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Ridiculous rich smell at idle, no changes editing tables

 
Old 03-11-2019, 01:39 PM
  #1  
camzarco
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Default Ridiculous rich smell at idle, no changes editing tables

Hi all
My car is a 2002 c5 z06, I am from Spain Europe. The car was sent to LPE 4 years ago to be prepared with a 427 CID LS7 660 HP package. The package was installed, tuned and dynoed at LPE.
When the car arrived to Spain the gasoline smell was aceptable considering the large cam (GT 21). Idle was around 11.8 AFR and 1000 rpm.

4 month ago the idle went to 10.1 without any reason, idle smells now super rich, eyes stitching and is embarrasing stopping at ligths
we checked everything on the car, potential intake and exhaust leaks, we changed o2 sensors (front and rear), changed cats 1000 miles ago, we did check injector leaks (no issues), we change coils, cables and sparks. My tuner was working with HP Tuners to see if something is wrong. He was working
all the afternoon checking and modifing tables but nothing changed. here you have the things he did;

-Move the ECU to open loop.
-edit MAF table, i moved to stupid values to see any change?( from 17 g/s to 4g/s)
-edit VE table, same as maf (from 60 to 10)
-edit MAF table at Cranking, nothing
-edit lambda demand (14.7)
-edit lambda table rich/lean voltajes

Maf values are ok, if we change the table wecan see the same frecuency gets me different g/s. Map sensor Works correctly too. Checked with engine stopped and reads atmosferic pressure, with engine started, reads about 65 kpa

if we put the car in closed loop, we can see the short and long trim go to 10.1, and are near to 0% correction at this value, if i modify the Maf table, closed loop (long and short trims) starts to add fuel to go again to 10.1. Car has some DTC deleted like, lambda, Throttle, AC, Air pump etc, like a race car.

For me the car looks like it is in limp mode and goes to a very rich escenario for safety. Not sure if could be posible with this sort of ECU (GM), we mean is there any hidden table thaat
can be active and we cannot see and modify?

