r0nin89

Alright I have a 350 setup with TBI ontop in my truck. When the truck is warmed up for about 5-10mins it runs awsome. Absolutly great, with only 35,000 miles on the motor mated to a 4speed granny box.

When I jump in the truck and try to take off quick it wants to stall easy and if I rev it high to get it going it will stutter in first gear and be very unresponsive. Any idea whats up?

90c350

Have you done any prom tuning to it? Or is there any performance mods that started all this??

UnderCover89TBI

iTrader: (25)

most likely its a bad coolant temperate sensor..that is what it sounds like to me.

r0nin89

It has a cam in it but nothing wild from what I'm told. I'm gonna get it tuned once I can find someone to do it...

I was talking to my mechanic and he said it sounds like a temp sensor.

BMmonteSS

Pretty much any cam will cause drivability problems with the TBI ECM. I would double check the sensors but most likely it just needs tuned.

r0nin89

But why only when cold? IDk I picked the $8 sensor up I'm gonna throw it in before work we'll see how it goes.

r0nin89

Hey I forgot to ask. The truck had a true dual exhaust put on it and my o2 sensor is in one header collector. That would mean my fuel injection is only reading half my exhaust output. Is there anyway that I could rig up a second o2 sensor or should I just put and x pipe after the collectors and run the o2 in the center of that?

BMmonteSS

It runs bad when cold because it runs on the factory hard coded fuel tables, once warm the O2 sensor fires off and correct the fueling at part throttle. The crappy part is that at WOT the ecm reverts back to the fuel tables which don't match your engine.

Don't worry about the O2, thats how every GM vehicle was made up to about 95'.

r0nin89

To be honest the only time the truck sees wide open throttle is in the mud for about 2 seconds at a time. Even when I get on it on the road it still runs awsome but i think that its because the motor is moving so much wait it doesnt think its at WOT.

Is it possible for me to get a reading of my fuel tables when my truck is cold and then get a reading of what my fuel tables are doing off my o2 sensor reading when it runs awsome and use them as my standard on a new chip?

PS: I buddy of mine was telling me he was talking to a guy that builds big blocks. He said that when they cam a big block they hook a second MAP sensor into the other side of the intake manifold and T off the vacuume input so it gets more of an average reading into the TB. He said its not as good as tuning but it almost fools the ECM into thinking the cam isnt as lumpy.

Any thoughts?

PS: I did the temp sensor that wasnt it.

BMmonteSS

What you are describing is the BLM reoutine, or BLOCK LEARN MEMORY. It's the factory corection factor used to compensate for any mismatch between the fuel tables and what the engine really wants.

Your buddy is trying, but he's just overcomplicating things.

Serously, take an hour and read through the "free tune" thread. It'll be an eye opener.

r0nin89

I know I'm gonna read through everything again tomorrow. I'm just asking if until I get my bearing straight to tune a chip will T-ing to another map sensor help?

rocko350

not really. as bmontess stated above its just not neccesary to do that. one side of the engine is going to pull the same vacuum as the other (think 2 independant 4 cylinder engines). the important thing is to give info on the cam. tbi can be finiky,but still be able to run, a cam with less than 112 degrees lca. beyond that only a tune can save you. as a truck owner i would pay alot of attention to fast355's posts as the majority of the info he shares is relevant to your truck. (read the FREE TUNE sticky at top)
also post you cam info or part number. hell even give your base timing and fuel pressure. lets start there.

i also just read(reread) that you have a 87 truck dont forget to give your ecm #.