1994 Firebird Formula DTC 55
07-29-2013, 07:35 PM
#1
Staging Lane
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1994 Firebird Formula DTC 55 1994 Firebird Formula V8 5.7L six speed manual
Car is throwing me DTC 55 - Fuel System Lean
The car has little power particularly when taking off from a stop.
On my way to work I was doing 90 in 6th and it suddenly happened and it's been this way ever since.
Naturally I started in the fuel system, I have replaced the fuel filter and the fuel pressure regulator, both new parts. I have a "spare" fuel pump, it's brand new and I was thinking of putting it in though I don't think it will fix my issue.
I did notice while monitoring real time data that the egr valve only opens in low rpms, around 1200 but I don't know if this is normal or not. I don't have much experience with this side of auto knowledge so where do go from here?
Car is throwing me DTC 55 - Fuel System Lean
The car has little power particularly when taking off from a stop.
On my way to work I was doing 90 in 6th and it suddenly happened and it's been this way ever since.
Naturally I started in the fuel system, I have replaced the fuel filter and the fuel pressure regulator, both new parts. I have a "spare" fuel pump, it's brand new and I was thinking of putting it in though I don't think it will fix my issue.
I did notice while monitoring real time data that the egr valve only opens in low rpms, around 1200 but I don't know if this is normal or not. I don't have much experience with this side of auto knowledge so where do go from here?
07-30-2013, 12:43 AM
#2
Check fuel pressure before you go replacing anything else.
EGR is supposed to open in low rpm's. Upper limit is 2,500 I think. It also takes into account speed and throttle position IIRC.
Your O2 millitvolts are way low indicating pretty much pure air passing the O2. Did those numbers bounce around a lot? Or did they hang around at that level?
Your fuel trims look okay which is weird.
I wanna say exhaust leak.
EGR is supposed to open in low rpm's. Upper limit is 2,500 I think. It also takes into account speed and throttle position IIRC.
Your O2 millitvolts are way low indicating pretty much pure air passing the O2. Did those numbers bounce around a lot? Or did they hang around at that level?
Your fuel trims look okay which is weird.
I wanna say exhaust leak.
Last edited by AdsoYo; 07-30-2013 at 12:49 AM.
07-30-2013, 08:21 AM
#3
Second the fuel pressure check idea.
Post the entire log, and I will look at it.
Your left hand (dr side) fuel trim is adding a bunch like 20% in that snapshot. If I remember correctly fuel system lean will only trigger once you have maxed out the trim(s).
O2 mv are nothing to be concerned with from one frame of data, its perfectly normal to bounce from 100-200mv up to 800-900mv but it has to be quickly. Even if it is not that quick it doesn't necessarily indicate an o2 sensor problem.
Post the entire log, and I will look at it.
Your left hand (dr side) fuel trim is adding a bunch like 20% in that snapshot. If I remember correctly fuel system lean will only trigger once you have maxed out the trim(s).
O2 mv are nothing to be concerned with from one frame of data, its perfectly normal to bounce from 100-200mv up to 800-900mv but it has to be quickly. Even if it is not that quick it doesn't necessarily indicate an o2 sensor problem.
07-30-2013, 09:47 AM
#5
Staging Lane
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Check fuel pressure before you go replacing anything else.
EGR is supposed to open in low rpm's. Upper limit is 2,500 I think. It also takes into account speed and throttle position IIRC.
Your O2 millitvolts are way low indicating pretty much pure air passing the O2. Did those numbers bounce around a lot? Or did they hang around at that level?
Your fuel trims look okay which is weird.
I wanna say exhaust leak.
EGR is supposed to open in low rpm's. Upper limit is 2,500 I think. It also takes into account speed and throttle position IIRC.
Your O2 millitvolts are way low indicating pretty much pure air passing the O2. Did those numbers bounce around a lot? Or did they hang around at that level?
Your fuel trims look okay which is weird.
I wanna say exhaust leak.
o2 sensors bounced around 90-900 mv indicating they are good
I don't know what fuel trim is, but it is highlighted in yellow in the snapshot.
There's no exhaust leak unless its a check valve in the air injection system.
Second the fuel pressure check idea.
