Author Topic: Lumpy / erratic idle  (Read 7720 times)

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Offline michaelwood89

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Lumpy / erratic idle
« on: April 11, 2015, 05:27:52 PM »
Hi, my Mazda 3 (1.6 petrol) has been driving me around the bend!

For the last couple of weeks when on idle it will drop rpm for a moment and then go back to normal. About a week ago the engine light came on and it was for the bank 1 lambda, too lean.

I've replaced the lambda today and reset the ecu but it's still doing it!

It is fine under load, it's only on idle.

Idle is about 700 rpm and when it drops it goes to about 400-500 before it recovers. It's almost like a hiccup...

Any ideas?

Offline Doc.

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Lumpy / erratic idle
« Reply #1 on: January 13, 2017, 10:13:38 PM »
Apologies for dragging this back up, but didn't think it warranted another topic . . .

New owner/Member, '09 (58-plate) 1.6 Petrol Takara, 36,000 miles, FSH, no mods/tweaks.

Mine does this too, after stopping at lights, and after 20 secs or so, the idle 'dips' momentarily, then returns to normal.
It's as if the Ignition or Fuel has been cut for a split-second.
Repeats every 30 secs or so.

Searched on here, found a few topics/threads, but there doesn't seem to be a definitive fix for it?

Offline speedy mazda

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Re: Lumpy / erratic idle
« Reply #2 on: January 14, 2017, 12:06:05 AM »
try using the high octane branded  fuel I always use the esso supreme unleaded  higher octane petrol, with more additive for superior cleaning power.

Offline Doc.

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Lumpy / erratic idle
« Reply #3 on: January 14, 2017, 12:58:54 AM »
I would think that if it was a fuel issue, it would happen most/all of the time, not just after 20secs~30secs.
The fact it's so regular suggests to me that it's an ECU 'glitch', or something similar, like a sensor issue.

Offline StevenRB45

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Re: Lumpy / erratic idle
« Reply #4 on: January 14, 2017, 02:39:05 PM »
What load is the engine under at the time? I mean in terms of electrical load? Eg if you the steering wheel at idle because the pump is electric the sudden increase in the load can lower the revs momentarily until the ecu sorts it. Also you got the AC on automatic? It can be it cycles the compressor to keep the air dehumidfied even if it doesn't actually need to cool the incoming air which again applies load.

Also is the car fully warm at the time? It may be its attempting to come off the auto choke otherwise and going a bit far due to the current cold weather.

Offline Willpower

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Re: Lumpy / erratic idle
« Reply #5 on: January 14, 2017, 04:35:00 PM »


Lot of common sense there.   


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Offline Doc.

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Lumpy / erratic idle
« Reply #6 on: January 15, 2017, 07:09:37 AM »
Thanks Stephen.
I'm aware of the A/C, Engine temp, and Steering Pump possibilities, they're covered in the other topics I've found when researching this.

It does it when the Engine is up to temp (>15mins/5miles), A/C off, no Steering input, Handbrake on (so no Servo Vacuum 'load' either).

It's almost like it's programmed into the ECU, for example to cycle the idle control Stepper Motor (I assume it has one?) for some reason, which would only be noticeable at idle of course.

Offline StevenRB45

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Re: Lumpy / erratic idle
« Reply #7 on: January 15, 2017, 09:21:41 AM »
Unfortunately that's above my current level of technical expertise. Last time I had an idling problem to sort the car had an idle control valve..

Was just making sure you'd covered off the basics before taking things to bits. I have the same engine and it doesn't do this except for when the AC is on Eco otherwise it idles at 600rpm if memory serves. It may be the 02 sensor isn't giving consistent readings but hasn't failed entirely so the engine is fiddling with the fuelling to compensate. However as the OBD should throw an error code if this happens this is very much speculation. Any other symptoms e.g. poor fuel economy or flat spots?

Offline speedy mazda

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Re: Lumpy / erratic idle
« Reply #8 on: January 15, 2017, 11:30:14 AM »
Hi Steven im Not sure if his 1.6 is thé same father inlaws 58 plate 1.6 has a throttle câble plus few other différent bits on intake side. We had an old 323 owned by an old lady before it had carbon build up problems in intake manifold.thats why i use higher octane fuel plus High revs Now and then  ;D

Offline StevenRB45

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Re: Lumpy / erratic idle
« Reply #9 on: January 15, 2017, 02:43:24 PM »
Tbf I always use super and I'm not scared of the top end of the rev counter either so my car tends to get the "Italian tune up" multiple times a week.

Regards the issue this guy is having it's worth a go but if it was carbon build up I wouldn't expect to be like clock work every 30s.

Offline deanparkr

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Re: Lumpy / erratic idle
« Reply #10 on: January 15, 2017, 11:59:54 PM »
Apologies for dragging this back up, but didn't think it warranted another topic . . .

New owner/Member, '09 (58-plate) 1.6 Petrol Takara, 36,000 miles, FSH, no mods/tweaks.

