missing over 40% tps
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Joined: Aug 2006
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From: Mobile AL.
missing over 40% tps ls1, t56, long tubes
tps= throttle position sensor
my car was missing under 40% tps. it kinda always done this when it was raining i just didn't drive it in the rain. if you got over 40% tps it would run fine.
i let my car set up for 8 years. cleaned everything up put it back together.
ran it for the first time and it ran fine. it did miss a little below 40% tps like before and then it straightened up. thought all was well.
now it missing above 40% tps. bad.. (edit: change from below to above, now missing above 40%)
i did replace the o2 sensor extension and the plug wires. plugs were replaced when i got it running again.
only code is p0154 which is bank2 sensor1 o2. i dont think this is the cause but have new ones on the way. it threw this code sometimes long ago.
the 40% tps should be a clue but im not sure. i remember reading something about the pcm running off one sensor (o2/maf/map) and then another at wot which i think starts at 50% tps?
please.. help.. i fell kinda beat down. and thx
tps= throttle position sensor
my car was missing under 40% tps. it kinda always done this when it was raining i just didn't drive it in the rain. if you got over 40% tps it would run fine.
i let my car set up for 8 years. cleaned everything up put it back together.
ran it for the first time and it ran fine. it did miss a little below 40% tps like before and then it straightened up. thought all was well.
now it missing above 40% tps. bad.. (edit: change from below to above, now missing above 40%)
i did replace the o2 sensor extension and the plug wires. plugs were replaced when i got it running again.
only code is p0154 which is bank2 sensor1 o2. i dont think this is the cause but have new ones on the way. it threw this code sometimes long ago.
the 40% tps should be a clue but im not sure. i remember reading something about the pcm running off one sensor (o2/maf/map) and then another at wot which i think starts at 50% tps?
please.. help.. i fell kinda beat down. and thx
Last edited by fouz65; Feb 14, 2018 at 07:21 PM.
When an engine is stone cold it runs in open loop (NO o2 usage). Once warm around 160* in jumps into closed loop, and uses the o2s. If it had a code for o2 thin is most likely bad.
Tps% doesnt have anything to do with the o2 unless when u reach 40% its likely going into Power Enrichment mode. In PE mode o2s are not used. So there is a possibilitie the o2 could be screwing with the pcm. U can try unhooking the o2s completely and see how it drives. This will force the ecm into open loop.
Tps% doesnt have anything to do with the o2 unless when u reach 40% its likely going into Power Enrichment mode. In PE mode o2s are not used. So there is a possibilitie the o2 could be screwing with the pcm. U can try unhooking the o2s completely and see how it drives. This will force the ecm into open loop.
Thread Starter
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Joined: Aug 2006
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From: Mobile AL.
ill try that but as soon as i fired it up today and hit the road it was missing but i didn't look at the temp so ill try that tomorrow. but anything below 160* the o2 aren't used so kinda be the same as unhooking them if driving below 160*?
new o2s on the way. i just don't think its them. only other things i can think of is a coil of maybe the maf. at this point im buying parts and installing them one at a time. not very scientific . but im out of ideas.
new o2s on the way. i just don't think its them. only other things i can think of is a coil of maybe the maf. at this point im buying parts and installing them one at a time. not very scientific . but im out of ideas.
Thread Starter
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Joined: Aug 2006
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From: Mobile AL.
well i think i just found the problem. fuel pressure drops from 60 psi to 40-30 psi while reving the engine. unless im wrong i dont think its suppose to do that.
guess ill add new fuel pump to the parts list. the one in it is only a month or so old.
guess ill add new fuel pump to the parts list. the one in it is only a month or so old.
Thread Starter
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Joined: Aug 2006
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From: Mobile AL.
walbro 255 from amazon, vendor was walbro. went back reading the reviews and some others saying same thing. maybe an oddball. try em again?
any other good 255lph fuel pumps out there?
any other good 255lph fuel pumps out there?
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Thread Starter
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From: Mobile AL.
new pump came in. put it in. ran much better but still not perfect.
pulled fuel filter. cleaned it. ran perfect for one maybe 2 pulls. than bad, really bad.
new pump was much quieter than the old one which got real loud in its last few days.
then the new one got loud too.
i have a little bit of rust in my tank. i thought i got most of it out. a very very fine powder was in the filter.
i'm going to assume this small amount of rust is killing my pump and walbro pumps aren't that bad. this second pump last maybe 5 mins. i thought the pre scrren on the pump would stop it.
or can a low voltage kill a pump in 5 mins. volts look good at the gauge but haven't checked volts at pump yet. little bit of searching have lead to a few ideas with bogging at high rpms.
bad pump, bad filter, bad voltage at pump.
going to drop subframe, drop gas tank and clean tank to rule that out and lets face it,
it needs it to not be a half *** job. fuel pumps are getting expensive.
will try the aem340 next
anyways. just updating and always open to ideas. thx...
pulled fuel filter. cleaned it. ran perfect for one maybe 2 pulls. than bad, really bad.
new pump was much quieter than the old one which got real loud in its last few days.
then the new one got loud too.
i have a little bit of rust in my tank. i thought i got most of it out. a very very fine powder was in the filter.
i'm going to assume this small amount of rust is killing my pump and walbro pumps aren't that bad. this second pump last maybe 5 mins. i thought the pre scrren on the pump would stop it.
or can a low voltage kill a pump in 5 mins. volts look good at the gauge but haven't checked volts at pump yet. little bit of searching have lead to a few ideas with bogging at high rpms.
bad pump, bad filter, bad voltage at pump.
going to drop subframe, drop gas tank and clean tank to rule that out and lets face it,
it needs it to not be a half *** job. fuel pumps are getting expensive.
will try the aem340 next
anyways. just updating and always open to ideas. thx...
