can running 91 octane on a 88 lo3 with the spark timing set @ 0* TDC cuase an incoplete burn ? "run rich " i have tried changing two o2 sensors , pluggs are gapped @ .35 , no SES light or codes , what can be causing me to run rich ?

 

Are you sure your car is rich? Your fuel injectors could be in need of some servicing and or you could have an issue with your cat converter. Lots of things can make a car run rich.

Clogged air filter
Improperly working EGR
Worn our injectors
Bad 02 sensor
Bad fuel filter
Faulty fuel pressure regulator (check the diaphram in it)
Vacuum leak

91 octane is not ideal for a swirl port head LO3 motor but it won't cuase you to run rich. You will not get an optimum burn though.

 

so 91 octane fuel is not good for an lo3 motor? I use it all the time. Wouldn't the ses light come on if the car is clogged or has a egr problem, fuel injectors?

 

ses light wont come on for injectors or cloggs.

 

What is ideal?

 

87

 

Its not that is bad, its that it is not optimal. The swirl port heads in these motors are fast burn heads that don't necessitate a lot of timing (factory setting of zero degrees TDC). These heads were desinged to run on low octane fuel with little timing. 91 octane is less volitile than 87 and takes more initial engery (in the compression stroke) to extract the most energy from it. These motors just don't need it and in some cases, some tuners have reported power losses from using it.

 

Agreed. 87 is just fine unless you have a high mileage motor that you suspect has some carbon buildup causing ping, when hot. Anything higher you are just wasting money.

 

That's what I figured and have been using. Just making sure

 

the mileage is 147k and i just rebuilt the tbi unit "reb-build kit " so the diaphragm is new and about the injector spray , when cranking the engine bif droplets of gas come out then it turns into the cone shaped spray once running . it has the stock injectors with new filters on them , i have no clue what else could be making me run so rich

 

Bad CTS

 

brand new CTS , it had been clipped and had a crimp on it , i solder it together instead , newo2 sensor , no vaccum leaks , new msd blaster coil , new cap and rotor , new pluggs and plugg cables

 

still could be a improperly working egr system. bad catalytic converter. did you put the correct plugs? too cold of plugs caus a lot of unburnt fuel.

 

the pluggs are new AC Delco's , and as for the egr system , im not getting anycodes, , this thing runs so rich that the asphalt right below the tail pipes gets moist , and if you put your palm right in front of the exhaust you get raw gass buildup on your hand , i went through my whole ignition system and evrything checks out ok , i suspect one thing though, i bought some spectre cable organizers , and the guy who put them on possibly disconnected the cables and mixed them up , and there might be some crossed cables somewhere, could the car stil run like this ? it shakes a little "more than normal" .

 

I would be in a hurry to check the fuel pressure. Possibility of restricted return line, stuck or clogged pressure regulator.

 

just got the injectors from witch hunter , they said they were flowing fine , still flowed and tested though

 

hey guys.....i know this is somewhat off subject of what yall are discussing, but i dont know where to start a thread at as i am still new to this site....
i just replaced my factory injectors with a set of summit fuel injectors last night, but im having problems with the car...well the best i can describe it as is loping....it will fire up, but shortly after its starts it will start to lope then die....but after a while it will run ok and i can drive it, but when i stop at a light or put in park...it starts to lope like it wants to go out.....does anyone have any sugestions as to what the problem could be?....im thinking that its a vacuume issue, but i could be wrong....the injectors were alittle bit shorter than factory, but they still fit well enough for them to work....