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98 Ford Tarus 3.0L Engine Faults: P0174, P1131, P1151 - Diagnosis and Solutions

Model: 98 Tarus 3.0 eng Fault Code: P0174 Posted: 2009-04-16 00:09

I've been troubleshooting a persistent engine issue on my 1998 Ford Tarus 3.0L engine. After installing a code reader, I'm now seeing fault codes P0174, P1131, and P1151. The symptoms include engine stalling under load, rough idle at low throttle, and failure to accelerate past 4000 RPM—especially when not in gear. I initially cleaned the Mass Air Flow (MAF) sensor, replaced the fuel filter, and inspected for vacuum leaks, but the problem persists. When applying throttle, the engine dies unexpectedly. After towing it home, I noticed it runs jerkily at low throttle and reaches 4000 RPM in neutral before stalling. I'm seeking advice on how to properly diagnose these codes—particularly P1131 (O2 sensor downstream bank 2 fault) and P1151 (O2 sensor downstream bank 1 fault), which suggest fuel mixture issues. I've heard of a 'smoke test' for vacuum leaks—what does that involve, and how is it performed? Any insights or step-by-step guidance would be greatly appreciated. Bob

Related fault codes
P0174P1131P1151
Comments (11)
Anonymous 2009-04-16 16:54

Two key diagnostics to prioritize: fuel pressure and volume, and the camshaft position sensor. To test the cam sensor, simply unplug it and drive the vehicle. If engine performance improves, the sensor is faulty and should be replaced—along with the synchronizer located beneath it.

Anonymous 2009-04-16 23:56

Thanks for the tip—I'll check a new fuel pressure regulator tomorrow. However, I'm not sure where exactly the camshaft sensor is located. I'm relatively new to fuel-injected, computer-controlled vehicles. Bob

Anonymous 2009-04-17 14:32

A fuel pressure regulator alone won't resolve the issue—first confirm actual fuel pressure. If it's low, the fuel pump is likely faulty. Regarding the camshaft sensor, it’s mounted under the throttle body, attached to what looks like a half-distributor (this is the synchronizer).

Anonymous 2009-04-17 14:45

I'll check both the camshaft sensor and the synchronizer today. Where exactly should I measure fuel pressure? I see a flat round component at the end of the inlet fuel rail—could that be the correct location? Bob

Anonymous 2009-04-17 17:22

Yes, it appears to be a Schrader-type valve. You'll need a proper fuel pressure gauge and an adapter compatible with Ford’s design.

Anonymous 2009-04-19 18:43

Hi—I found the camshaft sensor under the throttle body, but unplugging it made no difference. I’ll get a fuel pressure gauge tomorrow to check readings. What should I expect in terms of normal pressure? We looked at several used cars today, but prices seem too high for my budget. Thanks again, Bob

Anonymous 2009-04-19 19:03

Normal fuel pressure should be between 35 and 45 psi under load.

Anonymous 2009-04-20 18:55

I bought a fuel pressure gauge today, but the hose won’t bend enough to fit over the Schrader valve with the standard Ford adapter. I had to order a new adapter—seems the newer Ford models have changed the mounting layout, causing interference when attaching the gauge. Bob

Anonymous 2009-04-21 16:14

Got the pressure test set up—I'm reading less than 20 psi. This seems too low and likely contributes to my engine issues. There's a flat round component on the inlet fuel line—does this act as a check valve? Does it restrict flow? I don’t have data on required fuel flow rate (in GPM). Can anyone provide typical values for this setup? Thanks, Bob Edit: Fuel pressure doesn't change significantly when the engine is off versus running.

Anonymous 2009-04-21 16:18

If your pressure is below 20 psi, there's no need to check fuel volume—pressure alone is too low and indicates a faulty fuel pump or delivery system.

Anonymous 2009-04-21 16:21

Thanks for the quick response—I now know what to do next. I'll replace the fuel pump and retest. Bob