[the_bear]

Hi all,

I am a new member to the list, and the new owner of 1989 s10 blazer (4.3l). The guy who I bought it from had done some extensive modifications, some I am even unfamiliar with. The
mods are:

- new 4.3 motor (rebuilt?) with 10 k on it, 150 k on truck
- eldebrockheaders, with flowmaster duall exhaust 2 1/4"
- elebrock aluminum intake
- new fuel pump, stock
- custom grind 268H CompCams Camshaft
- 670 cfm holly throttle body
- k&n filter
- custom made fastchip to work with add-ons
- and under-driven pullies (whaterver that is)

The problem:

Code 13 - Oxygen sensor circuit. The ECM throws this code after a bit of driving, often well after the 2 minute start up loop. Comes on the soonest once 50mph is exceeded, much slower if speeds are kept under that level. The SES light does automatically come on during startup, but the conditions seem to have to be met every time it is driven for it to appear. In short, when the vehicle is shut off it goes away (although it stays in the ECM memory, of course).

As a result, I think I am thrown into "open loop" mode when this code occurs (remember it comes on every time at highway speeds) so my mileage and power on the highway stinks. Very noticeable lack of power/gas guzzling.

The question:

According to Haynes, I should replace the 02 sensor. I did that, with absolutely no change. I didn't think it would, as the old sensor seemed to work for the period every time prior to the light coming on? At any rate, I don't suspect it is either the 02 sensor or it's harness, after two sensors.

This is where I get lost. Haynes also talks about the TPS possibly causing this code, if it is broken or something. Wouldn't that throw TPS codes as well then?

Could this code 13 also be caused by some kind of temperature related matter with the 02 sensor? What should I check for the TPS?

Could the custom programmed chip have anything to do with this?

I am at a frustrated loss. Anyway, if you are still reading after all of this rambling, and have any thoughts/ideas/suggestions it
would be really appreciated!

Thanks,

Scott

 

[Tha_Boom]

k I remember someone saying about headders keeping the o2 sensor too cool sometimes. it has to be a certian temp to operate correctly a easy fix is to get a 4 wire o2 sensor and use it since it has a built in heater you will have to make a harness for it but it should fix the problem if it is that.

also the o2 sensor is ignored untill the engine has warmed up. thats probably why its not comming up right away.

oh a quick way to see if the o2 sensor is reading lean and rich conditions is to jump the aldl the same way that you get your codes and run the engine. the check engine light will flash randomly when it is on the o2 is showing a rich condition and when off it is showing a lean condition. if it is hangin on one or the other there is something messed up with the sensor or wireing to it.

I am not sure why the tps is said to possably be the problem but it might be worth looking into if you cannot figure it out.

Any other questions just ask!

 

[the_bear]

02 sensor aldl test

Tha_Boom,

Just to confirm the details of the 02 sensor test...

When the engine is hot (so it shouldn't be in open loop mode), I jump the aldl, then turn on the engine while still jumped? If so, then if the SES flashes randomly everything is ok with sensor and harness, but if it hangs on steady or not at all - there is a problem with the sensor or harness.....correct?

Thanks again for the help! BTW, are there instructions posted somewhere on how to construct that multiple wire 02 harness?

Thanks!

Scott

 

[Tha_Boom]

ya thats pretty much it with that test. light on = rich. light off = lean. and it should go back and forth.


oh just thot of another thing. check and make sure your headers have a good ground since the one wire sensor uses the exhaust system as a ground. just check with a ohm meeter between exhaust and a good ground on the truck you should have little to no resisance.

 

[the_bear]

o2 sensor test

Tha_Boom,

Ok, and one last thing.....should this be done with the engine hot, or does it matter? I think I jumped the diagnostic port once by accident when the engine was not at running temperature, but running nonetheless; and it immediately began to idle VERY erratically....so I immediately unhooked the jumper. Is that normal?

I had thought about the grounding thing, and will test it tomorrow. I assume the engine should be running when the resistance is tested? How many ohms would be acceptable?

Thanks again,

Scott

 

[Tha_Boom]

Re: o2 sensor test

Tha_Boom,

Ok, and one last thing.....should this be done with the engine hot, or does it matter? I think I jumped the diagnostic port once by accident when the engine was not at running temperature, but running nonetheless; and it immediately began to idle VERY erratically....so I immediately unhooked the jumper. Is that normal?

I had thought about the grounding thing, and will test it tomorrow. I assume the engine should be running when the resistance is tested? How many ohms would be acceptable?

Thanks again,

Scott

ok yes it will run bad at any temp with that jumped it is because its in diagnostic mode.

the grounding thing no it shouldnt really matter if its running or not. but maybe you wanna try it hot and cold to see if its maybe an expansion problem. as for resistance i would say as close to none as possable is best. as for an ammont i couldnt venture a guess off the top of my head.

its no problem thats what we are here for!

 

[TECHRF]

I would also look to see what temp t-stat is in the engine or if there is one. the factory is 195* , if a 160 or lower is in ther at hiway speed the engine is running too cool . go to 180* and see what that yeilds. at the very least check it.
just my $.02

 

[wis bang]

get some input on the chip

Try to get info on the chip, some are made to work w/ lower temp t'stadts.

 

[the_bear]

More info...but what does it mean?

Hi guys,

An update on my code 13/02 sensor delema:

1. At this point I am certain the both the 02 sensor and the 02 sensor harness are ok.

2. Chip is a custom fastchip. I believe it is made to work with 160 degree thermostat. Confirmed with previous owner that infact that is what has been placed in the truck ....160 degree unit.

3. I am almost certain at this point that when driving on the highway, the cooler exhaust gases in the larger headers, coupled with the increased cooling flow over the header where the 02 sensor is located, is dropping the operating temp of the 02 sensor below the required 600 degrees. Thus tripping the code 13.

Does this make sense or sound possible? In addition, does anyone have any suggestions on how to deal with this problem?

Header Wrap?

O2 Sensor replacement with heated unit? (if so, is there a conversion kit for sale, or instructions on how to mount one?)

Thanks guys for the continuing help!

Scott

 

[TECHRF]

if you can get the specs on the chip or pull it out take down the #'s off it call fast chip and see what they can tell you. it can never hurt to call .

 

[Tha_Boom]

heated o2 is probably the best way to go there isnt much to the wireing for em they typicaly have 4 wires two are power and ground for heater and 2 are for the o2 function 1 being ground and the other being the singal wire. I will look around in my bookmarks for a pinout of the sensors. I am almost certian that all o2 sensors have the same threads so you wont have to modify anything special for that. the only specail wireing ya are going to encounter is finding a key on power wire somewhere to power the heater and the two grounds can be put together and the sensor wire hooks to the lead to the computer.


but wraps might help with the problem also.