Mine does this too, after stopping at lights, and after 20 secs or so, the idle 'dips' momentarily, then returns to normal.
It's as if the Ignition or Fuel has been cut for a split-second.
Repeats every 30 secs or so.

Searched on here, found a few topics/threads, but there doesn't seem to be a definitive fix for it?

I have an 09 Takara and my car used to do this. At somepoint I ran into the P2187 MIL code. I'm not sure if this issue is related to that code but to resolve the code I had replacement inlet manifold seals fitted.

I'm pretty sure that after that fix the idle RPM dip stopped happening too.

Info:

http://smg.photobucket.com/user/deanparkr/media/P2187.jpg.html

Again, might not be 100% related but I do remember having the idle dip issue well before the code and then NOT having it after the fix above.

Offline Willpower

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Re: Lumpy / erratic idle
« Reply #11 on: January 16, 2017, 01:00:27 PM »
Just to confirm the above, I have heard of this problem before. It's on the forum somewhere.  Could be worthwhile looking into.

Found the following by doing a search. (always a good idea )   

My wife has a gen 1 mazda 3 1.6 petrol and we had the inlet gaskets replaced by our local dealer.the car started to idle a bit lumpy and gradually got worse and it started cutting out at junctions.the problem was caused by degrading inlet gaskets and causes the engine to suck in too much air making the air fuel mixture too lean. when we had them replaced the car then drove like new and we realised just how much performance the car had gradually lost unnoticed over time.this is a common issue on older mazdas with this 1.6 petrol and is pretty well known in the motor trade.my local dealer did a quick diagnosis  check and confirmed the inlet gaskets at fault and fixed the car the same day.
Sorry to rebounce this topic from the dead.

I've had the exact same issue. Check Engine Light initially, noticed the car had been idling rough for months and engine is a tad hesitant to rev. Also easy to stall if you don't give it enough gas.

Changed the MAF (cheap and easy fix), but no luck. Turned out I could hear a hissing/vacuum noise coming from the left had side of the engine/inlet manifold area. Took the car to a local mechanic and he found the intake gaskets were shot. One was split and the others were overly pliable and brittle. Replaced the whole set for £240. He said Mazda say it's a common issue and they had plenty of genuine gaskets in stock at the local dealership.

I chose the petrol for reliability too, so a bit miffed that this has happened in the first place. Had a 2.0 Gen1 before with nearly 100k miles and zero engine issues.

Not sure what causes the gaskets to go on some cars and not others.

Hope this info helps anyone that gets the P0171 Lean check engine light error in future on their 1.6 Mazda 3!
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Offline mart_haj1986

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Re: Lumpy / erratic idle
« Reply #12 on: January 16, 2017, 01:12:10 PM »
I had to get my intake manifold gaskets replaced in November for the same things, lumpy idle + P0171 CEL I think it is quite common with the 1.6 Petrol.
Martin H - Nuneaton, Warwickshire UK

Offline Doc.

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Lumpy / erratic idle
« Reply #13 on: January 18, 2017, 09:09:47 AM »
Thanks for all the ideas/input.

Just to clarify though, in case the original subject title is misleading;
My idle isn't really 'lumpy' or 'erratic', it's just the slight 'hiccup' after 20 seconds or so at idle, followed by fairly regular repeats (30 seconds apart or so).
No fault codes/warnings.
Played with A/C~Steering~rear Screen heat etc, they all increase revs slightly, programmed into the ECU no doubt.

I discounted those two topics when I did my searching Willpower, as the symptoms don't really fit.

As for the Intake leak issue, I'd be surprised (and a little disappointed) if mine had that problem at only 36,000 miles.
I would also expect, again, that it would play-up all the time with a constant intake leak.

Offline deanparkr

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Re: Lumpy / erratic idle
« Reply #14 on: January 18, 2017, 10:30:35 PM »
Thanks for all the ideas/input.

Just to clarify though, in case the original subject title is misleading;
My idle isn't really 'lumpy' or 'erratic', it's just the slight 'hiccup' after 20 seconds or so at idle, followed by fairly regular repeats (30 seconds apart or so).
No fault codes/warnings.
Played with A/C~Steering~rear Screen heat etc, they all increase revs slightly, programmed into the ECU no doubt.

I discounted those two topics when I did my searching Willpower, as the symptoms don't really fit.

As for the Intake leak issue, I'd be surprised (and a little disappointed) if mine had that problem at only 36,000 miles.
I would also expect, again, that it would play-up all the time with a constant intake leak.

I had the intake leak issue on my 09 Takara at around 40k miles.

I do remember having the "hicup" on idle as you describe, it eventually turned into a more lumpy idle and MIL. I dont think it was as regular as clockwork as you describe though. It was a little more random than regular repeats.

Worth looking at the intakes if possible, methinks.

Mazda 3 Forums UK

Re: Lumpy / erratic idle
« Reply #14 on: January 18, 2017, 10:30:35 PM »