It barely starts, I'm getting constant spark, it won't Rev up at all. Won't run for more then 15 sec, and if it does it won't move. Had get car towed home. I'm out ideas has new optispark, plugs and wires. Just started doing it while driving one night. Anyone have any idea?

 

Did you scan it for codes, and check the fuel pressure? Any possibility of a plugged cat?

 

Got code for random missfire, and might have clogged cats cuz there stock with 155××× miles on them

 

If you got P0300, the code isn't really for "random" misfire.... it just means there is "a" misfire. It could be on ore two cylinders. The misfire count, by individual cylinder, can be accessed with a scanner with "GM enhanced parameters".

Check the fuel pressure.

 

How do you check fuel pressure.

 

Attach a fuel pressure test gauge to the Schrader valve:

Courtesy of Shoebox

http://shbox.com/1/fp_reg.jpg

Turn key to "run" (not "start"). Pump will prime for 2 seconds and shut off. Pressure should exceed 40 psi, and bleed down slowly. Rapid pressure loss can indicate:
-faulty check valve in pump
-leaking injectors
-leaking fuel pressure regulator
-leaking lines

Start engine, remove vacuum control hose (hold finger over vacuum connection to prevent vacuum leak). Pressure should be 43.5 psi. GM accepts anything from 41 - 47 psi as within acceptable limits.

Reattach vacuum line. Pressure should drop by about 8 psi (stock cam, less drop for a more aggressive cam). If you got 43 psi with no vacuum, should drop to about 35 psi with vacuum.

Tape pressure gauge to windshield, put engine under load. Take it up to as high an RPM as you can, pressure should never drop below 40 psi.

 

Can't even get the car to start for more then 15 sec, it turns over and it sounds like it wants to start but won't and if I give it gas jus cuts out

 

fuel pump is no good

 

Sounds like the fuel pump is Walking out on you, Like fred said don't start the vehicle just turn the key on and checking pressure

 

Alright, thanks

 

the fuel filter be issue of car not starting, or fuel pump? It ran fine now jus doesn't want to and I'm trying to fix it, with out having to replace over 1000 dollars worth of parts, when don't have the money. Car starts if I pump gas pedal but 6 times then hold it about half throttle to stay running.

 

A plugged fuel filter could cause the problem. But it would show up if you checked the fuel pressure. Checking the pressure is a lot cheaper than playing "parts replacement roulette", which seems to be your preferred method of chasing problems. This has been suggested multiple times, but you don't appear to have checked it. Engine does not have to be running, as noted in my response to "how do you check fuel pressure".

You can usually borrow a fuel pressure test gauge at a local auto parts store. May have to place a deposit until you return it, but usually no charge.

 

Alright, it jus hard to find time been in in the military and trying to work on ur car. Never have time, and I've never done a fuel pressure test. What's the psi it's got to have before starting?

 

It should prime to 40psi, and not drop rapidly. If the test shows it does drop rapidly (example - drop to 30psi in a few seconds), cycle the key a few times before turning it to "start". That will build pressure. I believe there is actually a pulse of fuel each time you cycle the key. The closer it is to 40psi, the faster it will start.

Some info on the throttle.... pumping the accel pedal doesn't really do anything, except admit extra air. That would help it start if it was flooding. Holding the pedal on the floor before turning the key to "start", and keeping it there while you try and start the car will put it in "clear flood" mode.

Next question.... where are you located and what is the ambient temperature? If it's very cold, the coolant temp sensor may not be providing accurate info, and the PCM needs to know if the engine is extremely cold in order to richen the mixture for cold start.

 

Fort Lewis ,WA and been like high 40s this year. I had replace the coolant sensor already I broke it trying to swap water pumps