Rich Mixture
Senior Member
Joined: 12-05-2014
Posts: 3,371
From: Northern Ohio
Oh come on! Any parts store can read the ethanol %. Do it for me, so I can sleep. It can correct itself, so if you wait too long, you’ll never know.
MAF sensor can look very clean but have a hidden bit of cottonwood fuzz or something and give you trouble.
MAF sensor can look very clean but have a hidden bit of cottonwood fuzz or something and give you trouble.
Thread Starter
Senior Member
Joined: 02-01-2006
Posts: 1,471
From: lockport,ny
I did the fuel pressure leakdown test.
The allowable amount is 5psi drop in 1 minute.
Ignition on and the fuel pressure immediately jumped to 55psi. Shut ignition off and after 1 minute it dropped only 2psi. I kept watching it and it dropped very very slowly after that. So it appears leaky injectors aren't the problem. Time to take it to the local garage to have him read the Ethanol %.
To repeat the problem: car is hard to start and gas pedal must be pressed down all the way (as done for a flooded engine) to start it. It starts and runs rough for a second or two and then is fine. It runs perfectly otherwise. If you restart the car with a short time, it starts fine normally. If it sits a longer time, the the startup problem shows up.
Steve
The allowable amount is 5psi drop in 1 minute.
Ignition on and the fuel pressure immediately jumped to 55psi. Shut ignition off and after 1 minute it dropped only 2psi. I kept watching it and it dropped very very slowly after that. So it appears leaky injectors aren't the problem. Time to take it to the local garage to have him read the Ethanol %.
To repeat the problem: car is hard to start and gas pedal must be pressed down all the way (as done for a flooded engine) to start it. It starts and runs rough for a second or two and then is fine. It runs perfectly otherwise. If you restart the car with a short time, it starts fine normally. If it sits a longer time, the the startup problem shows up.
Steve
Senior Member
Joined: 12-05-2014
Posts: 3,371
From: Northern Ohio
I did the fuel pressure leakdown test.
The allowable amount is 5psi drop in 1 minute.
Ignition on and the fuel pressure immediately jumped to 55psi. Shut ignition off and after 1 minute it dropped only 2psi. I kept watching it and it dropped very very slowly after that. So it appears leaky injectors aren't the problem. Time to take it to the local garage to have him read the Ethanol %.
To repeat the problem: car is hard to start and gas pedal must be pressed down all the way (as done for a flooded engine) to start it. It starts and runs rough for a second or two and then is fine. It runs perfectly otherwise. If you restart the car with a short time, it starts fine normally. If it sits a longer time, the the startup problem shows up.
Steve
The allowable amount is 5psi drop in 1 minute.
Ignition on and the fuel pressure immediately jumped to 55psi. Shut ignition off and after 1 minute it dropped only 2psi. I kept watching it and it dropped very very slowly after that. So it appears leaky injectors aren't the problem. Time to take it to the local garage to have him read the Ethanol %.
To repeat the problem: car is hard to start and gas pedal must be pressed down all the way (as done for a flooded engine) to start it. It starts and runs rough for a second or two and then is fine. It runs perfectly otherwise. If you restart the car with a short time, it starts fine normally. If it sits a longer time, the the startup problem shows up.
Steve
For effs sakes read the stored ethanol %.
Moderator
Joined: 01-23-2009
Posts: 26,539
From: Fredericksburg,VA
That ox is gored good.
THE TITLE OF P0172 IS FUEL TRIM SYSTEM RICH. NOT SYSTEM RICH. Code readers have limited memory so they tend to truncate verbiage, leading to much misinterpretation.
That means the O2 sensor is sensing a LEAN A/F and the trim system is adding fuel to compensate for too much AIR in the A/F.
Maybe, the alcohol % being higher than expected could be misinterpreted as too much O2. More likely unmetered air somewhere between the MAF and the #1 O2 sensor.
THE TITLE OF P0172 IS FUEL TRIM SYSTEM RICH. NOT SYSTEM RICH. Code readers have limited memory so they tend to truncate verbiage, leading to much misinterpretation.
That means the O2 sensor is sensing a LEAN A/F and the trim system is adding fuel to compensate for too much AIR in the A/F.
Maybe, the alcohol % being higher than expected could be misinterpreted as too much O2. More likely unmetered air somewhere between the MAF and the #1 O2 sensor.
Last edited by donbrew; Jan 1, 2025 at 11:18 AM.
Administrator
Joined: 10-13-2011
Posts: 40,096
From: Welland,Ont Canada
Didn’t you just install new flexible fuel lines Steve? Is this the 2011 you changed the transmission a year ago? And a new exhaust? I would check the throttle body bolts, and gasket. The MAF sensor, are those 2 fasteners tight? The intake manifold fasteners? How about the exhaust manifold, the gaskets and fasteners, a cracked exhaust manifold or the flex pipe.
Some where unmetered air is leaking into the system before the upstream O2 sensor.
I wish I was feeling better, I would drive over and have a look with you, Steve.
Happy New Year!
Some where unmetered air is leaking into the system before the upstream O2 sensor.
I wish I was feeling better, I would drive over and have a look with you, Steve.
Happy New Year!
Senior Member
Joined: 12-05-2014
Posts: 3,371
From: Northern Ohio
That ox is gored good.
THE TITLE OF P0172 IS FUEL TRIM SYSTEM RICH. NOT SYSTEM RICH. Code readers have limited memory so they tend to truncate verbiage, leading to much misinterpretation.
That means the O2 sensor is sensing a LEAN A/F and the trim system is adding fuel to compensate for too much AIR in the A/F.
Maybe, the alcohol % being higher than expected could be misinterpreted as too much O2. More likely unmetered air somewhere between the MAF and the #1 O2 sensor.
THE TITLE OF P0172 IS FUEL TRIM SYSTEM RICH. NOT SYSTEM RICH. Code readers have limited memory so they tend to truncate verbiage, leading to much misinterpretation.
That means the O2 sensor is sensing a LEAN A/F and the trim system is adding fuel to compensate for too much AIR in the A/F.
Maybe, the alcohol % being higher than expected could be misinterpreted as too much O2. More likely unmetered air somewhere between the MAF and the #1 O2 sensor.
Your assertion is contradicted, among other places, in this thread:
https://www.chevyhhr.net/forums/prob...-please-60572/
DTC P0172, after OP chases his tail for like 6 months, finally finds alcohol at 42%, zeros it, problem solved. See comments 144, 150, 154.
In the same thread, Oldblue recommends a link that explains P0172, completely contradicting your claim.
There are other threads on the same subject in which the problem was similar. I’m not in the mood to go mind them all.
Please, instead of Pooh-poohing a valid possibility, let’s encourage to OP to get a simple check done and see what the stored alcohol % is.
Again, I’m not saying it’s the problem, I’m saying it could be.
ps - here’s a much more succinct and focused thread that supports what I’m saying in just 2 pages.
https://www.chevyhhr.net/forums/prob...or-code-65196/
In another thread comment #7 (not OP) requests help with similar problem, despite my begging, dismissed my suggestion to check alcohol content, until comment 123 (not kidding!) finally got it checked, and guess what?! 52% alcohol.
I must be a glutton for punishment.
Oh, yeah, and it happened to me, too. Dealer charged me $65 or so to reset the ethanol to zero. If it ever happens again (been a couple years) I’ll do it myself.
Last edited by PulpFriction; Jan 1, 2025 at 02:34 PM.
