SureTrack Community Fix: Hot Cat Transit

Real Fixes from the SureTrack® expert information resource are documented issues from actual shop repair orders and community discussions. Read on to see how SureTrack can help you correct issues that are not easily diagnosed using OEM information alone. SureTrack is currently available free with the purchase of a current Snap-on® diagnostic software version.

Your customer comes in with what should be a simple misfire issue, but things go down hill once you start digging into it and end up having to replace the engine. That should take care of it, right? SureTrack community member mastertech1978 had a Ford Transit van in the shop that still had a misfire problem even after replacing the engine. They posed the question to the community, and with the help of fellow community member DAG1365 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.

2016 Ford Transit-250 3.7L

Multiple random misfires, replaced catalytic converter

Customer complains that vehicle runs rough at times.

Diagnostic Steps Performed/Parts Replaced
Customer came in three weeks ago with this condition. Test drove vehicle and found that it will run fine and not misfire at all and then after driving will start to misfire mainly on cylinders 1 and 3. Sometimes when loading it up in drive then returning to idle misfires are there and worse. Installed 6 new spark plugs and reset KAM.

2 weeks later vehicle came in with no start, engine was cranking very hard. Removed timing cover and checked timing and it was ok, but noticed when turning engine over by hand with plugs out had a major tight spot in it. Removed engine and removed oil pan to find metal filings 1/4 inch deep in bottom of oil pan. Replaced engine with 24,000 km one out of 2018 model but same misfire issue. Removed cats from manifolds to check to see if they were plugged and did not appear so. Installed new Ford OEM spark plugs. Swapped coils from bank 1 to bank 2. Installed 6 new injectors. Replaced intake manifold gaskets and throttle body.

Has anyone ever had such an issue or have any idea? Going to reprogram the PCM next.

Best Answer from Community Member DAG1365
Just misfire codes present? Are both front oxygen sensors readings normal/switching as they should? Rear sensors changing also when system goes rich or lean? I know on some of these Fords they have misfire relearn reprogram. When it goes to misfire I would scope crankshaft sensor for signal glitches. Be sure grounds tight/clean. Look for internal vacuum leak in intake?

I warmed it up real good and did a back pressure test in the O2 bung and found that catalytic converter was in fact plugged up. Thanks for your help.

Replaced catalytic converters and vehicle operates as it should.

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About the Author

Nick Taylor

Nick Taylor is the SureTrack Community Administrator and a Senior Applications Specialist at Mitchell 1 with over 25 years of experience with electronic repair data systems. Nick previously worked in the automotive dismantling and engine rebuilding industries.