90 GT suddenly running very rough
07-11-2008, 05:26 PM
#46
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Good luck Stan!
I've come to believe that an MAF is like a coked-up stripper hiding in your bedroom closet. It WILL turn on you and cause you horrendous problems - the only question is when.
I'm ready to start carrying a spare with me...
I've come to believe that an MAF is like a coked-up stripper hiding in your bedroom closet. It WILL turn on you and cause you horrendous problems - the only question is when.
I'm ready to start carrying a spare with me...
07-11-2008, 05:45 PM
#47
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Stan,
I had a rebuilt MAF in my car and it started acting just like yours.
Did not trigger the relay LEDs though.
I found a short in my harness nest to the MAF connector when cutting off the bot on the connector.
Bought a new connector and boot and had the MAF fixed again.
All work perfect again.
/Peter
I had a rebuilt MAF in my car and it started acting just like yours.
Did not trigger the relay LEDs though.
I found a short in my harness nest to the MAF connector when cutting off the bot on the connector.
Bought a new connector and boot and had the MAF fixed again.
All work perfect again.
/Peter
07-11-2008, 06:01 PM
#48
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Looks like I am still searching for a final answer. I installed the old MAF and it started to behave badly again.
I presume when the MAF is disconnected the LH runs on defaults as it gets not signals from the MAF, so perhaps the LH is tuning improperly when the MAF is connected....
I presume when the MAF is disconnected the LH runs on defaults as it gets not signals from the MAF, so perhaps the LH is tuning improperly when the MAF is connected....
Stan,
I had a rebuilt MAF in my car and it started acting just like yours.
Did not trigger the relay LEDs though.
I found a short in my harness nest to the MAF connector when cutting off the bot on the connector.
Bought a new connector and boot and had the MAF fixed again.
All work perfect again.
/Peter
I had a rebuilt MAF in my car and it started acting just like yours.
Did not trigger the relay LEDs though.
I found a short in my harness nest to the MAF connector when cutting off the bot on the connector.
Bought a new connector and boot and had the MAF fixed again.
All work perfect again.
/Peter
07-11-2008, 06:04 PM
#49
When the MAF is disconnected the car should run fine at idle and at around 3K or so RPM..and behave oddly inbetween those ranges. Usually when your car runs crappy, and then disconnect the MAF...idle will smooth out. Not sure if the brain needs a reset or not..can't hurt to disconnect the battery and disconnect the MAF..and try again.
07-11-2008, 06:17 PM
#50
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Tom's comments about how the engine should run with the MAF disconnected are commonly claimed, but I have found that two of my cars ran very poorly with their MAF's removed.
07-11-2008, 06:35 PM
#51
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Correct with the mass air unpluged the car goes into LIMPMODE the true only LIMP MODE idles sort of OK will only take a bit of throttle.....just good enough to get you OFF the Autobahn...
07-11-2008, 07:01 PM
#52
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It's worth remembering with MAF degradation on Cat/O2 sensor equipped cars, that the O2 sensor and LH will compensate for a degrading MAF up to a certain degree of degradation. Once degradation reaches a certain amount (IIRC from JDS it's about 3 or 4 % error) the LH and O2 basically give up and can't compute. Although the MAF degradation is gradual, the cut off point where compensation can no longer cope and it all goes **** up is pronounced. Hence the apparent sudden failure. If you don't notice the pronounced sudden lumpy performance ( through a car that is driven irregularly say) the next phase of degradation is that the car will not start at all until the MAF is disconnected.
EGT sensors can fail intermittently. IIRC you can eliminate them from the list of possible issues very simply by unplugging them from the loom (round connectors under the airbox) so that the signals that the IGN monitoring relay recieves are guaranteed to be the same - No signal.
EGT sensors can fail intermittently. IIRC you can eliminate them from the list of possible issues very simply by unplugging them from the loom (round connectors under the airbox) so that the signals that the IGN monitoring relay recieves are guaranteed to be the same - No signal.
Last edited by jon928se; 07-11-2008 at 07:02 PM. Reason: extraneous text
07-11-2008, 07:59 PM
#53
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Good information, thanks.
I will try disconnecting the battery for a while to reset and see if this replacement used MAF behaves differently.
If no change, then I will investigate disconnecting the EGT sensors. Nice to know there is a way to do so without getting the jackstands out, removing the belly pans, etc.
Thanks all
I will try disconnecting the battery for a while to reset and see if this replacement used MAF behaves differently.
If no change, then I will investigate disconnecting the EGT sensors. Nice to know there is a way to do so without getting the jackstands out, removing the belly pans, etc.
Thanks all
07-11-2008, 10:28 PM
#54
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It happened to me again today - it was running just fine on a short trip, then it suddenly switched into the half-power mode. I stopped, shut down the engine, restarted, and it was fine again. I was planning on taking it to the Catskills for the weekend, but I don't want that kind of hassle all weekend long.
07-11-2008, 11:37 PM
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Disconnected the battery for 30 minutes, so no question on it, on restart basically the same issue with old MAF and stock relay.
Just added enough Stabil for 20 gallons and added 10 gallons of fresh premium. Still running ugly, but I suspect I have to work through what is in the lines before getting to the new mixture.
Will probably go back to the old MAF tomorrow, check vacuum and perhaps disconnect the EGT sensors. One thing at a time of course
Just added enough Stabil for 20 gallons and added 10 gallons of fresh premium. Still running ugly, but I suspect I have to work through what is in the lines before getting to the new mixture.
Will probably go back to the old MAF tomorrow, check vacuum and perhaps disconnect the EGT sensors. One thing at a time of course
07-11-2008, 11:54 PM
#56
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Stabil?
How OLD was/is the gas in the tank?
The interweb buzz is that the newer formulations of gas is 'degrading' after about 3 ? months.
And Stabil wasn't able to hold the newer gas stable.
I didn't catch if there was gas recently put into the tank.
How OLD was/is the gas in the tank?
The interweb buzz is that the newer formulations of gas is 'degrading' after about 3 ? months.
And Stabil wasn't able to hold the newer gas stable.
I didn't catch if there was gas recently put into the tank.
07-12-2008, 01:10 AM
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07-12-2008, 01:49 AM
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