Mechanics

WHAT WOULD CAUSE AN INTERMITTENT SLOW CRANK AND HARD STARTING

1996 Jeep Grand Cherokee • 159,000 miles

Hi my name is shawn, I recently within the past month, purchased a 1996 jeep grand cherokee laredo, quadra-trac V8 5.2. I have had this jeep approximately 3 weeks, last week I went to the laundry mat, I was in there maybe 20 minutes I came back out, went to start the jeep it cranked normally turned over and idled around 300rpm, so I immediately turn the ignition off. Tried to start again and it cranked fine and started and ran normally. I figured it was just a fluke thing and thought nothing of it. I came out this morning to go to work around 530 in the morning, I tried to start the jeep, got a very slow crank with the battery was dying, after trying to start it several times it would, start up and die
right away, after attempting to start at 5 to 7 times I put my foot on the gas pedal. It finally started and ran until I took my foot of the pedal and then stalls out again. The next attempt I started it kept my foot on the pedal and put it in drive, I drove it around the block when I came to a stop sign to let it idle it didn't stall, it has only been running for maybe 3 minutes. I took a chance and went to the wall of my morning coffee, I turned it off when inside what a bout my business and then came back out to the jeep and it fired right up with no problem, ran fine all day and started several times after that just fine, it did rain a little bit last night but the jeep has never had any problems before. Can anyone suggest wgat the problem may be? Thanks in advance! Shawn
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Negronremodeling
June 13, 2012.




I would have the idle control valve checked for operation. It is a calibrated vacuum leak and if it sticks or is inhibited from moving, it may produce these symptoms of stalling.

As far as the slow crank, have the battery, alternator and all the connections especially the grounds checked.

Roy

ASEMaster6371
Jun 13, 2012.
Do you have a check engine light?

Have the charging system checked to rule out a failing alternator also the IACV-to include the fuel pressure if its within specs-start here

Tiny
Rasmataz
Jun 13, 2012.
Ok I had the alt, batt and ground points checked, all good. Cleaned iac valve. Now as I had stated before this seems to be an intermittent problem, if it should happen again, what other possibilities could there be? Also another quick question, my trans feels like it shifts a little hard, also from park to reverse it kinda has a light clunk ad a very light clunk and a light quick sqeal when trans engages. Any ideas?

Tiny
Negronremodeling
Jun 14, 2012.
No check engine light, pulled diagnostic codes and no codes were stored. How difficult is it to check fuel pressure, if easy. Learn me please lol
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Tiny
Negronremodeling
Jun 14, 2012.
Allow me to jump in and make a few observations. If the slow cranking is intermittent, clean and tighten the battery cable connections first to eliminate that possibility. If you can get it to act up more often, pull out the automatic shutdown (ASD) relay so it won't start, have a helper handy to turn the ignition switch, then use a digital voltmeter to measure the voltage drops across both battery cable connections. If you want to try that, I'll suggest a page that gives the complete description.

Also measure the battery voltage with the engine off first. It should be near 12.6 volts if it's fully charged. If you find closer to 12.0 volts, it's good but discharged and the engine will crank slowly. Next, measure the voltage again with the engine running. It must be between 13.75 and 14.75 volts. If it's low, measure the voltages on the two smaller wires on the back of the alternator. That must be done with the engine running.

Charging problems are often intermittent and you have to catch them and do any testing when they're acting up. Watch for a low volts reading on the dash gauge, dim head lights, or lights that dim noticeably when you turn on the heater fan. You have the little silver Nippendenso alternator that commonly develops worn brushes. That causes intermittent operation and can go on for weeks before the failure is permanent. Those brushes can be replaced for less than 20 bucks.

If the battery voltage got drawn down far enough due to a poor connection, or if it is disconnected for any reason or run dead, the Engine Computer will have to relearn "minimum throttle" before it will know when it has to be in control of idle speed. Until that relearn takes place you also may not get the nice idle flare-up to 1500 rpm when you start the engine. The other clue is you have to hold the gas pedal down 1/4" to get it to start and stay running. The relearn takes place when you drive at highway speed with the engine warmed up, then coast for at least seven seconds without touching the pedals.

The Transmission Computer also goes through a learning cycle, then it constantly updates its shift schedules and harshness to mask any wear that has taken place. It may shift sloppy but it usually shifts rather hard until the relearn is complete. You do that by driving and just letting it shift. The relearn typically takes a few miles or a few shift cycles.

You're probably hearing the solenoids buzzing when you shift into reverse or drive. That is done to modulate, or soften the engagement of the clutches to give a more comfortable feel instead of a hard clunk into gear. If you listen closely, you should also hear that ratcheting sound when you come to a stop and it downshifts into first gear.

Caradiodoc
Jun 14, 2012.
@caradiodoc, wow lots of info here! Lol, I would definitely like to see that page you speak of. I will test the batt again tomorrow exactly the way you described. I will also keep an eyeball on the voltage gauge and irregular dimming, not sure if this is related but the info center and odometer dim and get bright once in awhile. All other displays (dash, radio) stay bright. Also forgot to mention that when all this happened in the morning I had to set the info center as if it were reset. I will try to correctly let the computer relearn. About the trans im not sure if it is associated with this issue but, it definitely jerks the jeep and sounds kinda like a quick metallic low squeal (split second). Also, from 1st to 2nd it feels like it starting to shift and floats up 300 rpm then engages 2nd, 2nd to 3rd shifts rather quickly like it dooesnt ride out to many rpms before shifting, and lastly 3rd to 4td shift seems ok except I can feel a slight vibration under my feet just as it engages 4th, sorry to pummel you gurus with questions, but you all seem to really know what your talking about.

Tiny
Negronremodeling
Jun 14, 2012.
Here's the link for measuring voltage drops:

http://randysrepairshop.net/voltage-drop-tests-in-a-high-current-circuit.html

For reference, your starter is the same as the older GMs and the last test point is accessible.

Caradiodoc
Jun 14, 2012.

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