95' sierra misfiring from idle on through acceleration.

[GhiaJake]

I have a 95' Sierra 5.0 TBI. It has been "misfiring" since I bought it and I can't figure out what's going on. It is worse at idle, a distinct loping like the timing is off. I have checked timing (dead on), replaced plugs, wires, cap and rotor. It has recently started giving me a trouble code 45 (O2, rich) and is now running rougher. Bad fuel economy and smells rich. Cleaning TBI system now to see if that helps.

 

[Molson02536]

I have a 95' Sierra 5.0 TBI. It has been "misfiring" since I bought it and I can't figure out what's going on. It is worse at idle, a distinct loping like the timing is off. I have checked timing (dead on), replaced plugs, wires, cap and rotor. It has recently started giving me a trouble code 45 (O2, rich) and is now running rougher. Bad fuel economy and smells rich. Cleaning TBI system now to see if that helps.

The TBI is sensitive to fuel pressure, so it would not hurt to also replace the fuel filter and sound like your EGR valve is dirty and needs cleaning.

Also inspect all your vacuum lines and replace any lines that are cracked and damaged.

Good luck and keep us posted.

Molson02536

 

[GhiaJake]

Took the fuel meter assembly apart and cleaned everything. The injector screens were quite filthy, along with the entire assembly, but everything looked good otherwise. Haven't fired it back up yet. What's the best way to clean the EGR, just choke cleaner through it? Will do it and clean O2 sensor tomorrow, fuel filter Wednesday when stores open. Vacuum lines are good. Merry Christmas!

 

[98trck]

i imagine it is a crank fired ignition and the distibutor is only used fire the correct plug
if that is true look at the rotor you removed if the burn mark on it is all at one end of the rotor the distributor is not phased correctly my '98 had the same symtoms when i replaced the rotor i noticed the burn on it i turned the distributor alittle and it ran great

 

[Molson02536]

Took the fuel meter assembly apart and cleaned everything. The injector screens were quite filthy, along with the entire assembly, but everything looked good otherwise. Haven't fired it back up yet. What's the best way to clean the EGR, just choke cleaner through it? Will do it and clean O2 sensor tomorrow, fuel filter Wednesday when stores open. Vacuum lines are good. Merry Christmas!

Just remove the EGR valve and clean it out with carb, cleaner and make sure the valve is not binding. Re-install and keep us posted.

Good luck and keep up the great work.

Molson02536

 

[pondscum]

Etc me think a minute. The ignition timing can be on target, but the valve timing way off, if the timing chain skipped, right?