Po172 [Archive] - GrandAmGT.com Forum


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05-29-2009, 03:17 PM
I've searched, and I know what it is. I have done everything really to try and fix it. The code just will not go away. I have put a new FPR, MAF,MAP, O2 sensor and seaformd. The car is not misfiring what so ever and i have reset the computer, goes off, but comes back on. I just don't know what to think or do...any ideas?

05-29-2009, 07:38 PM

06-02-2009, 12:14 PM

06-02-2009, 03:37 PM
Did you check your fuel pressure? This code can also the thrown if you are having fuel pressure or delivery issues. Also check for a possible exhaust leak before the O2 sensor.

If i remember correctly you just replaced a FPR since it was dumping fuel into your TB. Make sure that you dont have your pressure set to low as that will cause a lean mixture.... just something to check for ;)

06-02-2009, 05:09 PM
Well heres an update. I went back to a stock FPR. So far i have changed my MAF,MAP, air idle valve and O2. Most of which were due to be changed. But today i was driving and my car started misfiring like crazy and i couldnt go past 35mph,well i could, but it was hard with the hesitation and misfiring. So i went to advanced, and its the same damn code, p0172....talked to my dad and he said its probably and injector gone bad...I have them all out now....Is there anyway to test which one is bad? I really don't have the money to buy a couple. Im so stressed, im at school and without a car...Im hopinh you guys can help me out with this mess ::(:

06-02-2009, 06:01 PM
Update: just did the resistance check on the injectors, all came out at 12.5 ohms. Which is in the range of 11-14ohms given in the haynes manual...ugh

06-02-2009, 07:10 PM
if i ran the injectors out of the car and watch for fuel, would that work?

06-02-2009, 07:26 PM
Another thing to add, the car used a 1/4 tank of gas only driving 15 miles....ugh ideas?

06-02-2009, 07:44 PM
Sorry all to be a pest...but if i get the trailblazer 28Ibs injectors, i know they are a direct replacement, will these require a tune? I have a DHP, and a set of six of these is a hella of a lot cheaper than stock...

06-02-2009, 08:56 PM
have you checked your plugs perhaps, i don't know what that code means but if you got a misfire it would have to be your plugs or their is no fuel. my guess is the plugs because your getting bad gas milage or you have a leak on the fuel rail.

06-02-2009, 09:04 PM
well i changed the 3 plugs in the back today...bank 1....and thats when i started having issues, like hardcore issues. My uncle seems to think its the wires rather than the injectors....I am gonna pull out the plugs in the morning to check the condition....I really dont mean to be annoying....its just im stuck at school with no vehicle until this is fixed. I mean it could also be a bad coil pack to? i dont know

06-02-2009, 09:11 PM
it could be the new plugs, i know this motor only likes a couple types of plugs. i would also get new spark wires. when i did just those two things when i bought my car i gained about 50 more miles a tank. manily because their was nothing left of the plugs.

2000 GT Coupe
06-02-2009, 09:21 PM
it is possible you put the wrong wire on the wrong plug?

06-02-2009, 09:31 PM
that is the other problem i've seen many people do, i would double check that

06-02-2009, 10:01 PM
no, when i first put on the wires i took the car for a drive it didnt do anything. Well i got back,cleaned the air idle valve and then took the car for a drive and it all started......

sugar ray
06-02-2009, 10:45 PM

I may be experiencing DEJAVU while reading your post. Especially the part about HORRIBLE gas millage and top speed of 65. You have described the SAME symptoms that I went through last summer with my 02 Grand Am. "SAME" exact code Po172 spit out when I hooked my laptop up to my elm-scan tool.

I didn't get as far as replacing sensors though. I wanted to be sure BEFORE throwing money at it. My problem......drum roll..........my Cat. Converter was plugged huge! It was a very COMMON problem with these cars. The converters GM used on these cars were complete CRAPOLA!

My money is on your converter. Climb underneath and give it a nice bang.

After replacing my converter with an aftermarket one life was good! No more code. no more SES light and everything went back to normal.

I do feel for ya! I was there. Checking EVERYTHING. Hvae a look at the Cat. good luck:hay:

06-03-2009, 10:52 AM
well just replaced the plugs...they were all black...big time....

06-03-2009, 11:11 AM
well i just hit the cat...and it worked a little then started acting up again...ugh...the new plugs are solid black from the carbon...something isnt right...

Lab Rat
06-03-2009, 11:33 AM
When my cat was plugged the car would not even start. And it died on the highway. Luckily for me it was only about 10 blocks from home.
I took an 1/8th inch drill bit and put a hole in my pipe in front of the cat. Started right up. Went to the local muffler shop and had them weld in a new cat. No more problem. Maybe disconnect the down pipe if you don't want to drill the hole. You will be running straight pipe thou until hooked back up. Good luck.

