Hey everyone, got a question on my wife's truck (one in signature). 201,200 miles give or take a few. It's acting sporadic, sometimes it idles rough, other times it's fine, when driving, sometimes it wants to hesitate and almost surge or jerk when at cruising speed, brake and abs lights come on at random, and cruise control works when it wants too. Oh yeah, several times before (and 1 time since alternator replacement) the voltage gauge would peg out on the high side and throw a code for high voltage. Only code thrown now (that I can't seem to fix) is P0455 for Large Evap Leak. So I'm wondering if it might be time for a new ECM? Here's a list of everything else I can remember doing to the truck aside from what's in sig. It's also had new a/c condenser, compressor, heater core, water pump, power steering pump, fan clutch, trans rebuild about 40,000 miles ago, trans cooler, new radiator, recent tune up with plugs and wires, and brakes done not too long ago. I'm sure there's more I'm forgetting, but hopefully this will give y'all enough info to work off of.

Thanks in advance for the assistance.

 

I doubt your pcm is bad. Most evap codes are vacuum(lack of) related. Did the tune up include cap-rotor? Was the fuel pump ever replaced? Might want to check pressure.

 

Replaced fuel pump at 197,00, tried to track down evap leak, including replacing all rubber hose I could get my hands on, even the one attached to the evap canister under the truck against the frame. and replaced the evap solenoid. and tune up consisted of cap & Rotor with brass contacts, plugs, wires. Plugs are NGK copper plugs, and wires are Taylor 8mm run following the TSB about the plug wires.

 

How's your gas cap? The canister itself?

 

lol gas cap was first thing replaced and canister itself looked ok but haven't had ability to do smoke test of evap system yet. issue of most concern right now is the sporadic stuff happening; running funky one min and fine the next, and the abs and brake lights coming on and going off and cruise working when it wants too (more of my wife's concern haha). also checked cat and replaced o2 sensors, as well as idle/air control valve. AHHHH almost forgot also had cylinder 3 misfire come up twice, but hasn't come back up in a few months. I'm starting to think the truck is possessed lol

 

May be a vacuum leak in the vapor recovery system, that makes the engine run wonky when the valve opens.......

 

ok, that makes sense. so whats the best way to locate said leak?

 

Check the vac line coming off the the front of the throttle body. Mine was cracked and threw a code, easy fix.