Freaking lean code 44

[Dont fake it break it]

Freaking lean code on my 87 5.7 TBI has been plaguing me for years. There doesn’t seem to be any rhyme or reason to it. Sometimes I’ll go weeks without seeing it. Sometimes it will come on while the truck is idling at warm-up. Sometimes it will come on after driving for a minute and stay on, or go off. Sometimes it won’t come on until I’ve been on the road for a few miles, or a few hours. Sometimes it comes on when I drop from 55 to 35. Sometimes it will come on if I stay at 45 too long. It used to always go away if I mash the gas, and now sometimes it won’t. Sometimes it comes on just when the wind blows. New fuel pump measured 13 PSI at the chassis mount fuel filter. Couldn’t manage to get the adapter and gauge hooked up at the throttlebody. New O2 sensor but old connector to ecu. Couldn’t find one online anywhere that leads to the computer, only the side connecting to the sensor. New map sensor. New throttle position sensor. New every other sensor imaginable. Fresh top end rebuild at home with professional valve job and adjustment. New injectors and throttlebody rebuild kit. Here’s a funny thing. Never had a real running rich code before until I was messing around trying my own on valve adjustment. Got it dialed in a little better with no codes. Took it in for a smog and failed for excessive CO2, running rich but with no codes. Since getting the valves adjusted at a shop, now it runs lean more than it ever has before. Did a voltage test back propane the O2 sensor and it looked good. Tested the map sensor and it’s also got the right voltage. Tested the coolant temperature sensor and the resistance matched the thermostat. Replaced it anyway since it was old. No change. I even disconnected the knocks sensor thinking maybe it was playing with the timing because of something I read. I’m open to any thoughts or ideas… I mean anything. I am running around on a two month expired, two month extension from December. LOL. I’m desperate and sick of driving in my mirrors.

 

[Wes Harden]

re-torque your intake and tbi. The EGR could be leaning out at cruise, and or have a little it of crap keeping it from seating fully on de-cell. Is the exhaust factory? sometimes the o2 placement can cause it to cool down at certain speeds. Early CCC systems had this issue, by 87 I think GM was pretty good at keeping the o2 out of the breeze. I didn't think there was a CO2 limit, and I am not seeing how valve adjustment is changing the air fuel ratio. Unless the valve where to tight and not closing, but it would have run like crap.

 

[dyeager535]

I'd be looking at EGR as well. Constant throttle relatively low load cruise, or decelerating from cruise, is within the realm of the EGR.

These things like to carbon up, and I'm not sold on aftermarket replacements of them. Personally I'd remove and inspect, cleaning out the passageways and making sure the EGR operates properly...moves smoothly, and holds vacuum.

Theoretically you can "field test" the EGR by lifting up on the diaphragm when it's idling to see if the idle changes (it should stall if you open it enough) and it should go back to idling normally after you release, but I'd not think this to be a 100% reliable test.

 

[Dont fake it break it]

re-torque your intake and tbi. The EGR could be leaning out at cruise, and or have a little it of crap keeping it from seating fully on de-cell. Is the exhaust factory? sometimes the o2 placement can cause it to cool down at certain speeds. Early CCC systems had this issue, by 87 I think GM was pretty good at keeping the o2 out of the breeze. I didn't think there was a CO2 limit, and I am not seeing how valve adjustment is changing the air fuel ratio. Unless the valve where to tight and not closing, but it would have run like crap.

Yeah I hear you on retorquing the intake and had done that after the first couple days but I’ll check it again. The EGR is relatively new and the diaphragm was working properly when I checked it during rebuild. The exhaust is stuck on the driver side and a stock replacement on the passenger side. I thought about replacing the driver side in case there was a hairline crack but couldn’t find any with a pretty good inspection although I can get a little backfire when I mash the gas in the park. When the shop did my valve adjustment, he did tell me that some were tight and some were loose and yeah it did kinda run like crap and I don’t even worse. That’s why I had it professionally done.

 

[Wes Harden]

Your truck has Air injection? The check valves on the air injection tube, will cause a back fire if they are leaking.

 

[Dont fake it break it]

I'd be looking at EGR as well. Constant throttle relatively low load cruise, or decelerating from cruise, is within the realm of the EGR.

