Dead battery replaced, new installed, won't idle and engine revs cycling up/down on throttle
02-13-2009, 01:50 PM
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Dead battery replaced, new installed, won't idle and engine revs cycling up/down on throttle
Found my 1999 A4 Q 2.8 with a totally dead battery this morning. Not even any juice to unlock the doors with the remote.
AAA came over and confirmed the battery was completely dead.. no output, and jumped the car. Upon starting it the idle was really rough:
- Idle is too low, and engine stalls without some throttle applied to keep the revs where they need to be.
- Applying more throttle, as though preparing to shift into first to pull away... the engine revs increase, but then drop back down again, then jump up, then back... cycles every second or two with no help from my foot.
I replaced the battery and tried again... the symptoms remained unfortunately.
CEL came on too at some point during this process.
Did a little research here, and wondered if it could be that the ECU's settings for the throttle body range had been lost... requiring a TBA. I've tried leaving the key in switched to the accessories setting for 4 mins or so, then turning off and starting again... but the idle and ability to keep engine revs are just as bad.
Suggestions?
The car was running fine before I shut it off last night, so I have to think the idle/engine speed issues are related to the flat battery... I just have no idea how to clear the problem. My attempts as initiating a TBA seem to have failed miserably :-(
Does this sound like it could be a mis-calibrated ECU / TBA, or something wor$e?
On a side note... anyone know where you can get a VAG COM in the San Jose CA area? This car's had so many CEL's and repairs recently I'm beginning to think it's time I picked one up.
AAA came over and confirmed the battery was completely dead.. no output, and jumped the car. Upon starting it the idle was really rough:
- Idle is too low, and engine stalls without some throttle applied to keep the revs where they need to be.
- Applying more throttle, as though preparing to shift into first to pull away... the engine revs increase, but then drop back down again, then jump up, then back... cycles every second or two with no help from my foot.
I replaced the battery and tried again... the symptoms remained unfortunately.
CEL came on too at some point during this process.
Did a little research here, and wondered if it could be that the ECU's settings for the throttle body range had been lost... requiring a TBA. I've tried leaving the key in switched to the accessories setting for 4 mins or so, then turning off and starting again... but the idle and ability to keep engine revs are just as bad.
Suggestions?
The car was running fine before I shut it off last night, so I have to think the idle/engine speed issues are related to the flat battery... I just have no idea how to clear the problem. My attempts as initiating a TBA seem to have failed miserably :-(
Does this sound like it could be a mis-calibrated ECU / TBA, or something wor$e?
On a side note... anyone know where you can get a VAG COM in the San Jose CA area? This car's had so many CEL's and repairs recently I'm beginning to think it's time I picked one up.
02-13-2009, 03:40 PM
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TBA sounds like a good bet, others on here were dealing with this recently...
the Vag com can be had from this distributor list:
<a href="http://www.ross-tech.com/distributors.html">Distributor List</a>
I know that avalon motorsports (1.303.400.3001) can get it for you as well as Pure motorsport.
If I were in your shoes i'd go onto the classifieds forum and post up a wanted.Someone probably has one laying around.
<a href="http://www.ross-tech.com/distributors.html">Distributor List</a>
I know that avalon motorsports (1.303.400.3001) can get it for you as well as Pure motorsport.
If I were in your shoes i'd go onto the classifieds forum and post up a wanted.Someone probably has one laying around.
02-13-2009, 06:26 PM
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Mr Mc Feely
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How long have you driven the car since the new battery was put in?
Same thing happened to me each time I had the battery out for long periods of time.
Take it out for a good 30 min drive.. You should be find after that. With low volts the ECU is not happy. once it gets its footing back you will be just fine.
If not. let me know.
Take it out for a good 30 min drive.. You should be find after that. With low volts the ECU is not happy. once it gets its footing back you will be just fine.
If not. let me know.
02-14-2009, 05:06 PM
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Re: How long have you driven the car since the new battery was put in?
1.7 miles of unpleasant driving.... the car performs so poorly it's difficult to stop the car without stalling... and when I apply throttle the response is so flat and full of dead spots it's tough to drive in traffic :-(
I've tried the ignition key method suggested in the forums, but it doesn't seem to be triggering the TBA. If it is... it's not doing anything to help, so I think it might not be happening.
I'm about to disconnect the battery at both terminals, and then connect the two cables together to try to re-clear the ECU. I'll leave it over night and see if reconnecting the battery again, and doing the suggested "insert key, turn key to power up instrument panel display - but don't turn engine over, leave for 4 minutes, turn off ignition switch (then repeat as I've seen suggested)... then insert key and start engine" sequence works this time.
Is there a possibility that this ignition key method isn't supported on a 1999 A4Q 2.8?
I can't believe a flat battery is so catastrophic for these cars.
