Author Topic: 11 Volts at idle, stall problem  (Read 733 times)

Southofantarctica

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11 Volts at idle, stall problem
« on: May 16, 2018, 04:42:35 AM »
I picked up a 03 Limited back in January with 127K. I knew it had some issues and have been slowly working them out and getting this thing back into prime running condition. It's my wife's main means of transportation currently, but we're planning on taking it up to CO next summer if life permits.

Now down to the nitty gritty. When I test drove the truck, I knew that it hadn't been driving hardly at all in the last 2 years and wasn't terribly worried about it stalling on me at the time. Found out the battery terminals were loose and figured things would be peachy. Which they were until my MAF died and I was back to stalling out. New MAF and the car is doing good, excellent apart from poor milage from the new tires, but I noticed that the condenser fan is seized giving me weak AC in traffic and warm engine temps. New condenser fan and things seem to be good, but ambient temperature have only been in the high 80s so I haven't needed to been cranking up the AC too much, until this last week and we saw over 100F.

I been using the AC on max now, but noticed that the engine would stall any time I was stopped in gear. By chance I lower the AC blower to the lowest setting and the car stays running, bring the blower up past about the 3rd spot and the rpms start to drop.

I check in on my Torque app, trying to see if I get any abnormalities that were easy to find. I noticed that my volts were reading between 12.7v-12.9v while driving, not the 13+ that I was expecting to see. So I check it at idle in drive, 12.7v with the blower on low. Do the same test again but blower on high, I am now showing 11.4v. If I turn headlights, heated seats, AC, and radio at idle in drive I can see as low as 10.2 before the engine dies. Tests at 65mph with AC high shows 12.8.

I swapped out with a known good battery, with same results. I then took it to the parts store and had it checked, but the alternator came back good in both park and drive with AC on, even though the engine stumbled.

The battery light does not come on.

My gut says that my alternator is dying, but the lack of battery light and the clean bill of health is making me leery of dropping $130 just to have the same problem.

Any help or suggestions would be appreciated.

TOASTY

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Re: 11 Volts at idle, stall problem
« Reply #1 on: May 16, 2018, 07:23:36 AM »
Maybe you have some bad grounds, these trucks don't have many to start with. Doesn't hurt to add a few AND its a cheap thing to try.

haolepinoy

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Re: 11 Volts at idle, stall problem
« Reply #2 on: May 16, 2018, 09:20:45 AM »
I've had the exact same problem, and to spare you the endless rabbit hole that this can spiral into I recommend starting with figuring out why your alternator is not putting out volts north of 13v even when moving (1500+ rpms).

When my '03 Limited was exhibiting this issue, my voltage would be relatively normal up until I stopped and came to an idle (while the A/C was on)...at which point it would drop down to < 12.5v and begin to stall. You say you're only seeing 12.7v under normal driving. Seeing only 12.7v "while driving" is a bad sign for your alternator. Should be 13.8 - 14.3v when engine rpms are 1500+. Do you have a cam seal oil leak on the passenger side? It's a common leak, and has killed many a Gen3's alternator. Like Toasty said, check grounds and terminals also. The alternator may not be the only problem, but it looks like it is an issue that has to be eliminated before you can get a clear picture of other things down the line.

The alternator's internal voltage regulator may be shot, and replacing it may solve the issue, but if a cam seal oil leak is causing the alternator death you need to fix that too or it will just kill your replacement alternator in short order.

Once this is dealt with you may then delve down any of the many possible rabbit holes in chasing the idle gremlins of the 3.8L Gen3 Montero, one of the principle holes being the infamous MAF sensor...which you have already replaced. OEM sensor? Junkyard? Ebay? Or it could be a fuel trim issue caused by a vacuum leak, or EGR clog, or butterfly valve leak, or...it literally could be about a dozen other things. Hopefully it's just your alternator.



Here's some reading in what not to do, mixed with a little blind squirrel finds a nut type stuff too if the alternator isn't the culprit.

https://www.expeditionportal.com/forum/threads/how-is-the-idle-controlled-on-a-2003-3-8l-gen3-monty.158781/
https://www.expeditionportal.com/forum/threads/a-story-about-slaying-electrical-gremlins.158784/#post-2096173
'03 Montero Limited - being repaired slightly faster than it's falling apart (debatable)

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Southofantarctica

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Re: 11 Volts at idle, stall problem
« Reply #3 on: May 17, 2018, 02:30:51 PM »
Well, pulled the old alternator off and it was looking pretty worn out and everything appeared promising. Everything went well as far as removing and installing the new one, pleasantly surprised on that front. Access was a lot better than I expected it to be from initial glance before tackling the project.

Hower upon startup I was disappointed to see that I was only marginally better than before, a mear 12.9v-13v while driving and no change to idle output.

