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Old 08-17-2018, 07:28 AM   #1
Tinovolpe
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Hard start and degraded gas mileage

Hey everyone. Been awhile since I posted. All has been quiet on the Taurus front. Can't believe my 2001 DOHC is still running but a problem has popped up. I know I have to start searching for solutions this weekend but figure I throw it out here before I get completely frustrated.
My son did a few minor mods to the car since he drives it now. He's an electrical engineering student so he like to tinker. Added some switches to turn off the daytime running lights (?) and shut off the interior lights even when doors are open. Go figure. So he was playing around under the hood. All of a sudden the car cranks a long time before turning over. Sometimes he has to try twice. It always started immediately. And he has told me his gas mileage has gone down the tubes. He used to get over 300 miles per tankful and now barely 200 so big drop. I'm thinking he accidentally disconnected something or knocked something off when working under the hood but does anyone know the most likely culprits to start looking at that would cause these symptoms? MAO sensor? Vacuum line? Battery is measuring a 12.79 volts and is only 2 years old so that won't cause the hard start and certainly not the poor gas mileage. Any hints before I start digging into this tomorrow would be appreciated. Thanks.
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Old 08-17-2018, 03:00 PM   #2
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Re: Hard start and degraded gas mileage

My suspicion would be he either disconnected the MAF sensor or he failed to get the intake air tubing correctly and securely installed. Have you asked him what areas he was experimenting with under the hood just prior to this fuel economy issue starting? If he remembers, focus your energy on looking for disconnected sensors and hoses in those areas.


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Old 08-17-2018, 04:14 PM   #3
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Re: Hard start and degraded gas mileage

He did tell me that he had to take apart the air intake to get at the firewall to run wires so i'm guessing it may very well be something in that area. Looks like that is where I'll start looking. As usual thanks for your sage advice!!!!!
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Old 08-18-2018, 09:07 AM   #4
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Re: Hard start and degraded gas mileage

Took a look under the hood and didnt see anything disconnected or out of place. I ran the Forscan diagnostics and it didn't show any faults for the MAF or the injectors. Did get some DTC codes but unrelated to anything to do with gas mileage attached are screen shots. Is the reading for the Mass air flow normal for a warmed up car at idle in park?

PS: It won't let me upload the jpeg screen shots don't know why. Size is small enough. Anyway MAF reading is 3.43 g/sec. I get no faults on the MAF, EGR and the fuel injectors
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Old 08-18-2018, 09:25 AM   #5
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Re: Hard start and degraded gas mileage

You're not allowed to upload directly to this site. You need to upload to a photo-sharing site, then link to that photo here.

Per the factory service manual, the MAF flow at hot idle should be 3.5 - 4 g/sec. At 2500 rpms the flow should be 12 - 14 g/sec.

I'd suggest you also check at 2500 rpms and if it's off a bit too, carefully remove the MAF sensor and clean it with MAF sensor cleaner. The cleaner is getting common enough that many of the chain auto parts stores carry it.

-Rod
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Old 08-20-2018, 07:51 AM   #6
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Re: Hard start and degraded gas mileage

Thanks Rod,

If I can't upload directly then they probably should give that option!

At any rate the MAF at 2500 rpms is about 13.5 so that seems good. What other parameters do you think I should look at. fuel pressure maybe?

Also did some online searching on hard cranking of Tauruses and everyone seems focused on the fuel regulator.

Another thought. Could the coil pack be going bad? I already changed it once at least 6 years ago. Any diagnostic data I can look at that might lead me to that?

Trying to get this car to last 2 more years until my son graduates college then I'll treat him to a new car.
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Old 08-20-2018, 01:44 PM   #7
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Re: Hard start and degraded gas mileage

You should also monitor short and long term fuel trims (STFT and LTFT). There is probably one of each for bank 1 and bank 2. You'll also want to monitor the O2 sensor voltages at the same time to attempt to correlate the STFT with the O2 sensor readings. If you're able to pull the camshaft position sensor value that might be interesting to monitor as well.


