'97 ZJ 4.0 - RPM stalling during acceleration - JeepForum.com
Search  
Sign Up   Today's Posts
User: Pass: Remember?
Advertise Here
Jeep Home Jeep Forum Jeep Classifieds Jeep Registry JeepSpace Jeep Reviews Jeep Gallery Jeep Clubs Jeep Groups Jeep Videos Jeep Events Jeep Articles
Go Back JeepForum.com > Models > Jeep Grand Cherokee & Commander Forums > ZJ Grand Cherokee Forum > '97 ZJ 4.0 - RPM stalling during acceleration

The Boss is away but Erin is here to STAY with a F.Y.S. SaIntroducing MONSTALINER™ UV Permanent DIY Roll On Bed LineFS: 2007-2013 Jeep Wrangler "HALO" Angel Eye Kit

Reply
Unread 04-22-2015, 09:15 PM   #1
SoKyOps
Registered User
1997 ZJ 
 
Join Date: Mar 2012
Location: Bowling Green, KY
Posts: 14
'97 ZJ 4.0 - RPM stalling during acceleration

My ZJ has given me numerous problems lately from not wanting to start, stalling and dying while rolling down the road. Since the computer wasn't giving any codes, I started throwing parts at it to try and fix it based on what I know and others mechanics suggestions.

So far, I've replaced the crank sensor, ignition coil, idle air control sensor, map sensor, temp. control sensor and now the ECM since all else failed. Also checked plugs, plug wires and distributor. That resolved most of the problems except one, RPM stalling during acceleration. Normally happens between second and third gear around 2000 RPM. It'll drop to 1600RPM and stick for a few seconds regardless of how much gas I give it. Other times it'll drop to about 500 RPM and die if I don't continue giving it gas. It'll do it maybe once or twice a week.

Any ideas?

SoKyOps is offline   Reply With Quote Quick reply to this message
Unread 04-23-2015, 09:55 AM   #2
Uniblurb
Web Wheeler
 
Uniblurb's Avatar
1996 ZJ 
 
Join Date: Jan 2012
Location: Central, Ohio
Posts: 4,935
A bad crank sensor often doesn't throw a code and curious if you replaced it with a Mopar crank sensor? Many don't have any luck with aftermarket ones and I installed 2 new good brand name aftermarket crank sensors which were just as bad as my bad Mopar crank sensor.

There's a couple tests in my signature and below is even a better one where you're testing for the crank sensor signal by turning the engine over by hand.

http://troubleshootmyvehicle.com/jee...crank-sensor-1

Have you cleaned all your grounds particularly the ones on the engine block? The PCM is grounded on one of the coil studs on the 4.0 which in turn grounds all the sensors. This rusted/corroded PCM ground on my 96 4.0 took out 2 PCM's along with 2 crank sensors.

Read through the real good dirty dozen thread in my signature and there's photo links in the grounds section showing the PCM ground.

Have you checked your fuel pressure on the rail to make sure it's within 49psi +/- 5psi spec and not dropping off? If you don't have a fuel pressure tester you can borrow a loaner from many parts stores. Good luck!
__________________
96 4.0 ZJ Laredo, 2004 4.7L WJ Limited, 93 4.0 XJ (spare), 96 4.0 XJ (son's)

-Stalling ZJ? 12 things to check before replacing a sensor; the Dirty Dozen
-Crankshaft position sensor multimeter test. & video of testing.
Uniblurb is offline   Reply With Quote Quick reply to this message
Unread 04-23-2015, 10:05 PM   #3
SoKyOps
Registered User
1997 ZJ 
 
Join Date: Mar 2012
Location: Bowling Green, KY
Posts: 14
Initially it threw two codes, ignition coil and crank sensor. Whatever brand Advanced Auto carries is what I replaced it with. Since it runs fine 99% of the time, I'd assume the crank sensor is ok. The 1% it's not is usually when I'm pulling out in to traffic

I'll start cleaning up ground connections and get the fuel pressure checked. The pump and filter are fairly new, but who knows. Honestly wouldn't surprise me if it was just trash in the tank. Gas station monopoly here likes to peddle low quality goods.

