I just talked to the BlueDriver company. It wont read the stored Ethanol%.

Any suggestions for a reader that will?

Steve

 

Once again: P0172 is fuel TRIM rich not Mixture.
Check the under hood EVAP purge valve, it might be stuck open, it should be normally closed.

 

Parts store. (May have to encourage them to search for it buried in the menus. May be cleverly disguised — some abbreviation of alcohol and/or ethanol and/or percent, i.e, “ALCPCT” or something, according to the whim of the programmer. May be expressed as a proportion, i.e., 0.65, instead of 65%., or 0.11 instead of 11%)

Again, not an OBD code. Not freeze frame data either, maybe. Not that I understand freeze frame.)

My Torque app old free version (w/ any ELM or clone Bluetooth dongle) did it. One of our local mechanics just dives under the dash with his laptop when you have a problem and doesn’t even charge for it.

 

You could be right about the purge valve. I have no opinion without knowing stored and actual ethanol %.

But the meaning of P0172 has come up enough times that I would love to see an authoritative interpretation. Several instances seem to contradict your view.

Here’s recent thread in October of this year. OP found P0172, 67% ethanol stored, 5% sampled, -19 LT trim. Obviously rich, ECM trimming leaner.

Comment #10

Comment #27

The whole shebang

https://www.chevyhhr.net/forums/fuel...-repair-67225/

The thread might be useful to Fastsuv too.

 

There is a link to a free shop manual in my sig. the codes are explained in it. If you are on the mobile site scroll to the bottom of the page and choose "view full site".
Alcohol percentage is calculated from the amount of O2 in the exhaust, so is the A/F. If the EVAP purge valve is stuck open the engine sucks unmetered air in, making the computer to think "too lean, I will raise the fuel trim" causing a P0172 (fuel trim rich).

 

That’s why I posted a link for that P0172 code

 

OK, but what about the real-life example I cited right here, a recent thread? It suggest the opposite. There are others.

I do allow for diverse explanations involving errors. After all, if the programs can’t get the % right, they can also set the wrong code, just as a conjecture.

 

If you read the actual title of the OBD2 test you will find the answer. "Fuel TRIM System Rich. It can also manifest as P0171 depending on the state of the EVAP vent valve.
Hard starting is most often the result of a bad EVAP purge valve.

RTFM.

 

Could be, but I’ve had a couple of bad purge valves you could blow right through and it never affected starting.

Anyway I never meant to even imply that the problem is most likely the alcohol %. But checking the stored value is free and (should be) easy. Based upon my direct experience, I think it’s a good 1st move, and if it is the problem, however rare, a way to avoid chasing yer tail and buying a bunch of unneeded parts. Starting to feel like you’re working really hard to invalidate that. Maybe you’re right, but why not wait and see what the % is?

BTW, cleaning the MAF and throttle body would be a good move too If it’s been awhile, it ought to be done anyway. Poor-quality data from the MAF could hypothetically confuse the ECM.

 

The purge valve is fine, I tested it.

I cleaned the throttle body with cleaner.

I replaced the air filter while I was at it.

The problem was still there and didn't change.

I didn't clean the MAF sensor because I need to buy MAF sensor cleaner. Looking at the MAF sensor it did look very clean, almost like new.

My fuel pressure tester is broken so I need to get another one. The factory service manual gives an allowable amount of pressure drop after shutting off the fuel pump (I don't remember the exact numbers on how many psi drop after x minutes) so this might show if an injector is leaky.

One thing I noticed is if I restarted the car within a few minutes, it started normally. If it is left for a longer period of time (maybe 30 minutes or more, not sure) then it had the starting problem I described in my first post. It does seem to act like a leaky injector over time.

I am still planning on taking it to my local mechanic and asking him to read the Ethanol percentage. Also, I want to buy a better scanner that can do a lot more than mine does, which will probably be expensive but worth it.

Steve