1990 Chev K1500 - 5.7L Code 44

[nickscarcare]

This truck came to me, has lean code 44, check fuel pressure, and stays at 12 psi, idling, up hills don't drop out. The map reads 1v idling, and 4.6v koeo. The block learn numbers are 170 at idle closed loop, with o2 toggling, off idle still around 170 but o2 stays low around 60mv. I did spray carb cleaner in the throttle body and the o2 does respond then. Vehicle has a new AC Delco fuel pump, and a pcm has been tried. The fuel injectors were cleaned and flow tested. Any thought on this thing. Timing is on.

[brianp87]

Prolly the pump dead head the pump and see what it reads.

[nickscarcare]

I did that 17.5 psi where the fuel filter goes. All gounds are cleaned on the engine.

[jbadenoch]

I assume there are no vac leaks. Block learn should be about 128 if not mistaken. Does eng get up to temp? (t-stat) Is ect reading properly? Front 02's greatly affect runnability.

[brianp87]

How high does the fuel pressure gauge go? 100 ps.i it na==may not be accurate at that low a #

[nickscarcare]

I have not found any vacuum leaks either on top of the intake or testing the bottom(blocking off pcv, oil fill and breather and placing vacuum gauge in dipstick tube, it showed pressure, not vacuum). The fuel gauge is a digital one. I am going to try a steady flow of propane tomorrow(I ran out today and have to get another bottle).

[ricmorin]

How about the brake booster? Could it be causing a vac leak? Also TB gaskets were a big problem. You need to pull the throttle body to see it. Also make sure your EGR is not acting up. Also, check the grounds at the t stat housing. Can't remember where they go but they make a difference. I remember that the magnets on the distributor shafts used to crack and cause a code 44. Don't ask me why. Pull the rotor off and if you see cracks in that little magnet, it needs one.

That's all I can think of right now. My brain hurts.

[Tim Martin]

You could also have an intake manifold gasket leaking internally. If a vacuum test is done on the crankcase that would determine if there is any vacuum internally.

Speaking of vacuum, what is the vacuum at idle and say at 2500 rpm? Not what the MAP sensor reads but what an actual gauge shows. I have also seen MAP sensors fail even though the scan tool data would seem to say they are ok.

[steven kiser]

Faulty or worn out AIR systems will cause it. If air is being pumped in during closed look it will cause this code. Pinch off the hose while it's in closed loop and see if their is pressure going through it. I've seen (years ago) vac lines connected incorrectly causing this. The little brittle sweet hearts that would snap or crumble if you looked at the wrong. The ground at the t stat housing feeds the pcm along with one on the back of the right head (i think) that's where it is. The one at the housing may look good but i always cut it and attached it to the alternator bracket. The bolt corroded in the intake loosing ground. If the air going through the air intake sounds like a jet taking off then Ric is correct on the gasket being blown. An incorrect pcv will do this as well.

[nickscarcare]

Brake booster is blocked off, charcoal canister blocked off, 16 psi dead head at tbi, 12.5 psi running even down the road. Put in different injectors, and the block learn is now down around 128 at idle, but as soon as I go off idle the block learn stays there now, but the o2 goes to around 100mv and stays there, spray carb clean in and it will jump to 900mv then drop again. Like I said I blocked off the ports on engine and put vaccum gauge in dipstick hole and no vacuum showed, so that should mean no intake leak from the bottom, correct? Distributor shaft don't see any cracks there. I am getting closer.

[nickscarcare]

Call this one fixed. Ended up finding out that someone previously had swapped injectors and they were injectors out of a V6. Man what a difference V8 injectors will make!!! Truck will now light them up and not fall on its face.