P0172 System rich / Car dies

[alxndrk]

Hello, I did my research in this forum and internet and I found answers to a lot of questions that i had, but there's more questions that I have and I just need some pointers and I'd really appreciate it guys.

I'm having some problems with my 99 Grand Am. As far as I (think I) know there are three separate problems:

1) ABS / TRAC OFF lights are on and my ABS system is not working. What I found here is that I probably have a bad sensor in the hub assembly and the only way to get it replaced is to replace the whole thing. I'll do that in the next couple months since I don't have the $130 for new hub assembly (yea, it's tuition time again) ;-).

2) My SES light comes on from time to time for no apparent reason. Last week when it came on, I rolled up to the nearest autozone and got it examined. The check pulled up "P0172 - Bank 1 too Rich". The guy at autozone told it might be an o2 sensor but after the research I did online I found out there are some other probable causes.

3) Not very often but my car dies (the RPMs go down, the engine starts to stutter and if I don't rev it a little it dies) when I am waiting at a red light or when the car is not moving and my foot is on the break. Again, it doesn't happens very often but I think it has something to do with my SES light and the "system too rich" deal. I read somewhere on the forum someone was having the same problem and the cause was cracked vacuum line. I'd really like to check my vacuum lines but I have no idea what they look like or where they are located. I thought it might be a bad sprak plug, so I replaced them all but didn't fix the problem.

FIXES:

1) I guess I have to replace the hub assembly and see what happens!?

2)Any advice would be appreciated!

3) What the vacuum lines look like? Where are they located? Also, could this problem be 'cause of dirty air or fuel filter? I haven't replaced neither one of them since I bought the car 2 years ago or 15-17,000 miles ago!? Now the car's at 120,000 miles. Also any advice would be greatly appreciated.

Thanks!

P.S. Also, it might be helpful for pinpointing a problem: whenever I start my car for the first time and the engine is cold my brakes are really touchy for the first 5-10 times I use them. I don't know if this is related to anything but it is really strange. I almost broke my nose in the wheel once, while pulling out of the parking lot.

[rixGAphx]

A REALLY dirty air filter will cause all your problems, 1, 2, 3, and the PS.

Replace that thing!!
* * *
1. Check tha ABS fuse (and other fuses).
Your problem *prolly* is a bad hub (don't know which one), but it's best to make sure it's not a 25-cent fuse before laying out $130.

2. The O2 sensor is what TELLING you the P0172 code, not causing it.
The cause is either too much fuel (like an injector stuck partially-open) or too little air (like a totally-clogged air filter).
The O2 sensor on the exhaust manifold *might* be faulty and giving a false signal, but I doubt it unless you have other symptoms/codes.

3. Rich mixture/clogged air filter will cause this stumble/stall.

Your fuel filter should be changed about every 30k miles, so I don't doubt it needs it.
But, none of your symptoms are related to an overly-dirty filter.

Hope this helps.
-Rick

[alxndrk]

Thanks rixGAphx,

1) I did check all the fuses that have something to do with the ABS. I also removed both front wheels and unplugged the ABS sensor plugs and checked the connections - they seem ok. That's why I think the whole hub needs replacement. I'll probably buy one off of ebay for about $90 (s&h included). I'll try hooking it up to both plugs separately before install to determine which one is the faulty one.

2) I thought it might be an injector causing the problem but I recently used two bottles of fuel injector cleaner consecutively, so I ruled it out. Not that it can't still be the problem... but as for now, I ruled it out.

"The cause is either too much fuel (like an injector stuck partially-open) or too little air (like a totally-clogged air filter)."

Since, I have cleaned the injectors, I'll try changing the air-filter and see what happens. I bought the car at 104K miles and it's at 121K right now - I've never changed the air filter.

I'll probably change the fuel filter also, but later on.

I don't get this tho, you say:

A REALLY dirty air filter will cause all your problems, 1, 2, 3, and the PS.

and at the end you say:

But, none of your symptoms are related to an overly-dirty filter.

