Hesitation Issues
- Thread starter MadStang
- Start date
OP
OP
MadStang
Well-Known Member
the LTFT is adding 20% more fuel than it should for some reason. Vacuum leak?
STFT is very unstable and jumping around.
I'm eating lunch right now but I'll fire the laptop back up and post a screen shot
STFT is very unstable and jumping around.
I'm eating lunch right now but I'll fire the laptop back up and post a screen shot
OP
OP
MadStang
Well-Known Member
Idle
1500RPM (Steady)
2500RPM (Steady)
3500RPM (Steady)
Rev from Idle to 4000RPM
1500RPM (Steady)
2500RPM (Steady)
3500RPM (Steady)
Rev from Idle to 4000RPM
i cant see your pictures but if the PCM is adding 20% fuel you most likely have a vacuum leak. the air coming in past the MAF is unmetered so no fuel is being delivered for that amount of air until the o2 sensors recognize the condition and the PCM then starts adding.
i would pick up a can of starting fluid or brake cleaner (make sure its flammable, not all is). and start spraying everywhere there could be a leak until the engine RPM increases. with the extra quiet exhaust it should be pretty easy to find/hear the leak.
i would pick up a can of starting fluid or brake cleaner (make sure its flammable, not all is). and start spraying everywhere there could be a leak until the engine RPM increases. with the extra quiet exhaust it should be pretty easy to find/hear the leak.
OP
OP
MadStang
Well-Known Member
Lee12609 said:
Question, could a header leak cause this issue since it's pre-o2? I have a tap tap tap coming from the passenger side header area and when I stick my head down by the valve cover it's like sticking your head into an oven vs. on the driver side that is not the case.
Otherwise, Carb cleaner it is.
OP
OP
MadStang
Well-Known Member
So my tuner Joe @ Trick Tuners said it sounds like a vacuum leak. Gonna get some carb cleaner and resolve this issue once and for all.
OP
OP
MadStang
Well-Known Member
so I check for leaks, I literally sprayed the entire bottle of carb cleaner, no difference. no vacuum leak.
Figured out I gapped my plugs incorrectly, .044 vs. .054. But that didn't really make a difference still having issues, I'm stumped. My tuner is stumped.
Figured out I gapped my plugs incorrectly, .044 vs. .054. But that didn't really make a difference still having issues, I'm stumped. My tuner is stumped.
OP
OP
MadStang
Well-Known Member
I'm going to my sponsors shop tomorrow. For shits and giggles I picked up a new IAC valve, no change in idle hang. So I'm returning it tomorrow and calling this trouble shooting a loss on my part. I'm normally very confident in my mechanical abilities, being able to build a 3.8 pushrod motor when I was 16, but, this... this makes me question myself over and over. it's embarrassing.
OP
OP
MadStang
Well-Known Member
sponsor didn't charge me a dime for the work we did today. smoke test found a small vacuum leak. the car no long has the idle all over the place. BUT, we noticed the pressure drop across cylinders is 48-60 depending on throttle position. So that accounts for the excessive fuel smell from the exhaust. How do we fix it? Beats me... we ran outta time and now I'm back to being confused.
OP
OP
MadStang
Well-Known Member
fuel injector pressure drop (that's the denotation on the sct datalog)Lee12609 said:
OP
OP
MadStang
Well-Known Member
I'm suspecting the FRPS or injectors being bad. Those two are the logical issues.
now you have me confused...
you dont have knock sensors, or any way to monitor detonation, so you lost me.
also, the pressures you listed are WAY too high. this could be partly due to the fact that the car is running lean during closed loop, the rail pressure is increased (along with injector pulse width) to add more fuel.
alot of people complain about raw fuel smell when infact its not even close to running rich. when i first installed my vortech the base tune had my car at 11.2:1 afr at idle, could i smell unburnt fuel, NOPE. my best friend has a 500whp lightning, at tip in it blows a HUGE cloud of black smoke (extremely rich) and you cant smell a thing. on the other hand a 2000 gt i tuned with o/r exhaust and bolt ons smells horrible at idle, but a/f is perfect as are fuel trims obviously.
i would invest in a wideband, or see if you can get some time on a dyno, not just for WOT tuning, but to ease your mind about the rich condition you possibly have at idle/part throttle, but i'd personally just get a wideband and street tune it.
give it a few days now that the vacuum leak is fixed and see how you feel. where was the leak btw?
