Diablosport Forums

I drive a 2005 Corvette C6 with the LS2 engine. Over here in the Netherlands all cars have to be tested for emissions every year, and so far this was never a problem.

Without changing anything to the engine this year it seems the car is running way to lean, therefore the lamba is to high, and the car will not pass the test.

Please help me in finding out where to look for the problem, and how the Trinity can help me in finding the cause of the engine running lean.

I'm not a mechanic but to me it seems that the engine might have a leak where it is sucking in extra air which is not being recorded by the MAF.

Please feel free to make suggestions on where to look for the problem.


Below are the figures from the test, they measure at idle and 2500 rpm.

Engine idling:

CO (max 0.3%) 0.46%
HC PPM Vol 120
Lambda 1.102


Engine 2500 rpm:

CO (max 0.2%) 0.53%
HC PPM Vol 48
Lambda (max 1.03) 1.040



Greetings

Fred

any mods on the vehicle?

mikel wrote:any mods on the vehicle?

I'm sorry for not answering sooner, somehow the forum doesn't send me an email when there's a response.

Mods are:

Callaway Honker
Ported throttle body
Ported intake
Crane Cams 1.8 ratio rockers
Kooks Jet Hot coated headers
Pfadt Johnny O'Connel shocks
Hotchkis sway bars
Diablosport Trinity with custom tune
Brian Tooley Racing valve spring kit

I have a custom tune made by Monte, however when I install the factory tune it still doesn't pass emissions test, values are roughly the same.

I'm no mechanic, so this is an UN-educated guess, but the figures don't make sense. (feel free to correct me)

According to the CO the engine runs rich, however according to the lambda the engine runs lean

Before the winter hibernation of my C6 I send a logfile to Monte, he told me the engine runs lean. Now that the season is starting over here I'm trying to sort this problem out.

A mechanic friend is trying to borrow the smoke pro machine from his workplace to see if we can find an air leak somewhere.

Like I said for me (no mechanic) it seems the engine is sucking in air somewhere after the MAF, or there's a leak somewhere in the exhaust system.

We tried finding a leak in the exhaust system by listening and visually inspecting all the pipes and joints, but could not find a leak.

One more thought springs to mind, could there be something wrong with the (front?) O2 sensors, maybe a wrong signal from the faulty O2 sensor tricks the computer into leaning out the engine ????

Can I test the O2 sensors with my Trinity ??

So many questions, I hope you can find the time and patience to answer them.

HELP, any input is highly appreciated !!!!!


Fred

OK....you need a custom tune

mikel wrote:OK....you need a custom tune

he's got a custom tune already.. I did a tune for that car back in 2012.. so it's been fine for the 3 years since the tune was done, heh.. car has been fine all this time, and the tune doesn't change, unless you changed it or changed something on the car since then.. .

so I don't know what the issue is.. something changed on the vehicle to cause the issue, like air leaks as mentioned..

so, not sure what's causing the issues...

check your cold air intake, make sure it's fully together/connected, all clamps are TIGHT so no air leaks anywhere..

check the headers and exhaust, make sure all bolts/clamps are all TIGHT so no air leaks anywhere...

check the intake manifold for any air leaks around it...

clean your MAF sensor...

etc. etc..

something is up with the car somewhere...

06MonteSS wrote:

mikel wrote:OK....you need a custom tune

he's got a custom tune already.. I did a tune for that car back in 2012.. so it's been fine for the 3 years since the tune was done, heh.. car has been fine all this time, and the tune doesn't change, unless you changed it or changed something on the car since then.. .

so I don't know what the issue is.. something changed on the vehicle to cause the issue, like air leaks as mentioned..

so, not sure what's causing the issues...

check your cold air intake, make sure it's fully together/connected, all clamps are TIGHT so no air leaks anywhere..

check the headers and exhaust, make sure all bolts/clamps are all TIGHT so no air leaks anywhere...

check the intake manifold for any air leaks around it...

clean your MAF sensor...

etc. etc..

something is up with the car somewhere...

Hi Monte

Still very happy with your tune

And happy that you took your time to read my entire posting, including the bit where I write that I have one of your excellent custom made tunes.

Am I mistaken when I deduct that the air leak (is it an air leak??) must be after the MAF, if it was before the MAF say in the cold air intake, the ecu would adjust for the extra air.

I will check the headers and exhaust, make sure all bolts/clamps are all TIGHT so no air leaks anywhere...

I will check the intake manifold gaskets etc. for any air leaks around it... (smoke pro machine)

Not sure how, but I will clean my MAF sensor...

To be continued.

Fred

get a can of CRC Mass Airflow Sensor Cleaner.. and you spray the maf sensor wires to clean it...

06MonteSS wrote:get a can of CRC Mass Airflow Sensor Cleaner.. and you spray the maf sensor wires to clean it...

Today I changed the oil + filter and cleaned the MAF with the CRC Mass Airflow Sensor Cleaner. Unfortunately when we tested the emissions they were still the same. I did notice something that might mean nothing, but I wanted to bring it to your attention.

I hooked up the Trinity and wanted to make a new log, when I noticed that there is a huge difference between Long Term Fuel Trim bank 1 and bank 2.

Feel free to correct me, but to me this seems weird, shouldn't the LTFT from bank 1 and bank 2 be roughly the same ??

Bank 1 2.34
Bank 2 0.78

Am I correct to assume that the reading of bank 1 is (more or less) correct, and bank 2 is not ??

And if so, when you look at the engine which one is bank 2 (and 1), can we narrow the problem down to this bank ??

My UN-educated guess would be that one of the O2 sensors might have a problem, although there are no trouble codes present according to the Trinity.

Maybe it's time to buy new sensors, the car has done 85.000 miles.

Any ideas / suggestions to narrow down the problem, please advice.

Regards,

Fred

that difference is normal.. they won't be exactly the same... there's no issue/problem there...

06MonteSS wrote:that difference is normal.. they won't be exactly the same... there's no issue/problem there...

OK, thank you Monte, maybe it's time to buy new O2 sensors, the car has done 85.000 miles.

To be continued, I will post results here when I find out what it was (or not)

Fred

The car was tested on equipment from a different shop and with those readings it would pass the mandatory emissions test.

So the emission test problem is sorted, now there's the running lean problem. I made a new log-file which I have send to Monte.

no you didn't.. I didn't get any file from you..

06MonteSS wrote:no you didn't.. I didn't get any file from you..

I'm sorry, this forumsoftware hates me, it seems despite the fact that I see messages send in my outbox that they are not realy send.

I have send them to you via normal eMail.

Can you PLEASE have a look if the problem is now sorted or still there.

And BTW I remembered that I did clean the washable filter from my Callaway Honker, that is the only reason why I can imagine the engine is running lean.

Best regards

Fred

I heard back from Monte, log-file is perfect, no lean issues anymore

I'm so happy, this problem has been bugging me for ages.

MONTE thank you very much

Best regards

Fred

Just curious what was the root cause for running lean issue?
How did you fix it?