-Rod
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Old 08-20-2018, 03:30 PM   #8
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Re: Hard start and degraded gas mileage

Sounds good. I'll let you know what I find!
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Old 08-20-2018, 06:31 PM   #9
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Re: Hard start and degraded gas mileage

Here's what I got so far. The is car fully warm at idle
Fuel tank pressure -.2Kpa
IAC 38.67%
long term fuel trim 1 - 6.25%
long term fuel trim 2 - 7.02%
short term fuel trim 1 -.78%
Short term fuel trim 2 -3.13%
O2 sensor Bank 1 Sensor 1 - .51 V
O2 sensor Bank 1 Sensor 2 - .81V
O2 Sensor Bank 2 Sensor 1 - .13V
EVAP canister control valve - 0.0%
throttle position sensor status - NO
Throttle position - CT
MAF - 3.23g/sec
Evap emissions monitor - not running
EGR status - no fault

This is what I capture. There is plenty more to look at. Do you see anything that stands out. The fuel tank pressure seems low to me. Unfortunately the one thing I don't see is fuel pressure monitor. One thing I noticed sitting in the car is the smell of gas. But there is no smell under the hood. Something going on with the fuel system?

Thanks
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Old 08-20-2018, 10:07 PM   #10
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Re: Hard start and degraded gas mileage

I'm not real sure what to expect the fuel tank pressure to be.



Nothing really jumps out at me. The fuel trim values are well within specification, although you'd normally want to see them a bit closer to zero. The positive numbers suggest the ECM is increasing the fuel injector pulse width to account for a slightly lean condition. That lean condition may be false though since you smell raw fuel and the fuel economy is less than typical.



The sensor 1 oxygen sensor voltage would need to be monitored over a period of several seconds to get a feel for how well it's switching and between what values it's switching.


-Rod
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Old 08-21-2018, 07:25 AM   #11
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Re: Hard start and degraded gas mileage

Let me graph just the oxygen sensors and see how they run over time. I did pull one spark plug and the plug was a nice light gray. no sign of a rich mixture. I also have to figure out how to upload the screen shots and graphs

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Old 08-21-2018, 06:59 PM   #12
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Re: Hard start and degraded gas mileage

Rod

More testing. Looks like I'm getting an error on the fuel system status (open/closed loop) Bank 2. Bank 1 is showing a closed loop for a fully warmed up engine.

I did graph the O2 sensors and the sensor 2 bank 1 and sensor 1 bank 1 is showing a nice sine wave. the bank 2's on 1 and 2 sensors are not as clean but still pretty consistent. Did some online googling and its possible I'm getting an error on Bank 2 because there is no bank 2 fuel system status. So far have not found anything out of the ordinary.
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Old 08-22-2018, 08:18 AM   #13
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Re: Hard start and degraded gas mileage

The sensor 2 should not track the sensor 1 sine wave, assuming the vehicle is up to temperature. Seeing that would suggest your bank 2 catalytic converter is not functioning properly or possibly the heater element is not working properly.


-Rod
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Old 08-22-2018, 11:10 AM   #14
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Re: Hard start and degraded gas mileage

Rod I wish I could show you the graph but I can't figure out this whole file sharing thing. I asked the forum administrator for help but haven't heard back yet.
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Old 08-24-2018, 02:42 PM   #15
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Re: Hard start and degraded gas mileage

Wanted to bring everyone up to speed with this issue in case it happens to to anyone else. turns out the car was leaking gas from the fuel filter,. I mean really leaking. My son said he was sitting in the parking lot with the car running for about 20 minutes and there was a huge puddle of gas under the car. At home this car is parked over a gravel driveway so no one noticed the leaking gas, and when the car was off the leak was very slow, but enough to drain the gas line, hence the hard start. When the car was running the pressure from the pump was literally squirting gas. Certainly would explain the hard cranking and lousy gas mileage. Keep thinking of that scene from the die Hard movie where the plane is spilling fuel and Bruce Willis flames it by lighting the gas trail.
Anyway I'll monitor it for a few days and run the diagnostics again just to make sure. The Bank 1 sensor 1 fuel trim was very weird and don't know if this issue was causing it. Once again Rod thank for all your help. Oh and folks, if you smell gas and your mileage goes down, that should be a hint. Duh on me.
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