Thread: knock & P0172

Soo my scangauge tells me I've got a code P0172 & 10* of knock sitting at idle. & 50+ when I get moving! I just made a trip to McDs' & on the way back the car started surging. Thats nvr happened b4. I did just replace my rear header gasket yesterday maybe its leaking? I'm not certain if thats the problem of not as I've had this code come & go for a while now. I've checked my vacuum lines, can't find any leaks. Replaced my O2 sensors numerous times. Replaced the PCV valve just a few weeks back as well as the MAF & TPS. I also just ordered a new IAC valve. I'm stumped. Help?????

headers hitting anywhere?

no don't think so.

So I guess I hafta check everything this time & eliminate the possibilities one by one. From what I know these could be the problem anybody feel free to add on if I miss something;

Vacuum leak
Bad MAF
Bad O2
Bad MAP
Bad Injector O-ring seal
Bad IAC Valve(the only thing I haven't replaced)
Exhaust leak before O2 sensors

I'm guessing with that much knock I've got more than one item ticked off on that list. I've tried clearing the code with the scanguage & it comes right back in a few minutes.

Guess it could also be bad spark plugs. Could it be a bad BBV maybe? I'm trying to think of everything. I've been battling this DTC forever...

Feel like I'm answering my own questions. Anyone know if an air bubble in the coolant could be the culprit? I notice my engine is running a bit hotter than normal.

^^BUMP

To help you answer your question, I'm going to suggest you look up the name of that code.

Once you do that, you won't be looking for a header or vacuum leak.

It's not an O2 sensor, The O2 sensor is the sensor that is reporting the issue to the pcm, the pcm is then alerting you of it.

It bothers me when guys will say "had this issue for a long time" and "I'm replacing sensors etc" Reason being is..you didn't look up the code, you didn't research it and you don't seem to really care, since it's been happening for a while. Sorry if I'm a bit harsh, but I didn't get laid last night and you are being mean to your car by not researching the issue.

My last piece of advice is to search on your code at Gearchatter.com. Then read the diagnostic aids section for your code. Usually the problem is fixed by checking those aids.

That was mean. I have been researching the code. I take the code go to google look up the code and go to as may links as I can and look up every possible solution to the problem. I have been taking action & Im not ignoring the problem. Were I ignoring the problem I wouldn't have asked for help.

Thank you the wensite. I forgot about gearchatter.

I'm taking the car and having it scanned by a proffessional. We'll use the DTC trouble shooting list givin for p0172 from gearchatter and work our way down the list. I'll let you know what we find out.

Yeah, that does sound pretty mean when I reread it. Sorry....

So you know the code is Rich Bank One. Which is the front O2 sensor telling us the motor is too rich. It's odd that you'd look at vacuum lines for something that says you are getting too much fuel, not too much air.

Diagnostic aids suggest checking the MAF, you mention that it's possible... did you scan it and come up with good maf readings?

You are getting serious KR and are super rich....somewhere. Have you checked for a bad injector by pulling the plugs and reading if one was badly carboned up?

Here's your list of stuff you posted to check

Vacuum leak - You aren't getting enough air. Can't be a vacuum leak.
Bad MAF - It's in the diagnostic aids. Definately a possibility, or the wiring to it.
Bad O2 - this is the sensor that is reporting the issue. Not a possibility.
Bad MAP - Highly doubt it's an issue.
Bad Injector O-ring seal - this would cause a vacuum leak, not a fueling problem. Not a possibility
Bad IAC Valve(the only thing I haven't replaced) - This controls air to the motor for idle only. Do you have an odd idle that you aren't mentioning? The motor would want to choke out and die if it didn't get air to stay idling.
Exhaust leak before O2 sensors - this would cause a lean issue with additional air being introduced. Should not be a possibility. But if you think you have a leak, you should fix it.

Things that are common to causing overfueling:
New injectors that haven't been programmed/tuned properly (did you swap injectors for bigger ones?)
Stuck injector dumping fuel into one cylinder (check plugs)
MAF giving the wrong reading to the pcm about the amount of air entering the motor. (Either a wrong maf or bad maf. If you modded and changed a maf to a different one w/o tuning for it)

Here's what I just got with my aeroforce;

Ignition advance 20.5-22
2 Missfires idling for 5 minutes
IAC 2667-3615
MAF .79-.81
IAT 91
Coolant 179
RPM 780-809
MAF frequency 2556
MAP inHg -21.2
MAP kPa 26
Zero knock on both sensors
The AIT did go all the way up the 114. Its 92 out.



Another scan for DTC's netted me 3 codes; P0107, P0172, P1107. MAF values seem low. Its a new aftermarket MAF.

I checked the plugs recently and they are good.
I beleive I have a mishmash of injectors. Some from my old motor some from the new motor. All are stock.
I'm thinking I need a OEM MAF.

It would help if we didn't have to look up the codes.

BTW 107 is map sensor. Have you addressed this yet?

Right now im getting a reading of 2026 IAC

I did unplug the MAP sensor to see if anything haopens. Nothing happened. Except set off a code it seems.

those numbers for IAC don't seem like they could be possible. usually it's 0-200ish.. if that.

Ok, to help the diagnosis, please mention if the code appeared because you unplugged a sensor.

Both the first and third code I listed are for MAP sensor.

What could be causing my IAC numbers to be so high?