P0171 Code Need Some Help Please. I did search first!

[alfieferenzo84]

So i found out it means its lean and checked all the things and i still cant find the problem

Replaced pcv
plugs
cleaned maf, egr, iac With the right cleaner not break cleaner!!!
thottle body screen there and clean
vacuum is at 42 cmgh at idle witch is about 16 in inches
compression check was 160 all 6 within 3 psi
maf idle is 4-6g/s also did the tap check no changes!
map is about 38kp idle/ 5.5 psi
front o2 sensor is all over the place 0.1- 0.9 volts idle
rear o2 sensor is about the same always 0.3-0.5 idle
sparyed carb cleaner on vac lines no changes in rpms
fuel psi is 42 idle/52 without fpr hooked up, Dont know wot!
New fuel pump, and filter, tried the relay bypass nothing changed!

so as you can see i dont understand what my problem maybe, Besides my front o2 witch is all over the place?

I have a cheap scanner i can post a scan if anyone wants it but i dont know how so i could email it or tell me how and i will send logs!

Please if anyone has any idea please let me know as this is driving me crazy Thanks

[BNaylor]

DTC P0171 indicates the system is in a lean trim mode. Ideal fuel trim = zero. Greater than zero indicates the PCM is adding fuel to compensate for the lean condition. If fuel trim is less than zero the PCM is reducing the amount of fuel to compensate for a rich condition.

Here is the course of action per the GP GM service manual:

Check all vacuum hoses at intake system.
PCV Valve
Possible throttle body blockage (clean input screen and body)
IAC (idle air controller valve)
Check fuel injectors (bad o-ring seal)
MAF sensor
EGR valve
02 sensor

[alfieferenzo84]

i guess i need to replace the o2 sensor and check the o ring on the injectors then right?

How does my scan look?

Will somone look at one of my scans so i dont waste alot of money on o2 sensors please?

Thanks

[jonsonton]

Originally Posted by alfieferenzo84

sparyed carb cleaner on vac lines no changes in rpms

That just seems weird, because you should have had an RPM change(maybe some carbon build up in the intake or on the valves?).

Does your scan tool let you see O2 voltage? If so B1S1 and B2S1 should fluctuate between about .1V and .9V, and B1S2 should stay kind of steady around .4V(+or - about .1V).

[BNaylor]

Forgot to ask what engine and model GP?

Remove the front 02 sensor and clean the element with carb cleaner. Make sure you can see light through the vanes. Carefully remove as much carbon as you can. Also, disconnect (unplug) the MAF sensor and then check 02 sensor reading.

[alfieferenzo84]

Originally Posted by jonsonton

That just seems weird, because you should have had an RPM change(maybe some carbon build up in the intake or on the valves?).

Does your scan tool let you see O2 voltage? If so B1S1 and B2S1 should fluctuate between about .1V and .9V, and B1S2 should stay kind of steady around .4V(+or - about .1V).

front o2 sensor is all over the place 0.1- 0.9 volts idle
rear o2 sensor is about the same always 0.3-0.5 idle

98 gtp 3.8 s/c

I was going to clean the o2 sensor but we are getting hit with a cold front so it will be a cuple of days i will get back and thanks for the info!!!

[alfieferenzo84]

how do you check injectors thats the last thing to check/ replace

[duke_winchester]

I am having a similar problem with a p0171 code after just replacing my intake manifold gaskets, s/c gasket, etc., although I do not have a scan tool to check all the stats. When I unplug the MAF, the rough idle almost completely disappears, but I cleaned the MAF, it was working before I did the work, and it is relatively new. Anyone have any ideas on this?

What kind of scan tool was used above? (Did it give you the vacuum reading, or did you have to use a vacuum gauage) And where did you get the acceptable range values from to compare the ones the scan tool gave you?

One more thing which is kind of stuck in my mind. I had to replace several vacuum lines, including the one that connects to the large port at the throttle body near the IAC. I replaced the hard plastic tubing with rubber tubing, and I didn't use the large 90 degree boot that goes on throttle body and reduces to 1/4 inch tubing. Could that cause a vacuum problem in the throttle body.

Thanks

[snupytcb]

what did you clean the maf sensor with?

[duke_winchester]

I cleaned with MAF sensor cleaner

[BNaylor]

Originally Posted by duke_winchester

I am having a similar problem with a p0171 code after just replacing my intake manifold gaskets, s/c gasket, etc., although I do not have a scan tool to check all the stats. When I unplug the MAF, the rough idle almost completely disappears, but I cleaned the MAF, it was working before I did the work, and it is relatively new. Anyone have any ideas on this?

What kind of scan tool was used above? (Did it give you the vacuum reading, or did you have to use a vacuum gauage) And where did you get the acceptable range values from to compare the ones the scan tool gave you?

One more thing which is kind of stuck in my mind. I had to replace several vacuum lines, including the one that connects to the large port at the throttle body near the IAC. I replaced the hard plastic tubing with rubber tubing, and I didn't use the large 90 degree boot that goes on throttle body and reduces to 1/4 inch tubing. Could that cause a vacuum problem in the throttle body.

Thanks

One thing you have to remember is a typical odb-ii scanner does not properly check MAF sensors. The output is actually frequency related. Maybe your MAF got damaged. What brand was it replaced with before? If your idle improved to include overall driveability with MAF disconnected then consider getting a replacement MAF sensor. A bad MAF will cause the lean trim DTC P0171. A cleaning may not be a total remedy if the ASIC chip went South.

Get an automotive vacuum gauge (0-30 in hg) and test the engine vacuum to see if in specs.

[duke_winchester]

Also, with the MAF plugged in, when I rev the engine and then let up, the rpms drop to about a 1000, hold there for a few seconds, and then drop to around 500-600 and rough idle/fluctuate here. If I unplug the MAF, when I rev, the RPM falls right back down to 600 to 700 rpm. Any thoughts?

I really don't want to have to tear my engine back apart to check the supercharger gasket, injector o-rings, etc.

[duke_winchester]

I replaced my bad MAF (which threw the MAF code) with an OE MAF from a grand prix 3.8 with 60,000 miles on it. What is the vacuum range for a 97 grand prix GTP?

Thanks

[BNaylor]

Originally Posted by duke_winchester

Also, with the MAF plugged in, when I rev the engine and then let up, the rpms drop to about a 1000, hold there for a few seconds, and then drop to around 500-600 and rough idle/fluctuate here. If I unplug the MAF, when I rev, the RPM falls right back down to 600 to 700 rpm. Any thoughts?

I really don't want to have to tear my engine back apart to check the supercharger gasket, injector o-rings, etc.

You can run without the MAF connected. The initial idle may be erratic until the engine warms up and fuel economy may suffer a little. I ran with mine disconnected for over a week until the part came in.

Take it out for a full test drive with MAF disconnected to make a thorough evaluation.

[duke_winchester]

I've driven it without the MAF for the past couple of days, and it runs much better (when warmed up) than with MAF plugged in, but I am still concerned with vacuum leak. Where can I find the ideal vacuum range for my 97 GTP?