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2007 SRT8 Jeep Grand Cherokee
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Discussion Starter #1
So randomly I started getting a slight hesitation with cold starts. Instead of just "vroom" when you turn the key, I now get "Vr, vroom" if that makes sense. I can post audio if needed but anyway. After that first start, every subsequent start is fine, no hesitation once the engine warms up. I normally run 91 octane, no ethanol. about a month ago I stopped at a different gas station, which only had 93, with ethanol. I noticed a change in the cold starts, the hesitation was either gone completely or very slight compared to 91. So the past few gas tanks, I've been rotating back and forth from 91 to 93. Every time I go back to 91 the hesitation come back. The Jeep runs fine otherwise.

This doesn't make sense to me as I'v been running 91 for the past 3 years with no issues. Plugs are new as of last summer. Battery and alternator are new as of 2018 I think.... No codes are showing up either. I was running the Diablo canned 91 octane CAI tune (modified for a 180 stat). On Sunday I switched back to the stock tune for testing.

Thoughts, as the octane thing doesn't make sense to me at all??

Thanks!
 

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2007 SRT8 Jeep Grand Cherokee
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Discussion Starter #2
Today when I started the Jeep, it really hesitated to start, kinda like it was well bellow freezing..... So I was curious and had the battery, alternator and starter tested at a local auto parts store. It was where I bought the battery. According to the tester, everything checks out.

The battery and alternator are only two years old. I guess this weekend I'll pull a couple plugs to see but i don't know. If the engine is warm or has ran in the last few hours it starts fine, over night, not so much.

Thoughts?
 

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2007 SRT8 Jeep Grand Cherokee
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Discussion Starter #3
I haven't pulled any plugs yet, I had to deal with a leaking thermostat housing/bad thermostat causing the Jeep to get a little hot. Didn't get over 215.

Update.... I thought it was a bad battery as while fixing the above issue and as a test, I put the jump starter on the battery and it fired up normally. It was still under warranty, so I convinced the place I bought the battery to replace it under said warranty. That wasn't it. So the other thoughts I had was maybe I'm getting some parasitic loss from something in the Jeep. So I'v been unplugging anything I can think of that could cause it. This morning I did a voltage test and after sitting over night the battery was at 12.46 volts. The engine was slow to start. Drove 5 minutes to get gas. After filling up it started normally.

Anyone have an idea or thoughts on what to check next? Figuring out an electrical issue is above my pay grade.
 

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Anyone have an idea or thoughts on what to check next?
I had the same problem happen in my 10' Ram 1500. When the truck sat for a couple of days the battery would be dead, even a day it would be slow to turn over. Tracked it down to a faulty head unit. It kept waking up and cycling draining the battery. It's the same unit as in these Jeeps. Look at yours and see if its doing the same thing.
 

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2007 SRT8 Jeep Grand Cherokee
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Discussion Starter #5
I have an aftermarket head unit, but thanks for the idea. Maybe start pulling different fuses and see by trial and error which one it is.
 

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If you are serious about finding if you have parasitic draw you can buy a clamp on meter for about $150 such as the Extech 380950. It will read down to the normal parasitic draw (about 30mA).
 

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2007 SRT8 Jeep Grand Cherokee
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Discussion Starter #7
Don't know if I have to go that far into this, I think I'm on the right track. After cleaning the bolt for the chassis ground, very rusty, I've been having no issues. Today I'm going to try and clean the threads more.
 

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2007 SRT8 Jeep Grand Cherokee
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Discussion Starter #8
Update..... Since cleaning the chassis ground near the battery, I've had no start issues.
 
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