PS, did you get the injectors yet?
you dont have knock sensors, or any way to monitor detonation, so you lost me.
also, the pressures you listed are WAY too high. this could be partly due to the fact that the car is running lean during closed loop, the rail pressure is increased (along with injector pulse width) to add more fuel.
alot of people complain about raw fuel smell when infact its not even close to running rich. when i first installed my vortech the base tune had my car at 11.2:1 afr at idle, could i smell unburnt fuel, NOPE. my best friend has a 500whp lightning, at tip in it blows a HUGE cloud of black smoke (extremely rich) and you cant smell a thing. on the other hand a 2000 gt i tuned with o/r exhaust and bolt ons smells horrible at idle, but a/f is perfect as are fuel trims obviously.
i would invest in a wideband, or see if you can get some time on a dyno, not just for WOT tuning, but to ease your mind about the rich condition you possibly have at idle/part throttle, but i'd personally just get a wideband and street tune it.
give it a few days now that the vacuum leak is fixed and see how you feel. where was the leak btw?
PS, did you get the injectors yet?
OP
OP
MadStang
Well-Known Member
Lee12609 said:
I said denotation not detonation!
yeah when the car is cold it runs smoother. Starting it when it's warm feels like something is holding it back and then after a second bam ignition. then rough idle like crazy with car up to temp.
Yeah I'm fine with the raw fuel smell honestly, the car hesitating and sputtering... not so much.
Well the car is going back to my sponsors shop tomorrow, I understand it needs to relearn itself but I'll be damned if a car relearning itself runs this shitty. The vacuum leak was on the back side of the plenum, the hose was too big for the fitting.
yeah I got them last Saturday. I've had no reason to put them in since it's the rail pressure not the injectors themselves that are flipping out.
Also, just for shits and giggles I tried to check the rail pressure from the schrader valve vs. just using my datalogs. the valve does not register any fuel and if I just press the pin in no fuel comes out, even when priming the pump...
OP
OP
MadStang
Well-Known Member
okay, here's the deal. The car runs damn near flawlessly when the motor is not up to temp. Then when I start getting temps, I start get idle hang, missing at idle, and hiccuping. By no means is the idle 100% smooth when I have no temps, but, it's way better than when I do!
OP
OP
MadStang
Well-Known Member
well I dunno why and I started laughing as I did it. I turned the a/c on, the idle spiked for a couple of seconds then dropped to 700. and idled more smooth than my rotary and rotary cars idle super smooth! i turned the a/c off and no change idle quality was great. But when I gave it gas and the idle dropped back down it started to miss again...
OP
OP
MadStang
Well-Known Member
well I datalogged it once more to see what the vacuum leak fix did.
I have an average of 39 psi for the pressure drop, so that's not the issue anymore.
The car still has a LTFT of an average of 1.20. STFT at idle is about correct. I start to see the STFT did into the low 90's when I get into the higher rpm's. The o2 voltage is an average of .4v and fluctuates as it should.
Now the kicker. I datalogged misfires on all 8 cylinders. 1 and 2 had the most (cylinder 1 was way ahead of 2) and the rest of the cylinders either had just 1 or 0. Cyl#1 got up to a count of 6 in a row at one point...
I really wish I can figure this out. It bug me because my gas mileage is suffering...
oh and lee, I just noticed the injectors you sent have a different part #. Mine are F0TE-D5B, yours are F0TE-D5A. no idea what the difference is.