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Verdad Gallardo Probably some type of electrical issue. I doubt the rust is the issue, but it could be.
If your up for it i would rewire the complete fuel pump setup. Run some decent sized wire like 12gauge to the pump for hot and ground. Add a relay with 10gauge fused from the battery. Use your original fuel pump hot wire to trigger the relay. Ive done this to alot of high hp cars and it helps keep the pumps alot happier!
Higher flowing pumps draw more amps and need the extra voltage and bigger wire.
If your up for it i would rewire the complete fuel pump setup. Run some decent sized wire like 12gauge to the pump for hot and ground. Add a relay with 10gauge fused from the battery. Use your original fuel pump hot wire to trigger the relay. Ive done this to alot of high hp cars and it helps keep the pumps alot happier!
Higher flowing pumps draw more amps and need the extra voltage and bigger wire.
Thread Starter
TECH Apprentice
Joined: Aug 2006
Posts: 301
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From: Mobile AL.
going to take care of rust and voltage just to make sure. battery is in the truck right by the fuel pump so its not a big deal.
only thing im trying to figure out is how to bypass the plug on the tank access panel. cant see running a bigger wire and have a choke point at the plug with the old wire. so need to figure that out. after searching it seems most just run the bigger wire close to the panel and keep about 3 inch of the old wire.
only thing im trying to figure out is how to bypass the plug on the tank access panel. cant see running a bigger wire and have a choke point at the plug with the old wire. so need to figure that out. after searching it seems most just run the bigger wire close to the panel and keep about 3 inch of the old wire.
" but im out of ideas."
Here's a few.
1. Do a data log, instead of throwing parts at it.
2. A rusty tank is JUNK. Change it.
3. If the engine was run w/ rust in the fuel, it's in the injs, too.
4. All of these>> "bad pump, bad filter, bad voltage at pump."
5. Guaranteed a problem w/ injs>> "i let my car set up for 8 years."
6. A dirty/faulty MAF? Tap on it w/ a screwdriver handle. Stumble?
7. Do a VOM test on the TPS.
Here's a few.
1. Do a data log, instead of throwing parts at it.
2. A rusty tank is JUNK. Change it.
3. If the engine was run w/ rust in the fuel, it's in the injs, too.
4. All of these>> "bad pump, bad filter, bad voltage at pump."
5. Guaranteed a problem w/ injs>> "i let my car set up for 8 years."
6. A dirty/faulty MAF? Tap on it w/ a screwdriver handle. Stumble?
7. Do a VOM test on the TPS.
At the risk of offending -- have you changed spark plugs and wires? Running a effed up mixture can destroy the plugs. My wife's vette was detonating like crazy when I bought it. Actually used as a price negotiating ploy. Plugs were toasted and the fuel trims were sky high indicating lean. Fixed the mixture, new plugs, new wires, boom shackalacka
Thread Starter
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Joined: Aug 2006
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From: Mobile AL.
to clear up a few thing the tank is plastic. the source of the rust is a small bracket in the tank the fuel pump hangs from. i tryed to clean it the best i could without dropping it but it obliviously was a fail. its a small amount of rust, but yes there is rust in the tank that will get removed now.
new part list:
spark plugs
starter
alternater
fuel pump
injectors
cleaned fuel filter (its a cleanable one)
air filter
fresh gas
oil pan gasket
knock sensors
valley cover gasket
intakes gaskets
radiator fan
engine pre oiled with a pump and hose to going the oil galley on the front of the engine. then slowly turning the rotating assembly.
change all fluids engine, trans, rear diff.
and a complete outside cleaning with a SS brush on a drimel with most stuff removed form engine.
just throwing that out so no one thinks i threw a hot battery in the car after 8 years and wondered why it runs like ****. lol, i can see how someone would think. completely understand.
since this thread:
o2 sensors
o2 extensions
plug wires
fuel pump (again)
and thanks for the ideas. definitely wont get offended.
wouldn't have posted if that was the case.
old geezer; i dont know what a VOM test is but will google it but I a have a scan gauge 2 that gives me the TPS% on the fly so i think its working.
