with a/c on , the dash gauge wanders quite noticeably to discharge , that warrants an amp output test under load. Thanks again , Greg

[MudderChuck]

The IAC is the idle air controller. With the throttle plate closed (foot off the gas pedal) it is the only way for the motor to get air at idle (foot off the gas pedal). They get sticky and/or the charging system gets weak and the IAC acts up. When they stick closed at idle or when releasing the gas pedal, the motor dies. One indicator of a sticky IAC is not being able to start the motor without depressing the gas pedal slightly, it should start without having to depress the gas pedal.

Other things can cause stalling, a CPS (crank position sensor) that is failing can cause it to stall also. The CPS may miss a few pulses at higher RPM's and you may not notice. If it misses a few too many at idle or low RPM's the PCM (powertrain control module) will open the ASD (auto shutdown relay) and the motor will die. The CPS can have a partial failure and not trip trouble code.

A seriously clogged exhaust system (the CAT) can also cause stalling at low RPM's. They usually start to rattle before they really fail though. Sounds like a tin can full of rocks, mostly noticeable at startup.

There are other reasons, these are some of the more common.

[greg92jeepxj]

Thank you so much for adding more checks as it is always good to check early before disaster strikes . If any of these faults are found now and corrected , we know that's a good thing. If CAT is slow slowing clogging due to carbon build up from poor idle quality causing rich mixture to burn in CAT , this needs to be addressed NOW before little fixes become huge ! I always stress to someone clean throttle body but thanks for CPS check as they tend to be like a faulty ignition module , little errors and glitches in performance then outright failure. Different part , same effect. Glad travman151 wants to address it now immediately upon purchase . Thank you MudderChuck for your welcome advice ! Hopefully the PO has maintained better and all else kept up with . Thank you again , GregGreg