Okay, folks...I need some help here. My 1996 850 Turbo wagon with 253K miles runs and idles beautifully, but will not pass CA emissions. No engine codes. Mileage: 28 hwy / 22 City.

One month ago, it failed emissions twice due to high NOx (10x max limit). This engine does not have an EGR valve. Since the catalytic converter is original, I did some research and decided the cat is dead and possibly plugged a bit. I had it tested and replaced last week and then went in for another test...NOx plummeted to a tenth of max limit, but it still FAILED!!!...due to HIGH HYDROCARBON this time, but only by a few points. Mileage increased about 5%. The 2 previous tests showed "acceptable" HC at 15 & 25 MPH. Now it is high? What happened?

Within the past 2 months, I did a complete stage 0 tune-up (EVERYTHING, WITHOUT EXCEPTION), Mobil-1 oil, all new hoses and vac lines, oil separator & hoses, EVAP lines, etc., EVERYTHING! There are NO detectable vacuum or intake leaks of any kind, anywhere.

Today, I performed a compression test & leak-down on a hot engine. Here are the results (Cylinder 1 to 5) -- Compression: 172, 162, 175, 172, 165 -- Leak-down % Loss: 23.3, 17.7, 18.0, 27.3, 21.7 -- Using a stethoscope I detected escaping air from the dipstick tube (could feel it too), no coolant, exhaust or intake leaks.

Engine does not smoke or leak engine oil, BUT I am adding 2 quarts of oil per month, which seems like a pretty high rate. I know the turbo is allowing oil through the air induction system (heavy oily residue in pipes), but I do not know how much. Could be valve guide seals, but again, there is no visible smoke coming out of the exhaust. I have even driven in another car following my wagon (with wifey at the wheel) and when the engine is accelerated hard, there is no smoke.

My best guesses at this point are: Excess oil being introduced at the throttle body, bad O2 sensor causing rich condition (but no DTC code), oil leakage at valve guides, low engine temp at time of test.

Any ideas would be appreciated. Thanks! Greg

 

First solution, leave California!!! Really though, it seems like the PCV might be plugged. If you have some "air" coming out of the dipstick then it's in need of a PCV. That would push oil through the turbo. I'm dealing with that issue right now, myself. I took off my busted TB hose today to find it full of oil. Also, a vacuum leak would lean the motor out at idle or low throttle driving so the HC emissions would be lower. My guess is an off spec O2 sensor if the PCV doesn't fix it.

 

For high HC the usual suspects are:

1. rich mixture; given your gas mileage good compression numbers i would discount that one..
2. lean misfire; runs well and no misfires codes so..
3. weepy fuel injector causing gas to accumulate in engine oil; possibility that you should probably rule out (by cking).

Are you in southern CA (or somewhere where it's pretty warm year round)? And what engine oil weight are you using?


Assuming you're using 10-30 or even 10-40, i would change the oil with good quality 20-50 and then take it in for a test asap.


My N/A was smoking out the tailpipe using 10-40 this past summer after the oil got more than about 1000 mls on it. Wasn't thinking about it and had to take it in for state smog test; it failed because they saw visible smoke and excessive HCs. First time this car ever failed. Took it home, changed oil w/20-50 valvoline, took it back and passed w/flying colors.


Not the first time i've made a car pass by just changing the oil. Old oil, especially on an old high mileage engine, has more blow-by, etc.; really contributes to HCs.

BTW: If your turbo is original it's probably overdue for an overhaul. This very well could be contributing to your oil usage and high HCs. Also if it does get cold where you're at, I would go back to a lighter oil over the winter.

See Chrisp_T types faster than me; yeah new PCV wouldn't hurt too.

 

My family has passed numerous cars on nothing but SeaFoam in the gas. Not even kidding. Give that a shot too if you want cheap. It's like 7-8 bucks for a can. One can in half a tank of fuel should do it. Like I said, get the PCV done. Best way for you to check is to warm up the motor to normal operating temp and put a rubber glove over the open oil fill neck. if it tries to suck it in it's ok. If it pushes it out even a little bit then you are in need. High HCs can be caused by all kinds of things. Start with what is definitely wrong with it and work your way down to what wasn't very likely.

 

Thanks for all the tips...but I cannot leave southern CA...wifey would kill me!

1996 Turbo's do not have a PCV valve, per se. It utilizes an oil trap and vacuum hose to pull blow-by gases into the intake snorkel by means of the PTC fitting just in front of the turbo inlet. All of this is new and in perfect working order.

The car is NOT blowing gases through the dipstick tube when running, but air during the leak-down test, when the engine is off. This is normal and expected in a new or used motor in good condition. The rings will always allow some air to escape, hence blow-by gases are generated when running. According to everything I have read, below 30% is acceptable. Certainly, new rings and a valve job would help, but this does not appear to be the problem.

When idling, the engine is pulling a small amount of vacuum as it should. I tested this by removing the oil filler cap and placing a small square of cardboard over the opening...it is firmly held in place. Again, I have replaced and/or verified the proper operation of EVERY intake part. The oil trap and all related parts are new and all engine openings have been checked for crud that could impede the flow of gases. All vacuum lines have been replaced.

I DO feel that the Mobil-1 10W-40 could be an issue and will try dino 20W-50 for the test. I bought the car 2 years ago with dino oil in the motor and switched to synthetic about 8 months ago. For the record, the air filter, oil and oil filter and plugs were changed 2 days before the test.

I also plan to run Seafoam or similar product (lacquer thinner) in the tank to see if this will help. Others swear by this method. It's worth a try.

Tomorrow, I will pull the O2 sensors and bench test them. Afterward, I will test them in place with a hot engine. This may prove futile, but may also give a clue as to their condition. With a quarter million miles, I suspect they are slow to function. The fact that I am NOT getting a DTC code tells me they are within limits...but you never know.

As for the turbo, I plan on pulling it for overhaul, but need the car now. Once I get my '98 S70 running, I can swap cars and get the turbo fixed. I would prefer to replace it with a 16T, if I can find one at a good price.

Thanks, Greg

 

Here are some pics of my 850 -- taken early 2012 shortly after I bought the car...it needed a lot of TLC. More pics to be added shortly...

http://www. facebook.com/media/set/?set=a.10201311174553903.1073741825.1008976850&typ e=1&l=ed53a54522

 

I got a break (I think) today...Driving 25 miles home today on the highway, I decided to drive hard, then easy, then hard, then easy, etc. after slowing from 95 mph, the check engine light came on...P0172. The MAF is 1 year old, Bosch, so I do not think that is the issue. I did notice that my Turbo gage was not working, so I know the 1/8" ID hose is an issue and is creating a tiny vac/pressure leak. Not enough to generate P0172, I think. O2 sensor? What do you all think? I was not feeling well all day and did not work on the car...maybe tomorrow.

 

+1 on Seafoam

+2 on using mineral spirits --> buy in bulk @ Lowe's/Home Depot

 

I have a 89 chevy truck that NEVER passes smog (8 years straight). What I have been doing the last four years is going to Lowes and picking up a gallon of Denatured Alcohol. Run the tank down to about 2 gallons then pore the Denatured Alcohol in the tank. Go get it smogged....Pass with ridiculously clean numbers then go fill the tank and move on.