The car is currently trying to idle at ~400-500 rpm, but if I apply some throttle it'll idle OK at ~1000rpm. If I add more throttle, it seems to reach a point at about 1200 rpm where the revs are dropped down, then cycle back up to 1200, repeating this. Pushing through this odd spot in the throttle range the rpm's stabilize. Driving the car is tough.. its a stick, so braking and keeping enough throttle to keep the engine from stalling is tough, and there are power flat spots through the throttle range... the car feels like it's running at ~20% power available, and the power varies through the throttle range.
Does driving the car like this for 30 minutes really help out, or is a successful TBA a pre-requisite?
Thanks in advance to anyone with some answers!
I've tried the ignition key method suggested in the forums, but it doesn't seem to be triggering the TBA. If it is... it's not doing anything to help, so I think it might not be happening.
I'm about to disconnect the battery at both terminals, and then connect the two cables together to try to re-clear the ECU. I'll leave it over night and see if reconnecting the battery again, and doing the suggested "insert key, turn key to power up instrument panel display - but don't turn engine over, leave for 4 minutes, turn off ignition switch (then repeat as I've seen suggested)... then insert key and start engine" sequence works this time.
Is there a possibility that this ignition key method isn't supported on a 1999 A4Q 2.8?
I can't believe a flat battery is so catastrophic for these cars.
The car is currently trying to idle at ~400-500 rpm, but if I apply some throttle it'll idle OK at ~1000rpm. If I add more throttle, it seems to reach a point at about 1200 rpm where the revs are dropped down, then cycle back up to 1200, repeating this. Pushing through this odd spot in the throttle range the rpm's stabilize. Driving the car is tough.. its a stick, so braking and keeping enough throttle to keep the engine from stalling is tough, and there are power flat spots through the throttle range... the car feels like it's running at ~20% power available, and the power varies through the throttle range.
Does driving the car like this for 30 minutes really help out, or is a successful TBA a pre-requisite?
Thanks in advance to anyone with some answers!
02-14-2009, 08:33 PM
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Re: How long have you driven the car since the new battery was put in?
Not good I suspect... will have to flat-bed the car and hope I've not made things worse. Drove it for 3 or 4 miles around the neighborhood to see if it (ECU) would start to sort itself out. But, it didn't and my nose started picking up a slightly burnt rubber smell. Sigh...
02-17-2009, 10:55 PM
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Re: How long have you driven the car since the new battery was put in?
As an update: I had the car put on a flat-bed and taken to my usual non-dealer shop. They confirmed that the TBA was the issue, and initiated it through their diagnostic software.
I mentioned the ominous burning oil smell that I caught a whiff of while out trying to coax it into life... so they checked. Turned out to be an unfortunate coincidence... At the moment I was out bucking around the neighborhood a leaking cam plug happened to drop a spot of oil on the exhaust manifold. I had the cam plugs replaced a year ago because of leaks, but it looks like the problem returned. Not serious enough to warrant immediate work, but something to note. Freaked me out though...
So... onward... I wonder what maintenance delight my aging A4 has in store for me next... ;-) Seriously considering trading it in for something 2 years old with a warranty to fall back on. As much as I LOVE this car, the unpredictability of its increasingly frequent maintenance costs is becoming a distraction... Nothing compared to the depreciation on a 2 year old car, plus a car payment... but at least its a more predictable cash flow drain ;-)
Thanks for your responses.
I mentioned the ominous burning oil smell that I caught a whiff of while out trying to coax it into life... so they checked. Turned out to be an unfortunate coincidence... At the moment I was out bucking around the neighborhood a leaking cam plug happened to drop a spot of oil on the exhaust manifold. I had the cam plugs replaced a year ago because of leaks, but it looks like the problem returned. Not serious enough to warrant immediate work, but something to note. Freaked me out though...
So... onward... I wonder what maintenance delight my aging A4 has in store for me next... ;-) Seriously considering trading it in for something 2 years old with a warranty to fall back on. As much as I LOVE this car, the unpredictability of its increasingly frequent maintenance costs is becoming a distraction... Nothing compared to the depreciation on a 2 year old car, plus a car payment... but at least its a more predictable cash flow drain ;-)
Thanks for your responses.
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06-30-2009, 02:46 AM
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I've got a Euro Spec 2.6 12V V6. I had a similar issue a couple of years ago when a failing battery required a couple of jump starts.
I reckon the ECU loses data & for some reason doesn't fall back to the basic closed loop settings.
After replacing the battery, I had the same alternating idle problem, with it nearly stalling on occasion. I found that driving it around gave the ECU time to either reset or adjust its idle control back to normal, I drove it some way before it settled mostly constant rev non stop driving on the highway.
I reckon the ECU loses data & for some reason doesn't fall back to the basic closed loop settings.
After replacing the battery, I had the same alternating idle problem, with it nearly stalling on occasion. I found that driving it around gave the ECU time to either reset or adjust its idle control back to normal, I drove it some way before it settled mostly constant rev non stop driving on the highway.