08 stumble and nearly stall (but doesn't)

[m5pa]

My 08 5 with 40k miles has developed an odd problem. Every so often, getting more and more common, it stumbles and nearly stalls while braking to a stop. It never stalls, but the power drops off, the EPAS warning light goes on as do some other warning lights. Also, the center display (where the radio station and air con information are displayed) flickers and shows the start-up "Hello!"

My wife mentioned it a while ago and I've finally seen it do it a few times to know it's not a fluke anymore. But the other day, it was really bad. I was pulling into a parking space when it did it and it kept doing it. So I sat there for a minute in park and played with it.

- Idle speed drops off enough to cause warning lights and flicker, EPAS goes dead.
- Blipping the throttle causes it to go away, but starts again as engine speed reduces.
- Went away after a minute or two and didn't happen again during my short errand.
- No A/C or lights on at the time, seems to do it regardless.

I have a Mazda manual at home, but it will be a few days until I get home. Doing a quick search shows this seems to be an issue with the 2.3. The battery was replaced about two years ago and no problems until about 3 months ago. This is an 08, built outside the TSB for earlier cars and it was bought new, there have been no other problems like this.

Finally, I have the Mazda remote start installed and was wondering if I should suspect it as well.

Thanks

 

[tweiss3]

I want to say that sounds like the battery is going, or the alternator isn't putting out enough juice.

My 6 kills a battery every 2 years almost on the dot.

 

[flcruising]

I would start with the charging system as suggested. Take to Advance Auto parts and have them do a free test. Secondly, the throttle body may be in need of cleaning. All you must do is remove the intake duct, take a rag, wet it with carb or brake cleaner fluid, and wipe it out. Open the butterfly and reach as deep as you can. You can also remove the throttle body assembly for a more thorough cleaning.

 

[DougNuts]

I have the same issue, but to a lesser degree than the OP. I put in a brand new battery and there was no change.

I'm starting to think that it's the alternator, I'll have to check that here soon.

 

[Rally Man]

Please do because mine will drop in RPM's like it want's to stall as well. I doubt it's my battery because I got it replaced 8/17/13.

 

[m5pa]

Cleaned TB and checked filter. Now we wait and see, maybe a check at Autozone. My next suspicion is the PCV valve, which I hope it's not because some idiot Mazda engineer decided it needed to be buried under the intake manifold. Which must come off for replacement of the PCV valve.

 

[loosenut]

I highly recommend cleaning the throttle bore around the blade first. Just be careful not to get any liquid cleaner into the blade shaft seal area as it can damage the throttle body if it does. Sounds like the throttle is having trouble keeping idle. The idle will most likely need relearned by disconnecting the battery for a couple of minutes and then letting the vehicle idle for 10-15 minutes. It may still stall when coming to a stop until it has completely relearned idle strategy. (maybe first 2 or three stops). If that doesn't work then look at the charging system.

 

[m5pa]

If it did it all the time, I'd agree that it's an idle problem. But this is a once in a while problem, with no particular trigger. Engine load doesn't really matter, it does it with the air on or off. And it will be a long time between instances.

I thoroughly cleaned the throttle body by removing it, as well as the MAF sensor. It's been a few years, so the TB was a bit dirty. But it's never had this stumble problem before. I'll keep an eye on it and keep the forum informed!

 

[Rally Man]

Thanks m5pa for keeping us informed.

 

[DougNuts]

This morning I checked my alternator, 13.9V while the car is at idle, so that appears to be working. I'm going to look into cleaning the throttle body when I get a chance, but it may be a few weeks since I'm very busy at home right now.

 

[m5pa]

Hasn't done it yet since cleaning the TB, but it was a really random problem anyway. Cleaning the TB and MAF sensor easy enough.

 

[DougNuts]

Hasn't done it yet since cleaning the TB, but it was a really random problem anyway. Cleaning the TB and MAF sensor easy enough.

I should have clarified, mine hasn't done the drastic dip when coming to a stop in a while either. Now I am chasing the occasional rough idle, which may or may not be related.

 

[m5pa]

Did it again to the wife the other day, this time under load and climbing a hill. Time for some more investigation today.

 

[flcruising]

Did it again to the wife the other day, this time under load and climbing a hill. Time for some more investigation today.

That's different than what you described as the original condition. Are you now saying it does it when accelerating and idling?

 

[m5pa]

Yeah, I know it's different than the original posting. That's why it bugged me so much. I've only seen it do it at idle or coasting to a stop. But the wife was climbing a rather substantial hill and it did it.

I finally had a chance to put a multi-meter to it. Battery only showing 12 volts while running, drops immediately to 11 or even 10 when engine off. No cold start issues, but it's been warm. Thinking battery, but also alternator. Anyone do the alternator on a 5 yet? Rock Auto showing about $150-185 minus core, job doesn't look too bad, except for running the accessory belt.

Battery last replaced by dealer at least two years ago (I have every record to the car but that one of course). Looking on the forums, this isn't uncommon.

 

[flcruising]

The charging system could likely be the culprit. Even though you don't have the service record for the battery visit, if you register at mymazda.com it should appear after you enter your VIN. This is where I've always kept personal records and the dealer services were added automatically as well. Though you shouldn't need to hand-deliver that record, the replacement battery may not be under full warranty. Even if they pro-rate the exchange, but they will probably want to perform a diagnostic for a $$ fee.

If you have a reliable battery charger, I would remove it from the vehicle and give it a full charge at least overnight. Upon re-installation, immediately drive to the nearest auto parts store so they can do a free charging system test. I've had reliable results with Advance Auto.

About the alternator replacement...
The a/c compressor belt is a stretch type that must be cut off to get to the other belt, so that will also need a new one. The alternator is accessible from below, and if you are used to performing your own maintenance will be pretty easy to replace.

 

[DougNuts]

About the alternator replacement...
The a/c compressor belt is a stretch type that must be cut off to get to the other belt, so that will also need a new one. The alternator is accessible from below, and if you are used to performing your own maintenance will be pretty easy to replace.

I did not have to replace the A/C belt when I did the alternator on my wife's Mazda3. The alternator swap was very straight forward, it took about 20-25 minutes start to finish.

 

[flcruising]

Good point. You can just relieve it from the tensioner and let the belt hang.
When I take them off to replace a component, it's normally time for the belt replacement too.

 

[m5pa]

Pretty sure it's the battery now. Hooked up an OBD scanner to it, no codes and voltage on the system is hanging out around 13.7-13.9 volts. It's also the cheapest and easiest variable to replace.

 

[m5pa]

Put new Exide Silver battery in yesterday. Pretty sure that will fix it. I took the old battery out and hooked it to a charger and nothing happened. Charger might have died, it's a 20+ year old Craftsman, so not totally out of question, but pretty sure the battery was done.

Whatever the issue (bad cell,etc.) the little bit of jostling taking it out of the car finished it off. Hopefully this is it.