kglaize

Wanted a Vette for 20 years and finally have an '06. Purchased with 28K miles with mild mods - headers, x-pipe, Borla's, dyno tuned.

If the car was tuned with NGK TR55 plugs gapped at ~.058", can I switch back to OEM plugs without retuning?

I get the dreaded "service charging system" message at idle and the GM Tech said there was a TSB regarding aftermarket plugs. I asked him to go back to OEM plugs but he wouldn't touch it because of the tune. He indicated that doing so would cause the engine to run too rich or lean.

In my opinion, new plugs would have no impact on the air/fuel ratio but I wanted to consult with the masters on this forum before changing plugs myself.

This is my 1st post so if I posted in the wrong forum, you can publicly flog me after my car is fixed

BlindSpot

Do you have any method to log data? TR55s are the normal factory heat range, so going to the Iridiums in the same heat range shouldn't have any impact. If you had TR6s in, then I'd caution trying. But, from my standpoint, I don't see the issue. BTW, by what you have modified, the tune cannot be that radical.

I tried TR55s in my LS3 for 3K miles. After which, I checked gaps and they had opened significantly from install, so I removed them and replaced with NGK iridiums. TR55s are copper/copper plugs, so very soft and not expected to be high mileage plugs. Where did the 058" come from? Did you measure? BC that's pretty wide to have set them that way.

kglaize

I pulled the plugs to measure the gap and the average was 0.058". Right now I don't have a way to measure data but sounds like I need to invest in a data collecter.

BlindSpot

Not to overreact and buy something just to data collect. I was more just asking the Q if you had one. Net, net, you're not modded enough that a tuner could have gone very far with a tune, and you're still using factory specced heat range plugs, albeit the TR55s are a popular aftermarket.

If it were my car, based on what I know, I wouldn't hesitate to put factory iridiums back in. Dealer techs are in business with liabilities so are cautious. There is nothing that would indicate the plugs are related to the CEL, except some have had spark plug wires back off causing a miss and it does crazy things like set unrelated CELs. Try a little dielectric grease ON THE RUBBER PART OF THE WIRE ENDS ONLY, not the metal connection ends and you can burp the coil connection ends to relieve any air trapped in the connector with a small screw driver. Reset the CEL and go from there.

Dcasole

Just change the plugs back to the factory plugs

the ECM will vary fuel trims will up or down 20% and with the mild tune yuo have for headers there should be absolutely no problem at all

Dave

kglaize

Thanks everyone for the feedback! Heading out now to get some OEM plugs

Internets_Ninja

Stock plugs are fine. If the car was tuned on T55's then the stock range will be almost identical.

kglaize

New plugs solved the issues. No more pulsating headlights or "service charging system" messages. Thanks to everyone for their feedback

BlindSpot

Good to hear! Did you use dielectric grease and release air pockets at the coil end connections? If not, and the CEL comes back, check each boot at the coil and make sure one hasn't popped off from air pressure trapped in the boot.

Unreal

Ecu only trims at part throttle. Doesn't help a lean or rich issue at wot.

Dcasole

Yep ... but with the mods he has I am reasonably certain that there was not modification to the wot tables.......

And if there was changing plugs is not going to affect it ....
Dave

Unreal

Agreed it's probably not an issue but if they did a Dyno tune and didn't touch wot he got ripped off.

BlindSpot

Many of the tunes on a stock setup are mail order tunes. OP is essentially stock. There is room to grow from a factory tune, but not much.

Unreal

Tons of room to grow over a factory tune and he said he has a dyno tune.

kglaize

I bought the car 2nd hand with the mods and tune completed by the previous owner. Pretty sure it was a garage queen. 10 years old, original tires, 28K miles, and not one paint scratch, chip, or ding on the whole body. The Borlas had a moderate coating of carbon on the outlet. Was worried that it was running rich, so I scrubbed them clean and the discoloration hasn't reappeared.

I've always wanted a vette but wasn't looking. Had to get tags for a new F-350 and popped into the local Ford store to pick the plates up. There she was, a perfect Corvette, in a Ford showroom. The rest is history.

Thanks to everyone for their support in helping me fix the issue.

Internets_Ninja

Not exactly true. The ECU does the fuel adjustments at part throttle below a certain MAF value. However, the values (+ or - ) of learned fuel trims is carried over into the Power Enrichment calculation at WOT.

Example: If your fuel trims learned 7% more fuel in the cell right before the MAF cutoff threshold, then 7% more fuel will be added to the base commanded fuel value when you go full throttle.

BlindSpot

I am actually getting this.....that's a good sign....

Unreal

Yes, if you have LTFT enabled, positive ones can be applied to PE, but depending on the car to adjust is beyond stupid. You should't expect the car to adjust for WOT tuning based of fuel trims.

schpenxel

Exactly. Shouldn't be relying on LTFT's to fix PE fueling regardless. It's better than nothing, but not by much.

Unreal

I see time and time again on FB, and locally where people are constantly saying "Stock ECU can adjust for up to 20%, so don't worry about tuning for that mod". Just throw headers, or a new CAI, or bump the boost up, or whatever. Only reason I posted was because I wanted to make sure people understood what that meant. Hell I wouldn't want my FTs to be +15% at part throttle, let alone WOT.