Did you mean, ALL of my symptoms in the final sentance, cuz I'm a little confused!?

Thanks for the reply, really appreciate it. If you have more advice, keep it coming.

I have a little question, tho. Where is the air filter in the 99 GA located? :)

[cage47]

Those bottles of injector cleaner will only help on a moderately clogged injector. I've got the same problem on my 98 blazer and run through 3 bottles. If the injector is totally stuck they won't help.

[alxndrk]

I was driving with my SES light on all day (P0172). Went back home and then I had a small 5 min trip to the post office and the light disappeared. When I got back home, I replaced the air filter. I took it for a test drive but the light didn't come on. Later tonight I have a 25 min trip to play soccer and then 25 min back. I'll see if the light pops up again. I also wanna see if the car dies on me, while waiting at a red light. I'll be damned if all these problems were just cuz of a dirty air filter.

The old one looked pretty dirty btw. I don't have much experience with cars and I don't know how bad the old one really was but my dad said it was very dirty.

Any input would be greatly appreciated.

[rixGAphx]

When I said, "But, none of your symptoms are related to an overly-dirty filter."
I was speaking relative to the sentence immediately above ("Your fuel filter should be changed about every 30k miles, so I don't doubt it needs it.") regarding the FUEL Filter not causing your present symptoms.

Sorry, I shoulda been clearer.
* * *

The air filter MUST be changed regularly;
Every 3000 miles (at each oil change) it should be inspected, and cleaned by just bending it and knocking the dirt loose from the inlet side.
The old rule-of-thumb was to hold the thing up to the sun, bend it, and make sure you could see light thru most of it.

With the Arizona desert, I change mine twice a year (basically, every other oil change, therefore every 6000 miles).

I don't know what GM recommends, nor the dustiness factor of your driving.
* * *

The injector is a tiny tube (kinda like a hypodermic needle) with a pin inside at the top of the tube.
The pointed pin tip sets against the tube to seal it, and is held in place by a spring. No gas flows thru it.
Each time the injection 'squirts', a tiny electro-magnet pulls the pin back a bit, allow fuel to flow for a few milliseconds.

The tube can become clogged with a kind of varnish that builds-up a coating. This makes the tube smaller, so less fuel flows thru on each squirt.
This makes for a LEAN burn.
The bottles of cleaner are intended to dissolve this varnish and restore problems.
Good gasolines, like Chevron, already have this chemical in them to PREVENT the build-up in the first place. Chevron's stuff is 'Techroline'.

BUT, a tiny piece of sand can become wedged between the pin tip and the top of the tube.
This allows pressurized fuel to flow ALL THE TIME!!!
Just a little bit, but constantly while the ignition is 'on'.
So, when the injector 'squirts' (for a few milliseconds every other revolution) the cylinder served by that injector gets the proper amount of fuel; but in between 'squirts', that cylinder is getting a load of gas that builds-up in the intake passage and then enters to create a RICH mixture.

The liquid Fuel Injector Cleaners generally will NOT dislodge the tiny grain of sand (since all they do is dissolve varnish), so the injector would still leak.

Conclusion: Even though you used the FI cleaner, your injectors may STILL be the cause of the 'richness' problem.

Good luck, and report back after soccer.
-Rick

[alxndrk]

Thanks for the info rixGAphx, it really helps a car rookie like myself.

OK, on my way to soccer everything was cool and I even felt a difference while driving, it was as if my car had more horsepower and it was accelerating faster. Anyways... on the way back tho, the SES light came back on. I haven't examined the code, but I'm pretty sure it's the same P0172 since that's the only code it's been throwing for the last 2-3 months. I'll unhook the battery tomorrow to clear the computer. The code was still in the computer when I replaced the air filter.

Also, not only the SES light came on but the car tried to die on me again (on the way there) before the light came on. I gave it a little rev and it went away as always.

