91 C1500 wont start unless gas petal is on the floor

[stuntmanjake]

I recently put a cam in my truck .292 dur .552 lift. the engine is a 385 fast burn from gm performance. It was running great and then all of a sudden developed a horriable miss. Now it wont start unless the gas petal is on the floor and when it does start it runs like something horriable and wont rev up pass 300 rpms. it just barely hangs on untill you let up on the gas and then it dies. I have ck all the ignition, and fuel componets. (and replaced most of them) Yet It still continues to run like sh*t. Any ideas ???

[Bryan C. King]

Timing is way off........

[stuntmanjake]

Naw.. I have double double ck the engine is place at TDC. Then drop the distributor with the rotor face #1. Then placing the cap on. Then ordering the wires accordingly. Starting #1 where the rotor was facing. Doing so in the order of 18436572 (i do believe is the timing on small block chevy)

I have tried damn near everything to fix this crapy running problem. I am not a parts changer, however this is one of them where trouble shooting gets shot.
Here is a list of parts that I have either ck or replace but are certain they are in tip top shape.

Cap, Rotor, Ingintion Control, Ignition Control Moduel, Coil, Coil Pick Up, Distributor Gear, Intake Manifold Gaskets, TBI gaskets, All Sensor connections, and all wires that were not up to par, Checked and pipe taped all fittings into the intake, Checked the computer, Checked Wireing, Checked Voltage, Checked Vavle adjustment, Checked all torq specs on the intake after a few warm ups and cool downs,..... What next?

I am at my wits end with this F/in truck but i love her to death, so someone please

[2000CAYukon]

Does the MAP sensor hold a vacuum? Also make sure the MAP sensor vacuum hose is in good condition, including that the port on the TBI is not plugged.

//2000CAYukon

[stuntmanjake]

Nope all that is fine it accually is an accell dfi map sensor speacially built to read low vacum presures that the cam causes.

[2000CAYukon]

Ok. Since this is not the original engine, perhaps the timing does not need to be at TDC. Have you tried moving the timing to see if makes a difference?

Also, are you using the stock TBI or a different one? Can you get a scan tool on it to see what the sensors are seeing with the engine is being started?

What port is the MAP sensor hooked up to? Needs to be manifold vacuum (i.e. below the butterflies).

Since you say that it was running great, and then developed a misfire, something had to change. Check for vacuum leaks at the base of the TBI and intake manifold.

Are both injectors spraying fuel?

Have you checked the compression? Maybe some went wrong internally.

//2000CAYukon

[stuntmanjake]

Cool thats one thing i wasnt sure about was the map sensor. I had tried both places, and really the only differance I noticed was how rich at an Idle it ran. As for the tbi and intake gaskets I just finished changing them cause I figured what the hell atleast by doing this I could scoope out the pushrods and lifters and what i could see of the cam so that to cause that warm fuzzy feeling inside when you know the intrenals are ok. Lol
It did seem to help however did not slove the problem, so I ck all fitings, and the egr block plate and that all has ck ok.

As for the flash of the comp, never happing all that extra stuff gone. However it is the stock housing that has been ported and has had holley injectors, holley fuel pressure regulator, and even the holley lil holder thingy for them all installed, and yes they both spray very well.