Thanks.
SoKyOps is offline   Reply With Quote Quick reply to this message
Unread 04-23-2015, 10:56 PM   #4
Uniblurb
Web Wheeler
 
Uniblurb's Avatar
1996 ZJ 
 
Join Date: Jan 2012
Location: Central, Ohio
Posts: 4,935
Hate to say it but the 2 new aftermarket crank sensors I bought which acted just as finicky as my bad Mopar sensor also came from Advance. Not saying all are bad but I sure didn't have very good luck with them which drove me nuts!

Believe if nothing else I'd run the resistance test in my signature on the crank sensor when it starts acting up. Any resistance at all in checking with a meter set to low ohms and it's bad.

Real poor design in having the fuel filter w/built in pressure regulator on top of the pump module on the 97-98 ZJ's where you have to drop the tank to change it out. On top of that a new off-brand filter/pressure regulator is about $75 when you can buy a whole new Bosch pump module with filter/regulator for $154 from Rockauto.

It should be noted there was a TSB issued about the inside of the plastic fuel tanks breaking down causing a fine black residue in the tanks clogging up even new pumps. I know when I cleaned my tank out it was filthy black when I wiped it out with a rag.

Too bad about your gas situation and you may want to try some fuel injector cleaner or "Heet" in your tank to break down any water in your fuel. With these huge temp swings it makes condensation even worse on top of any water in the fuel coming from a cheap station. Good luck!
__________________
96 4.0 ZJ Laredo, 2004 4.7L WJ Limited, 93 4.0 XJ (spare), 96 4.0 XJ (son's)

-Stalling ZJ? 12 things to check before replacing a sensor; the Dirty Dozen
-Crankshaft position sensor multimeter test. & video of testing.
Uniblurb is offline   Reply With Quote Quick reply to this message
Unread 04-23-2015, 11:07 PM   #5
SoKyOps
Registered User
1997 ZJ 
 
Join Date: Mar 2012
Location: Bowling Green, KY
Posts: 14
Yea, the gas situation isn't ideal, but I normally run fuel treatment. I hadn't thought about condensation forming from temperature fluctuations though. Kentucky weather is bad about that. A foot of snow one day, 75 degrees the next. Side note, snowballs hurt a lot more when you're not wearing a shirt

I'll start with what you mentioned and may drop the tank next time I need a fill up. Will post any updates.
SoKyOps is offline   Reply With Quote Quick reply to this message
Unread 04-23-2015, 11:10 PM   #6
xrunndonex
Registered User
1994 ZJ 
 
Join Date: Dec 2012
Location: coffeyville, Kansas
Posts: 2,101
Vacuum leak?
xrunndonex is offline   Reply With Quote Quick reply to this message
Unread 04-24-2015, 01:21 PM   #7
jgphreaky
Registered User
1993 ZJ 
 
Join Date: Feb 2014
Location: rincon, pr
Posts: 70
I agree with Uniblurb to thoroughly check your new CPS with the tests he suggested. I also think you should inspect the connector for the CPS too. My crumbled apart.

I also think you should inspect your pickup coil (camshaft sensor). If you're still using the original distributor from 1997 it might have burnt out. If you remove your cap and rotor you should be able to see it. Take a look at the connector too, make sure it's not falling apart.

Also, did you thoroughly clean out your throttle body when you replaced the IAC sensor? I mean really, really get it spotless.
jgphreaky is offline   Reply With Quote Quick reply to this message
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.
Note: All free e-mails have been banned due to mis-use. (Yahoo, Gmail, Hotmail, etc.)
Don't have a non-free e-mail address? Click here for a solution: Manual Account Creation
Email Address:

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.


Thread Tools






Jeep, Wrangler, Cherokee, Grand Cherokee, and other models are copyrighted and trademarked to Jeep/Chrysler Corporation. JeepForum.com is not in any way associated with Jeep or the Chrysler Corp.