I'm thinking this rich mixture and these dying are somehow connected but I can't figure how. I'll probably go for that injector replacement job but the thing is I'm a little short on cash right now.

I was thinking I should check these "vacuum lines" but I have no idea what they look like and where are they located.

Also, I might change the o2 sensor but not sure which one, since I found out that there are more than one.

The fuel filter would be changed also if the above don't help.

And also, I read something about a "canister", I have to look it up in more detail.

Please, any advice would be appreciated. Thank you!

[4kQuad]

Vacuum lines are the little rubber lines ( like straws ) that run all over the motor area.

They can get soft so the colaps (sp) when vac is added, they can slide of connectors they were put on, they can just plan crack.

lots of times you can here a little whistle sound kind of like when there is a small hole in a straw.

Hope that helps some.

A clean air filter you can see through it if you hold it up to a light.

[4kQuad]

Any more questions?

Did Rick give you his clean the battery terminals good and all the stuff paragraph? It really is important that they are clean.

[rixGAphx]

Originally posted by 4kQuad
Did Rick give you his clean the battery terminals good and all the stuff paragraph? It really is important that they are clean. Isn't that a 'sticky' by now? :roll2: :D :D

Nah, his current problems won't come from bad cables IMO, and I don't want to distract him from the present mission.
* * *

There is a diagram decal of all the EMISSIONS vac hoses, located under the hood, on the left front spring/strut housing.
One of these lines (about 3/8" round hard black plastic) runs acroos the upper part of the firewall and dives under the Coolan Reservoir and then attaches to the Charcoal Canister (which absorbs gas fulmes when the care is setting with engine 'off', then releases those fumes back into the hose/intake manifold for burning).

Additionally:
* There is the large (~3/4" round) vac line to the Brake Booster ('cake pan' shaped thing between the firewall and the Master Cylinder); and,
* Another smaller vac line goes to the HVAC controls, and Tee's to the vacuum reservoir (black plastic grapefruit-sized and -shaped ball under the battery) which might be considered a 'canister'.

Vac leaks cause a LEAN mixture, which isn't your problem.
IMO, the only way a vac leak could cause a RICH condition would be at the EGR Valve. Since only the V6's have EGR's, and your 4-cyl doesn't, I wuold just check the lines but not expect to find a solution there.

Hope this helps.
-Rick

[alxndrk]

Good to know the rich mixture is not caused by a problem with the vacuum lines. Can you give me guideline on what I should check next. I was thinking I should check the o2 sensor, since it's not a very costly repair but I'm not sure which sensor might be the problem the one, before or after the catalytic converter!? Any advice? Is it true that the PCM uses the downstream sensor to monitor the system? If so, I should check that one, right? Just not sure there, need some clarity.

Do you think the fuel filter would cause rich mixture? If it's too dirty and clogged wouldn't it allow less fuel to pass thru, causing LEAN mixture!?

What would be another possible solution to the car dyings and the rich mixture, apart from the injectors?

[rixGAphx]

Originally posted by alxndrk
I was thinking I should check the o2 sensor, since it's not a very costly repair but I'm not sure which sensor might be the problem the one, before or after the catalytic converter!? Any advice? Is it true that the PCM uses the downstream sensor to monitor the system? If so, I should check that one, right? Just not sure there, need some clarity.

Check it (or replace it if you like to spend money), but that's not the source of your current problems.

It is the front O2 sensor that is TELLING you the system is rich; it's not causing the problem, and it's not faulty.

