O2 sensor issues and error codes

[JSSuper455]

This might be a little bit long with explanation but bare with me.
I'm working on an intermittent check engine light issue that is getting more frequent and longer intervals. I get a check engine light after the car warms up and I drive for a while maybe 10-20 minutes the light will come on. Some times it stays on for a while and some times not so long. If I shut off the car the light stays off for a while then comes back on.

Now, this same issue started to appear not long after I switched to a O/R H-pipe. I decided that I wanted to update the MAF and I figured that the O2's were very old as well so I replaced them. Now, some years later its started to do the same thing again and is much more frequent.

The KOEO codes show 41 & 91 in the CM. I've installed a 190lph pump and 3G alt, cleared the codes and drove the car. No more than 15 minutes into the drive it popped a 'CE'. I drove home and just as I pulled into the driveway the 'CE' turned off. I ran another KOEO and came up with 41 & 91 in the CM again.

Fuel pressure is better now with the 190lph, its right on 38psi at idle and increases to 40psi as the engine revs.

My question really is around the O/R H pipe. Would that shorten the life of the O2's since there isn't the backpressure from the Cats? The reason I ask is that I'm not sure what good O2's look like, but I pulled mine out and there is a whitish powdery film around the sensor tip until the bottom of the sensor (top of the threads) in that area its black & sooty.

BTW, this issue really has been in the last 3 months or so. The MAF I installed at the same time as new Bosch O2's is the C&L 76mm with 19# tube for my stock injectors. I cleaned the injectors when I did the intake change back in 2002.

Now I've searched the threads and found jrichker's post on 91 and 41 codes. I've checked my wiring over and everything looks good from that angle. Just to be safe however I did clean the plug with electronic parts cleaner. So I'm looking at the O2's directly and then vac leaks, but I doubt its a vac leak (I won't totally rule that out, but 1 thing at a time.)

So do those white powdery O2's sound right for older O2's? I was thinking I would try to clean them with the electronic parts cleaner, but not if they are shot. Is my thinking correct, in that the O/R H is contributing greatly to a short lifespan for O2's? And finally the C&L MAF, can these cause a lean condition or rather have any of you had trouble with the C&L making the car run lean? Or do I have something else wrong all together?

 

[srothfuss]

How long did you have the Bosch sensor's in the O/R H-pipe?

I wonder if aftermarket sensors have a shorter lifespan. OEM parts should last for 50,000 - 60,000 miles.

 

[Michael Yount]

I don't think the lack of cats will have much impact on the life of the O2 sensors - at least not if mine is any indication. It has never had cats -- I replaced the sensors a few years ago when I added the performance parts. Never had any problem with them.

Every used O2 I've ever seen is flat black/dark brown - pretty much like the inside of the tail pipe. How many miles do you have on them? How many miles on the motor/what kind of shape is it in? As motors begin to use more oil -- that is harder on the O2 sensors and shortens their life. Have you done any work recently where an engine assembly product (silicone for example) or some other fluid might have been ingested that damaged the sensors?

 

[JSSuper455]

I thought white-ish sensors was odd.

They have approximately 18-20k miles on the sensors. I changed them close to 3 years ago. The engine is great mechanically for 140K miles. It doesn't use much oil for that many miles at all, approximately 2/3ds of a quart in 3,000 miles. There isn't any fuel in the oil or antifreeze being burned, atleast I don't see the stuff dissapearing quickly and no white smoke out the exhaust.

I change the oil at regular intervals and I'm very particular about maintenance.

So is it possible, with all the air intake and exhaust pieces, the car requires 24# injectors? I now have 76mm C&L MAF, 70mm tb/EGR, Trickflow street heat intake, silencer removed, O/R H, etc. I also have a new set of BBK ceramic shorties to go on, but I'll fix the 91&41 first. I figured that still having the stock heads I'd stay with the 19# until I had the E7's ported/polished or installed aftermarket heads and at that point I'd install the 24's.

 

[srothfuss]

How about the fuel pump? Maybe yours is causing the lean condition in the upper RPM range of your car. Do you have a FP gauge to check pressures?

 

[jrichker]

If you read my 41/91 code post, re-read the part about using a voltmeter to check the output. It may give you some more clues.

I would also clean the MAF element and/or swap the sensor for another one if you have access to a spare.

 

[JSSuper455]

Srothfuss- Originally I figured it was the fuel pump in upper RPM range because I had the original pump still and it seemed weak with only 36psi at idle and dropped to 30-32 when I revved the engine. I just installed a 190lph pump and now pressure is 38psi idle and increases to 40 as I rev the engine. I did a test run with cleared codes and still got 41/91, however the damage could have been done to the O2 sensors at this point and they might be shot.

Jrichker- I'll test them and clean the MAF, then switch back to original MAF for testing.

BTW, as a side note.. I've been having trouble with it maintaining idle. There are times when the car idles very low at 550-ish rather than the 750-800prm. I think I may have a problem with my idle air control. I don't think its directly related to my lean condition, but I'm going to fix it because its directly related to an ANNOYANCE!

Thanks for the help :SNSign:

 

[Michael Yount]

It sounds more like an maf issue than an O2 issue to me....just guessing though. The 19's with the larger pump should deliver enough fuel with no problems. In any event, a lean issue would likely only show up at w.o.t. if it was an injector or pump capacity issue. Your CEL is showing up in normal street driving when you're nowhere near w.o.t. most of the time.

 

[JSSuper455]

It sounds more like an maf issue than an O2 issue to me....just guessing though. The 19's with the larger pump should deliver enough fuel with no problems. In any event, a lean issue would likely only show up at w.o.t. if it was an injector or pump capacity issue. Your CEL is showing up in normal street driving when you're nowhere near w.o.t. most of the time.

Thats very true, I rarely go WOT and the CEL will come on when I'm just loping along.

I've got a little time now so I'm going out to the shop to take the MAF out and have a looksee and do a little cleaning.

 

[Mike92GT]

If you're getting codes for both o2's, it often times is a mass air problem. Another possibility is a vacuum leak, or un-metered air getting in somewhere. Do you have any breathers on your valve covers, modifications to your PCV system, or anything like that? Just trying to throw some ideas out there...

 

[JSSuper455]

I'll take any and all ideas, and no I havn't modefied anything like that. Though I can see why that would cause the issue.

But I did just take the MAF out and even though the inside of the MAF itself was clean or appeared clean, the metal prongs and filiments in the sampleing tube were black. I cleaned them out with eletronic cleaner and they cleaned up good. That very well could be a major contributor to the problem since it can't possibly read the amount of air correctly. Also is there any truth to the rumor that I have to turn the sampling tube around backwards? Its the same way that it came from C&L but I heard I should turn it around so the curved end of the tube is facing the throttle body instead of the filter.

I'll post results to the issue when I get it back together, if it doesn't work I'll switch to the OEM unit for testing. It'll take me a while because while I have that all apart I'm going to install the headers. I'll post back in when I know more