Connection Between PO171 Code and A/C Problems?

[ruddneck]

I've been dealing with the PO171 "Left Bank Lean" problem since May on my 2000 Prism (94K miles). I've had sealant added around the manifold, replaced the O2 sensors, replaced the gas cap, had the dealer clean the system (including the MAF allegedly), used premium gas with Lucas injector treatment, all to no avail--the check engine light will go off (or I'll turn it off via the fuse) then come back again (always 171, though I did get a PO300 "Random Multiple Cylinder Misfire" once--I appreciated the variety).

It's an annoyance, really, since the only symptom other than the light is a hestitation sometimes when accelarating from a stop (I'm extra cautious about pulling into traffic now!).

Out of options other than having the fuel filter replaced, which I imagine would be expensive as heck given its location, I'm wondering whether the PO171 problem may be related to another issue I had at the beginning of the summer, namely my A/C refusing to cool. I added more refrigerant without any luck, then replaced the filter/orifice, which was completely clogged, and refilled with coolant. Both times the car cooled for a day, then stopped. I have an ultraviolet light to pick up the dye in the coolant, but I can't detect any leaks.

But since I'm out of answers, I'm wondering whether ya'll might think there's a connection, however unlikely, between the PO171 issue and the failure of the A/C to cool. Or, if you have more suggestions on how to remedy either, I'd welcome them!

Thanks!

[maxwedge]

Lean condition, low fuel pressure can be one cause of this, so can a misfire. Any unmetered air entering the engine, which covers a lot of areas. MAF cleaning is common, make sure they did it right. BTW do they stand behind there attempt to fix this?

[ruddneck]

"MAF cleaning is common, make sure they did it right."

Thanks for the suggestion--how can you tell?

"BTW do they stand behind there attempt to fix this?"

Excellent question. The dealership said they couldn't find anything wrong after running all their diagnostics and after cleaning the MAF out, which they were skeptical about when I related the advice and experiences of people on this forum. I'm waiting until Monday to call, then I guess I'll find out!

[maxwedge]

No dealer wants outside advice, they have the most sophisticated equipment and access to tech bulltens, the issue is you paid, they failed to fix the code, which in NYS would cause a failure of the emissions test, ask them now what? Talk to the SM. Make sure a certified engine diagnostic tech is the one working on your car, again only deal with the SM here.

[ruddneck]

"No dealer wants outside advice, they have the most sophisticated equipment and access to tech bulltens"

I agree and feel silly offering it, but I would always wonder in the back of my mind whether they thought of that option (a trust/faith thing, I guess--my old mechanic closed shop; the verdict is out on this dealership still)

"Talk to the SM. Make sure a certified engine diagnostic tech is the one working on your car, again only deal with the SM here"

Will do--thanks again for the thoughts.

[ruddneck]

Update: I took the car back to a dealership where the service manager told me to expect to leave it for several days while the mechanics drove it until the check engine light came back on. Because the Prizm computer is so small, he said, the best diagnostic info is obtained as soon as the light goes on.

However, I heard back from the service team leader an hour or two after I dropped the car off. As with other folks' experience with this problem, it was the mass air flow sensor. (I had to bite my tongue when he said that after I mentioned it beforehand!) Parts and labor and a new sensor cost me $352.99 overall. Pricey, but the car runs like new now, and even the A/C seems to cool quicker (though I reckon I have to wait til summer to test that out fully).

[johnholl]

I would have gone to a junk-yard before I ploped down 300 beans for a potentiometer. The labor should've be free seeings it was a muligan [do over] shit....It's right on top.

[johnholl]

Originally Posted by johnholl

I would have gone to a junk-yard before I ploped down 300 beans for a potentiometer. The labor should've be free seeings it was a muligan [do over] shit....It's right on top.

Of course they DID made more money by replacing it than cleaning it....Did they show you the old part? Maybe they cleaned it correctly this time and billed you for a new one.

I don't trust dealerships.

[carz1]

The dealership has no idea what they are doing!!!

The P0171 code is for a 'Fuel Injection System Lean.' You're also probably noticing some hesitation in accelerating and a decrease in power. The problem is in the MAF (Mass Air Flow) sensor. It's a $5 fix that will save you $500 from the dealership. The MAF sensor is probably dirty and just needs to be cleaned. With a dirty sensor, the rush of air coming into the engine doesn't register and causes a lean stumble.

All your need is a philips screwdriver and a $5 can of electric parts cleaner. From the repair manual from the Prizm, you will notice the MAF sensor is located in the air filter housing. Just unscrew the two screws to the MAF sensor, unlink the power and you can see just how dirty the sensor is. Now that the sensor is disconected, DON'T TOUCH THE MAF SENSOR WIRES INSIDE! The sensor is very small and delicate. With the electric parts cleaner, just spray and let the dirt and grime disolve. I also found compressed air to be handy to help release the dirt after using the electric parts cleaner.

Once the part is clean, connect the power and screw in the sensor. You will have better power and acceleration, as well as the check engine light ready for reset. Just reset the ECU or delete the code from the ECU.

[ruddneck]

Carz1--Man, I wish I had known it was that easy. I'm still pretty sore over the whole thing.

By the way, the a/c problem was a bad compressor.