LS1 TPS issue, maybe...
This is a discussion on LS1 TPS issue, maybe... within the General Help forums, part of the LSx Technical Help Section category; 2002 LS1 A4 35K miles w/ cam heads Fast 90mm TB intake and the rest of the normal bolt on ...
06-22-2012, 02:03 PM #1
LS1 TPS issue, maybe...
2002 LS1 A4 35K miles w/ cam heads Fast 90mm TB intake and the rest of the normal bolt on stuff.
Car is tuned with the JET software and runs great. PROBLEM... after a few long drives the TPS shows A random % like 6 or 11 and then high idle IAC counts. I've exhausted myself to figure this out, New tps(like 4 or so) relearn TPS procedure, PCM grounds TPS plug and ground, tried a new PCM. IAC counts are in the 30's at idle P/N the TB blade is returning closed, sits on it stop screw. The TPS voltage doesnt vary, it rests at .59v just were it does when it starts every time (telling me its not hanging open) but the % throttle on the scanner tool shows open a few % and then the IAC counts are in the 70 and 80's with a high idle. I believe I ruled out the TPS itself with trying a few new ones and relearn procedure, I dont get it. Can something in the tune cause the PCM to think the TPS % is open when its not or demand this to happen? It seems like this happends after the PCM learns in its trims after a flash or after a TPS relearn and a few long drives 100+ miles or so. this has been ongoing since all the mods and tuning began from its stock form. I cant for the life of me figure out what needs to be addressed. When its running good it runs great.
06-22-2012, 08:31 PM #2
I'm about half drunk so take this for what it's worth. You say when you're logging it that it's showing open 6-11%? You've also put a new tps sensor on it. That would make me think it's physically going to 6-11% and not the pcm randomly thinking it is. Have you tried swapping that tb off completely? What about the tb cable or the return spring on the cam? Have you looked at those at all? The symptoms along with the things you've tried makes me think you have a mechanical issue somewhere. I'll think about this tomorrow some when I'm completely sober.
just reread your post again....is it showing the open blade and high counts all the time after it learns the idle trims? Who did your tuning and did they do an idle airflow tune?
Last edited by 0rion; 06-22-2012 at 08:33 PM.
06-22-2012, 10:32 PM #3
until an unknown variable happends even when the scan shows throttle % above zero the TPS voltage is at its normal rest voltage of .59v, this is the voltage when KOEO or running at idle.
the tps voltage is .59v when everything is running great or when its doing its high idle high IAC counts. If i open the TB the voltage raises nice and smooth and let it go and it returns to its normal at rest closed voltage. its as if when im driving it relearns the TPS position on its own and the PCM decides its open a bit although it isnt. Cable is loose and the throttle bell crank is on its stop.I would expect to TPS voltage to be elevated as well if it was a mechanical issue causing the throttle blade to hang open. I cant force the blade any more closed by hand so I have ruled out mechanical issue holding it open. kill the engine and restart the % is zero and the voltage is still at .59v and idles perfect, drive for a while and bam. random % open value at idle, high IAC count but its normal closed voltage reading. freakin nuts
Last edited by blackonblackws6; 06-22-2012 at 10:37 PM.
06-23-2012, 06:35 AM #4
ok....I slept it off. The first time I read it I thought this was just popping up out of the blue but after reading again it sounds like an idle airflow issue. I'm not familiar with the JET stuff so I'm not sure what you can/can't do with it. What size cam are you running? Going off memory I don't think you want to open the blade with the set screw anymore. The idle base airflow table needs work. What rpm is the car idling at when everything is idling normal?
06-23-2012, 09:08 AM #5
850 rpm with IAC counts in the 30's. COMPCam XR277HR-12
224/228 .537lift 112LSA, P/N 54-418-11
I was told the JEt was just like TC software, I wanted the TC but couldn't buy it only the JET. anyway I have a SnapOn scan tool and Wester's data logger software.
Idle was always the issue with this car after the cam, a few small tweeks and the PCM handled everything until I cammed it. It took a while to make the car like the cam... I'm sure a veteran tuner could fine tune better than me but they dont exsist around here, so I've had to learn on my own over the past couple years with success only this car is fighting me. Mail order tunes didn't get it, I got ripped off a couple times so it was time to own software.
at first second and third attempts I was for sure it was mechanical but I'm not convinced now. Just dont know where to go from here. It does seem to run ok, I would like to see the idle a bit lower but It will search up and down for it and stall if I set it any lower. You're probly on track with idle air flow but I've hit a wall here and can't make sense of it.
06-23-2012, 10:09 AM #6
that's where something like hptuners shines......you can log those idle trims and make adjustments to your tune straight from the log. What part of the country are you in?
Here's a good read on setting a car up to idle with a cam. Like I say....I'm not familiar with JET or what it's capabilities are as far as adjustments it gives you. I always thought it was a canned hand held tuner but that was just my assumption. This thread has some old school tuning stuff in it but it also has some newer good theories in it.
Idle tuning - HP Tuners Bulletin Board
06-23-2012, 11:26 AM #7
the jet is laptop stuff, like TunerCats, it can use each other tune files. same guy developed it so i'm told, just sold the marketing to jet. Not as advanced as HPT or EFILIVE but it shoould be capable. I'm the weak link here admittingly, dispite my background. I live in South West lower Michigan by the big lake. Berrien CO. I don't doubt its tuning causing it just dont know what tables are steering this issue. it idles fine for days then bam this thing pops up and reads %open throttle like it learned it in while driving although the at rest idle TPS voltage reads the same as it always does. the link you posted has some great info, thanks!
the battle goes on
06-23-2012, 11:42 AM #8
ok....I remember the tunercat to JET thing happening several years ago. If memory serves me correctly it was very affordable compared to hptuners/efilive. Tunercat was the OBD 1 software everyone used. Do you have a base running airflow table with that? Should be p/n and in gear rows in that in g/sec based on coolant temp.
06-23-2012, 11:54 AM #9
its obd2 a bit fancier looking than say LS1EDIT, its there customer service that doesnt exsist.
yep and a list of other idle tables. idle air flow p/n gear was fudged some to get it idling. its as if this thing will run fine until it settles in to a learned running pattern then its not so good. dont know, I'm still learning, just when I thought I was old enough to relax.
06-23-2012, 12:18 PM #10
ok....with your logging software can you log desired idle airflow? I know in hptuners it's a pid that's "idle start up friction airflow initial vs ect". You go from a cold start and let it idle up to temp without touching the throttle and that'll populate your desired. Then you basically add or subtract that difference from your RAF table.
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