My 04 Z has small cam ported stock heads headers a few bolt ons . I installed new injectors ( stock 04 LS-6 ) was having some O- ring problems so through it might be the injectors they had 70,000 miles on them anyway .. Well with the old injectors the tail pipes tips would over time turn dark with the new ones I get a gray film not dark ,well my tuner said way to lean with the new injectors need to retune $600.00 . The way I see it the tune in the PCM telling the injectors the same as the old injectors . I think the old injectors were a little worn out and the new ones not so , maybe the tune for the old ones would be different I think they were a little Leakey compared to the new ones anyway .. and did run a little rich . My 04 runs great didn't run bad before just blowing O-rings bad pump fixed that .. Now $600.00 for a retune .. Retune or not the retune that's the question ??? Thanks ..

 

Lets see what the experts say but I expect with everything changed you'll benefit from the tune. That said who tunes the care makes a huge difference.

 

My not sure the tips should be dark anyway .. Grayish might be the right color ?/ Yep tune always helps but do I really need one ???the gray might be the color it should be anyway .. I don't know I think the old injectors were always worn out ??? and am going broke spending money one my 04 .. Just spent over $1500.00 on a new stock complete fuel sys.. What to do ..Thanks

 

Did you go from a higher flow injector back to stock?

 

No the originals were stock injectors with 70,000 miles ,just replaced with new LS-6 same ones.

 

All C5 injectors are NOT the same. You have to examine the part number on the injector and see if the FLOW RATE for that specific injector that you are using and the old one are the same. Some LS injectors for different years flow different rates than others. If the injectors that you have are the same flow rates that the ones that were removed, you should be OK. If they are different, you would need to tune the different flow rates into the PCM.

TUNE OR NOT TUNE.

What are your Long Term Fuel Trims telling you??????
You need to examine the LTFTs and see what they are reading.

They SHOULD be close to zero or very slight negative. If they are highly positive,, something is wrong or your tune is whacked. You can use a scanner that reads LIVE SENSOR DATA and O2 Sensor operation to gather valuable data to aid you in making your NEED TO RETUNE decision.

If your tuner is worth his weight in salt, he would data log your PCM and SHOW YOU the state of the tune.
Even if he charged you something for installing a Wide Band and examining the state of the tune, at least you would positively know if you needed to tune or not.

IF,,,, Your origional tune was done when your O2 sensors were OLD and not operating properly and the injectors were worn,,, installing new injectors would LEAN OUT the AFR.

You need to know that if you have POSITIVE LTFTs If they are significantly positive, it will add more fuel to the Wide Open Throttle (open Loop) AFR fuel trims.
A rich WOT Air Fuel will not give you all the power that is available.

O2 Sensors.

How old are they and are they working correctly???

A properly operating O2 sensor will switch voltages from (approx) 100 millivolts to 900 millivolts as seen at a steady state idle. You should examine yours and see if they are properly switching. If they are are OLD (many miles) it is would STRONGLY RECOMMEND that you change them out before you ever consider a retune/ tune.

Always do the following before you tune an engine/PCM:

Clean the MAF
New Plugs
Examine the O2 sensor operation. Replace if sluggish or if they dont switch properly..

New clean air filter
Clean the throttle body /blade
Add a catch can.

RECOMMENDATION.. PM me where you live and I will try to figure out a good tuner to send you to who will provide you that one on one assistane that you need to get you running smooth and efficient again.

Bill

 

Thanks for all the good info . Replaced the injectors with same part number as came off the 04 and checked and are the right injectors for the motor so to TRY to avoid problems ordered the same part number and checked and are the same number .. The O-2 sensors I'd say org. as came with the 04 so will be replacing them ASAP for sure .. Before the new injectors was running rich at start ,cold after start the smell of gas strong and had to let warm up to run right but after warm up ran great . The old injectors had 70,000 on them and the tips would be very dark after 50 miles .. The 04 has 231/236/ 595 /595 112+4 cam ported stock heads and Vera ran air intake headers bullet cats and X-pipe about it catch can ported T-body and very well serviced for sure .. Around 445 RWHP.. Tuned by LMR in Houston and runs very good . After the injector install sounds different and runs with a little more pep the gas smell is gone and the warm is very short .. The pipes looked way different for sure kind of gray not dark , was in the shop the other day with a friends Corvette and was talking to my tuner and told him about the injectors and he said you need a retune or he needed $600.00 for a car payment .. I am I Houston TX if you know a good tuner please let me know . Am going to check out the LTFTs and 02s etc.. Thanks..

 

it it were me I would get a tune, especially after changing something like injectors... different injectors all have their own injector data that the tuner will need to get everything right so if you just slap them in you could do more harm than good... if you are using the same tuner it should cost nowhere near $600 for a retune for an injector swap, usually they will do it for an hour or 2 labor time to make adjustments... now if you changed them with the same injectors that were in it to begin with then you will probably be ok

 

My tuner here in OKC charges $450 for a full dyno tune. Re-tunes after the fact (new parts, etc) are $150-200. Your tuner at $600 every time is gouging you. He is able to pull up your old tune and make some small adjustments and he can do it very quickly.

 

Thanks for all the info . I think the old injectors were about worn out and the new injectors just so much better prop. right to retune to the new injectors but I think just a check of the air fuel or what they check for?? . I don't think I need a full tune .. Going to see if can jus get a tune up tune . Having it retuned for ever little thing , I don't think is necessary and is starting to run into some big money ,this will be the third tune .. Going to check out the stuff Curlee subjected and start from there ..Going to do some scanning .. Thanks

 

before you spend $600 on a "tune" get yourself a wideband for $199 and see what your mixture is doing. then you might want to invest another $100 into an adjustable pressure regulator and maybe $50 into some fittings and manage the mixture yourself.

 

Yes the wide band for sure.. Ok Adj, regulator on a late 03 -and 04 (NO ) need a return fuel setup to make that work checked that to no end ,in late 03 and 04 no return fuel system on the C-5 .... There is on such thing as a none return Adj. regulator . I checked and rechecked .. People might say different ,if the fuel is not returned will go BOOOM . The regulator bleeds off the excess fuel and returns it back to the tank ,is possible to install an after market return line ..if want to go that route.. Just a FYI..