2010 Equinox 2.4 P0172 Running Rich
I have this Equinox throwing a P0172 , FF Data shows the code set @2200 rpm, CTS 140 degrees, Throttle 70% . Customer states this problem has been for about a Year and other shops have looked into it including replacement: HPFP High Pressure pump, MAF OEM sensor, Baro Sensor, Timing Chain and Related, Exhaust Manifold, Pre 02 Sensor.
On my Road test I found the Vehicle Starts and Runs Great, Just the MIL is on. I started by using GDS and Varify fuel Trims at 2200rpm = LTFT- 25% , STFT -4%, Rear 02 = Hanging about 750mv Steady, and Front 02 seems to be switching decently. At idle, my trims is about LTFT -5 STFT 0
Checked Air filter, Air intake OK, Checked Low Side Fuel Pressure for “leak down ” OK….pressure within Spec at 62, No Smell of raw fuel in Oil at all. Unplugged Purge Valve and Crankcase PCV and Plugged ( made no difference ) Physically removed HPFP and looked for signs of fuel…Nothing
Question to the group, Rear ( post 02 ) hanging high at 750 Steady ….do I question this ?? its the only thing I can think of that looks weird ….
What am i overlooking ?? what is making this run rich off Idle ??
So I decided to pull the oil cap off and Try PCV Vent , The Trims went down to 0 , now wondering if i have hydrocarbons in the Engine ? I know that the HPFP is known for leaks but again this has been changed twice now, and There is NO fuel smell in the oil at all. I then decided to look into the PCV System ….
# 14882: Special Coverage Adjustment - Plugged PCV Orifice in Intake Manifold Found this Bulletien by GM, talks about putting a Manometer in the fresh air vent and check for Pressure. I dont have a manometer that i can out inline. If I run a Vacuum Guage on the ENGINE SIDE of the fresh air line , at idle I pull about 2" of Vacuum ? This seem normal ? Suggestions ??
There's a bulletin (#12313B engine Balance Chain and Fuel Pump) that addresses this issue. There are a couple of other TSBs as well. Looks like they suggest replacing the balance chain due to it stretching, and replacing the HPFP as well. You mentioned it's already been replaced, but might be good to double check that the chain was replaced as well.
have you checked the ethanol content %? You may have to lie to the scanner for the reset to show up
yes i would question the rear o2. in the bay add oxygen or propane and watch the readings go up or down. also regarding the high fuel pressure pump. watch the desired vs the actual rail pressure. we just had on that the fuel pressure jumped to almost max after 45 min of driving. ending up the ECM sending improper duty cycles to the pump regulator.
Is the coolant temperature really 140 degrees? Does this occur during warm-up?
look at the plastic vacuum line from purge solenoid to throttle body. On my 2012 equinox it got brittle and cracked at the unsupported horizontal span. Do you have an ats escan scan tool so we can look at the fuel trims graphs? Also the exhaust manifold develops a hair line crack near the 02 sensor under the heat shield. The gm manifold is better than aftermarket version i am told. You can hear…
John, For fuel trim issues like this, nothing beats uploading a scan data file from your road test so we can all take a look. Please do so if you can. Your post says on your road test LTFT 25%. Did you mean -25%? Assuming that you did, and that the vehicle is consistently pulling fuel for no apparent reason, then Mike Craddick's reply above could be your answer. Some non-E85 GMs apparently…
Thanks for the Link to the Malibu 2.4 , So I looked at the pid on Fuel Alcohol content on the Equinox, States 0 ….
Thats exactly what i was going to say…you beat me to it…lol
Rear O2s, once fuel control is established, and the catalyst ‘lights off’ always run right around 600-700mV. Totally normal with a good cat. Not your issue.
What about an overestimating MAF? Fine at idle, but skews above. Rear O2S reading is fine once cat is lit off. If your actual and desired pids are matching, it leave injector flow or air measurement issue. Exhaust leaks are cause for leanness, not rich.
Please help clarify data. CTS 140 F ? Total Fuel Trim STFT and LTFT at Idle and cruise. MAF GPS idle and cruise. Downstream O2 seems ok. VE test could help.
So, you have normal fuel trims at idle with negative commands at higher rpm. This makes me think about an airflow calculation first and foremost. Ethanol content or mechanical problems would make it wrong at all times. Remember, this is a baseline not a hard and fast rule. There are other situations that may or may not apply. You need to confirm your fuel trim readings while driving the car. If…
So correct me here, IF i disconnect the MAF and Run the car It will bounce into “ Open Fuel Loop ” , can I trust this reading ?
It will not go open loop. It will set a code and continue to run closed loop with the remaining sensors. See what happens to fuel trims with it disconnected. If nothing happens, then that is NOT your problem.
I do not like the MAF 7.8 gps reading at 2285 RPM
Rick Elaborate ? This is a Factory GM ( 2 one ) MAF, Air filter is Clean and OEM, …. I didnt think 7.8 was bad at all for the Load Calc ?
Can you do a VE calculation? On all the data sheets I see no MAF gps greater than 7.8 gps. Not saying the Maf is bad I do not like the reading.
This needs the reset done for the 02 sensor resistance reading if the o2 was replace. It will freeze the reading on them if replaced and not reset. The alcohol percentage will need to be checked, this could have been refueled wrong causing this