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[polilara]

Yesterday when engine was hot I realized that the idling became bad. It stays first constant around 600 rpm and then suddenly drops for one second below 500 rpm and shakes. Then come back to 600 rpm. It happens perhaps after each ten second period. I tried to keep rpm in around 1000 rpm with accelerator pedal and gear in neutral. Same dropping happens there.  In 2000 rpm I did not find this effect. Engine behaves normally when driving and accelerates well without any problems. Breathing system cleaned some weeks ago - should thous be OK.

I remember this case have been discussed here but could not find it. What controls the idling in this engine?

[martin341]

Sounds like missfire. Get the codes and report back.

[TheBoy]

If you have facility, what are trims doing?

Also, look for any signs of airleak in the intake and vacuums.

[polilara]

Thanks for quick replies, I have quite good facilities like new version of "My Naff Code Reader" to see different things key programming and perhaps also live data. So I will check the codes but please tell me what are the the trims?

[polilara]

Hello

According to "My Naff Code Reader" no codes. Please inform what are the "trims" that TheBoy asked to check. I check the leaks soon.

[05omegav6]

Hello

According to "My Naff Code Reader" no codes. Please inform what are the "trims" that TheBoy asked to check. I check the leaks soon.

Pedal trick it and report back

[polilara]

Hello

No codes with pedal trick. Just continuous blinking. What are the Trims?

[Andy H]

Hello

No codes with pedal trick. Just continuous blinking. What are the Trims?

Fuel trims. The ECU learns from the lambda sensors. If there is a fault with any number of things that wouldn't normally cause a fault code you can often tell by the fuel trims being unusually high or low.

[Lazydocker]

STFT and LTFT. Should be 2 of each.

Sounds like an air leak... Any recent work?

[polilara]

Thanks for info. I continue tomorrow with air leaks and check that I did not destroy/forget to tighten something when changing thermostat, cam covers, etc. a couple of weeks ago. Report then.

[polilara]

Recent Work:

1. Bought spray Start Pilot/Quick Start. Engine was hot and idling. Sprayed everywhere in inlet side, to all hoses, joints, also those small ones controlling various things, even below plenum. No changes in rpm except this "normal bad idling" case. Could think no air leaks.

2. Put D on in gear box and hand brake on as well. With accelerator pedal I tried to keep revolution in 1000 rpm. This took 1-2 minutes. Car was not moving. Engine was shaking/rattling and rpm was changing almost every second. No engine fault lit went on.

3. I have last four weeks drove only exceptionally short and slow trips, only 5-10 km/time, with cold engine etc. I went to highway and put gear No. 2 on and drove 100 km/h (60 mph) a distance about 10 km (6 miles). Revolution was 5000 rpm all the time and engine was running perfectly. After that idling normally.

4. Put my tester on. Found codes 0300 and 0304, yesterday they were not present, so random general misfire and misfire in cyl 4. Perhaps they came due to test No. 2. I cleared the codes.

5. I started the engine. Found that these "Short Time Trims" were changing in banks 1 and 2 in a similar way from minus 1% to plus 2%. Long term was -1% in both. Mixture changes from "Rich" to "Lean" in a similar way everywhere. I found that I really can read "everything" alive. Data of all four sensors (two/bank), their heating on/off many other things which I did not learn what they are... I stopped the engine, no fault codes found.

Could this all be just deposit in spark plugs due to short trips (item 3). I have 220000 km behind and this engine is a morning (blue) smoker. I do not know the real oil consumption as crank back oil seal is leaking. I found also different live data form ignition side which I could report if needed. Found also that I can record the data for later evaluation if needed.

What next? Just enjoy life...

[Nick W]

Code 0304 is specific enough to check number 4 cylinder. It's always best to consider ignition first for this sort of thing and the spark plug is top of the list. Most plug faults are obvious once you've removed them, and are easily fixed with new plugs. But replace all 6.
It is likely you will find the plugs and ignition coil have been damaged by oil leaking from the cam-covers.

[polilara]

Sure, actually I changed all six spark plugs some weeks ago and new cam covers + seals as well (and even the thermostat). Cam covers were leaking outside in that time, I remember no oil was found inside. Idling was OK in that time. This is a new problem. I agree ignition is good to check, perhaps coils are coming to the end of their lives. And it is also possible that I did not succeed well when putting new covers. However, they are not anymore leaking outside, perhaps better to check anyway.

Are there any values in ignition side to record for analysis, Idling is OK now.

Best way I can describe this Idling Problem (I had) is that when idling and you put AC from auto to eco and back to auto and eco etc. it is just similar case what happens to rpm.

[martin341]

Told ya it's missfiring
 Check the plug wells for oil as said. I had leaking camcovers that leaked outside, after i replaced them they started to leak inside aswell. You should probably change the covers and aluminium ones are best way to go. My plastic covers went fubar at 215000 km and we are in the same enviroment. Take them off and inspect most carefully, if any wavey section discovered throw them away.

[polilara]

Ok, OK

Cam covers are only a couple of weeks old but I believe you all, they can leak inside now. Better to check. This 2-4-6 coil back is just that terrible to take away. I would like to avoid to do this twice as if everything is OK then the only case is to change the coil back or what do you think?

I could order a new coil back beforehand, is that a stupid idea...