Speedtoys

E85 would only force the ECU to richen up to "fix" running on E85.

This isn't fix.

jcorenman

Don, the wear item is the platinum hot-wire itself, the very thin wire that you see strung in the venturi. The challenge is keeping it clean, they see a lot of air going by and tend to get coated with oil vapor, etc. which would degrade performance. So each time the engine is shut down the LH does a "burn-off" cycle, heating the wire red-hot and burning off any contaminants. Over time the burn-off cycles erode the wire, causing it to get thinner and throwing off the calibration. The LH compensates for that, to a point, then things start getting funky.

I am not the expert on rebuilding them, but basically the wire gets replaced (not easy) and then the calibration gets adjusted for the new wire, by tweaking the electronics that is under the black cover.

What matters for MAF aging is the number of burn-off cycles. Chronological age doesn't matter much, and mileage is only a rough estimate, but with the usual mix of short and long trips 60-80K miles or thereabouts is the point where it gets to the limit of what the LH can compensate.

Cheers, Jim

Chalkboss

Perfect. Thanks Jim. I am going to look into getting mine rebuilt. No big problems but the idle is a bit high (900-1000) and the previous owner was told (by Greg B) it's running lean. Probably also do the 02 sensor also. Passed smog fine a year and half ago HC 0.01 and N0x around 360. Going in for a smog in a few weeks. I figure these things can't hurt and should be done anyways at this time.

x98boardwell

Jim,

Thanks for your input today. Extremely helpful!!! I think I was able to find a used S4 cat for my car so I should be good in that regard. I will also look into the injectors but after I pass smog (if I can help it) by doing some of the other things mentioned.

My MAF has only 30,000 miles and was purchased new in 2002 so it is 12 years old but to your point hopefully its more of a usage thing than a time issue.

Hopefully, it was a bad O2 but since I am trying to eliminate the actual cause I may do a smog before I change the cats to only eliminate one variable at a time rather than change both and not know what it was for sure. Also, if it passes then I will keep the cat I purchased as a back up for future issues or bringing back to stock. The stock exhaust was stolen when the PO had it off at someones shop during the motor work so that is why I have these on.

I do appreciate all the help from everyone that is why I come to this board due to all the wealth and friendly atmosphere. I may have to take you up on the MAF rebuild (I'll bring the beer or at least buy you some) but hopefully I won't need to right away based on what you said and the limited miles on mine. It appears as though the original one lasted 106,000 miles so not too bad!!

Cheers,
Bryan

x98boardwell

Not rebuild.. I meant your offer to test the MAF. That would have been one cheap rebuild and I'm sure you would get sick of all the beer you would have around.. hahaha.

Thanks,
Bryan

x98boardwell

I PASSED!!!

I changed the O2 and besides plugs which I am guessing it wasn't here are the details.

I am wondering what your interpretation of the data is below regarding all numbers now that the O2 is working in conjunction with the MAF properly. Also, when the car is hot it does run a little higher idle around 1,000 or 1,100 according to the gauge which could be inaccurate.

Thanks,
Bryan

First pic is new and second one is the last SMOG pre-O2 sensor replacement.

BC

The ethanol does a few things *Depending on the car*

With the 928, the injectors are sized so ridiculously small that running TOO much ethanol as a percentage of total volume will lean out the mix enough to cause EXTRA heat simply from a lean mix. That said, the ethanol is actually a way to COOL the combustion process, even if you are lean of stoich (NON load or low load).

The other reason for my suggesting e85 is that yes - it will scour the fuel system and he will truly find out what is up with those injectors he may be loath or touch.

Back to the original point - while there may be more heat, the HC and NOx will normally go down with E85 burning NEAR stoich even a bit rich.

My experience on a 928 has been positive with ethanol for most cases. As I have said, I nearly passed a stock car with NO cats on e85.

That said - I had a recent cat issue with a MB, that CLEARLY has injectors that are sized VERY large for the car. I can see this because I put a full tank of ethanol in to pass smog and what happened? Nothing. No ECU lights, no rough running from too-lean, and better power. Just for ****s and giggles I tested the AFR and it was basically fine. The fact that the ECU and injectors were able to cope with the 30% increase in volume requirements was amazing to me.