MAF i dont know much about. but the reason i wondered was cause of past problems that where never solved.
new part list:
spark plugs
starter
alternater
fuel pump
injectors
cleaned fuel filter (its a cleanable one)
air filter
fresh gas
oil pan gasket
knock sensors
valley cover gasket
intakes gaskets
radiator fan
engine pre oiled with a pump and hose to going the oil galley on the front of the engine. then slowly turning the rotating assembly.
change all fluids engine, trans, rear diff.
and a complete outside cleaning with a SS brush on a drimel with most stuff removed form engine.
just throwing that out so no one thinks i threw a hot battery in the car after 8 years and wondered why it runs like ****. lol, i can see how someone would think. completely understand.
since this thread:
o2 sensors
o2 extensions
plug wires
fuel pump (again)
and thanks for the ideas. definitely wont get offended.
wouldn't have posted if that was the case.
old geezer; i dont know what a VOM test is but will google it but I a have a scan gauge 2 that gives me the TPS% on the fly so i think its working.
MAF i dont know much about. but the reason i wondered was cause of past problems that where never solved.
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Joined: Oct 2014
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From: Virginia
It could easily be the MAF that would cause missing like that. Try unplugging it and see if it clears up at idle. I don't know if you had a full tune done, but if your VE table is good, it should run fine without it. If you don't know, and it has been tuned for injectors, cam, headers, etc, then a wideband is very useful to see what it's up to.
If you're not sure about the tune, then I wouldn't run it up higher with the MAF unplugged without a wideband. If you don't have any significant airflow changing mods (like a cam, heads, etc) then the stock VE won't be too far off. It should run okay without the MAF, but again, every engine is different, so be careful there. Part throttle and normal driving won't hurt anything.
Obviously solving your fuel delivery is the biggest issue to address before moving on. In my experience though, larger injectors can easily make up for a pressure drop from the pump. It's hardly even noticeable, but I don't know if you have bigger injectors or not. In either case, it won't cause missing like you explained, unless they're clogged.
If you're not sure about the tune, then I wouldn't run it up higher with the MAF unplugged without a wideband. If you don't have any significant airflow changing mods (like a cam, heads, etc) then the stock VE won't be too far off. It should run okay without the MAF, but again, every engine is different, so be careful there. Part throttle and normal driving won't hurt anything.
Obviously solving your fuel delivery is the biggest issue to address before moving on. In my experience though, larger injectors can easily make up for a pressure drop from the pump. It's hardly even noticeable, but I don't know if you have bigger injectors or not. In either case, it won't cause missing like you explained, unless they're clogged.
Thread Starter
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From: Mobile AL.
ChopperDoc:
car was tuned in 2006 when i did the swap. nothing change since then. replaced the injector with OE Number: 0280155715 which iirc are 24lb @ 43something psi. my psi is at 60psi. which is what it was tuned for.
when the pump worked it ran out great. so i agree, my problems atm should be fixed with clean tank,new fuel pump and a relay placed right at the pump with a longer gauge wire.
i do want a wideband but not in the budget at the moment. right now just wanna get it running then find out if i wanna keep it or sell it. been lucky and people are crashing 240sx all the time (yea drifting smh) so it has held its value i think.
car was tuned in 2006 when i did the swap. nothing change since then. replaced the injector with OE Number: 0280155715 which iirc are 24lb @ 43something psi. my psi is at 60psi. which is what it was tuned for.
when the pump worked it ran out great. so i agree, my problems atm should be fixed with clean tank,new fuel pump and a relay placed right at the pump with a longer gauge wire.
i do want a wideband but not in the budget at the moment. right now just wanna get it running then find out if i wanna keep it or sell it. been lucky and people are crashing 240sx all the time (yea drifting smh) so it has held its value i think.
Last edited by fouz65; Feb 21, 2018 at 09:39 PM.
TECH Fanatic
Joined: Oct 2014
Posts: 1,220
Likes: 179
From: Virginia
24 pounders might be about 28ish at 60, maybe even 30. I'd have to look up the data, which can be difficult to find with a lot of injectors.
I'm just suggesting that the MAF might have been your original issue. Fuel pump and bad injectors won't help obviously, but a bad MAF will cause a car to run HORRIBLE, especially at higher rpms.
If your MAF is good, then I'd also be checking for vacuum leaks after the MAF, especially at the intake. You can use butane gas or propane (unlit obviously) and blow it around the ports to see if the engine reacts. It's a quick way to find a vacuum leak. The rpm will jump up a bit if you have a leak. That can also cause some missing.
Case and point it sounds like you have an AFR problem. The PCM is likely not getting fueling correct... either mechanically (pump/injectors) or from the air/sensor side (MAF/vacuum leak/O2). A tune would definitely point out where the problems are. Wish I could help ya there.
I'm just suggesting that the MAF might have been your original issue. Fuel pump and bad injectors won't help obviously, but a bad MAF will cause a car to run HORRIBLE, especially at higher rpms.
If your MAF is good, then I'd also be checking for vacuum leaks after the MAF, especially at the intake. You can use butane gas or propane (unlit obviously) and blow it around the ports to see if the engine reacts. It's a quick way to find a vacuum leak. The rpm will jump up a bit if you have a leak. That can also cause some missing.
Case and point it sounds like you have an AFR problem. The PCM is likely not getting fueling correct... either mechanically (pump/injectors) or from the air/sensor side (MAF/vacuum leak/O2). A tune would definitely point out where the problems are. Wish I could help ya there.
