P5 Won't Start & Rough Idle

Hank3

Hank3

Asian Persuasion <><
Contributor
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2010 Mazda5 GT
P5 Won't Start, Stalling, & Rough Idle Issues

A few days ago, I noticed that my P5 would idle roughly right after the car would start; then it would go away. And then at times, I would notice a slight rough idle at stop lights - very random. Then today, after I got off work (car had been sitting for about 8 hours) I started the car; it idled little bit rough immediately after, but didn't really think anything of it. I drove for about 20 minutes; shut off the car, but then when I got back in to start the car (maybe 2 minutes after), it wouldn't start. I took 20 sec video of what happened (might have to turn up speakers).

<iframe width="854" height="510" src="https://www.youtube.com/embed/UZE7CH7y5Ww" frameborder="0" allowfullscreen=""></iframe>

I let the car sit for about 2-3 mins and then was able to start it after that. Drove home and that's where we're at now. Something that I've noticed recently that may or may not be associated with this issue:

  • I cleaned up a fair amount of battery corrosion on the positive terminal this past weekend. Battery is 3 months shy of being 3 years old.
So what's causing these issues? Battery, starter, EGR, IAC valve, MAF, plugs, or something else? No CELs have come up (yet).
 
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I'd maybe start with making sure the battery terminals are tight (if it's an autozone or similar battery, I've found the terminals to be slightly too small and really need to be clamped down) and cleaning the maf sensor. These are really cheap fixes that will only help rule things out if they don't work.
 
I think your battery and starter are fine,.. it's not struggling to turn over. (my car has been turning over at about 4 rpm during this "Arctic Blast" and still fires up)

I think you should do a seafoam treatment,... cheap fast and easy... could be dirty injectors so get some in the gas as well as the brake booster (it may take some time to wash through the injectors)

Then maybe check the EGR (could be all stuck) ,... possibly the IAC (could be stuck/fouled too),...

And make sure you've got spark,... (it could be electrical,... )


You may have had a bad batch of gas that fouled everything.
 
Thanks for chiming in, mp5la and pcb. I don't have much time tonight to troubleshoot - daddy duty for our 5-week old :)

I did, however, take out each spark plug and put them back in. Also tightened the battery terminals some more...didn't need much tightening from what it seems. Car started fine and no rough idling. If I have time this weekend, I'll troubleshoot further and more in-depth. I purchased a used lower mileage EGR a while back that was cleaned. Seafoam is a cheap thing to do as well so I can do that too.
 
I remember reading a thread a year or few ago where the guys car was running "weird" in some strange way (I forget what exactly)

It turned out to be the flimsy ass "straps" on the battery terminals. He replaced them with "lugs" and everything was fixed.

You would think a bad/weak connection on the battery would affect the starting when there is 100-200 amps running through them but his car was running all weird ass stupid after he got it started ???

So,.. a bit of a re-neg on not blaming the battery (but I still think seafoam will fix it)
 
pcb said:
So,.. a bit of a re-neg on not blaming the battery (but I still think seafoam will fix it)
Click to expand...

I still agree with your original conclusion, the battery isn't the problem. However, something that is dieing out could use that little extra boost from a fresh battery to get it running. My moms Caravan had a no crank no start issue, I replaced the battery and it started every time for a couple of days, then it was back to square 1. Turned out to be the cheap copper Nippon Denso contacts in the starter solenoid that thinned out to thinner than 1mm and wouldn't let enough current through to engage the starter. This same concept can be applied to a corroded or damaged wire.

If it was a really loose battery connection, you would hear a relay click and nothing. If it was a dieing battery, you would get an intermittent start condition or more commonly a relay clicking on and off rapidly (like 10 times a second).

I would check your fuel pump. I ALWAYS let my cars prime some fuel and warm up the O2 sensor for a good 5-10 seconds before I start. This helps when the fuel pump gets weak and gets the O2 sensor closer to temperatures before starting (although negligible, I do it for the fuel priming, this is just an added benefit).

Although you said the car started after sitting for 8 hours, I would check the fuel pressure, or if you have trouble starting again, try leaving the key in the on position and let the fuel pump prime for a bit of time before you go to crank.

Finally, the last thing I wanted to mention is that I noticed you have a full tank. Try not filling up all the way next time and see if the problem persists, if not, then you have an EVAP system problem, probably a soaked charcoal canister.
 
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Hank3 said:
A few days ago, I noticed that my P5 would idle roughly right after the car would start; then it would go away. And then at times, I would notice a slight rough idle at stop lights - very random. Then today, after I got off work (car had been sitting for about 8 hours) I started the car; it idled little bit rough immediately after, but didn't really think anything of it. I drove for about 20 minutes; shut off the car, but then when I got back in to start the car (maybe 2 minutes after), it wouldn't start. I took 20 sec video of what happened (might have to turn up speakers).

<iframe width="854" height="510" src="https://www.youtube.com/embed/UZE7CH7y5Ww" frameborder="0" allowfullscreen=""></iframe>

I let the car sit for about 2-3 mins and then was able to start it after that. Drove home and that's where we're at now. Something that I've noticed recently that may or may not be associated with this issue:

  • I cleaned up a fair amount of battery corrosion on the positive terminal this past weekend. Battery is 3 months shy of being 3 years old.
So what's causing these issues? Battery, starter, EGR, IAC valve, MAF, plugs, or something else? No CELs have come up (yet).
Click to expand...

