Random Weird idle

[Cla]

Hello,

Have a 06 euro auto (130k kms). I noticed yesterday that the idle of the car was off. It was normal then at random intervals it seems to miss a beat (can see tacho dial drops slightly and go back to normal). Guessing 650rpm.

I notice a bit of a splutter between 1k-2k.

Nothing has been changed lately on the car, fuel economy is normal.

Spark plugs replaced a year ago and fuel filter replaced/valve inspected 4.5 years ago.

Had a blown coil a while ago and it’s not that. Not a tractor sound, just sounds like a drop beat.

Happy for any ideas before taking it to mechanic if I can’t sort it.

Cheers!


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[Cla]

It seems like a random misfire but none detected on computer when scanning.

Physically visually inspected spark plugs and coils. Didn’t check spark plug gap (only 10k 1.5 years old).

The only thing I can think of that has happened lately is I left the car idling for 90 mins which may have heated something up but I never recalled the idle issue after that drive.


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[Fredoops]

random missing a beat..

can you do a load test on the alternator and battery? see if it's a electricity supply issue?

[Cla]

random missing a beat..

can you do a load test on the alternator and battery? see if it's a electricity supply issue?

The battery is only 8 months old (nrma) and the alternator is about 4 years old. Though, it’s an aftermarket one.

Haven’t really had any issues with the charging system. Can’t load test it at the moment.

I had my mechanic out yesterday, he said the brake booster was leaking and there was a noticeable hiss (under the bonnet) when turning the car off.

Clamped the vacuum hose and the idle
Picked up abit.

So going to replace the booster and see what happens. Hopefully that’s it


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[Cla]

Completed the following:
Replaced Brake booster
Fuel filter
Service + filters
Upper engine cleaner + TB clean

After all this the car went good for a day or so and then went back to normal idle issue.

It has now dropping random missfire CEL which goes away if I keep on driving it. CEL only appears to happen when driving around at low speed/low load.

Jumpy idle is noticeable in the cabin.

I cleaned the intake manifold (and the metal gasket) and the car runs good for 1-2 days and then goes back to normal and progressively gets worse.

Wits end... thinking with it going well after a Upper engine clean it must be either something blocked that gets temporarily unblocked or there is a temporary performance boost from the cleaner.

[Kodak]

I gather the car does quite low k's. Try a tank of premium and some injector cleaner to clean out fuel system

[Cla]

The Km's are ~136k and probably been on-going for 10K or so. It comes and goes, so have not been actively working on a fix.
Only appeared to start after a long idle one day, next step may be the IAC off the TB giving it a good clean as definitely when the motor gets upper engine clean it works way better for a period of time.

Car only runs on PUMP and have put a few injector cleaners in over the time.

Currently have a CEL, will review again but normally it's random misfire.

[Fredoops]

Sounds like a dead/dying ignition coil.

Check the CEL and move ignition coil around, if cel move with specific coils, then you will know which coil had gone bad.

[Cla]

Sounds like a dead/dying ignition coil.

Check the CEL and move ignition coil around, if cel move with specific coils, then you will know which coil had gone bad.

Thanks yeah... I was thinking that actually..... I checked all the coils and they appeared fine. I've had a dud coil before after going through a storm and flooded highway... it sounded like a tractor, swapped around coils and found it.
This time it does not sound like that or feel like that, I have fiddled with the coils and even pulled out the plugs out and shuffled them again, didn't make a difference really.

Only happens at idle really, I suppose it could be a coil but the weirdness is when I put the upper engine through it... it improves for 1-2 days

I think it's time to remove the TB and check out the IAC.

[Fredoops]

I think it's time to remove the TB and check out the IAC.

there is no idle air control in this car. it's drive-by-wire

check it anyuway tho, just in case it's gunk build up on the throttle plate.

[Cla]

there is no idle air control in this car. it's drive-by-wire

check it anyuway tho, just in case it's gunk build up on the throttle plate.

HAHA thanks! You saved me getting my tools out to take off a part that doesn't exist... though that's annoying as everything else has already had a good clean but something must be up around that as when its clean its good for a while so it might be really gunked up to go back to weird after a few days.

[amant02]

I would clean maf crank/cam angle sensors connectors and make sure its all connected properly.

This is also a symptom of MAF dieing.

[Cla]

I would clean maf crank/cam angle sensors connectors and make sure its all connected properly.

This is also a symptom of MAF dieing.

Will do thx!

[Fredoops]

CL9 accord euro does not have Mass airflow sensors.

[Kodak]

Will do thx!

Try cleaning/replacing the MAP sensor
https://www.diyautoworksng.com/map-sensor-replacement-accord/

[amant02]

CL9 accord euro does not have Mass airflow sensors.

Oh wow does it run speed density from factory?

Edit I see its got a MAP sensor.

[Cla]

Hello All,

Long time no reply, ended up getting to the bottom of this issue. It was the first thing expected but the last thing checked. Sparkplugs. They were only ~18K and 2 years old but the electrode was really worn down and the gap was large.

Got some new plugs and swapped them out, knock on wood went away straight away.

Thanks everyone for their suggestions

[Kodak]

Hello All,

Long time no reply, ended up getting to the bottom of this issue. It was the first thing expected but the last thing checked. Sparkplugs. They were only ~18K and 2 years old but the electrode was really worn down and the gap was large.

Got some new plugs and swapped them out, knock on wood went away straight away.

Thanks everyone for their suggestions

A worn or eroded plug is a sign of something else being wrong. Google what these mean for ideas, for example
https://www.onallcylinders.com/2012/12/20/reading-101-how-to-read-your-spark-plugs/
If you haven't fixed the route cause, it will likely occur again.
Were you using iridium plugs?

[Cla]

Suspected a few things
Purchased IZFR6K11 this time around but the plugs were IZFR6K11-NS, so could have been wrong from the get go.
I had a long term vacuum leak from the brake booster, thinking this could have leaned things out and caused it to overheat
Gap looked large
A lot of carbon build ups in the motor

Fixed all those issues and replaced plugs with the correct ones and fixed the other issues

So I guess, just have to monitor it and see what happens now after all those other potential issues have been removed.

Been driving for a few weeks now and hasn't missed a beat, fuel economy is up but thinking learned fuel trims might be off and need to either be reset or I'll just keep driving and it will work itself out.

Thanks for highlighting the root cause might be still there, definitely could be.. Will be keeping an eye on it and hopefully now a lot of those potential causes have been removed it might either show a different result or lead to a new direction of troubleshooting...


*fingers crossed*