If the front O2 sensor is faulty, you WILL get one of the following codes:
P0130 O2 Sensor Circuit Malfunction (Bank 1 Sensor 1)
P0131 O2 Sensor Circuit Low Voltage (Bank 1 Sensor 1)
P0132 O2 Sensor Circuit High Voltage (Bank 1 Sensor 1)
P0133 O2 Sensor Circuit Slow Response (Bank 1 Sensor 1)
P0134 O2 Sensor Circuit No Activity Detected (Bank 1 Sensor 1)
P0135 O2 Sensor Heater Circuit Malfunction (Bank 1 Sensor 1)

If the rear O2 sensor (on the cat itself) is faulty, you will get one of these codes:
P0136 O2 Sensor Circuit Malfunction (Bank 1 Sensor 2)
P0137 O2 Sensor Circuit Low Voltage (Bank 1 Sensor 2)
P0138 O2 Sensor Circuit High Voltage (Bank 1 Sensor 2)
P0139 O2 Sensor Circuit Slow Response (Bank 1 Sensor 2)
P0140 O2 Sensor Circuit No Activity Detected (Bank 1 Sensor 2)
P0141 O2 Sensor Heater Circuit Malfunction (Bank 1 Sensor 2)

The front O2 sensor works with the PCM to determine the injection for proper operation.

The rear O2 sensor senses how much O2 leaves the cat, and the PCM compares that to the O2 leaving the engine/entering the cat. The PCM can then monitor whether the cat is working properly. The PCM may also use the readings from the rear O2 sensor to slightly adjust the injection to ease the load on the cat.

Bottom Line: There's nothing for you to check at the cat or O2 sensors at this time, since the PCM is already checking and telling you there's nothing wrong (since it isn't giving any fault codes).
After all, THIS is the entire purpose of the OBD-II system: To monitor the engine emissions system and report troubles.

Do you think the fuel filter would cause rich mixture? If it's too dirty and clogged wouldn't it allow less fuel to pass thru, causing LEAN mixture!?
A paritally-clogged FF is NOT the cause of the rich mixture, basically for the reasoning you state.
However, a clogged filter will generally just cause poor performance at higher engine speeds, rather than a lean mixture.
The O2 sensor will determine when there's too much oxygen (therefore, too little gas caused by low fuel flow) and the PCM will increase the duration of each 'squirt'. This will prevent a lean mixture.
However, in the rare event of leanness, there is a special code: P0171 System too Lean (Bank 1)

What would be another possible solution to the engine dying and the rich mixture?

Fuel Pressure Regulator: The fuel pump produces fuel pressure around 50 psi, which is much more than the engine can use (only about 35 psi is required at higher revs (say 3500 rpm), and even less at low engine speeds).
So, there's a Fuel Pressure Regulator at the fuel rail, which kinda 'bleeds-off' excess pressure.

*The FPR has a vac attachment (on the V-6; dunno for the 4-cyl), and a failure here *might* cause the pressure to remain too high; so for every squirt, more fuel pushes thru the injector than is supposed to.
The O2 sensor will read a rich mixture, and the PCM *should* reduce the duration of each'squit' to compensate.

* The FPR can just plain fail. It is designed to 'fail closed', that is, to close and shut-down all fuel flow (as opposed to opening and causing very high pressure fuel to possibly spew-out and cause fire).
But, the FPR is made by humans (specifically, GM humans), so anything is possible.

The V-6's have a little pressure-test port on the fuel rail, so it's easy to test the psi at all operating speeds with the proper gage.
I understand the 4-cyls do NOT have a test port, and I don't know the test procedure. Prolly requires attention by a mechanic.

Hope all this helps.
-Rick

PS:
Are you just 'running rich' per the code, or did you flunk and emissions test?

The EPA requires GM (and everybody else) to provide no-cost repairs to every '99 vehicle so that it passes emissions for 8 years/80 k miles.
This is a 'silent warranty', in addition to whatever 2yr/24k warranty came with the car, and in addition to whatever 4yr/60k extended warranty you may have.
This includes plugs, coils, sensors, injectors, PCM, cat, etc.: whatever is causing your emissions to fail the state test.
BUT, the dealer CAN charge you the gawddang $80 'diagnosis fee' to scan the PCM, and if you don't HAVE state emissions testing it's kinda null-and-void.
And, if the emissions failure is a result of improper maintenance or repairs, they are off the hook.

