Hey guys I’m battling codes 44 and 45 on my 1990 3.1 V6 which are O2 lean and O2 rich if I’m not mistaken. I’ve changed out the O2 sensor and EGR. The EGR pigtail is partially melted so I’ll be fixing that as soon as I can however I’m not getting any EGR codes so maybe it’s just cosmetic.

The car is new to me, previous owner deleted the CAT fyi, not sure if that would have anything to do with it but the only thing I can think of doing next is checking the fuel pressure and testing the injectors. I was thinking a failing fuel pressure regulator and or injectors might contribute to these codes but wanted to see what you all had to say.

what should the fuel pressure be and what should I be seeing when I take my voltmeter to the injectors? Thank you

 

Well, I was going to give you some pages out of the ‘88 service manual but then I read “3.1” and I’m not sure how similar they are in this situation. Probably identical but I’d hate to give you bad info.

If you want to find a fuel pressure leak however, that’s pretty easy. Obviously get a fuel pressure gauge, slap it on the test valve (don’t lose the cap!) and prime the pump. Pump should be between 40.5-47 PSI. It should hold pressure for at least 20 minutes. Assuming it primes to the right PSI, if you have something leaking it will (obviously) drop as you watch the gauge. Release the pressure, then get a clamp or vice and pinch the rubber fuel pressure line. If that makes the pressure hold, then the fuel pump is leaking.

If it still drops, do the same thing but pinch the fuel return line instead. Make sure you’re reallyyyyy pinching these closed. If it holds, that’s a bad fuel pressure regulator. If it still drops, then prime it again and pinch both hoses. If it holds, you messed up one of the other two tests, and if it drops, then the injectors are leaking.

That’s what I did to find my leak (and then bought Southbay injectors, which is my recommendation for replacements) and haven’t had a problem since.

Not sure how much I can help with the EGR, I believe 90-92 had a different digital egr system, or something?

Diagnosis chart for the 88 2.8. I can get you the pages for the codes as well if you’d like. Would be similar charts.

 

bro thank you very much! This will undoubtedly help me.

 

Hey no problem man. There’s a lot more useful stuff in the 88 service manual, you can grab it Here. I have it saved to the “books” app on my iPhone so I can search keywords in it.

 

I’ll check that out thank you. I got to get up to speed on this stuff. It’s been a long time since I’ve worked on a third gen and I’ve never had a V6 before. Every bit of info helps and getting good source material is priceless.