I don't post here very often but I'm almost ready to give up on this car. Okay the car is a 97 formula and it's running extremely rich. Engine is fully forged 355 with low compression, I think about 9:1. Cylinder heads are LT1 casting ported/polished, Procharger D1SC pulleyed for 15 lbs boost (3.4 inch). MSD opti and ignition box. Running 42 lb injectors and a tune from Mark Romans. Car dynoed 2 years ago 480 hp with a 3.7 pulley which was about 12 lbs boost. Had the car emissions tested and hydrocarbons were off the scale, like between 500-1000. now questions...

1. A buddy of mine who is an old carb guy says my injectors are way too big and therefore the reason it's running so rich. Are they too big?

2. This is probably the major contributor but maybe not the whole issue but the coolant sensor that is in the drivers side cylinder head is not connected. Another buddy thinks (he looked at the electrical schematic) this is just to report the temp for the dash guage. Is this sensor the one that turns on the o2 sensors and closed loop? Also I can't find a loose wire so how do I find it?

Either way I don't think the car is going to closed loop. Any help greatly appreciated.

Dave

 

Your buddy is right on the sensor in the head. It's only for the gauge in the dash. The ECM coolant temp sensor is the water pump.

We will need to wait for the boosted guys to chime in on the programming and hardware requirements for a boosted LT1, but I think your injector size is fine. How good is your tuner? Are you absolutely sure that he knows what he is doing? Any SES codes? Is it missing? How do the plugs look?

What kind of exhaust are you running? Still have emissions hardware? Cats, air, egr..... I would assume so since your location shows Cali.

 

Thanks for the reply. Exhaust is pacesetter LT's with y pipe and single CARB legal Magnaflow converter (#46705). Then Magnaflow catback. Yes I have the emissions stuff on the car. Not original equipment but bought from fbody boneyard. The tuner is highly regarded on corvetteforum and LS1tech. The car ran very good right after the tune but steadily gets worse. The only code is for intake temp sensor and I think it's just the sensor. I don't believe it's missing but I'm sure there isn't burned wires. Haven't checked the plugs. I never get a code for that anyway. Even with 2 or 3 wires completely off it doesn't throw a code. Yes I'm in northern Cali and want it to be legal here. (I know the LT's are not SMOG but I'm just wanting it to pass the sniffer for now).

 

How do you add the extra fuel for the boost - an FMU, or a 2-bar MAP sensor?

 

Here's where my knowledge falls short. It is not running with an FMU. As far as I know it's running a stock MAP sensor. Do I need a different sensor? Just in case, this might help too. Cam specs are 224/236 duration @.050", .536"/.555" lift with 1.6 rockers, and I believe 115 LSA.

 

It's possible to tune it on the stock 1-bar sensor, but some people opt for the 2-bar conversion. If you don't have an FMU, only your tuner know how its set up to add the extra fuel. I think you would probably have better luck with this in the forced induction forum. I can move it if you want.

 

If you think that is better, I'll take any help I can...

 

DAVE! SUP DUDE! Damn, you sure keep a low profile. You still in the Force? Wasn't aware there were any base in northern CA aside from Edwards.

No expert but you running the stock map isn't helping regardless of your tuner being well regarded. Kinda have my own thoughts on that since he finds tuning w/ a stock map fine. As for your rich condition, sure you don't have any exhaust leaks anywhere? Sounds weird it just continues to get worse. And for the record your inj are too small but since you're on the stk map...I'd leave it that way. You running an inline pump in junction w/ your intank pump or just the one in the tank?

Silas,

 

What up Silas, been a while... Yeah I'm a little ignorant. The MAP sensor never even came up when doing tuning. The fist time was on the dyno and I knew it wasn't perfect but just wanted some numbers. There was issues with O2 sensors at the time so he set things out of range for the O2s to get that tune. Now I fixed that O2 sensor problem and added the required goodies back AIR pump and EGR (never got those back from Tony). Then changed the pulley and had to get new tune. We did that one on the road. Car ran great. But still high on the hydrocarbons. Now it starts hard but after a while it runs fine. Maybe a 2-bar and re-tune will solve it???

 

Sorry I didn't answer, 255 walbro intank. Have an inline but not installed. No exhaust leaks since I changed my headers to pacesetter. Dynatech can die a horible death... Pacecetters 2000 times better....

 

Mark romans also tunes my car.hes a veryyy good tuner and my car passes emmission with over 500 rwhp and long tube exhuast.He also has my car tuned on a 1 bar map.

 

Yeah I'm still with the Force, not active but AF reserves. Travis AFB is the location. Just off I-80 halfway between Sacramento and San Fransisco. I live like 5 minutes from the main gate.

 

Yeah Mark knows his stuff. I might just upgrade anyway to the 2 bar MAP. He told me he has a SMOG dyno at his disposal and would be able to schedule a time to just put my car on it and tweak the tune until it passes. Maybe that's the best thing. I still think the car isn't going to closed loop for some reason.... Mark works at a dealer in Roseville, might just take it to his peeps to get it solved.

 

vid of the car at startup

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just a quick thought, i had a problem with my car feeling sluggish the more i drove it. After a PCM reset it would be great, then would slowly get rich/slow again. Turns out my LT/1.6 rockers were a little too noisy for the knock module, switched over to the lt4 module and haven't had a problem since. If you pull the PCM fuse for 60 seconds, and the car runs much better it might be worth looking into.

Also, a simple Freescan or Datamaster log will tell you if the car is going into closed loop or not. Along with codes. Also, that IAT sensor is important and if its not working correctly it could be causing an issue. Also, fouling plugs can cause poor performance as well, so check and replace.