Spark Advance Problem
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Joined: Apr 2002
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From: Houston
Spark Advance Problem
OK, I'll admit it. This isn't a Ford truck question. But it is a Ford engine question and I figured one of you guys would probably know the answer.
I have a '94 T-Bird with the 4.6 L V-8. It has developed a horrible stumble whenever I mash the pedal suddenly. If I ease into the pedal slowly though, it seems to accelerate nicely. I've also noticed that the engine pings severely on anything but super unleaded.
The engine check light comes on periodically. AutoTap reads the code as either "Bank 1 Lean Condition" or "Bank 2 Lean Condition". I monitored several sensors and happened to notice that my spark advance runs 22.5 degrees at idle and then drops to exactly 20 degrees at all engine rpm above idle. Something seems to removing advance instead of adding it at high rpm.
Given the pinging and acceleration problems, it seems pretty clear that the spark advance is hosed - but what controls it? Is there some sensor that sets advance or is that handled by the engine computer based on many variables?
I'm hoping this is a common 4.6 issue that someone can enlighten me on. Any help is much appreciated.
Thanks,
I have a '94 T-Bird with the 4.6 L V-8. It has developed a horrible stumble whenever I mash the pedal suddenly. If I ease into the pedal slowly though, it seems to accelerate nicely. I've also noticed that the engine pings severely on anything but super unleaded.
The engine check light comes on periodically. AutoTap reads the code as either "Bank 1 Lean Condition" or "Bank 2 Lean Condition". I monitored several sensors and happened to notice that my spark advance runs 22.5 degrees at idle and then drops to exactly 20 degrees at all engine rpm above idle. Something seems to removing advance instead of adding it at high rpm.
Given the pinging and acceleration problems, it seems pretty clear that the spark advance is hosed - but what controls it? Is there some sensor that sets advance or is that handled by the engine computer based on many variables?
I'm hoping this is a common 4.6 issue that someone can enlighten me on. Any help is much appreciated.
Thanks,
Hotshot
Joined: Aug 2002
Posts: 12,679
Likes: 15
From: BC, Canada
Spark Advance Problem
The advance is totally controlled by the PCM...the car's computer.
It sounds like your MAF sensor may be dirty and need to be cleaned. The hesitation and pinging are very common signs of that.
It sounds like your MAF sensor may be dirty and need to be cleaned. The hesitation and pinging are very common signs of that.
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From: Houston
Spark Advance Problem
I'd already tried cleaning the MAF sensor with alcohol - didn't help noticably. I also priced one at $200 and decided that was too much to take a flier on just in case it might help.
That was before I noticed the frozen spark advance today. Also, The MAF voltage and flow readings do vary consistently with rpm as if it's reading something real, though I don't know what numbers it should be recording.
Might there be some other bad sensor that's tricking the cpu into mis-adjusting the spark advance?
That was before I noticed the frozen spark advance today. Also, The MAF voltage and flow readings do vary consistently with rpm as if it's reading something real, though I don't know what numbers it should be recording.
Might there be some other bad sensor that's tricking the cpu into mis-adjusting the spark advance?
Post Fiend
Joined: Jan 2002
Posts: 5,859
Likes: 7
From: USA
Spark Advance Problem
Okay ,look at it this way
Bank 1or bank 2 lean can be the following( maf,02 sensors ,leaky intake o-rings, TPS sensor,CMP sensor ,CKP sensor,)
If you have the manual for this vehicle chk the the resistance values for the 02 sensors first or replace them.
Just my .02
Rich
Bank 1or bank 2 lean can be the following( maf,02 sensors ,leaky intake o-rings, TPS sensor,CMP sensor ,CKP sensor,)
If you have the manual for this vehicle chk the the resistance values for the 02 sensors first or replace them.
Just my .02
Rich
Post Fiend
Joined: Jan 2002
Posts: 5,859
Likes: 7
From: USA
Spark Advance Problem
In my last post I failed to mention ,that the pcm takes all its info from the sensors and then determines your spark advance or timing based on those inputs.
My approach to this would be the o2 sensors first, if there input values are wrong .
I don't have an 4.6 l only a 5.4 l but engine controls are they same!
Rich
My approach to this would be the o2 sensors first, if there input values are wrong .
I don't have an 4.6 l only a 5.4 l but engine controls are they same!
Rich
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Joined: Jul 2002
Posts: 42,561
Likes: 423
From: Long Island USA
Spark Advance Problem
My '96 4.6L t-bird did the same thing when the MAF was dirty from an over-oiled K&N (from the factory).
Clean the MAF with something besides alcohol, like brake cleaner. Then, disconnect the battery and leave it off for an hour. Reconnect the battery and test-drive.
Stumbling on acceleration is usually the MAF. Using an Autotap, it usually said either Bank 1 or Bank 2 lean.
The timing is all wrong because the computer goes into open loop, because it has no idea what's going on.
CHECK THE THROTTLE POSITION SENSOR TOO! However, if you don't have a K&N filter, I think the MAF is bad.
art k.
Clean the MAF with something besides alcohol, like brake cleaner. Then, disconnect the battery and leave it off for an hour. Reconnect the battery and test-drive.
Stumbling on acceleration is usually the MAF. Using an Autotap, it usually said either Bank 1 or Bank 2 lean.
The timing is all wrong because the computer goes into open loop, because it has no idea what's going on.
CHECK THE THROTTLE POSITION SENSOR TOO! However, if you don't have a K&N filter, I think the MAF is bad.
art k.
Last edited by krewat; Jan 21, 2003 at 01:10 PM.
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