ShevrolayZ28

iTrader: (4)

Has anyone ever discussed our insufficient switching issues with the manufacturers?

I called Bosch USA and had a description of my problem forwarded to a tech person who will be calling me back within the hour.

I'm going to ask if they have a heated o2 sensor that is more suitable for being positioned further downstream. I guess this would be a sensor with a more effective heater.

Currently I am running recently installed 13111 rear Corvette sensors and they are switching so slow that they set codes on both banks.

While I have their ear, are there any other questions I should ask?

2xLS1

iTrader: (25)

Hope you get someone trained in actual tech and not just OEM replacement parts. Ask if the 13111 sensors actually have higher wattage heaters in them than the sensors with shorter leads, or if it is just internet myth.

ShevrolayZ28

iTrader: (4)

Will do. But I have a feeling that is only Internet myth.

ZL1Killa

iTrader: (17)

ShevrolayZ28, when did you start getting this problem? and corvette sensors don't work worth a damn, so noone go down that route ever again.

some people their oxygen sensors just die. I have noticed a LOT of cars where it is the injectors fault. you replace the stock injectors with something bigger as you need more fuel, and you forget to also correct the injector offset table, and def and min pulsewidth , as they are different injectors with different characteristics.

i have the insufficient switching crap happen multiple times. I had 36.5# injectors from Delphi/Luca (bought from racetronix.com). installed them. then about 1-1 1/2 months later (probably due to me tuning and changing the car for the time being so long) i started getting p1133 code, and p1153 code. so i started looking back at my logs.
sure enough my 02's were lazy as crap. so i thought back, well the only thing i changed was the injectors. so i start talking on the net here and find out oh, replace your 02's with vette ones... DIDN'T WORK (not saying it won't for you, or even replacing with factory trans am 02's) BUT i decreased the injector offset table by about 15% (multiplied by -15%) . turned on the car and drove around and logged. 02's were back to normal operation and possibly reacted better than before

ShevrolayZ28

iTrader: (4)

I just got off the phone with a nice gentleman from Bosch. I described our problem as insufficient switching and told him which modifications were done to our cars in general, and more specifically, about the LT headers. He sighted two likely causes for the problems we are having. No surprises here, he said that it's likely that the sensors are not getting hot enough, and that this is caused by the sensors being further from the heat source, and also due to the increased gas velocity, which, of course, is a product of high performance exhaust. OK, I think we knew this.

He made a couple suggestions on what would help get them hotter. Again, no revelations here. He suggested wrapping the headers to help retain heat and if possible, positioning the sensors closer to the heat source. The former has been tried and to my knowledge, has not been effective. The later is not reasonably possible unless we tap into a single pipe, and that presents us with a whole new host of problems in itself.

He did shed some light on some of the issues at hand. First off, he said that the heaters in the front sensor are the same as the heaters in the Corvette rear. However, there is a difference in the baffling of the sensors and that the baffling does effect the temp they run at, and due to this difference he thought that the rear Corvette sensors, when used as fronts, would be at an advantage over the fronts.

So in the end, he doesn't think there is a plug-in solution to our problem. He suggested that some PCM reprogramming will be needed to correct the problem. He recommended that I contact a place in Minnesota called Tuned Port Induction. He said that they are quite knowledgeable on this issue.

Unfortunately, I don't have time to call them now. If anyone wants their number, please PM me.

ShevrolayZ28

iTrader: (4)

I experienced the insufficient switching shortly after installing the LT headers.

There's another thread in this section where a member reported some success with PCM changes that he had made. Let me see if I can find it and I'll post a link.

ZL1Killa

iTrader: (17)

so how long before that did you change injectors?

2xLS1

iTrader: (25)

In reality, the best solution for 1133 and 1153 is to just turn them off. You still have all the other front O2 codes to let you know if there is a real problem with them like a heater going out or a sensor just dieing.

ZL1Killa

iTrader: (17)

if you turn them off, your car goes into open loop and you don't know it unless you have a wideband setup to see it.

i'm saying if you have new injectors, that more than likely is the fault. I have yet to run into cars that have the insufficient switching issues due to something other than the offset table. it could take a while for the computer to see whats going on a realize it, as you go from stock to new injectors by just adjusting the IFR table.

also other tuners i know haven't had issues with this. ShevrolayZ28 give the offset table a try. let me know. i have already fixed more than a couple cars on this issue, at least give it a try and let me know if that is your problem or not.