Stalling appears to be the same or possibly even worse as it now stalled coasting downhill. Not sure if that's attributed to the ECU not having enough time to relearn idle, but Volts are for sure still low regardless.

I checked out some of the other threads that Haolepinoy linked and through one of the rabbit trails that branched off of those found a video of the exact problem I'm having as far as stalling. He performed a trans flush which seemed to cure his problem... Weird.

https://youtu.be/20wzaTfkj-U

Anyways, so far this car has been the epitome of fix one problem, two more rear their heads.

P.S.

MAF was just a orielly's special. I needed the car running the next day and no junk yards around that carry Mitsubishi. Plan is to keep an eye peeled for a junked one by chance and switch it out down the road.

Also, a quick check makes me thing the grounds are ok but I'm sure it couldn't hurt to add a couple for good measure.

IncorpoRatedX

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Re: 11 Volts at idle, stall problem
« Reply #4 on: May 17, 2018, 04:29:05 PM »
have you checked all of your grounding locations, battery terminal conditions and connection points? You should be seeing a lot more output.

Where did you get the new alternator? Over-the-counter discount parts stores like vato zone, o'reallys and nappy units are known to fail or be weak, out of the box. Denso and OEM or OEM rebuilt with good stuff seems to be the common path for most long term owners.

Southofantarctica

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Re: 11 Volts at idle, stall problem
« Reply #5 on: May 18, 2018, 09:40:13 PM »
Well the alternator from oriellys was bum out of the box. They warrantied it out and gave me an another one, this time reburbed in USA if it makes a difference.

New alternator showed putting out 13v. Finally broke out the multimeter (which I should have done from the outset), and I'm getting 14.2V at the battery at idle in park with AC (while torque shows 12.9).

Checked for resistance and cleaned the main ground above the starter, battery contacts, posts, fusible links and everything checked out and cleaned thoroughly.  Still showing about a 1.4v difference between the actual battery reading and the ECU reading.

Neg post to block ground 0.0 ohm.

Approx 500 ohm resistance between the neg contact and the disconnected positive contact.

Found and cleaned a ground between the fuse box and battery ( not sure if it's an OME or not), it was pretty rusty and tested 1.0 ohm. Cleaned and reinstalled 0.0 ohm.

Retest resistance between neg and pos contacts come in mid 200s. Difference is now appox .9V from ECU reading and the actual battery reading.

Ran out of time to continue tonight, will try to pick it back up tomorrow. Idle seems stronger, but haven't taken it for a drive to test drive. However I was able to block the tires and get it to idle in drive with the AC on. 13.9V at battery, 12.8-9 ECU.

TOASTY

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Re: 11 Volts at idle, stall problem
« Reply #6 on: May 21, 2018, 10:19:39 AM »
Sounds promising!

Southofantarctica

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Re: 11 Volts at idle, stall problem
« Reply #7 on: May 22, 2018, 03:38:02 AM »
Well, I haven't been able to mess with the grounds anymore. HOWEVER, I have made success through other means.

Right before I started on this journey of low voltage to the ECU I was having an exhaust leak right before 3rd catalytic converter, under load and above 3K rpms. No big deal I thought, I'll just go in and replace the donut and tighten everything back down. If course the bolts snapped off and I was not able to reuse the little spring set up that was there before. Within the next two days is when the stalling problem started to make itself apparent, I thought it strange that they happened so closely together but when I saw that I was having such low voltage I focused on that instead.

Now this thing has always been kind of a dog since we got it, but I chalked it up to being a V6 and had seen most people thought that these things were on the weak side. It had gotten slower since we bought it, but it happened right around the same time as the addition of larger tires and I thought that it was just something that I was going to have to live with.
On one of the last trips into town I got it up above 65MPH and noticed that the truck really fell on it's face, like topped out at 68MPH, which I knew was wrong. So I slowed down and luckily we were close to home.  Saturday afternoon I decided that I needed to pull the 3rd cat and if nothing else eliminate that as a point of restriction.

Of course the car fought me the whole way, had to break out the grinder in order to get the rear bolts off, and so on and so forth. But I got it out. At this point I was just praying that it was bad because I didn't think I was going to be able to salvage the one I had taken off anyways. Turns out, chalked full and overflowing. I had about 2 cups worth of trash just fall out when I removed it, not to mention how completely blocked it was. I am amazed that the truck ran at all with all the back pressure that engine was experiencing.

A trip into town and I'm ready to throw in a good cat.... This thing just about flies compared to how slow it was before hand. (Obviously) Much more responsive all throughout the RPM range, more power and all that good stuff. Engine runs about 10F cooler as well. Idle seems to be much stronger as a whole and is now in the low 700s. It did stall on me once yesterday morning, going from 70MPH to stopped, so it still isn't perfect.

I think the next course of action will be get into where the ECU lives and try to clean up all the contacts maybe it has a corroded ground or something still.