engine only starts at full throttle

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guywithaproblem

2/1/2008 3:54:11 PM

ok, this is mind boggeling and i don't want to start throwing parts at this thing.

91 s10 blazer, 4.3 tbi. Died after driving, started stumbleing, and running really rough, then died.

could crank it back up but once gas was pressed it would shut off. kinda like it was flooding with gas.

since that i've replaced plugs, cap and rotor. i has spark but seems weak when held sparkplug to engine block, not a blue spark like i wanted to see. mostly orange. it has fuel pressure, how much who knows, the fuel injectors spray a big amout. it will kinda run if I press the gas to the floor, but then not so much. ive changed the fuel pressure regulator thinking it was recieving to much fuel. though it didn't fix the problem. it does not run with the map unpluged. all sensors tested fine with my dvom.map = 4.7in. mg (under 1000ft) tps=.67v at closed throttle/ 3.8v at wot. ect resistance value is correct to specs.no visible vacuume leaks. did pull code 45 wich is rich mixture, though engine light had been on for a long time, prob cause of 1 vacuume leak going towards the charcoal canister, which is repaired. engine as approx 300,000 miles on it. any help would be appreicated. thanks in advance.

Chevy Lover

2/1/2008 5:14:54 PM

I would suggest checking the fuel pressure, it does sound like it's flooding.
You said the ECT sensor is reading to specs, have you checked it cold and hot?
TPS is good.
I can't remember what the MAP is supposed to be and I don't have a book.

I guess it's possible to have a plugged injector but I'd hate to see you throw one in to check them.

If you have a timing light, you can hook it up and point it down the throttle body to see the injector spray and check for a cone shaped pattern. If it's just like water out of a tap it could be a faulty injector. Have a look and compare the 2 injector sprays.

guywithaproblem

2/1/2008 11:51:30 PM

yeah, the injectors spray pattern is a fine mist like it should be. with them unpluged there is no leaks around the seals or anything when cranking.

mitchell on demand said something about the fuel pump check ball being stuck and causing a hard starting issue. which could be a problem cause the person who drives the vehicle said she runs the tank empty alot and prob sucks all the crap at the bottom of the tank up in the pump. where are the test ports on the fuel lines on the tbi system? i saw none in the engine compartment, but i might have missed them. and mitchell says 9-13 psi is that correct? also when i bought the fuel pressure regulator it was like a rebuild kit, and the spring was shorter than the old one that came out but i used it anyways thinking they just revised it, is this right? or was it for the wrong model or something? also the iac makes a ticking noise constanly when key on, is that normal?

swartlkk

2/2/2008 5:47:46 AM

On a TBI, you have to add a fitting in-line to test. The basic fuel pressure gauge set doesn't include this fitting, but most stores have it available separately. Just ask for a GM TBI fuel pressure test port fitting.

Yes, the pressure required for a TBI setup is quite low.

guywithaproblem

2/4/2008 11:06:53 PM

well after testing fuel pressure, and seeing that it was fine, there was no way it was getting to much. it was right at 10psi

so after a once over to make sure I have tested everything possible with my dvom, it was the end of the line. The cataylatic converter

was completly plugged, took a nice sawsall too it and ran and idled mint. no wonder it was spitting back out of the throttle body.sounds like a monster with it off though, lol. getting a new one tomm. anyways, thanks for the help.

thegr81

2/4/2008 11:10:20 PM

Glad you got it figured out, if you need anything else let us know!!!

swartlkk

2/5/2008 4:57:39 AM

That'll do it.

I would keep an eye on your fuel mileage to make sure that something didn't cause the cat to plug other than age. Over fueling can clog a cat very quickly. The universal aftermarket cats are not as sensitive to this as the originals are though so you should be good.

Blazer has no power when full throttle.

Only starts w/ full battery? Coil?

4.3L Engine wants to quit while driving?

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