1999 GTS - Exhaust Manifolds Glowing Red

[emjohn43]

I know, I know...Vipers are hot. But this seems very very hot.

The car: 1999 GT-S, 9500 miles. No cats, rear muffler delete. Recently cleaned (RC Fuel Injection) injectors; after cleaning, all came back with a good bill of health. 100% OEM tune on the PCM.

If I start the car, let it idle for 5 minutes (or longer), the headers are already glowing red. I would understand if they were glowing after the car was just run through the gears, but literally not touching the gas on a cold-start idle for 5 minutes....seems off to me.

O2 sensors? Intake manifold gasket? Or just straight....normal?

 

[GTS Dean]

O2s are first check for proper function. Also check OBD tables for extreme adaptive trim settings. Maybe your mufflers are plugging up. Also keep in mind that the later Gen 2's came with thin-wall tubular steel headers instead of cast iron and it may not be uncommon for them to glow at idle. I just don't have experience with them.

 

[99RT10GTS]

It sounds like cats!!! Or as Dean said, mufflers. Go straight pipe or your injectors are ******. I have a set just cleaned and check for sale

 

[efnfast]

If you don't have cats/mufflers it's most likely unburnt fuel in the exhaust, either too rich or timing is too r-e-t-a-r-d-e-d. Checks O2s are working and what the fuel trims are as a starting point.

 

[TEALLIFE]

Id figure out why the fuel mixture is that far off at idle asap before running it anymore.. O2s, stuck injector...

Check the temps on each of the runners coming off the head to see if one isnt firing and dumping fuel.

 

[emjohn43]

Thanks guys!

Injectors have a clean bill of health from RC Injection.

No cats.

New O2 sensors have been ordered. They didn't appear laggy on the log, but for the cost, they're cheap to replace...and they're presumably 26 years old anyhow.

Both the short and long term fuel trims were near zero ...but the PCM has only about 7-8 minutes of run (idle) time on it since it was reflashed to stock (unsure if prior owner had a tune, cursory glances showed minor differences from other supposed OEM tunes of the same year and P/N, so I had the PCM reflashed to OEM).

I do have a Corsa exhaust order (ordered in December, hopefully it ships in March). Perhaps the center resonators are plugged up. That would make a lot of sense!

It's winter here, so car is not going anywhere, only future running would be idling in the garage to see if the new O2 sensors make a difference.

Will update once they're installed.

Thanks all!

 

[daveg]

STFT being near Zero is a good start even though the car hasn't run long enough for the STFT to reflect in the LTFT.

 

[GTS Dean]

On a reflash, your adaptives are all zero'd out. They won't move appreciably without driving some miles unless something is seriously out of whack.

 

[TEALLIFE]

Any chance the reflash was incorrect? I had this happen on another car when they put it back to "stock"

 

[steve e]

There is no way the stock resonators are clogged, they are nothing more than a straight pipe with small slits in the straight pipe with a chamber around it to soak up some noise, they do not restrict exhaust flow at all, the first thing I would check is the reflash and make sure all the pins in the connector are straight and clean

 

[Dyno Dave]

I would suspect the reflash but it sure is an odd set of circumstances. I used to retard the ignition timing to get those glowing header photos in the Viper brochures. Are both headers glowing red?

 

[emjohn43]

Both headers are glowing red, and they do appear to be glowing pretty evenly between banks.

I don't think it is the reflash, for two reasons. One, this happened before the reflash...and was one of the reasons for the reflash, and Two, the reflash was performed by a very reputable company that specializes in Vipers.

 

[efnfast]

If it was doing it before, and it's both banks, that really starts to sound like an ignition timing issue. I assume you didn't screw with the timing in the tune, so I wonder if maybe crank or cam sensor is doing it?

I once had an LS3 with ITBs ... to get it to idle we basically had to pull out all timing, which meant the headers got cherry red within 2-3 minutes of a stone cold start.

 

[emjohn43]

The timing questions got me thinking - I can log timing advance with the HP Tuners device.

Plugged it in, turned on the log, and started it up from a cold (60F) start in my garage.

Timing advance bounced between 0-deg and 4deg. The knock r-e-t-a-r-d was bouncing from 7.5-deg to 120-deg constantly. Even before the car was turned on. The bounce happened after turning it on too.

The fuel trims were different too. The short terms were about +12%, while the long term was about -3% and - 10% for bank 1 and 2, respectively.

I've got the O2 sensors on order, will install when they arrive. Does the Gen II car have a knock sensor? Or is it just cam & crank sensors?