Lacking power. Back pressure issue?
Thread Starter
Teching In
Joined: Jul 2015
Posts: 14
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From: Rutherfordton NC
Lacking power. Back pressure issue? My automatic 99 SS is completely stock besides LS6 intake and LTs and dumps at the axels. It's also slower than smoke off of dog crap. Like 99-04 V6 mustang slow. The boy that had it before me had the pipes put on and it didn't run right. I drilled a couple holes and put in some o2 sensors and now it runs fine but its not quite right when you floor it. The boy said it needed a tune. He also said he had replaced the plugs and wires. It's not misfiring. I don't wanna pay for a dyno tune if its not gonna fix it. I also don't wanna put exhaust on if its not gonna fix it. His theory was that the long tubes made it breathe better so it was dumping more fuel. I'm no mechanic and that sounds plausable. But I figured if it was running that rich it would throw a check engine code. Thanks in advance.
Thread Starter
Teching In
Joined: Jul 2015
Posts: 14
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From: Rutherfordton NC
Besides the o2 sensor codes, no. And it still does it when I clear the codes. I put the o2 sensors in some spark plug nonfoulers and it fooled the computer long enough to get it inspected. For the 400 miles that it stayed off, it was still slow.
False trimming is a common result of even the best header
swaps. Stock power enrichment is already overly fat and
laying down a positive fuel trim (from cold sensors) only
makes things worse.
The world is full of choices that lie between "do nothing"
and "find studGod tuner with everything guaranteed".
Insisting on only this either/or is liable to leave you exactly
where you sit. While you're waiting, study up.
swaps. Stock power enrichment is already overly fat and
laying down a positive fuel trim (from cold sensors) only
makes things worse.
The world is full of choices that lie between "do nothing"
and "find studGod tuner with everything guaranteed".
Insisting on only this either/or is liable to leave you exactly
where you sit. While you're waiting, study up.
Thread Starter
Teching In
Joined: Jul 2015
Posts: 14
Likes: 0
From: Rutherfordton NC
I watched a couple videos. I'm still a little lost. As I said I'm no mechanic. But I need to look at the LTFT. What should the scan tool show with headers? It sounds like a tune may be the way to go? Or is it something like an exhaust leak?
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you have mods that are altering the airflow characteristics of the engine on both intake and exhaust sides...it needs a tune
but that being said before you take it to be tuned be 100% sure the following are in order:
clean the MAF with cleaner, try unplugging it and see if the car runs better...could be damaged
check the plugs and wires, he could have cracked a plug during header install
change the fuel filter and run a good cleaner like seafoam through the tank
are the o2 sensors you installed new and correct?
is the engine temp sensor reading correctly?
is the intake air temp sensor reading correctly?
do you have vacuum leaks from the intake swap?
Research who you take it for to do the tuning. There are a lot of poor tuners out there looking to make a quick buck.
but that being said before you take it to be tuned be 100% sure the following are in order:
clean the MAF with cleaner, try unplugging it and see if the car runs better...could be damaged
check the plugs and wires, he could have cracked a plug during header install
change the fuel filter and run a good cleaner like seafoam through the tank
are the o2 sensors you installed new and correct?
is the engine temp sensor reading correctly?
is the intake air temp sensor reading correctly?
do you have vacuum leaks from the intake swap?
Research who you take it for to do the tuning. There are a lot of poor tuners out there looking to make a quick buck.
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Verdad Gallardo Thread Starter
Teching In
Joined: Jul 2015
Posts: 14
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From: Rutherfordton NC
Do you think it would hurt anything just to leave it like is for a while? I'm wanting to do a light build. Fast intake. Small cam. Exhaust. Maybe heads if I win the big prize on a scratch off lol. Why pay to tune it twice if I can wait and do it all at the same time?
Teching In
Joined: Dec 2013
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a vacuum gauge mounted in a plug mounted into the o2s bung will allow you to measure back pressure. any kind of pressure is bad, but 2psi is considered the line between good and bad. Do you hear air rushing that isn't an vacuum leak?
you have mods that are altering the airflow characteristics of the engine on both intake and exhaust sides...it needs a tune
but that being said before you take it to be tuned be 100% sure the following are in order:
clean the MAF with cleaner, try unplugging it and see if the car runs better...could be damaged
check the plugs and wires, he could have cracked a plug during header install
change the fuel filter and run a good cleaner like seafoam through the tank
are the o2 sensors you installed new and correct?
is the engine temp sensor reading correctly?
is the intake air temp sensor reading correctly?
do you have vacuum leaks from the intake swap?
Research who you take it for to do the tuning. There are a lot of poor tuners out there looking to make a quick buck.
but that being said before you take it to be tuned be 100% sure the following are in order:
clean the MAF with cleaner, try unplugging it and see if the car runs better...could be damaged
check the plugs and wires, he could have cracked a plug during header install
change the fuel filter and run a good cleaner like seafoam through the tank
are the o2 sensors you installed new and correct?
is the engine temp sensor reading correctly?
is the intake air temp sensor reading correctly?
do you have vacuum leaks from the intake swap?
Research who you take it for to do the tuning. There are a lot of poor tuners out there looking to make a quick buck.
This is a great guide. . I'd follow this for now. Something is not right, even without a tune it shouldn't be that slow and/or sluggish
It's not uncommon for sensors to be failing and not throw a code. The PCM does not trigger codes for many of them until it shows a drastically incorrect reading several times.
It's better to observe what they are reading with a scan tool and see if they are reporting logical numbers.
It's better to observe what they are reading with a scan tool and see if they are reporting logical numbers.
It's not uncommon for sensors to be failing and not throw a code. The PCM does not trigger codes for many of them until it shows a drastically incorrect reading several times. It's better to observe what they are reading with a scan tool and see if they are reporting logical numbers.