slight exhaust leak throw code 44?

[Blazer406]

I am trying to help a friend with an '87 GN. DS shows O2's to hover in the 200 mv range almost fixed and not moving while idling at operating temperature.... in closed loop. After a short period.... it goes into open loop and idles rough....immediatly it throws a code 44 (lean exhaust) ... but sounds rich..... but o2's show lean... BLM's are high around 150 too..... which tells me the ECM is adding fuel to compensate for the lean condition it thinks it has. My ear says otherwise..... It does have a slight exhaust leak at the connection close to the O2 sensor. Could it be sucking in air inbetween exhaust pulses.... cooling the sensor down.... and feeding it oxygen that didn't go through the engine..... causing it to think it was lean? ....... ?? We have tried many things.... but this seems the most promising theory.


O2's and x-counts seem to do ok ... while driving down the road..... just idling they go crazy.....

 

[salvageV6]

What chip?

Fixing the leak would be a wise thing to do regardless.

 

[Blazer406]

The chip is stock....

We put my stock chipped ECM in there to rule out a faulty ECM/chip. Nothing changed with my ECM. His is a stock chipped reman ECM.

 

[Blazer406]

ttt

anyone?

 

[6=8]

I've had serious leaks before and never once a code 44. I think you have other issues causing this. (But still a good thing to fix... Runs so much better with a tight exhaust!

As far as "Sucking in air" goes, that seems very remote to me. My opinion is that the exhaust system is pressurized, and not moving fast enough at idle to create a "vacuum." If you see black soot/carbon around the crack, the pattern will probably show its on its way out, not in.

Is it more likely that the O2 is getting weak? Either getting blasted with hot exhaust externally, or damaging the wire to it? Maybe the crack itself internally extends around the bung and the sensor is not getting a good ground?

The CC's at idle should take less than 90 seconds to count from 0 - 255...

Hope this helps a little!

 

[Blazer406]

It's odd..... the car just sounds super fat (rich)... idling.... O2's seem to not move..... around 150-250 mv.......cross counts not hardly moving at all........ (all this is at operating temperature... idling ... in closed loop). BLM's runnin 150...... and all of a sudden... (almost simultaneously) ...it stubles.....goes into open loop.....and throws the code 44......

You can race the motor up to 3000 RPm's or so... and it goes back to closed loop.... and repeats the process......

IAT seems fine.....
CTS..... seems fine.......
MAF seems to function like you would expect....
I reset IAC's and TPS..... per "how-to" on gnttype board......
fuel pressure is about 43 psi vac line off.

 

[moodym]

Might check for a crack in one of the hoses on the vacuum block on top of the plenum.

I had a problem like that. Seemed rich but would light up the service engine light at idle. Changed all the hoses and problem went away.

Mike

 

[SinistrV6]

It's a long shot, but...

My '86 GN threw a Code 44. After extensive searching, I remembered that it started shortly after installing an aftermarket, brass, positive seal PCV valve. I pulled it out, put a stock one in and Voila! no Code 44.

My best guess was that the stock PCV was accounted for in the air metering by the factory ECM and the aftermarket one just flowed too much. Not saying it makes sense, but it worked.

 

[Blazer406]

My '86 GN threw a Code 44. After extensive searching, I remembered that it started shortly after installing an aftermarket, brass, positive seal PCV valve. I pulled it out, put a stock one in and Voila! no Code 44.

My best guess was that the stock PCV was accounted for in the air metering by the factory ECM and the aftermarket one just flowed too much. Not saying it makes sense, but it worked.

I do remember seeing a small K&N style filter on the front of the pass side valve cover. Mine has some black plastic thing.... I assume mine is stock... and his is not. I'll tell him to go back stock with the PCV thing and check the vacuum block like moodym says.... and give that a try.

I tend to agree (after thinking about it a little) with 6=8 that the exhaust leak.... shouldn't cause the exhaust to register lean......

Supposedly tho O2 sensor was changed out recently.... but we bought another one anyway... to rule that out.......


If it makes any difference, his car has also been converted to vacuum brakes.... It used some vacuum brake conversion kit... and just a regular n/a regal master cylinder/booster.

 

[SinistrV6]

Vacuum brakes would just add places for a vacuum leak to occur. Check all of that. That K&N at the front of the valve cover isn't what I was referring to. The PVC valve goes into the intake, next to the passenger side valve cover.

Let us know if you get it fixed and what worked.