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1996 Ford Windstar 3.8L Misfire on Cylinder 4 with P0151 and P1151 Codes - Diagnosis and Fixes

Model: 1996 Ford Windstar Fault Code: P0151 Posted: 2006-05-04 05:17

Hello everyone, I'm new to this forum and seeking advice on a persistent issue with my 1996 Ford Windstar 3.8L. The vehicle is showing two diagnostic trouble codes: P0151 (O2 Sensor Bank 2 Sensor 1 Malfunction) and P1151 (O2 Sensor Bank 2 Sensor 1 Slow Response), along with a recurring misfire on cylinder #4. The check engine light initially comes on, then during driving I experience intermittent misfires—sometimes lasting just seconds, other times up to several minutes. The misfire appears and disappears unpredictably. I've already replaced the spark plugs and ignition wires, but the problem persists. I'm considering replacing the coil pack, EGR valve, or oxygen sensor, but before investing in parts, I'd like to understand the most likely root cause. Are there known common issues with this model year and engine configuration that could explain these symptoms? Any insights or experiences from others who have faced similar problems would be greatly appreciated. Thank you, Joe

Related fault codes
P0151P1151
Comments (11)
Anonymous 2006-05-04 06:09

Vacuum leaks around the intake manifold are a very common cause of P0151 and P1151 codes on the 1996 Ford Windstar. A proper tune-up is also worth considering if it's been some time since the last service. Good luck—please update us on your progress. Jeff

Anonymous 2006-05-04 09:00

I'm going to inspect for vacuum leaks, especially around the EGR gasket or the EGR valve itself. Could a leak there be causing the misfire and sensor errors? Thanks for the tip! Joe

Anonymous 2006-05-04 09:03

A leaking gasket is possible but less likely. The PCV valve and its associated hoses are another frequent source of vacuum leaks—especially on Windstars, where intake system issues commonly trigger multiple O2 sensor codes. I recommend checking these components thoroughly. Jeff

Anonymous 2006-05-04 09:45

I've already replaced the PCV valve, but I'll now inspect all hoses connected to it as well. Thanks again! Joe

Anonymous 2006-05-04 18:22

I’ve checked all vacuum lines and found no visible leaks. However, while inspecting and listening, I heard a distinct hissing sound near the EGR valve area. When I placed my hand between the intake manifold and EGR, the noise didn’t disappear—but it was muffled in front of the EGR. Could this indicate a leak at the EGR gasket or intake manifold? I know you can't hear it without being there, but it’s worth noting. Thanks for your help! Joe

Anonymous 2006-05-05 08:17

Try spraying brake cleaner or throttle body cleaner directly at the suspected leak area. If the engine RPM fluctuates, that confirms a vacuum leak. While an EGR issue is possible, intake manifold leaks are more likely—especially on this model. You could try replacing the EGR valve or gasket as a low-cost test, but avoid over-replacing parts without confirmation. Keep us posted! Jeff

Anonymous 2006-05-05 11:21

No change in RPM when sprayed with brake cleaner. I'm still investigating. Could someone clarify where Bank 2 Sensor 1 is located? I want to inspect all components before purchasing any parts, as I don’t want to waste money on unnecessary replacements. Thanks again! Joe

Anonymous 2006-05-08 09:40

Bank #2 refers to the side of the engine where cylinder #2 is located. Sensor #1 is the upstream oxygen sensor in that bank.

Anonymous 2006-05-08 10:59

Thank you! So it's on the rear side of the engine, near the firewall? This helps a lot. I'm not going to replace any parts yet—first I'll verify there are no damaged wiring harnesses or connections. Thanks again! Joe

Anonymous 2006-05-09 18:24

Problem resolved (so far)! Thanks to Jeff for the guidance. After removing the intake plenum, I found that five out of six exhaust ports were blocked by carbon deposits—90% to 99% clogged—and three of the six fuel injectors were also dirty or partially plugged. I cleaned all injectors with carburetor cleaner, cleared the exhaust holes, and replaced the intake plenum gaskets. I'm hopeful this fixes the issue. Thanks again for your help! Joe

Anonymous 2006-05-10 08:32

I've seen technical service bulletins (TSBs) online referencing carbon buildup in exhaust ports and EGR-related issues on older Windstars—though those often show EGR codes. There may be a revised front valve cover or similar update designed to reduce carbon accumulation. Keep us posted! Jeff