Blue smoke on extended idle. 2006 4.8is.

[TerminatorX5]

As I was monitoring cluster TEST 7.2, the digital tachometer, i have noticed the following:

from the cold start, the car start idling at 900 RPM, going up and down 10-20 RPMs... I have not timed it, but within a few moments of that, the RPMs drop to 700, give or take 10-20 RPMs, and within few more moments, the RPMs drop to "normal" idling speed of 600 RPMs. AC is off.

At 600 RPMs I observe 580 to 640 RPM floatations, which does not concern me... however, as I hear and feel the "hiccup", the digital tach registers DROP in RPMs to 540, once it was 520, and then it rebounds back up to 600 and vicinity... All of that happens at idle speeds, regardless if the gear is not engaged (Park), or if the gear is engaged (Drive or Reverse) and the foot is on brake. If I let the foot off the brake, and the car start moving under the idle of the engine, I feel the light jerking of the car as it propels forward or rearward, coinciding with the drop of the RPMs... The frequency of the "drop" is not ties to anything, it seems to be random but rather annoying...

Two incidents that occured and I have not seen them happen:
1. when going from cold start, idling at 700 RPMs , the engine surged to about 1200 RPMs and then dropped to 600 RPMs with the same symptoms as before

2. while at a traffic light, the idle dipped to about 500 (this is what the digital tach registered for a brif moment) and I saw the D in the gear selector indicator turn off, as if in FAIL SAFE MODE, and then the indicator lit up again - this was very fast, in the blink of an eye, and I saw it as my eyes were glued to the cluster...

I have not performed the flush yet, waiting for the weekend...

Can there be issues with the Throttle butterfly?
Can MAF be defective and I need a new MAF? I spray-cleaned it, to no avail
Can the issue be further into the engine? like coil packs?

What other symptoms should I be on a lookout to further narrow the possible culprit?

Thanks guys - I am somewhat OK with electronics, but get scared over the juicy parts of the engines!!!...

[Ricky Bobby]

I would take some WD40 and spray your vacuum hoses as you may have a leak somewhere, coilpacks you can pop the engine cover off and make sure they are seated down all the way, on my old VW they used to pop off.

Cleaning the ICV/throttle body would probably be helpful as well but on a 4.8is i'm not sure how to tell you to get them off. If you have no vacuum leaks and MAF is ok I'm assuming idle valve or throttle body related.

Sorry I'm not much help with my 3.0!

[bcredliner]

TerminatorX5,

Yes to all three of your questions. MAF is at the top of the list. I have never been successful cleaning the MAF, and I have tried each of the 4 times I ended up replacing it. Test of MAF is to disconnect it at idle and see if it goes away. If you need a MAF, google is as I recently got an email, can't remember source, that had Bosch on sale at $150. If it is throttle body associated you will likely hear a clicking noise. If not throwing ECU codes coil packs should be good.

[bcredliner]

Very respectfully, I don't don't believe that changing oil to a different type or weight that is not what is recommended for that vehicle is doing anything other than masking the problem. Yes, it is easy to and doesn't cost that much but I say don't bother unless it is due and only because changing oil frequently is a good practice. What would be your response if I said to you I don't like smoking cigarettes because of the nicotine, so I changed brands. Unless you are in VERY extreme conditions of hot or cold it is only masking the issue. Heavier oils will reduce blow-by and stay in the top end longer if it is extremely hot. Lighter oils will drain down quicker and lubricate the engine quicker, in an extremely cold climate. If it happens after the oil is in a safe operating range there it is not an oil issue. If the oil weight, type or brand of oil was the problem it would be a problem from day one. There are strong feelings about whether to flush or not to flush,I have no idea which is correct so I don't do it, other than the toliet. Assuming it is a good thing it could lessen the problem which will tell you something is/was restricting flow or more likely make it worse. The only plus side of getting worse is it will be easier to troubleshoot. In the age of muscle cars we would go to heavy straight weight oil when the engine was getting 'loose'. Engine would rattle on a cold start but burn less oil and show less smoke. When that stopped working it was time for to start using STP and deciding how you wanted to increase HP on the next rebuild. If you monitor oil loss by miles driven it will help with narrowing it down.