06-03-2009, 03:52 PM
I looked at the tail pipes, and they are solid black from all the carbon. This is new. Well i scheduled a diagnostic test for friday in the AM. I really dont know what else. I called the muffler shop that put on my DP and Cat,and they said "their product is not the issue" its my engine... thats bs...idk

06-03-2009, 04:54 PM
Alright justr seafoamed it . Ran good for 5 seconds and then went back to doing what it does. Rough idle and surging....ugh. And to add, i said earlier that the plugs were black and just installed new prior to turning black. Well all the plugs are in the same condition. It isnt just one cylinder.

sugar ray
06-03-2009, 10:21 PM
are you sure it isn't your cat? A plugged cat will cause a ton of back pressure. I have seen a few guys throw all kinds of money at sensors, plugs, wires, fuel pumps etc.....just to find out later its the cat.

sure sounds like a HUGE possibility especially after everything you have replaced.
A plugged cat can cause all sorts of described symptoms.
Even a LOW MILES cat. can be BAD. I had very low miles on my grand am when the cat plugged. I almost didn't want to believe that they could plug so early in its life span, but it did.

If you have an Elm scan tool (around $125 bucks) plus a laptop there is a ton of great software available to do your own diagnostic tests

Im eager to find out what your problem was when its all said and done. Post your findings after your diagnostic test

P.S. just tapping on the cat would NEVER fix the problem. A cat cat NOT be fixed only replaced. tapping on the cat would just give you a GOOD idea if it were plugged or not

If the cat is way far gone the engine will run poorly. Stalling, sputtering, hard starts, not start at all, backfire. You may actually not even get a code other than misfire or knock sensor which are symptomatic not fundamental to the problem.

The easiest test for converter plugging is done with a vacuum gauge

06-04-2009, 02:43 AM
At this point I would say disconnect the down pipe and start it up and see how it runs. If it turns out to be the cat then the shop that put it in is required to replace it for free under federal emissions laws. They are under warranty for like 90k miles or something like that.

06-04-2009, 09:43 AM
Yea...im gonna give that a try today....This cat issue would cause a rich condition and all that?

06-04-2009, 10:41 AM
well just tried to take it off, the fu**ers screwed the nuts on too hard....well after this attempt i seaformed it once again. Runs smoother each time i do it, and TONS of smoke comes out,wont stop. I took it for a drive and i noticed under 1500RPM the car is super hesitant and sputters,but when you gun it,it runs smooth. Just the lower RPMS are being really weird....

06-04-2009, 01:39 PM
I was reading. If i had a bad coolant temp sensor, since its in the fuel system loop. it woulc cause the car to run rich because it would be sending the wrong signal to the computer and telling it that its cold.....is this true?

sugar ray
06-04-2009, 05:48 PM
perhaps, but to go as far as SMOKE out the ass end due to a bad fuel sensor? Tough to figure.

Im tellin ya....cat....cat.....cat....cat My 02GA was doing almost word for word what you have described in this post. A new cat and the car ran like the day i purchased it new

I hope you get it figured out soon:hay:

06-04-2009, 07:58 PM
will find out tomorrow morning.....Ill be sure to post what the deal is....Would a bad cat foul out the plugs?

sugar ray
06-05-2009, 12:26 AM
I would think so! Alot of back pressure going on in there. Internal combustion engine com busts but has NO where to go because the Cat MAY be plugged, causing backfire, misfire etc....

06-05-2009, 10:02 AM
Well yall...just got back from the dealership......drum role please............................................ .................................................. Shotty MAF. Word of advice don't by re manufactured goods. It was the problem the whole time. Car runs amazing now, but the SES light came back on throwing the same code....I really don't care though because the car is running great. Everything else checked out fine. Injectors, O2 and all that Jazz was fine. The MAF was throwing bad numbers and just wasn't consistent. So i forked over the money and got an O.E.M one. And it's honestly the best its drove in a long time. So im a happy camper, just gotta get rid of the SES light. Im gonna try cleaning the K&N. The guy at the dealership told me if i have to much oil on there, which im a dumbass and do, that it will get the MAF all screwy. So just use a little oil. The had a huge issue with the new impala SS's doing that with the K&N...so yea thanks!

06-05-2009, 10:50 AM
glad to hear its running good but if your issue is caused by too much oil on the maf you wouldnt need to do anything more than clean the MAF

I just hope you didnt buy a new one for no reason

06-05-2009, 11:18 AM
No, the original one was ruined because gas got into it when i had the initial FPR go bad. So it was ruined...I got my money back from auto zone for the re manufactured ones

sugar ray
06-05-2009, 01:23 PM

If you have an elm scan tool and a laptop you could knock out the SES light. You think they would have done that for you! Glad to hear you got it fixed! Also glad to hear that you didn't have to take out a second mortgage to fix it

06-05-2009, 01:25 PM
haha well kinda...was a little pricey for what they did, but I'm definitely glad it's back.

06-06-2009, 07:02 PM
Question. When my FPR went out it soaked my k&n with gas. Will this ruin it? I cleaned it and all, but im just wondering if itll make it disintegrate or bad

06-07-2009, 05:00 PM

07-17-2009, 05:51 AM
exhaust leak maybe but check your fuel pressure to