Still have poor fuel economy, poor cold starting, idle studder.
10-19-2008, 01:17 PM
#1
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Still have poor fuel economy, poor cold starting, idle studder.
using a small amount of boost im getting 12 MPG, I imagine if i was using a lot of boost id drop into the single digits.
i have tested
-vacuum hoses and boost hoses
-Coils (swapped coil packs)
-POS channels
-cleaned ISV many times
-checked TPS, cleaned Throttle body
-Had injectors cleaned and tested off the car
The car accelerates and boosts fine, and starts great when warm (RPMs shoot up and settle down very nicely) and is also more responsive when warmed up.
i have said before the studder at idle is timed, like something is cycling at that time and causing a dip in idle.
I want to find the problem soon so i dont end up damaging the CATs or anything else for that matter, any ideas of stuff i can check without replacing part after part? Im also not getting any fault codes so i dont feel like its the O2 sensor, and why would that cause a hard cold start.
I talked to Kelly aka Ur-maninblack about using a spare MAF, which ill do later this week. He feels it is something else as do I, G62 sensor maybe? i searched the forum is there a diagnosis for this sensor?
sorry for post after post on this, Dave is about to perma-ban me im sure. Any advice is greatly appriciated.
i have tested
-vacuum hoses and boost hoses
-Coils (swapped coil packs)
-POS channels
-cleaned ISV many times
-checked TPS, cleaned Throttle body
-Had injectors cleaned and tested off the car
The car accelerates and boosts fine, and starts great when warm (RPMs shoot up and settle down very nicely) and is also more responsive when warmed up.
i have said before the studder at idle is timed, like something is cycling at that time and causing a dip in idle.
I want to find the problem soon so i dont end up damaging the CATs or anything else for that matter, any ideas of stuff i can check without replacing part after part? Im also not getting any fault codes so i dont feel like its the O2 sensor, and why would that cause a hard cold start.
I talked to Kelly aka Ur-maninblack about using a spare MAF, which ill do later this week. He feels it is something else as do I, G62 sensor maybe? i searched the forum is there a diagnosis for this sensor?
sorry for post after post on this, Dave is about to perma-ban me im sure. Any advice is greatly appriciated.
10-19-2008, 02:28 PM
#5
The G62 is a temperature-influenced variable resistance. The ECU drives out a voltage (5? 12?) to
the G62 via ECU pin T45/55 via a Grey with Brown stripe (GY/BR) wire. The return current is returned to ECU ground pin 30 (presumably via a brown wire).
From Bentley, the G62 (Engine Coolant Temperature (ECT)) sensor test procedure is as follows:
Allow the engine to cool to room temp (68F/20C)
Disconnect ECT sensor from harness connector
Switch multimeter to resistance range
Connect multimeter to terminals 1 and 2 of the ECT
Resistance must be 1500 to 3000 ohms
IF NO = replace ECT
IF YES = check wiring between sensor and ECM (ECU)
Reference: Bentley pg. J28-22<ul><li><a href="https://forums.audiworld.com/s4s6/msgs/150040.phtml">G62 (and MFTS) info in FAQ</a></li></ul>
From Bentley, the G62 (Engine Coolant Temperature (ECT)) sensor test procedure is as follows:
Allow the engine to cool to room temp (68F/20C)
Disconnect ECT sensor from harness connector
Switch multimeter to resistance range
Connect multimeter to terminals 1 and 2 of the ECT
Resistance must be 1500 to 3000 ohms
IF NO = replace ECT
IF YES = check wiring between sensor and ECM (ECU)
Reference: Bentley pg. J28-22<ul><li><a href="https://forums.audiworld.com/s4s6/msgs/150040.phtml">G62 (and MFTS) info in FAQ</a></li></ul>
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10-19-2008, 04:05 PM
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Results - My multimeter would just flash the number, it wouldn't stay there, normal? i was getting..
950-1900 (updated) range. Its 67 Degrees F outside and car has been sitting 24 hours.
I will order this part tonight regardless. But do those results sound accurate, as far as the number doesn't stay on the display the whole time? every time i would let off and put them back on it would read again.
And i really hope this could cause a poor idle... omg please let it be it.
Thanks again Dave, and others for the help, if its this easy... ill be very happy.
I will order this part tonight regardless. But do those results sound accurate, as far as the number doesn't stay on the display the whole time? every time i would let off and put them back on it would read again.
And i really hope this could cause a poor idle... omg please let it be it.
Thanks again Dave, and others for the help, if its this easy... ill be very happy.
10-19-2008, 05:30 PM
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How do my emissions numbers look...
Idle
%CO2-14.9
%O2-0.5
HC(PPM)-57
CO (%)-0.02
2500rpm
%CO2-14.8
%O2-0.7
HC(PPM)-199
CO (%)-0.04
Now, I watched the car the whole time, no one got in it and reved the engine, and i didnt hear it rev up ever, so the 2500 RPM numbers might be BS.
But how do those numbers look, i copied exactly what it says on the sheet idk what to make of the %co2 thing.
%CO2-14.9
%O2-0.5
HC(PPM)-57
CO (%)-0.02
2500rpm
%CO2-14.8
%O2-0.7
HC(PPM)-199
CO (%)-0.04
Now, I watched the car the whole time, no one got in it and reved the engine, and i didnt hear it rev up ever, so the 2500 RPM numbers might be BS.
But how do those numbers look, i copied exactly what it says on the sheet idk what to make of the %co2 thing.