[SlickGT1]

Term, don't you have INPA? You have NCS E, so you must have INPA. Connect it to your car and diagnose.

Similar surge stuff happened to me. Then I connected INPA and figured out that it was directly related to my Over-Votage, under-voltage conditions. It would rev so hard, that it would scare you while idling inside the garage.

Has not happened since I changed the voltage reg.

[fmugur]

Term, as Slick suggested it might be the alternator. I had similar problems on my n62 one and it was the voltage regulator. I used the cluster to read the voltage though (Test 9 I think) which showed under and over voltage even over 16V. It was throwing all sorts of codes when the voltage reached that level.

[TerminatorX5]

i sure suspected the alternator as well, just did not voice it as i thought it would be ludicrous to suggest that alternator can cause this... however, it seems that i am not too off - you guys don't discount alternator, i will keep that in mind as well...

I do have the hardware and the software but my problem is, when i rebuilt the XP machine with original restore disks, it restored to VISTA... now, i can't get it downgraded back to XP, i even bought OE disk off internet, installed it on brand new hard drive, and it still did not work... so, i have to rebuilt the comp in order to properly diagnose...

engine flush - when i looked inside the 4.6iS engine, it was scary!!! so much carbon, more than on summer barbeque day!!! so, the chemical detox is still on the to do list, i am going to change oil, and do the flush, as it is more related to the smoke on the idle... funky idling - is another issue, on top of the smoke... could be related, coulbe not related...

waiting for the weekend... hopefully will do something this weekend...

thanks for the suggestions, really appreciate it - it is always easier to diagnose somebody's else car, as opposed your own - for me there is a panic attack, will i get stranded on the side of the road, and the kids come home from school, and nobody home, will the engine blow on me, like the other one did, and will have to buy another bimmer... lol...

thanks guys!!!

[TerminatorX5]

i am going to get the codes read out, working on the laptop to get the things reinstalled...

meanwhile...

when i replaced CCVs, i have disconnected MAF, to clean it up, and of course, reconnected it... after i got the stutter on the idle, naturally, i thought, that the MAF is not plugged in right, so i unplugged it and replugged it... several times, with zero result... did all that plugging with engine off...

today, on the way home, the stutter was getting worse, and at one point i got flashing SES light which then set on permanently, and the engine was running very rough... I managed to make it home, and without turning the engine off, unplugged the MAF again... the engine surged, and then was running at a bit higher RPMs without the MAF... I plugged the MAF back in, and it felt like the stutter was diminished... so, i turned the engine off, turned it back on, it was running nice and smooth (MAF connected). I disconnected the MAF once more, with engine running. The engine surged, as in the previous instance, when it raced up - so, it made me think, that either a contact in the MAF somewhere is not good, the MAF is already bad, or the MAF is going to die rather soon...

damn computer is stubborn with that stupid VISTA... i need to read the codes and see what i have there... i will keep you posted...

[pezho405]

Voltage wouldnt have much to do with with idling problems. Fariz, unplug your maf and drive around with it off, see how it changes anything, a friend in an m roadster killed his by trying to clean it and and made bad/rough engine running, driving withought it made it slower but not as rough

[TerminatorX5]

Well, this is the beauty of the troubleshooting and diagnostics - pulling all the available brains to figure out where the likely culprit is... my idling was ok before i ventured into CCV and the MAF cleaning... after MAF, the idle became irregular - so naturally, i messed something up... plugging-unplugging the MAF did not yeild any positive results, checking for air gaps around the air intake shroud got nothing... so, i thought, something is going on deeper, just coincided with the MAF cleaning... I probably did not need to clean MAF, but I definetely had to change the CCV, as one was grossly torn...

unplugging the MAF one more time, while engine was running seemingly rectified the issue but raised concerns that something might be brewing in the near (or far) future...

I somehow managed to install the INPA on the VISTA machine and got some readouts - since I do not know if the values are good or not, hopefully somebody can let me know... the values are in the green, which makes me think, things are ok in general...