ShevrolayZ28

iTrader: (4)

This is OK if you're just trying to pass state inspection, but what about the loss in performance caused the slow switching? Have you tuned around that?

ZL1Killa, I'm still running stock injectors.

Check out post #27 in this thread, where Sidestep presents some PCM changes that helped him out. Is what he did similar to your adjustments, ZL1Killa?

https://ls1tech.com/forums/showthrea...9&page=2&pp=20

ShevrolayZ28

iTrader: (4)

Here's my scenario FWIW. I installed a lid and headers and soon after I got the p1133 and p1153 codes. Then I replaced the stock sensors with the rear Corvette Bosch sensors. Soon after that the codes came back.

I installed a HC combo and a number of associated bolt-ons and then put about 100 miles on the car with the stock tune. I then had it dyno tuned via EFI live by a local guy that has tuned hundreds of these cars and has a good reputation. While doing the tune he noted that the sensors were switching slowly. Sure enough about fifty mile later, after the tune was completed, the codes were back.

2xLS1

iTrader: (25)

How does it make the car go into open loop if they are set to No Error Reported?

What loss in performance and be specific?

ShevrolayZ28

iTrader: (4)

I called Tuned Port Induction Specialties and they said that they just shut the codes off. They think that as long as the sensors aren't flat lining, we should be fine. (Of course if they are flat, we should replace them.) They also mentioned that sometimes the threads on the sensors are too long and that this prevents the sensor from getting far enough into the exhaust stream to be effective.

2xLS1

iTrader: (25)

What they meant was that sometimes the O2 bungs in the headers can be too thick keeping the sensors from protruding into the exhaust stream far enough.

ShevrolayZ28

iTrader: (4)

I'm the one that should be asking the questions lol. I'm just a guy that's looking for answers, I'm no expert.

I don't know specifically but I would assume that trim levels are not being adjusted as quickly if the sensors are switching slowly. Perhaps it is insignificant from a performance perspective. IDK.

If it is programmed to "no error report" the car does not go into open loop mode?

FWIW, my car feels like it's running OK (Seat of the pants-o-meter.) even with the SES illuminated and the p1133 and p1153 codes set, but I do hear a little popping or gurgling that I don't think was occurring when there is no code set.

I misunderstood the thread comment that the guy from TPIS made. Thanks for clearing that up. I thought he was saying there was too much thread on the sensor, which did not make sense. The bungs on my headers are fine, they do not extend into the pipe, and the sensors poke out a good ways into the exhaust stream.

So I guess I'll go along with your recommendation and have my tuner set these codes to "no error report". Perhaps it's time to spend some bucks so I can keep an eye on things with a gauge and a wide-band sensor.

2xLS1

iTrader: (25)

You have to understand that a lot of the tests the PCM is constantly running are for emission purposes and don't have a lot to do with performance. The OBD2 specs dictate that. Yes, you can have codes set that indicate a bad component that will effect performance, but a lot are just warning that the car may be polluting more than the stock design intends. I'll tell you that I've set those codes to NER on several cars with no ill effects as long as those cars were not setting any other front O2 codes. It seems cars with SLP headers seem to be the worst for some reason. I feel if the sensors are really lazy enough to cause trimming issues, you would probably be setting P0133 and P0153 codes too.

ShevrolayZ28

iTrader: (4)

Alright man. Thanks very much for your help.

ZL1Killa

iTrader: (17)

if you turn the codes off, then your computer just doesn't set an SES light... it will still function and cause open loop.


I want you to try something that will NOT hurt your car in anyshape or form. i have posted my results and trying to help ya, thats all i can do. I do know about some headers not having the 02' stick 'in' far enough

2xLS1

iTrader: (25)

I disagree. I believe you are mistaking No MIL Light for No Error Reported. There has to be an error reported for the computer to cause an effect of that error.

Viper

iTrader: (6)

Obviously header design has a lot to do with it. I used to have FLP headers for 3 years, and replaced O2 sensors 3 times in as many years, always with stock as this was 2000-2003, before we all knew or tried the Bosch. The I got Stainless Works headers, bought the Bosch units and haven't had a single issue since late 2003. They also have both bungs on the inside whereas (if I recall) FLP had one in, one out, AND further down the pipeline.