350 tbi stumbles on acceleration and low on power.

[chevyprostreet]

1994 chevy suburban c1500. Hello I'm a new member. When I try to accelerate when it is cold it stumbles and shakes the truck like it is starving for fuel but doesn't die. It has no power when it does this. And the truck seems to be low on power when at wide open throttle even when warm doesn't move like it used to. Sometimes when it is cold and idling at 950 and take off right away it will throw you in the seat. All other time when warmer it's low on power.

I have put new cap, rotor, wires,spark plugs,new tbi gasket,new o2 sensor, new fuel pump assembly, tps, map, egr, fuel filter. Fuel pressure is 14 psi
I dont know what else could be causing it. Please help

 

[scott2093]

I dont know what else could be causing it

Until someone has more direction,
Getting a scanner to see what's going on while in operation is really going to be the best thing to try to rule out something obvious.
Your 94 service manual, the emissions and driveability one in particular, will have some more direction and troubleshooting you could try .

88-98 Service Manuals

Over the years I have collected a bunch of GM service literature. Links to PDF Scans of service and STG manuals and a links to the Parts manuals. You'll need the FREE Adobe Acrobat reader to open these files. Get it directly from Adobe here {http://get.adobe.com/reader/} If you're not...

www.gmt400.com

 

[Drunkcanuk]

Are your spark plug wires in the right spot.
Your fuel pressure is right around whee it's supposed to be I believe.
I had something similar a few times. One was the little chunk of hose connecting the pump to the fuel lines in the tank.
The other was a broken distributor shaft.

 

[chevyprostreet]

It has no codes. The fuel lines look fine and have constant fuel pressure when stepping on it.spark plug wires are where they suppose to be, had to double check.thanks for recomending to look at the distributor, pulled distributor and looked good.cant find any vacuum leaks with carb spray. Did notice the spark advance will go really low the more I put my foot into it when warm and jumps around when it is cold. The o2 sensor is the same way, will go low to around .03 when running rough and jump aroumd when timing is jumping around as well. Tested tps and the temp sensor looks good on the scanner and with a volt meter.

 

[D-Day]

Is the 14 psi coming from the fuel pump or the return line after the fuel pressure regulator.
I had the same issue and my pump was only supplying 8 psi. My new pump I used had 20 psi.
Recommending;
checking the Fuel Pressure Regulator in the TBI.

 

[Sean Buick 76]

I would replace the fuel pressure regulator in the TBI based on your symptoms. I agree with the gentleman above.

 

[docstoy]

You seem to have a scanner to look at data, you will need to ck fuel pressure and make sure it is correct, will also need timing light to set base timing, set timing coccector is located close to black cover on passenger side of firewall should break out of electrical harness, tan/black wire, if you haven't already done so as recommended above, download service manual, fuel and emissions there will be plenty of information there for you. If any other questions, ask but try and be specific. Hope this helps and best of luck

 

[chevyprostreet]

Thanks Sean buick 76 and D-Day. I rebuilt the tbi and seems to be running better now. Still have an issue with a little low on power but is way better to where I won't get rear ended now. Gonna be looking more into the sensors and electronics.