These things like to carbon up, and I'm not sold on aftermarket replacements of them. Personally I'd remove and inspect, cleaning out the passageways and making sure the EGR operates properly...moves smoothly, and holds vacuum.

Theoretically you can "field test" the EGR by lifting up on the diaphragm when it's idling to see if the idle changes (it should stall if you open it enough) and it should go back to idling normally after you release, but I'd not think this to be a 100% reliable test.

Two votes for EGR means I’ll check it again. I’m also a little sketchy on vacuum. Well I may be able to test a map sensor or EGR with my vacuum gauge, but not sure how to verify if achieving the right amount of vacuum in general at idle or during operation. I’ve done the whole carb spray test and never gotten any change in idle even after coating my engine bay with carb cleaner. Thanks.

 

[Dont fake it break it]

Your truck has Air injection? The check valves on the air injection tube, will cause a back fire if they are leaking.

Yes it has Air injection. I sucked and blew (stop laughing) on the check valve and it seemed to operate as a check valve should but I have one on the way anyway because I’ve never replaced it. I also haven’t checked or replaced the injection diverter valve for lack of knowing what to do about it.

 

[Wes Harden]

there are 2 check valves. I am having trouble remembering the air flow strategy for the diverter valve. Iirc air from pump should go to air cleaner at idle, and to the manifolds at cruise. The PCV could be wrong size for your cu inch, Putting in a smaller PCV might squeak you by on the emissions test, wouldn't be the first time it has been done .

 

[Dont fake it break it]

L

there are 2 check valves. I am having trouble remembering the air flow strategy for the diverter valve. Iirc air from pump should go to air cleaner at idle, and to the manifolds at cruise. The PCV could be wrong size for your cu inch, Putting in a smaller PCV might squeak you by on the emissions test, wouldn't be the first time it has been done .

Lol. So a smaller PCV would allow less crank case fumes back into the intake and therefore less to be detected out of the tailpipe? This is brilliant... If anyone was to ever do it. The field test of the EGR past by stumbling when I pressed it and return into proper idle when I let it go. I think my previous one didn’t hold vacuum and that’s Why I replaced it last year. I just went 2 straight days without a lean code But I hadn’t done anything to create that change. Replaced one of the check valves last night and was reexamining my vacuum lines. Vacuum tested the charcoal canister and it passed. This morning I’ve got a high idle but found a vacuum line disconnected. I reconnected it but it did not change the idle. It ran high idle until I shut it off at work, 5 miles away. When I left work the idle was fine but threw a lean code on my way back home, but just for about 15 seconds. Something else funny happens that might be related. Now and again I’ll be cruising along at say 45 to 55, holding it steady. For no reason it’ll pick up and takeoff like I gave it more gas. It will level off after a five mph increase or so.

 

[Wes Harden]

wow something very odd. reading the last entry IAC leaped to front of my mind. something is changing, possibly electrical. Do you have a nice crack free vacuum line to map sensor?

 

[Dont fake it break it]

wow something very odd. reading the last entry IAC leaped to front of my mind. something is changing, possibly electrical. Do you have a nice crack free vacuum line to map sensor?

So I vacuum checked that line from the map and it’s good. I haven’t checked the IAC yet but something else funny happened today. I switched out the secondary air check valves because they were suspect in a backfire I have. Then I retorqued the intake bolts which all seemed OK at 35psi but then it wouldn’t start. I went back and checked all the electrical’s and coil plug thinking maybe I knocked something loose moving wires and such out of the way. I didn’t find anything in particular but something worked because it fired right up but then it ran like shit. I had to advance the timing just to get it driveable. The only thing I had done was unplug and remove the TPS just to tighten down the bracket bolt underneath it, and unplug and remove the map sensor to get the TPS out. Now it runs like garbage and normally you would think I have a bad wire there in and couple quick tests will reveal it but I bet my next check that is not the case. if that were true it would be running like brand new with the amount of money and fiddle f@!&ing I do with this thing. Don’t get me wrong though, the love is real.

 

[Wes Harden]

Pull the distributor and check the gear and the roll pin that holds it to the shaft