Mixture too rich? P0172/5

[roshindelman]

Hi guys! I just want to preface this post with a couple of things. First off, if this is the wrong thread I apologize. Also, I’m quite new to working on vehicles. Lastly I love this forum! This is my first ever post.

Okay, down to business. I’ve been chasing these fuel mixture codes for a few months now and have tried quite a few solutions that haven’t seemed to fix the issue. I was hoping you mechanical geniuses would have some suggestions.

So far I’ve replaced the fuel injector spider, MAP, PCV valve, both upstream o2 sensors, air filter, and cleaned the MAF. I’ve also tested the fuel pressure which came back normal. While I’m learning a lot by tinkering with all these parts I’m starting to get a little nutty since I haven’t actually fixed anything.

Thanks for reading!

[Leeann_93]

I don't see any testing of ignition components. You need three things for proper ignition: suck, bang and blow. If you have proper fuel pressure at the schrader valve, and the air filter, MAF and throttle body (not just the throttle plate, but the bore where the throttle plate seals) are clean, it's time to inspect bang, aka spark. One bank being 'rich' could be caused by either not enough air or not enough spark; in other words, the ratio is off so the final result is screwy.

Pull a plug; is the spark good, hot blue? If not, test upstream at the cap. Is the spark out of the cap good, hot blue? If yes, your problem is the wire or plug - or both.

If no, inspect the cap and rotor. Are they worn evenly (and not overly worn) or are there weird burn marks or carbon tracking? Is the button on the cap that contacts the rotor intact? If it looks worn or weird, replace both and test again.

If still no good, hot blue spark from the cap, time to test at the coil. Is the spark good, hot blue? If not, replace the coil. Test again. Is it good, hot blue spark? If not, your ICM (mounted on the bracket with the coil) could be bad.


Having said all that, what brand spider, MAP and oxygen sensors did you install? If you installed Bosch oxygen sensors, get AC Delco, Delphi or NTK and test again. Bosch sensors don't switch fast enough for our vehicles and they just plain don't work.

Also, you say the fuel pressure 'came back normal', but what are the readings:
1- KOEO (Key On, Engine Off) at prime?
2- KOEO 10 seconds after prime?
3- KOEO 10 mins after prime?

The MAF sensor could be bad. They do fail, either from age or from being cleaned by someone who isn't incredibly gentle with the sensing wires, which are fragile.

Also, believe it or not, the coolant temp sensor (rear of the driver's side head) could be bad, lying to the computer. If you have a scantool, check the coolant temp when the van's fully warmed up. If it isn't 192° or higher, the coolant temp sensor is suspect. The computer will alter the air:fuel ratio accordingly.