The actual issue with the car after sticking a camera down where the 02 sensor was was a PLUGGED cat. Solid.

Anyway....

As I mentioned, my suggestions regarding e85 and smog tests are not about the proper fix when there, through numbers, is CLEARLY something wrong. I am suggesting in that case to replace the cats, as Greg has. My e85 comments were about just passing smog, which has worked several times for me and the people that I suggested it to personally.

But if you think about it, what would happen with a richer (if it could even GET rich, remember that those are 19lb injectors - VERY small) - mixture was created? Wouldn't NOx go down? He has a bit of room on HC.

GregBBRD

You missed what was perhaps the most important thing....look at the picture of the plugs again. The second plug from the top on the right side is green with corrosion. The inside of the sparkplug connector will look exactly the same way! Replace it.

Basics first. More complex issues second.

BC

Oh, I was thought I saw you replaced the o2 and resmogged. You never did. So this is the first test with a flipping working o2 sensor.

James Bailey

We may all look at the same thing but few really see it.....what makes Mr. Brown, Mr. Brown !

jcorenman

Congratulations! This was was with the same aftermaket cats?

The only curiosity I see in the numbers is a normal/high-ish CO at 1500, but zero at 2500. Testing artifact? Curious but who cares, it passed!

The high idle is a mystery. It could be an air leak, or a stuck/flaky idle valve (ISV), or maybe the MAF. Bill Ball had a recent thread on this topic, his turned out to be the MAF-- the original one idled very low, a borrowed one was high, rebuilt MAF fixed it. I can understand the low idle (mixture way off), but the high idle is confusing.

ptuomov

I agree with basics first.

However, how could any spark plug problem in one cylinder cause that kind of NOx readings with no HC and no CO?

The spark plugs are at most an indication of some other issue in this case, in my opinion. Perhaps that's what you meant.

The high idle could in principle be something as simple as using GT ignition and fuel maps with S4 cams. I'd guess that S4 cams will create more vacuum, flow more air, and produce more torque at low rpms. This _might in theory_ be a significant enough effect to cause the ISV to peg out. Luckily, you can test this with an S4 and a ST2, I think, by simply loading GT maps in an otherwise stock S4. My guess based on tuning for a higher idle speed target with the ignition map is that it's not enough to cause the idle to go to 1000, but who knows without trying.

To me, the numbers look good on the surface. But you may still have some significant issues left that are simply masked by the O2 loop and adaptation.

For example, you could have a vacuum leak. Now, idle is too high, but the 02 loop and adaptation get the fueling right so you pass smog.

Taking better pictures of those plugs one by one and posting them might still make sense.

Hilton

Congratulations!

The needle is innaccurate, but on the 3 S4's I've owned, only out by around 150rpm (oddly, mine all read low on the needle).

You can confirm the actual rpm using the digital dash. Put it in diagnostic mode (bridge terminals 13 and 5 on the diagnostic connector) and follow the instructions in the booklet "Diagnosis of the instrument cluster" on the Moorehouse DVD to read engine speed.

Or you can do it by using an automotive multimeter or a data logger by plugging it into the round diagnostic port by the passenger seat in pins 14 and 10 (rpm and ground respectively).

I'm guessing your idle is high and you've got a couple of slight intake leaks.

x98boardwell

Thanks for the insight everyone.

1) Yes, I do have the aftermarket cats still on working great.
2) When the plugs were removed it wasn't after a hard drive.. I was just replacing them to see what they looked like and hopefully help the smog issue. These were removed from the car when cold and sitting for a while. I actually started the car a couple times to move it in the garage but definitely not a hot ran plug by any means. The green corrosion on the plug top where it connects to the plug wire.. great catch Greg... I never even looked there as I was so focused on the other side.. hahaha Thanks, I will change for sure.

Now, for some engine work... finding these damn oil leaks and other items but she is running well and looking good.

Thanks again for all the help.

BC, yes this was the first test with a new O2.. which we now know the other one wasn't working.. at all. Actually in 2013 it appears as though it was fading some as the NO numbers were higher even though it passed, now look at them... very low and looking good.

BC

Replace some corroded wires per greg and look for that vac leak.

You will be surprised how quick the car can be if you get it running right. I know you think it is slow compared to the TT, but it can catch up.