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1989 blazer 350tbi, has no o2 sensors or cats.

J

jaybuller

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well i bought this truck a week ago and it runs good an all but i have engine codes of 12, 13, and 43. i crawled uder it to look for the 02 sensors and it has none. it has strait pipe dual exaust strait from the manifolds with no cats muffs or 02 sensors anywhere. now do i need to wire in some 02 sensors somehow to get the engine to run like it should? it seems to run fine just smells rich to me.
 
Yes, adding a O2 sensor will help with power and MPG.

If you have the stock manifolds then you need to get someone to weld in the O2 sensor bung at the correct location on the downpipe (just one). You may need a 4-wire heated O2 sensor if you have headers as it won't reach operating temp.
 
thanks yes it has the stock manifolds just strait piiped off the stock manifold collectors. i checked up and down both sides no o2 sensor anywhere. No my problem comes that there is no o2 sensor wire and i havent the foggiest where to wire it up to? also anyone know how far down stream in the exuast it needs to be away from the exaust manifold? also did these trucks come with cats from the factory?
 
I have a Y pipe from my 89 V3500 that has the O2 sensor bung welded in at the junction of the two pipes. If you want it, you pay shipping and its yours, gratis
I just pulled it last night, it's sitting outside my garage.
 
thanks but im gonna keep the dual exust i just need to know where in the pipe it goes(how far from the colector) and also did these things come with catalytic convertors stock?
 
Stick the sensor as close to the collector as you possibly can. O2 sensor need to be very hot to work properly. I'd highly recommend a heated O2 sensor for your truck if you have long tube headers.

Chances are, your truck would have had cats from the factory, but the TBI system doesn't know or care if it is there or functioning like the newer OBDII injection systems.
 
thanks guys, it doesnt have headers just the stock exuast manifolds so i should be good just to put it close to the colector. now just need to figure out where to wire it up into the system. also does anyone know if that exuast recycle valve that dumps into the aircleaner is nessassary for proper efficiant opperation? i would like to delete that if it wont affect the engines power or mpg it just doesnt seem nessassary to me.
 
I think its in the manifold on those ones isnt it?

I though my 88 K5 parts truck had it in the manifold anyways, I have headers now though.
 
jaybuller said:
also does anyone know if that exuast recycle valve that dumps into the aircleaner is nessassary for proper efficiant opperation? i would like to delete that if it wont affect the engines power or mpg it just doesnt seem nessassary to me.
Click to expand...

Hmm, are you talking about the A.I.R. diverter valve? If so, it does not dump exhaust into the air cleaner.

The A.I.R. system (assuming that's what we are talking about) pumps clean air into the exhaust system to aid in consuming hydrocarbons remaining in the exhaust gasses. It's harmless to performance or mileage.
 
If they are the stock manifolds, they have a port for an O2 sensor. They may not be stock to that Blazer.

Yes it had cats from the factory.

No air is dumped into the air cleaner, it is pulling air from the air cleaner.

Martin
 
it's common knowledge that she'll run better with a well designed single 3" exhaust. it's my understanding that anything you "delete" (like the EGR) from the operating system needs to be deleted on the chip too. why would you not want mufflers?

my guess is that it's running rich because it's constantly trying to "warm up". what thermostat is in there?
 
i want mufflers, im gonna go with flowmasters. i found where the o2 sensor should be. it is pluged off right in back of the driver side manifold above the colector. im gonna go buy an o2 sensor today and put it in and try and figure out what wire it hooks up to. also the air diverter valve is there and is functioning but i dont want it on there if i dont need it just one more thing to mess up plus i can hear it from in the cab when it opens up and blows air.... at least thats what i think im hearing. just driving down the road i hear somthing like loud air intermittantly when im at different throttle levels and rpms.
 
Be sure to get a heated O2 sensor, otherwise you'll have issues with those headers.
 
Jessie James said:
Yes, adding a O2 sensor will help with power and MPG.

If you have the stock manifolds then you need to get someone to weld in the O2 sensor bung at the correct location on the downpipe (just one). You may need a 4-wire heated O2 sensor if you have headers as it won't reach operating temp.
Click to expand...





So if i use headers i won't have any problems bypassing oxygen sensor
 
Or headers with an O2 sensor bung. You can also weld a bung into any set of headers. You should probably run a heated O2 sensor with headers though.

Martin
 
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