We are desperate because we are not sure if we have a mechanical issue or a tune issue.
Could you help please? What do we have to look at?
Thank you in advance to everyone
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Old 03-11-2019, 11:04 PM
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tblu92
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Modded engines can be troublesome to tune at P/T
Depending on what type of tune your tuner did would help sort it out
1 stock open loop/closed loop tuning using the front 02's and the MAF
2 semi open loop tune using only open loop
3 a speed density tune
If you car is using the MAF and your are getting LTFT readings it is the stock system
So 1st if your car has LT headers they always create a rich P/T condition due to the further mounted front 02's This is why LT's are illegal in most US smog states
There is NO 100% fix but you can make it better by lowering the front 02 switching points which will "trick" the ECM into a lower AFR
2nd I always DELETE the LTFT fuel trims on a cammed or modded engine then verify the AFR with your wideband---
REMEMBER when 1st started warm or cold the fueling is commanded by your "open loop normal" table Often you need to command a LEANER setting again to trick the ECM into the goal of 14.68 -1 AFR at P/T in open loop I often have to command like a 16.1 in the low fueling areas to end up with 14.68
Once warmed the engine switches to CLOSED LOOP where the front 02's command your AFR's and are adjusted via your fuel trims or if they are deleted your MAF table ( this is where you get erroneous readings from LT headers as the 02's do not heat up correctly and read wrong due to the further aft locations)
Do you have larger than stock injectors ? If so this can be an issue if your tuner did NOT scale the injector slope correctly
So many things can cause a rich mixture---Only by data logging and the use of a wideband to verify actual AFR's can sort this out PLUS a tuner who knows how the fueling systems work and where to make corrections
PS I have never had any modded LS or LT engine no matter what mods even boosted that I could never sort out --so your tuner should as well--
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Old 03-13-2019, 06:02 AM
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camzarco
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Originally Posted by tblu92 View Post
Modded engines can be troublesome to tune at P/T
Depending on what type of tune your tuner did would help sort it out
1 stock open loop/closed loop tuning using the front 02's and the MAF
2 semi open loop tune using only open loop
3 a speed density tune
If you car is using the MAF and your are getting LTFT readings it is the stock system
So 1st if your car has LT headers they always create a rich P/T condition due to the further mounted front 02's This is why LT's are illegal in most US smog states
There is NO 100% fix but you can make it better by lowering the front 02 switching points which will "trick" the ECM into a lower AFR
2nd I always DELETE the LTFT fuel trims on a cammed or modded engine then verify the AFR with your wideband---
REMEMBER when 1st started warm or cold the fueling is commanded by your "open loop normal" table Often you need to command a LEANER setting again to trick the ECM into the goal of 14.68 -1 AFR at P/T in open loop I often have to command like a 16.1 in the low fueling areas to end up with 14.68
Once warmed the engine switches to CLOSED LOOP where the front 02's command your AFR's and are adjusted via your fuel trims or if they are deleted your MAF table ( this is where you get erroneous readings from LT headers as the 02's do not heat up correctly and read wrong due to the further aft locations)
Do you have larger than stock injectors ? If so this can be an issue if your tuner did NOT scale the injector slope correctly
So many things can cause a rich mixture---Only by data logging and the use of a wideband to verify actual AFR's can sort this out PLUS a tuner who knows how the fueling systems work and where to make corrections
PS I have never had any modded LS or LT engine no matter what mods even boosted that I could never sort out --so your tuner should as well--
Thank you Tblue, Inyectors are not stock. These are the specs of the LPE pakage just in case give you more info to help us.
Mods are as follows:
- LS7 427 CID
- Nick Williams 102 mm throttle body
- FAST 102 Intake Manifold
- CNC porting & polishing of cylinder heads
- multi-angle valve job & surfacing for 11.5:1 compression
- high performance dual valve springs, titanium retainers & valve locks
- GT21 camshaft by Competition Cams . here you are the link to the cam specs: https://www.lingenfelter.com/PDFdown...L210146006.pdf
- Haltech air intake
- FIC 660cc 72 lbs hour fuel injectors
- 160 degree thermostat
- GM Head gaskets & head bolts
- LG Long Tube Headers & high flow catalysts

How do you usually lower the O2 switching points? Thank you very much for your response
We did not work with a wideband cause we thougth was not necessary at idle but we will do it and let you know the readings

Last edited by camzarco; 03-13-2019 at 06:04 AM.
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Old 03-13-2019, 11:35 PM
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1st of all most all aftermarket injectors are rated at 3 bar (43 PSI) however an LS engine operates at 4 bar 58 PSI make sure at what pressure rating your injectors are rated at For example a 3 bar 50 LB injector on a LS engine must be scaled to 4 bar at 58 PSI where the IFR would now be 56lbs rather than 50 lbs
2nd remember at P/T the front 02's rule ---they command the AFR at P/T and if off somewhat they are corrected via your fuel trims However if you have erroneous 02 readings all the data is wrong The ECM is making corrections based on false info
Correctly operating front 02's ( after the engine is warmed) should have an "AVERAGE" 02 voltage reading on both sides from .400 to .550 MILLIVOLTS If the average is higher the AFR will be RICH at P/T If lower it will be LEAN----LT headers are notorious for false 02 readings beacsue the bungs can be as much as 3 ft further aft and they won't heat up or read correctly---In return the LTFT fuel corrections will be all wrong as well-----Depending on what your average readings are dictates how much to lower the switching points Typically most stock switching points can be like 550 to 450 millivolts It is a trial and error procedure I 1st always try lowering the entire switching point tables by .100 and try again You can only get so far with this fix I would never lower them lower than .300
The othee option which many tuners do with LT headers is to install the REAR 02's onto the front locations The rear 02's are far more sensitive and tend to heat up quicker and faster---Like I said there is no 100% fix with LT;s but you can get the 02's working much better
If you would liek to discuss over the phone send me a message with your phone # and we can talk about your issues----
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Old 03-14-2019, 08:05 PM
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schpenxel
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