TBI emissions control adventures

[Coal creek Chris]

Been reinstalling/replacing various emissions control parts on an 89 7.4L TBI where a previous owner had removed the AIR pump/pipe/valve system, cat, 02 sensor and various TBI vacuum lines were incorrectly hooked up. These parts are all back in. The AIR pump/parts were used but the cat, O2 sensor and vacuum lines were new parts. The Service Engine Soon light comes on and off intermittently once it is warmed up, usually after 20-30 minutes of driving. I get code 13 for the O2 sensor and a noticeable sulfur/egg smell. I don't get the service engine light or the egg smell at startup and while the engine is warming up, just after it has run for a while.

I have several questions.

My understanding is that the AIR system only injects air while the engine is warming up rather than continuously, is that correct?

Since the O2 sensor is new, are there other likely causes for Code 13? Guessing a still overly rich mixture could do this even if the O2 sensor is fine?

When the service engine light comes on for Code 13, does the AIR system re-engage and inject air? Might that be the reason the light goes on and off and back on, basically following the AIR system going on and off?

I operate this truck at high elevation, usually between 8,000 and 9,000 feet. Might there be elevation reasons for the O2 sensor code, or other fuel system/AIR system limitations?

Any thoughts and suggestions welcomed. Overall the truck runs well, just would like to get the service engine light to stay off and to solve the stinky smell.

 

[bucket]

Is it a Bosch O2 sensor?

 

[Coal creek Chris]

Denso

Should I get a Bosch one and try it?

 

[bucket]

Nope, Denso is good. I've disabled a lot of AIR systems and never had a single driveability issue because of it, so I doubt your AIR system has anything to do with the problem if it's all fitted properly. My hunch is that the engine is running rich for another reason and the ECM thinks the O2 readings are faulty because of it.

Unless the new sensor actually is bad, but that would be surprising for a Denso.

 

[Rusty Nail]

I operate this truck at high elevation, usually between 8,000 and 9,000 feet.

Any thoughts and suggestions welcomed.

This !

Yeah other things..
A vacuum leak at the TBI can cause that.

Verify correct/proper EGR function and PART NUMBER.

ALSO...!

(this is probably it) HEAT CROSSOVER.
#3,5,4, or 6.
Vacuum leak.......bad intake manifold gasket. You could try re-torquing it but that wont fix it. You have a bad intake seal you cant see. I bet its shot between two cylinders...lemme know but dude...

Post a pix ffs.

 

[Coal creek Chris]

Thanks. The Denso sensor has maybe a couple hundred miles on it so it is really new.

It would be a bummer if the intake manifold is leaking.

 

[1987 GMC Jimmy]

When I’ve gotten Code 13, unless the O2 sensor is absent, I’ve gotten either Code 44 or 45. You haven’t gotten these? I’d like to see what temperature the CTS thinks the engine is vs. what it actually is. If you have elevation concerns, it’s the MAP sensor’s job to factor that in, and it wouldn’t hurt to test it, although I don’t see any reason to suspect it at as your culprit at this time. Maybe it’s just a bad O2 sensor. Is it out of warranty? What’s the injector spray pattern looking like? You’re not dripping are you?

 

[Coal creek Chris]

O2 sensor only cost about 10 bucks, so not very expensive. But it only has a few hundred miles on it. The injector spray looked ok, but I'm not exactly sure what is it supposed to look like. I did notice a few slow drips from one injector after the truck is shut off. It would drip a little bit, then stop, then drip a bit more. I thought that was how it depressurizes, but could be wrong.

Just checked the codes again and I'm only getting 13.

When I replaced the O2 sensor I also had to crimp on a new harness side plastic connector. It had been cut off. Any issues with using those aluminum butt connectors for that?

 

[1987 GMC Jimmy]

It’s supposed to a cone-shaped, fine mist. If you’re noticing a drip after shutdown, it’s probably as bad or worse when running. All depressurization that occurs should be within a closed circuit not like that. Just curious, is the drippy injector on the driver side bank with the O2 sensor? The injectors should have around 1.2 ohms resistance on the lowest DVOM setting. If they have that or real close, the coil’s probably okay, and you’ll need to send the injectors off to be cleaned and flow tested. Appreciably cheaper than buying new ones.

I’ve done the same connector surgery; it worked fine for me.

 

[Coal creek Chris]

It was the passenger side injector, opposite the O2 sensor. In general, yes they are spraying in a cone shape, almost appears like it is pulsing when you look at it from certain angles. Maybe the extra drips are causing it to run overly rich/uncontrolled? Might that lead to a code 13 if it is dripping while it is running? I'll take a closer look while its running to see if I can see drips in addition to the spray.

Your post reminded me of something else that I thought would be unrelated. There is a white wire on the top of the ignition coil that is cut, I can get a photo later. I have wondered if that may be a problem but have not spent time on it. This was a farm/ranch/work truck so lots of things were probably "fixed" just to keep the thing running, rather than being done correctly. Part of the fun actually.

 

[Bextreme04]

Any highly sensitive circuit like that which is exposed to the elements should be soldered and heat shrunk at a minimum. You might get lucky and not have an issue right away, but having the connectors open to the elements will allow them to corrode and butt connectors in general are not very reliable. Leaking injectors on shutdown will cause hot start issues as well. They should definitely have NO leakage when the engine is off. Fuel pressure should ideally not leak down at all.

 

[1987 GMC Jimmy]

Yeah, those extra drips are not enough to result in vehicular Armageddon, but it’s enough to push you over the edge into being too rich. I would ohm them out and see what’s going on there first. It’s not a big deal if there’s crud in them allowing them to stick open a little. If the injector coil itself is weak, it’s time for a new injector.

 

[Coal creek Chris]

Well, thanks for the help all. I attempted the emissions test today and failed, but not by much. Just over the requirements for HC and CO. Guess I'll have to tinker around with it some more.

 

[Bextreme04]

also, if you had cut O2 sensor wires, make sure you have the right sensor connected for the right side. Also, you might have had 2 bad sensors and having only replaced one sensor you might still have the same code because the other sensor is still bad

 

[Rusty Nail]

Part of the fun actually.

This is why we buy old trucks.
Still no pix tho.
Cool points -1