Hi all

I have a V35/G35 and am having some problems which I can't figure out.

It is blowing huge amounts of black smoke when accelerating under load. I know this often indicates rich fuel mixture but I can't work out why. I have replaced the faulty o2 sensors and have checked the EGR sensor, I have cleaned out the massive carbon deposits from the intake manifold, I have put some injector cleaner through it twice, but still no difference. Can anyone suggest what to check next? Pull the injectors? PCV?? MAF sensor???

I am also concerned about a compression test I had done, the engine has only 57,000 miles on it. Four cylinders came out at 175psi (which is fine) but 3 and 5 (adjacent cylinders) came out with 150psi, a 15% drop. I know because they are adjacent it could indicate a blown or leaky headgasket between 3 and 5, but there are no signs of cross-contamination between oil and coolant. There are no visible bubbles in the radiator or combustion smell, but when I remove the cap and start the engine, as it warms up the coolant level rises and spills over. I don't know if this is normal or not, I assume the radiator builds pressure naturally as it warms up? The car does not lose coolant and does not burn/lose oil. How can I accurately diagnose this loss of compression without pulling the heads off? Is the 15% drop worth worrying about??

Need help and would appreciate your answers!

Thanks!!

 

Hmmm this does indicate perhaps a hurt ring on 3 and 5. I'd pull the plugs on those cylinders and see if the tips are oily in anyway.

If there was excessive carbon maybe the car was run for alot of short trips. How does the valvetrain look? Varished or aluminum color?

You could try AutoRX. It's a very gentle cleansing agent that you put in your oil that cleans out the carbon deposits over time. It might be worth a shot. BITOG forums like the stuff and they are the oil gurus.

You could try cleaning the maf sensor. couldn't hurt. Also replace the PCV too.

 

Do an "Italian Tune-Up"

 

Are you sure its black and not blue?

Have you pulled the plugs in the 2 questionable cylinders to inspect yet? I'd pull a plug from the opposite head as well and go from there.

Any codes stored?

 

Looks to be black, certainly dark, looked almost brown to be honest.. Definately not white which is good.

Got someone to drive the car today and I stood on the footpath to watch it, at about 5000 rpm it started absolutely billowing dark smoke, huuuge amounts. Continued until the revs dropped down to about 2000.

No engine light at the moment so no codes. I had oil pooling in the spark plugs months ago but had it fixed so it shouldn't be that, and it wasn't 3 or 5 that was pooling from memory.

Could it be carbon getting blown out under high pressure?? Car is driving well other than this, getting poor mileage though.

 

I put money on the head gasket or valve seating issue which would explain the loss of compression. More then likely the headgasket... easy fix!

 

haha
easy fix huh?

 

I'd see if someone can read data for you with you peaking over their shoulder. What if the ECT sensor is "off" telling the computer to dump more fuel? Check the MAF sensor. Is it dirty? An over oiled or dirty factory filter will let all kinds of crap build up on that little hot wire. Any leaks down stream of the MAF? usually the car will run like poop if this happens but I've seen weirder things happen.

Remember, if you try your own repairs, reset the computers Keep Alive Memory. I have fixed cars before and didn't know it because the computer took too long to learn my repairs. Just unhook the batt. neg for 5 minutes or so.

 

Thanks for your input guys, much appreciated.

Just continuing with it though, if it had a blown or leaky headgasket wouldn't I know about it? It doesn't have any coolant in the oil (or vice versa) and isn't rough driving at all. No sign of white smoke in exhaust (only dark smoke) and it's never overheated..

 

Ok been doing further research.

I've read that black or grey smoke can be caused by an ignition timing control problem. I believe this can caused a couple of ways:

1) Ignition timing control sensors malfunctioning
2) timing chain a cog or two out

I have also read that having the timing chain out a cog or two can cause low compression in some cylinders because the valve doesn't fully close at the right point in the cycle.

I previously have had error codes P1100 and P1135 which is ignition timing control malfunction banks 1 and 2.

Anyone think I might have found the answer? I just don't know if the error refers to a sensor problem or something else (eg timing chain)..? There seems to be a few timing control errors on the list?

 

I wouldn't think the timing chain would be out after only 57,000 mi, but I guess it is possible. I would def check that out and be sure

 

Have you actually pulled the spark plugs and visually inspected the electrodes of the questionable cylinders? That could tell you a lot right there. Compare to a "good cylinder" after.

Mainly look to see if they are burning hot, soaked in oil, black, the tips are melted off, etc etc.

 

Ok have ruled out blown or leaky headgasket between 3 and 5. There is just nothing to suggest it could be this, just a coincidence they are next to each other. No coolant mixing with oil, no coolant or oil loss, never overheated, no white smoke from exhaust, runs smooth. Ruling out cracked or warped head too, no oil or coolant leaking from engine anywhere, engine externals completely clean and dry.

I'm thinking it's the rings. Not sure how hard it is to change the rings?

Regarding the smoke, looks like it is deposits being blown from the exhaust under high pressure and not fuel, not rich enough and doesn't smell like unburnt fuel at all. Could be clogged cats? I had a huge amount of carbon buildup which I had cleaned out a while back.

Haven't pulled the plugs out, had them replaced about 5000 ago because I had oil pooling, had it fixed up. Other than that I think the plugs were ok.

 

Rings are usually blue smoke, and you'll notice oil consumption.

Replacing rings requires a total engine rebuild with the cylinders being machined

I don't think this is your issue though...so don't plan on yanking the engine just yet

 

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