Mine did that this morning! We've been hit with nsaty cold temperatures and it usually fires up no problem. Today was much warmer and that's when the thing wouldn't start.

Mine also does it occasionally after driving for a while then stopping somewhere (like a store for 10 minutes or so). Then when I try and leave, it does that. Very rarley does it stutter like that after sitting long periods (except for today).
 
davemsc said:
Mine did that this morning! We've been hit with nsaty cold temperatures and it usually fires up no problem. Today was much warmer and that's when the thing wouldn't start.

Mine also does it occasionally after driving for a while then stopping somewhere (like a store for 10 minutes or so). Then when I try and leave, it does that. Very rarley does it stutter like that after sitting long periods (except for today).
Click to expand...

Oh, and I just got the plugs changed (NGK) and still does it.....so it's not a plug issue.
 
ignition coil(s) thats a classic sign. when they start to fail on this car they can either go instantly or slowly get weak. it sounds like your got weak. theyre fairly cheap and very easy to replace
 
kms1990 said:
ignition coil(s) thats a classic sign. when they start to fail on this car they can either go instantly or slowly get weak. it sounds like your got weak. theyre fairly cheap and very easy to replace
Click to expand...

Funny you mentioned this. I swapped out the ignition coils last year with some aftermarket ones and it triggered a CEL. So I returned them and went back to the stock ones. Don't know how old they are...might be the original ones AFAIK (purchased the P5 back in 2010). Might be time to invest in some new ones. Car has been running fine ever since I posted this thread last Thursday. Maybe I tightened up a connection somewhere took out the plugs and put them back in?

Would coils cause rough idle?
 
yes coils can cause rough idle as they provide the energy for spark plugs to spark and if one is weak or dead then on these cars you can have 1 or 2 plugs not firing right or at all. idle is when you usually notice a coil getting weak as you have all cylinder firing in a slow steady motion and there is no noise or other things to keep you from noticing an issue (like when your moving) also at idle if a cylinder does not fire right it will be more pronounced as this is a 4 cylinder engine and any cylinder acting up will cause rough idle but the less cylinders you have the more you will notice.

and yes you may have had a loose plug on the coil or on the spark plug wires that was causing your issue.

symptoms of bad coils are hard or no start
rough/erratic idle
cylinder misfiring
check engine light
hesitation
stalling
and a few others
 
Thank you for the additional info, kms. I'll probably go ahead and replace all of the plugs and coils sometime in the near future. Any recommendations on what coils to get? OEM? RockAuto?
 
oem are good personally i have autozone ones on mine without issue but many others have. they all seem to have about an even amount of issues from what i have read on here and other places.
 
Updating this thread:

This past Friday, on my drive home from work (been driving for about 10-15 mins), the car shut off while I was cruising at 55 mph. Startled me to say the least. I pulled off to the side of the road. The car wouldn't start for about 10 mins (see video in original post). After that, the car started fine and I drove home. I went ahead and changed out the fuel pump and fuel filters this weekend to eliminate one more thing. Still the same thing. IT started fine after replacing the fuel pump and filters; shut car off for about 10 mins; go back to start it and it wouldn't start. Then it would start again 2-3 times fine. I didn't drive it our of the driveway fearing that it might stall again. Last thing I did was start it and move it back in the garage and shut if off.

Car starts most of the time, but when it goes through these cycles of not starting, it always starts after giving it some time 5-10 mins). But this whole stalling/shut off thing is a pretty concerning. Also, the car threw a P0453 CEL (Evaporative Emissions Control System Pressure Sensor High Input) when I started the car after installing the fuel pump and filters, but I cleared it with my OBDII tool. Don't know if that has anything to do with my issue? I figured it was from the fuel pump replacement.

Here are the things I've done to try to eliminate things:

1. Changed out spark plugs
2. Replaced the coils with used OEM ones that were about 50K miles old
3. Changed out fuel pump and filters
4. Checked the fuel pump relay and it's good
5. Battery as far as I know is good

Not sure what I should troubleshoot/replace next (injectors, ?
 
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hotcracker69 said:
I had a toyota Avalon with similar symptoms, i cleaned the MAF sensor and it went away.... try that
Click to expand...

Wouldn't a dirty MAF throw a CEL? In any case, it's easy enough to do and I have some MAF cleaner on hand. Could be a faulty MAF sensor as well I suppose.
 
hotcracker69 said:
I had a toyota Avalon with similar symptoms, i cleaned the MAF sensor and it went away.... try that
Click to expand...

Might as well check it since it's easy enough to do and I have some MAF cleaner on hand. Could be a faulty MAF sensor altogether instead of it being dirty, but the fact that it happens so randomly and not a majority of the time puzzles me. Logic says that something is in the process of going obviously, or else I wouldn't be able to start the car at all?
 
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Check all your plugs, connectors and wires for bad, loose or corroded connections.

(cam and crank sensors send out a very tiny signal that need good connections,... check for a wire that's worn through the insulation and shorting out)

You may wanna consider a new set of coils,.. It does sound like something bad coils can cause.
 
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