Running Lean Trouble Code 44

[Jon87V20]

Hi Everyone,

I have a 1987 Suburban V20 w/ a 350 TBI / TH400.

TLDR: Is it safe to drive the truck while its showing a 44 code for running lean?

After putting a lot of fuel in the tank for the first time in a while (I hadn't been putting much in each time lately), it threw a trouble code 44. I was able to drive it around a few more times before it came back again.

You may have seen a few other threads with me asking about the injectors making weird noises and erratic idle etc. I started this new one because there is the new code coming up.

Anyway, my question is, does anyone know if the ECM compensates for the lean condition when it sees it to prevent damage and what not? I'm asking because I've been wanting to change the fuel pump for a long time and I finally went and picked one up just in case this one is going bad. Either way I'm going to change it. The problem is, the tank is half full and I want to drive it around a bit to run it out before dropping the tank. I just don't want to damage my new engine I put in. The temperature looked normal when I was driving it before but I don't know if that's a bad idea or not.

I went out to do a pressure test today, but I'm getting really frustrated with trying to fit the adapter in by the fuel filter. The lines don't want to move forward or back at all and I've already unbolted a bunch of the hold-downs. Also, I threw some dual exhaust on this a long time ago and it's blocking a lot of the fuel line so there may be more bolts.

Thanks.

[MIKE S]

The computer on a tbi can compensate some but not much. If you have made any modifications to the engine or exhaust like cam profile, heads, compression, headers or even removing the cat converter which alters back pressure the software in the stock prom chip will not be able to compensate. If you have made changes to these systems and continue to have drivability issues and fuel and ignition are dialed in you will probably have to have a custom prom chip made.

[VileZambonie]

You can just take the fuel filter out and check your fuel pressure if needed. Your TBI pressure tester should have flexible hoses allowing you to make it fit in its place. Have you checked for vacuum leaks? What is the O2 voltage showing when driving?

[Jon87V20]

Vile,

I bought a testing kit that bd recommended (I think) from Harbor Freight.

https://www.harborfreight.com/basic-fuel-injection-service-kit-64939.html

The trouble is, the fitting that’s designed for TBI has a male end, and a female end. The lines in the truck that attach to the filter are both male, and the filter is much wider than the tester as well. So I was thinking the only way to attach it would be between one of the lines and the filter.

I couldn’t find any vacuum leaks. I was just thinking, haven’t checked the modulator vacuum line down by the transmission, but it’s upshifting normally.

You need an OBD1 scanner attached to check the o2 voltage while driving right? I don’t have one. I haven’t looked at the sensor troubleshooting guide for that one yet. I’ll take a look at that. I also bought a new o2 sensor for it since it was cheap and hasn’t been changed for who knows how long.

[Jon87V20]

I actually just ordered a scanner. Should be here tomorrow.

[Jon87V20]

Okay so I took a video of the data from the computer. It looked like the o2 sensor voltage was jumping around a lot. Is that normal? Also, it was bouncing between LEAN and RICH a lot although it seems like that’s a binary condition and it’s probably a good thing it’s not stuck on one or the other.

I should also note, I replaced the o2 sensor before doing this reading. The light has not come back on yet at all. I also haven’t actually gone out and driven yet. Just idled in the driveway.

The exhaust is definitely leaky, but it’s past the sensor where the manifolds meet up with the collectors. That shouldn’t affect the sensor right?

https://drive.google.com/file/d/1scOZrhXqZEH6M4Y7IxGWYanbJYbQn9DL/view?usp=sharing

[TexasRed]

Access denied on the video.

The sensor should be switching from rich to lean quite a bit. The sensor should be the old style O2 sensor so it only really tells you if you are rich or lean, and not truly precise on HOW rich or lean.

If the exhaust leaks are AFTER the sensor, it really shouldn't affect the reading.

[Jon87V20]

Thanks, Texas. The link should be working now too.

[TexasRed]

Well, idling in the driveway, the fuel volume should be enough to not throw a code, IF it is the fuel pump or filter.

Idling also doesn't introduce a ton of exhaust for the sensor to sample. And I'm guessing it's the style of O2 sensor that needs heat from the exhaust to warm it up and not one with a heater wire.