i've noticed it recently, I start my car early in the morning, and i can smell slight raw fuel, only when in closed loop. once it gets into open loop, it seems to level out. if i shut the car off when it's cold it will diesel @ times. my fuel economy sucks now that i read the thread with average of 250-280 miles to the tank. my car has a slight miss which seems to get worse when the car reaches 200-210 @ idle. Also @ cold starts there are times when i hear a whurring, buzzing, humming sound comming from the ls1. I pin pointed it to the A.I.R pipes. i know the pump is supposed to work on cold starts to pre heat the cats, but the sound is only erratic, it will get really loud at times, then cut off, then start again maybe lower, and cut off, and it only does it sparingly not every cold start.

any one have the general data stream range they can supply me, so i can check my data stream with the scanner?

 

I am by no means an expert, but all vehicles run richer on a cold start - that is the function of the "choke".

Also, on start up you are in Open Loop mode - only when the cats have come to temp & other sensors are at their proper operating range does the engine go into Closed Loop, or feedback mode.

At any rate, my ' 99 T/A used to get a black dust on the top of the rear bumper that I assumed was from the exhaust , but I never worried too much about it as the other cars that I knew of did it, too.

On my ' 99 SS w/ 43K this doesn't occur anymore.

The AIR pump does seem to operate @ random - I know that their are certian parameters that cause it to go on/off, but have no clue what they would be.

I also know that all the LS1's that I have had experience with seemed to have a slight miss - I do not believe it is truly a miss but more of a slight camshaft caused lope.

The dieseling is an issue - I have not had that occur.

Are any check engine lights getting thrown ? If so, Auto Zone will scan for free & tell you what they are.

I hope maybe some of this is helpful !

Good Luck !

Britt

 

You start in open loop then go to closed.

You might want to check your plugs and wires

there really isnt a "general date stream range"

if you have something you can log with, do that and give it to me.

 

i always seem to cross open and closed loops. i know the car is supposed to run richer when cold, but i smell raw fuel, and this started recently. before i would start it up and it ran fine when cold. your not supposed to smell raw fuel, and im affraid of damaging my cats. i did have a check engine light a while back, infact the same day i bought the car. It's a 98 with only 28k miles so it hasen't been driven much, now it's my daily driver so it's seeing more road time than before, till i can find a beater. but either way the code was p0404 if i remember correctly, which was egr circuit range/performance problem. I checked it out turned out the egr valve was bad, stuck, i put a jumper wire to terminals a and d on the valve and the pintle was stuck, got a new valve and haven't seen the light since. with the miss i checked the resistance on the coil(s) whiched checked okie, and the plugs are fine, YET THEy SEEM TO HAVE ALOT OF CARBON BUILD UP for only 28k miles. the wiring to the coils seems okie also, but i haven't checked them with a multimeter. reason i complained about the miss: i got inside a friends 00 z with 39k miles and the car idles much smoother than mines, and the other thing is the dieseling,

so there is like no print out of a data stream for this car which could show you like a basic range for all the sensors? I remember back in school we had this program that would give you a print out of the cars data stream, you would hook up a scanner, and then compare the readings on the scanner to the values on the print out, and you could see if any sensors were outta range etc. problem is my job dosen't send me back to school till march, so i have no access to this.

I think it's my temperature sensor going bad, for the car running soo rich @ cold start. Anyone had a problem with their temp sensor before? and the carbon build up due to the fact that the car has not been driven much, and probably @ slow speeds. anyone used that decarbonizer GM sells? thanks again