350 TBI o2 sensor

[squaredeal91]

This ones already got the thing welded in, assuming it’s the correct nut, new o2 should just go right in? Could no o2 sensor cause the issue cranking? Once it’s warm it seems to start right up but cold it cranks longer than my 87 by a mile and it won’t stay running unless it’s got a little throttle for a few seconds.

It's a shot in the dark but try unplugging the coolant temperature sensor (near the thermostat) and try to start it and see if it acts better or not.

 

[iamtherealJayy]

@squaredeal91 you see I considered that since I had an issue with the cts on my 87, but it’s below 30° today here in Tennessee, so I’m trying to come up with everything to do at once before going outside lol

 

[iamtherealJayy]

Alright so I bought an o2 sensor went to put it in and the bung placement is right in the way of the shifter linkage, so what now? Put a bolt in it and move the o2 sensor elsewhere? Find factory manifolds and put back on?

 

[squaredeal91]

If it were me I'd plug the hole and move o2 away from obstructions.

 

[iamtherealJayy]

Does orientation matter in the pipe? It’s at 12’ oclock on the collector at the bottom of the headers. I think I’m going to have to extend the wire by around 3” to have some wiggle room. It might reach but it’ll be tight. I can put it at 3oclock towards the middle of the truck if that would work or I can move it closer to the individual tubes If that’s better?

 

[squaredeal91]

I've heard some places work better than others depending on what o2 you have. I'm not certain where that is but I don't think it matters what position it is like 6 o'clock or 12 o'clock. It's It's more of how far up or down.

 

[bucket]

It's not critical, just somewhere near the merge point of the primaries and at enough of an angle that condensation doesn't collect in the sensor.

 

[Ricko1966]

No o2 sensor will do nothing until the engine reaches operating temp. O2 isn't a part of things until closed loop which you are never going to be in until you get an O2 sensor.

 

[Ricko1966]

Just read about being rich etc.check the cts. Check fir vacuum leaks,check engine vacuum if the cts thinks it's 40 below the computer adds lots of fuel. If you don't have enough engine vacuum the map sensor thinks you're in the throttle. And as for 18mm fitting 7/8 wrench 22mm wrench Jay when people refer to a nut, a bolt,a fitting,etc they are referring to the ID or OD not wrench size and usually they will refer to thread pitch. Example 1/4 20 bolt will be 1/4 inch 20 threads per inch. But cold be allen head, torx,hex,12 point so wrench dimensions don't stay constant. Bucket is right. 18mm 1.5 thread pitch.

 

[Scott551]

So same truck as my 700r4 thread.
1990 Chevrolet Blazer, original 350 tbi 127k miles. I got it and it cranked forever and idled super high. Rebuilt the tb and it idles fine now(has gasket was shot) if it’s cold it still cranks forever but you also have to give it just a little throttle or it stumbles and just stalls as soon as it starts. I believe I reset the IAC per procedure, jump ab on aldl, ign on 30 seconds unplug iac and remove jumper? I noticed when I bought it that it had headers, later found out that’s all it had, really didn’t seem all that loud for open headers lol. Anyways, it’s headman headers, clearly not super old because they aren’t completely rusty. There’s an o2 sensor **hole** in the drivers side collector. Would just a factory replacement work here? Is the o2 sensor super required? They’re cheap enough I’ll replace it and hopefully it’ll resolve my issue a little and make me get the best fuel mileage I suppose?
They’re long tube headers, I forgot to mention that. I’m working on getting the exhaust done but I need an o2 sensor or plug the hole

you need an o2 sensor man

 

[iamtherealJayy]

@Scott551 ive got it, gotta figure out what I want to do for exhaust and have a new bung welded in

 

[Bextreme04]

The O2 sensor MUST be mounted in the upper half of the exhaust pipe or it is going to get trashed quick. Anywhere from 3 o'clock to 9 o'clock in the upper half of the pipe is fine. I would also upgrade to a more modern heated sensor. They aren't hard to wire in and they have much better reliability and more consistent readings, especially with anything other than a stock engine and exhaust system.

 

[iamtherealJayy]

I purchased a direct replacement single wire, inform me on the newer style? I’ve currently got the truck gutted because the carpet behind the front seats kept getting wet, found out the rear seat floorboard is rusted up the whole way around the seatbelt mounts for front seats, I have no idea what was holding my seat belt in.

 

[Bextreme04]

I purchased a direct replacement single wire, inform me on the newer style? I’ve currently got the truck gutted because the carpet behind the front seats kept getting wet, found out the rear seat floorboard is rusted up the whole way around the seatbelt mounts for front seats, I have no idea what was holding my seat belt in.

modern=heated
Single wire is unheated and relies on the exhaust to get the sensor up to temperature. A modern sensor has 3 or 4 wires and is independently heated by an element in the sensor. This lets the sensor get up to temp faster and also keeps it a consistent temperature.

Three wire would be a direct replacement for the single wire sensor in the factory TBI system. A four wire sensor has the same three wires plus an additional ground for the sensor signal when you have an ECM that has a signal and reference signal.

The three wire sensor would have the same single sensor signal wire go to the TBI ECM and then would have a switched, fused 5 amp power feed to the sensor and a ground from the sensor to the battery.

 

[squaredeal91]

If need be I might have the heated o2 part number for my tuned port. I think its the same. Maybe someone else will know.