GeorgeC

My next door neighbor just purchashed a 98Z28 A4 w/50,000 miles. The car looks and runs great, but is setting two DTC's, P0172 and P0175. These codes are Bank1 rich and Bank2 rich. I've skimmed through the Helm's manual and done most of the preliminary checks, and found nothing wrong yet. The fuel pressure is a steady 59psi and does not fluctuate abnormally under load. The car is totally stock at this point.

Tomorrow I'm going to pop the fuel rails up and check for leaky injectors. The only other thing referenced in the Helm's manual is the possibility of fuel in the oil. We're going to check this out as well by plugging up the PCV valve temporarily and seeing if we find major changes on the Sterm and Lterm fuel trims.

Anything else we should be checking out? I think he's getting kind of freaked out by the SES light coming on since it's a new (to him) car.

I don't know what I should be looking for really as far as Lterm and Sterm fuel trim values. They are both in the negative at most times, at both idle and cruise. The O2's seem to be OK and read in the lower .900mV range at WOT. The Lterm fuel trim for both banks stays steady at -10.9%, but goes less negative at cruise.

To make a long drawn out question short, what could be making the car run overly rich (to the point that the PCM obviously can't compensate)?

Thanks...

gwj

Maybe some really crappy gas? i.e. water in the gas or other crud?

GeorgeC

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by gwj:
<strong>Maybe some really crappy gas? i.e. water in the gas or other crud?</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">I doubt it, since the car seems to run fine... No sputtering or missing. Just the SES light and the two DTC's.

Any other ideas?

GeorgeC

Has nobody got any idea about this? We checked the injectors this morning, and none seem to be leaking. We didn't really see any noticeable difference in the Ltrims and Strims with the PCV system blocked off.

PaiN

just a shot in the dark George.

DO you think it would be possible to throw your MAF on his car and drive it for a bit then ATAP it?

It could be a relatively easy thing to do. Also do the o2 sensor values seem sluggish?

GeorgeC

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by PaiN:
<strong>just a shot in the dark George.

DO you think it would be possible to throw your MAF on his car and drive it for a bit then ATAP it?

It could be a relatively easy thing to do. Also do the o2 sensor values seem sluggish?</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">I was thinking the same thing about swapping MAFs since mine isn't being used right now...

As far as I can tell, the O2's seem to be responding OK, but I could be wrong... I've thought about swapping them out as well just to check.

Thanks for the suggestions.

XLR8NSS

iTrader: (4)

Could it be an exhaust leak before the O2's?

If extra air is getting in the exhaust before the O2's it would cause the computer to add more fuel.

Hope you guys find the malfunction. <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" />

John

GeorgeC

So far we haven't made much progress... We did swap my MAF on to the car today, so I'll let him use it for a few days and see if it changes anything...

I doubt it's an exhaust leak, since a)we'd probably be able to hear it, and b)both banks seem to be simultaneously affected, i.e. tripping the DTC at the exact same time...

We'll keep pecking away at it and eventually get it figured out.

Hell, I've got a complete spare '98 car sitting here waiting for a motor, so spare parts aren't a problem... <img border="0" title="" alt="[Wink]" src="gr_images/icons/wink.gif" />

PaiN

any luck George?

GeorgeC

Well... We ran my MAF on the car for a couple of days, and the SES light has stayed off. We put his MAF back on the car, and it hasn't come back on either... We're kind of stumped at this point. When he bought the car, the battery was dead, and had to be replaced. Because of this, the PCM was obviously reset. I'm wondering if slightly "slow" O2 sensors just made the car take a little longer than normal to get the fuel trims "in check" where they're supposed to be?

He's going to keep his MAF on the car and see if it starts acting up again.

Terry Burger

iTrader: (4)

I think P0172 is when you install your new high performance engine and throw a rod the same day. <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" />

GeorgeC

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by Terry Burger:
<strong>I think P0172 is when you install your new high performance engine and throw a rod the same day. <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" /> </strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">Terry, if you're going to be a wiseass, at least get the facts straight...

a)It's not my car that was setting the code.
b)I didn't "throw a rod." I had a defective wristpin, which broke. Nobody's fault, just a bad luck thing...

Besides, I think the right DTC in that situation would be P0666 <img border="0" title="" alt="[Wink]" src="gr_images/icons/wink.gif" />

Jon Green

well i think we have got it down to the MAF being bad going to get a new one on order <img border="0" title="" alt="[Sad]" src="gr_sad.gif" /> as of now im running George's MAF (the car is running good <img border="0" alt="[hail]" title="" src="graemlins/gr_hail.gif" /> )

2kta--89formula

iTrader: (2)

Just curious, did the MAF fix the problem? (I'm currently experiencing the same codes in my '00 T/A)

GeorgeC

I still to this day don't know what fixed the problem (hell, it's been two years now, so I can't really even remember it anyway)... Somehow it magically just went away, even after putting his car back to exactly how it was when it was setting the codes...