When a symptom arises after something was replaced on a vehicle it causes you to focus on that system. But it could be something totally different. SureTrack community member kgoble had a Ford F450 truck in the shop that developed a surge after a stolen catalytic converter was replaced. They posed the question to the community, and with the help of fellow community member juniur, Ericsautomotive and others, they were able to resolve the issue quickly.
The following Community Fix summarizes the interaction between members of the community that led to the solution.
Vehicle
2015 Ford F-450 Super Duty XL 6.8L
Title
Intermittent surging after catalytic converter replacement, replaced PCM.
Complaint
Customer complains that vehicle surges at time after stolen catalytic converter had been replaced.
Diagnostic Steps Performed/Parts Replaced
Engine surge at times while accelerating. Other times pulls smoothly, even during same drive cycle. Intermittent setting of P219A and P219B (Air-fuel ratio imbalance) and P0420, only one catalytic converter on this vehicle for both banks. Have replaced B2S1 HO2S for another code/concern. Catalytic converter was stolen previously and replaced with aftermarket cat at exhaust shop. For reference, engine was replaced about 20k miles ago and has been running smoothly until exhaust issue according to driver. Has anybody had issues with aftermarket cats on 6.8L V10’s causing these concerns? We work on a lot of the older V10s and have not had issues with aftermarket exhaust. Are there any other common issues with these mid-2000’s V10 that can cause these concerns?
Best Answer from Community Members juniur and Ericsautomotive
Smoke the intake for vacuum leaks. Also smoke test the exhaust, a small pinhole can drive this system crazy!
Cause
The PCM was sending .25 volts out on the signal return circuit for the rear HO2S causing it to read incorrectly, but in the valid range. When the MAF was unplugged it forced the PCM to run in open loop and would perform perfect. In closed loop it would surge. I have never seen a vehicle change the running performance so much based on a downstream oxygen sensor. Definitely learned a bit about Fords on this one. Thanks for all the input!
Correction
Replaced the PCM and all is well.
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