Post the entire log, and I will look at it.
Your left hand (dr side) fuel trim is adding a bunch like 20% in that snapshot. If I remember correctly fuel system lean will only trigger once you have maxed out the trim(s).
O2 mv are nothing to be concerned with from one frame of data, its perfectly normal to bounce from 100-200mv up to 800-900mv but it has to be quickly. Even if it is not that quick it doesn't necessarily indicate an o2 sensor problem.
Post the entire log, and I will look at it.
Your left hand (dr side) fuel trim is adding a bunch like 20% in that snapshot. If I remember correctly fuel system lean will only trigger once you have maxed out the trim(s).
O2 mv are nothing to be concerned with from one frame of data, its perfectly normal to bounce from 100-200mv up to 800-900mv but it has to be quickly. Even if it is not that quick it doesn't necessarily indicate an o2 sensor problem.
I ALSO WANT TO ADD
Before the car reaches operating temperature, if i rev the motor past 4k rpms the car lets off a hell of a backfire.
07-30-2013, 06:25 PM
#7
The big bang from the exhaust when cold is from the cats/air system.
The fuel trim I was referring to is the LTerm on the left side. Being 144 on one side indicates a fuel being added on that bank and a possible problem... depending on what lead to that snap shot.
As an explanation 128 LTerm Sterm being no added fuel or subtracted fuel to maintain the air fuel ratio. 144/128 = +12.5% fuel since I was too lazy to do the math this morning. The STerms will tell you about the stability of the LTerms. The further off of 128 the STerms are the faster the LTerms will change. When the STerm is 128 the LTerm will stop changing. BTW you can view these in % by altering the units setup in data master.
The yellow trim cell 16 just indicates you're in the idle cell and is not really any concern.
From memory DTC 55 will only set after 3 seconds of wot/pe with the o2 sensor indicating a lean condition.
The fuel trim I was referring to is the LTerm on the left side. Being 144 on one side indicates a fuel being added on that bank and a possible problem... depending on what lead to that snap shot.
As an explanation 128 LTerm Sterm being no added fuel or subtracted fuel to maintain the air fuel ratio. 144/128 = +12.5% fuel since I was too lazy to do the math this morning. The STerms will tell you about the stability of the LTerms. The further off of 128 the STerms are the faster the LTerms will change. When the STerm is 128 the LTerm will stop changing. BTW you can view these in % by altering the units setup in data master.
The yellow trim cell 16 just indicates you're in the idle cell and is not really any concern.
From memory DTC 55 will only set after 3 seconds of wot/pe with the o2 sensor indicating a lean condition.
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08-10-2013, 01:20 PM
#8
Staging Lane
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The big bang from the exhaust when cold is from the cats/air system.
The fuel trim I was referring to is the LTerm on the left side. Being 144 on one side indicates a fuel being added on that bank and a possible problem... depending on what lead to that snap shot.
As an explanation 128 LTerm Sterm being no added fuel or subtracted fuel to maintain the air fuel ratio. 144/128 = +12.5% fuel since I was too lazy to do the math this morning. The STerms will tell you about the stability of the LTerms. The further off of 128 the STerms are the faster the LTerms will change. When the STerm is 128 the LTerm will stop changing. BTW you can view these in % by altering the units setup in data master.
The yellow trim cell 16 just indicates you're in the idle cell and is not really any concern.
From memory DTC 55 will only set after 3 seconds of wot/pe with the o2 sensor indicating a lean condition.
The fuel trim I was referring to is the LTerm on the left side. Being 144 on one side indicates a fuel being added on that bank and a possible problem... depending on what lead to that snap shot.
As an explanation 128 LTerm Sterm being no added fuel or subtracted fuel to maintain the air fuel ratio. 144/128 = +12.5% fuel since I was too lazy to do the math this morning. The STerms will tell you about the stability of the LTerms. The further off of 128 the STerms are the faster the LTerms will change. When the STerm is 128 the LTerm will stop changing. BTW you can view these in % by altering the units setup in data master.
The yellow trim cell 16 just indicates you're in the idle cell and is not really any concern.
From memory DTC 55 will only set after 3 seconds of wot/pe with the o2 sensor indicating a lean condition.