I have an average of 39 psi for the pressure drop, so that's not the issue anymore.
The car still has a LTFT of an average of 1.20. STFT at idle is about correct. I start to see the STFT did into the low 90's when I get into the higher rpm's. The o2 voltage is an average of .4v and fluctuates as it should.
Now the kicker. I datalogged misfires on all 8 cylinders. 1 and 2 had the most (cylinder 1 was way ahead of 2) and the rest of the cylinders either had just 1 or 0. Cyl#1 got up to a count of 6 in a row at one point...
I really wish I can figure this out. It bug me because my gas mileage is suffering...
oh and lee, I just noticed the injectors you sent have a different part #. Mine are F0TE-D5B, yours are F0TE-D5A. no idea what the difference is.
OP
OP
MadStang
Well-Known Member
so for shits and giggles I put in Lee's injectors. Slightly better idle but nothing significant. I did have one injector with the plastic nozzle boot cracked but nothing significant.
I test drove it and really played with it, when between 1700-2200RPM's, and I let off the gas, I get a severe hiccup. Verified when I got home that those rpm's is where my STFT spikes low and runs incredibly rich.
Average STFT is .97 (on both bank 1 & 2) though which is only slightly rich and the car feels great driving at every other rpm, no hesitation or problems.
My LTFT those is kinda wack though. Bank 1 is 1.15 and bank 2 is 1.05. the 1.05 is fine but WTF is the deal with Bank 1 being 10% more?
Datalog found no misfires with these injectors.
Pressure drop is high at an average of 48.6 but temperatures are in the high 80's Pressure drop spiked at 54.8 at the highest.
At idle the pressure at the rails is about 48-49.... but STFT is between .95-1.0.
Anytime throttle is increased it drops the STFT down into the .8x range....
Either I have another vacuum leak, exhaust leak (pre-o2), or my tune is screwed up...
I test drove it and really played with it, when between 1700-2200RPM's, and I let off the gas, I get a severe hiccup. Verified when I got home that those rpm's is where my STFT spikes low and runs incredibly rich.
Average STFT is .97 (on both bank 1 & 2) though which is only slightly rich and the car feels great driving at every other rpm, no hesitation or problems.
My LTFT those is kinda wack though. Bank 1 is 1.15 and bank 2 is 1.05. the 1.05 is fine but WTF is the deal with Bank 1 being 10% more?
Datalog found no misfires with these injectors.
Pressure drop is high at an average of 48.6 but temperatures are in the high 80's Pressure drop spiked at 54.8 at the highest.
At idle the pressure at the rails is about 48-49.... but STFT is between .95-1.0.
Anytime throttle is increased it drops the STFT down into the .8x range....
Either I have another vacuum leak, exhaust leak (pre-o2), or my tune is screwed up...
next step is to get that miss gone.
take both coils from the misfiring cylinders and move them to the other bank so take the coils from cyl. 1 and 2 and swap them with cylinders 5 and 6. datalog misfires again and see if the misfire moves with the coils. i dealt with an 03 town car today with similar conditions and i even though i was only getting slight misfires from cylinder 3 replacing the coil to cure the misfire got rid of all problems.
your fuel trim data confuses me because i'm used to seeing it written differently. is anything over 1.0 positive fuel trim and anything under 1.0 negative?
i wouldnt worry too much about the pressure drop unless its low...
take both coils from the misfiring cylinders and move them to the other bank so take the coils from cyl. 1 and 2 and swap them with cylinders 5 and 6. datalog misfires again and see if the misfire moves with the coils. i dealt with an 03 town car today with similar conditions and i even though i was only getting slight misfires from cylinder 3 replacing the coil to cure the misfire got rid of all problems.
your fuel trim data confuses me because i'm used to seeing it written differently. is anything over 1.0 positive fuel trim and anything under 1.0 negative?
i wouldnt worry too much about the pressure drop unless its low...
