Car Leaning out above 4K
Thread Starter
On The Tree
Joined: Jan 2004
Posts: 144
Likes: 0
Car Leaning out above 4K Hey all.....I know this is a little early to ask, but just wanted to get a heads up on the problem. Every once in a while, I will watch my A/F guage during a WOT romp. At about 4K, the guage drops to lean and I notice a huge power loss. I always let off at this point and just chock it up a problem I have to fix. Any clues I can check. I am planning on changing fuel filter. I have had several bent push rods, so I am planning on check all of them for straightness. Bad springs? Bad knock sensor?
Jonathan Hays
Jonathan Hays
Knock sensor will only affect timing. Bent pushrods
may trigger false knock detects but this is also a
timing-only issue. Really need to get an idea of
what your fuel pressure is doing at the point of
problem. Most fuel pressure gauges are too short
of hose to work with hood closed on the road but
maybe you could cobble something up. The full
time electric-sender in-car type are way pricey.
Fuel filter, line kink/crush, poor electrical connection
are all possibilities for fuel fade.
may trigger false knock detects but this is also a
timing-only issue. Really need to get an idea of
what your fuel pressure is doing at the point of
problem. Most fuel pressure gauges are too short
of hose to work with hood closed on the road but
maybe you could cobble something up. The full
time electric-sender in-car type are way pricey.
Fuel filter, line kink/crush, poor electrical connection
are all possibilities for fuel fade.
Thread Starter
On The Tree
Joined: Jan 2004
Posts: 144
Likes: 0
Ok, this is a big help...thanks....Can I take this and pretty much eliminate springs and valves? Clogged injector, pump, filter, line (probably not), poor connection? I guess the next step is to do some FP tests...If I am not getting pressure drop, then I would probably be only the injectors or something more mechanical, correct?
Jonathan Hays
Jonathan Hays
I think springs & valves are pretty much unlikely
culprits in a mixture drop problem. Though there
have been TSBs for bad rockers (needle bearings
in oil pan) etc. and if you suspect the valvetrain
(pushrods) you might as well eliminate all the
known mechanical problems (by replacement)
first. It seems to me that the only way you should
see a PCM-commanded mixture drop would be to
fall out of WOT / power enrichment, and the
stock thresholds for PE are so low I don't think
this is happening.
One other possibility is some sort of engine
electrical problem, like a poor ground, that
is corrupting some sensors' readings (like
O2s that rely on engine-to-PCM ground
for signal reference, engine ground coming
up relative to PCM ground could manifest
in other single-ended sensors too). You
might check ground integrity with a meter
with engine running, engine to chassis
and engine to PCM ground (like the black
wire on MAF or TPS). Just to eliminate
the simple things you can from topside.
Right answer = 0.00V difference between
any two of the three.
culprits in a mixture drop problem. Though there
have been TSBs for bad rockers (needle bearings
in oil pan) etc. and if you suspect the valvetrain
(pushrods) you might as well eliminate all the
known mechanical problems (by replacement)
first. It seems to me that the only way you should
see a PCM-commanded mixture drop would be to
fall out of WOT / power enrichment, and the
stock thresholds for PE are so low I don't think
this is happening.
One other possibility is some sort of engine
electrical problem, like a poor ground, that
is corrupting some sensors' readings (like
O2s that rely on engine-to-PCM ground
for signal reference, engine ground coming
up relative to PCM ground could manifest
in other single-ended sensors too). You
might check ground integrity with a meter
with engine running, engine to chassis
and engine to PCM ground (like the black
wire on MAF or TPS). Just to eliminate
the simple things you can from topside.
Right answer = 0.00V difference between
any two of the three.
TECH Addict
Joined: Jul 2002
Posts: 2,261
Likes: 0
Originally Posted by Twister
Hey all.....I know this is a little early to ask, but just wanted to get a heads up on the problem. Every once in a while, I will watch my A/F guage during a WOT romp. At about 4K, the guage drops to lean and I notice a huge power loss. I always let off at this point and just chock it up a problem I have to fix. Any clues I can check. I am planning on changing fuel filter. I have had several bent push rods, so I am planning on check all of them for straightness. Bad springs? Bad knock sensor?
Jonathan Hays
Jonathan Hays
Recent Gameover (see sticky above) info states that PCM relies 100% on the MAF at and above 4000 RPM - bad MAF???
Thread Starter
On The Tree
Joined: Jan 2004
Posts: 144
Likes: 0
Originally Posted by Bink
Is your car stock? What mods? Stock PCM??
Recent Gameover (see sticky above) info states that PCM relies 100% on the MAF at and above 4000 RPM - bad MAF???
Recent Gameover (see sticky above) info states that PCM relies 100% on the MAF at and above 4000 RPM - bad MAF???
FormerVendor
Joined: Jan 2003
Posts: 525
Likes: 0
From: Melbourne, Australia
floating valves will show as a lean spike in your AFR's, although 4k seems a little low, although if they are the stock springs and you have had valvetrain probs before it sounds likely. If it were me I would get them all checked, repair after dropping a valve ain't cheap...
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Thread Starter
On The Tree
Joined: Jan 2004
Posts: 144
Likes: 0
Originally Posted by gameover
floating valves will show as a lean spike in your AFR's, although 4k seems a little low, although if they are the stock springs and you have had valvetrain probs before it sounds likely. If it were me I would get them all checked, repair after dropping a valve ain't cheap...
Jonathan Hays
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Verdad Gallardo You know, I have gotten into a behavior like this
through my own tuning meddling, I believe it is
about the abuse mode settings. Do you know
whether this car has been retuned? Basically it
seems if I "flutter" the pedal while accelerating
I can get "stuck" in a low power output state as
you describe, but once I back out of WOT and
resume, full power. This is not lean-out, though
(which would give KR signature) but a straight
spark pull. I've gotten it better but still something
is not quite killed yet - the closer I get to killing
it, the less frequently it shows up to be tagged.
It might be worth the small fee to go into a
dealership and have your PCM reflashed to stock
(after removing the HPP3 tune, just so it's
either resellable or set to program you again),
start over w/ stock MAF and stock program and
see if you get a more "normal" behaving ride.
through my own tuning meddling, I believe it is
about the abuse mode settings. Do you know
whether this car has been retuned? Basically it
seems if I "flutter" the pedal while accelerating
I can get "stuck" in a low power output state as
you describe, but once I back out of WOT and
resume, full power. This is not lean-out, though
(which would give KR signature) but a straight
spark pull. I've gotten it better but still something
is not quite killed yet - the closer I get to killing
it, the less frequently it shows up to be tagged.
It might be worth the small fee to go into a
dealership and have your PCM reflashed to stock
(after removing the HPP3 tune, just so it's
either resellable or set to program you again),
start over w/ stock MAF and stock program and
see if you get a more "normal" behaving ride.