Rough Idle Headache

[Maniac]

Hi guys,

I've recently bought a K11 2001 1.4L Activ 89K miles and thought I'd join the community and ask to see if anyone had some ideas to my issue.

I bought the Micra as a project to do it up, but before doing any major cosmetics I've been focusing on sorting the engine first of course. Although its apparently not a simple fix, the issue is basically rough idle.

On a cold start its almost non-existent, but the warmer it gets the more the engine shakes. Its also not continuous, it seems to chug at a rhythm but occasionally vibrate then goes back to chugging.. hard to explain yeah..

So anyway here is a list of changes/tests done so far. I know some probably are pointless/unlikely to make a difference, but like I say its a project for me so want to get it tip-top.

I should note as well that the OBD reader I've used, and garages have used, have not found any codes.

Any thoughts or tests I can do would be much appreciated!

1. New Camshaft Sensor
2. New Upstream O2 sensor
3. New Spark Plugs (x4)
4. New Ignition Coils (x4)
5. New coolant temperature sensor
6. New throttle position sensor
7. New air filter
8. Wynns Engine Flush then Oil change /w Wynns Super Charge Oil Treatment + Oil filter
9. New Battery
10. New Coolant temperature sensor
11. Cleaned throttle body
12. Checked engine codes, none found

Works claimed by local garage

1. Removed Throttle Body and sent off for testing. They were unable to find a fault.
2. Checked Fuel pump
3. New MAF sensor
4. New Crankshaft Sensor
5. Compression test

[Trevor]

Hi...welcome to the Forum

First thoughts are drawing air on the air intake system (vacuum leak somewhere upstream) which is causing it to hunt.

Listen out for hissing or even spray brake cleaner or similar around the inlet areas with the engine running at idle to see if the revs increase when the gas is drawn in.

Failing that, use a smoke tester (some garages have them) to see where any smoke is coming from and hey presto...there's your leak!

Also, the slightest air leak on the exhaust system (pre-Lambda sensor) can cause hunting as the Lambda sensor cycles to compensate for the extra air once the engine is warm....check for high oxygen content in the exhaust gas (should be zero) when the hunting occurs at idle.

Let us know how you get on with it.

Cheers,   Trevor

[Maniac]

HI Trevor,

Many thanks for the tips pal, i'll give these a go and let you know how I get on

[Trevor]

Here's a link that may assist you in sorting the idle

 

[Maniac]

Thanks for your advice Trevor. I had already cleaned the throttle body so that's all good.

Done a smoke test to find air leaks, but didn't find anything.

I've been to 2 separate garages recently, and both have suggested it could be the timing chain after they had a look.

How likely is it that's the cause?

[Trevor]

Sometimes timing chains can suffer from slack through insufficient oil pressure so maybe change/flush the oil again and replace with better quality oil?  

It's a cheaper way than chain replacement and see if that works first

[Maniac]

Thanks pal.

I might just do the chain anyway as the car has zero service history, and where I bought from it wouldn't surprise me if it hadn't been maintained..

Micra's seem to be cars that get run into the ground because their market value is so low, so if the chain is slack if I get it done then it'll add years to its life. Plus I'll actually maintain the engine, as its a project/keeper

[Trevor]

Go for it...as you say, it is worth it in the long run.

Post up some piccies of the job with a description if you like?

Cheers,   Trevor