[alxndrk]

rixGAphx, thanks for all this info once again - it's really helpful.

No, I didn't flunk the emissions test but I feel kinda lucky because I just passed it around the middle of December. The SES light with the "running rich code" has been coming on and off for the last couple of months and when I passed the test the light was off. Next test is not until February of 2008, so I'm not worried about it. It's just that I can feel the car is burning more fuel and with the gas prices today it's kinda frustrating. I used to get 260 miled per tank and now I only get about 200 miles (that's city driving, occasional freeway). Plus, I don't feel right when my dashboard is lit up like christmas tree, lol. My ABS/TRAC OFF lights are also on but at least I'm sure 90% what the problem there is (hub assembly).

Anyways... I'll check into that Fuel Pressure Regulator. So, the most probable causes are the Fuel Injectors and the FPR, right? Can you tell me if the replacement of these components is too complex or is it something that I could do myself? Thanks once again.

[alxndrk]

OK, I found out something today that I'm not sure about and I'm gonna need your help to figure it out.

I removed this black "cover" that sits right in front of the engine, I think it's called "resonator" but I'm not sure... anyway.. you can see it on the picture.

Underneath it, right between the middle two of all four "big pipes" (sorry for the lame technical dictionary of mine) there is a pretty large hose that comes from underneath and it ends there... I circled it in red on the picture. It is supposed to go into that opening that sticks out of the "resonator" (again in red circle). The thing is though that this connection is very loose and I'm not sure if that how it's supposed to stay, cuz when i looked at it for the first time today, the end of the hose was all wet as it there was something leaking from there...

Can someone tell me if tightening that connection would fix anything and what is that hose used for? what is its purpose?

Thank you!

[alxndrk]

Second question:

I removed the Idle Air Control valve today and it was VERY dirty.. there was (carbon!?) deposits all over the rubber (plastic!? felt like rubber tho) pin so I wiped it clear with a cloth and pretty much tried to clean everything that I could reach. the O-ring was in a very good shape so I did not replace it. Anyway.. do you think the Idle Air Control valve could be a reason for my troubles, since I haven't had the chance to drive my car for a long distance, since the stuff I did today and I don't know if the problems would persist.

Also, how can I reset the computer so the codes would disappear and my SES light would go off? My battery was unhooked for about an hour but that didn't do any good.

P.S. Sorry for the triple posting but I don't know how to post multiple pictures with one post! sorry...

[rixGAphx]

Sorry, I don't know enough about the 4-cyls to tell you what that hose is.
My *guesses* would be either Positive Crankcase Ventilation (PCV, which sucks oily vapors from the crankcase into the intake, for burning) or Exhaust Gas Recirculation (EGR which actually cools the intak air to prevent lean burn).

But IIRC, the 4-cyl doesn't have EGR; and since there's no PCV valve visible, I'm lost.

*Most* PVC hoses are loose like that; clamping helps reduce oily vapor buildup on the outside.
* * *

A 4-cyl expert should be along shortly.
* * *

Yeah, a bad/dirty IAC will cause a TON of problems.
* * *

Don't worry about resetting the 'puter.

If the problem disappears, the SES light will go off within a few miles.
If it's still 'on' then the problem is still present.
The codes will remained stored for 30 'on-off' cycles of the key (so the mechanic can 'look inside the computer and determine recent history').
But the 'puter doesn't illuminate the SES if nothing is wrong NOW (mebbe some exceptions for a MAJOR problem, but I don't think so).

-Rick

[alxndrk]

Hey Rick, thanks for all your help and guidance man. I guess that IAC valve really hit the spot. Couple of hours after i cleaned it, I took the car for a drive around the 'hood and within 2 miles the light went off. I really hope that was the culprit cuz if it lights up again and I might lose it. ;-)

As far as the "stalls at red light" go, I still haven't had the chance to drive it for a long distance but tomorrow I'm goin downtown, in and around the city, and I'll definitely see if the problem is gone.

Thanks again.