Hi Folks,

We've had Scarlett, our 2005 MCS convertible, a long time now...11 years and 140,000 miles worth (205k total miles). It has occasionally over the years done a weird thing, I've read I'm not alone, where lights come on and it dies or goes to limp. We pull over, key off, back on, and it's fine. It's done this, oh, 8 or 10 times in all these years. Not sure if that's related... Recently my wife was driving and it did this, but wouldn't restart. I went and towed her home.

CLUES:
P1125 code, means there is too much variation between the redundant throttle position sensors built into the TB. I've researched this and some folks have this where it quits and restarts, a couple seem to have had it die completely. Some replace the TB, some wiggle the connectors on the TB and ECU, some squeeze down the connector contacts on the TB (not sure how, they are tiny). No consensus, and none of the wiggling and such have helped Scarlett. The electronic throttle is responding to the pedal.

When it first happened, you could restart it and it would chug and run poorly. Not viable to drive home by any means, but it would sorta run for a few seconds. It did this a number of times. Now, home in my garage, it won't fire at all. It cranks normally with starter, but not a hint of fire. So something happened when it quit on my bride, but something else has changed since then. I'm wondering if the fuel pump went out, but maybe at first there was either residual pressure, or the pump was trying to turn, now it's quite completely. I say this because the behavior is a little like running out of gas (It's not out of gas, BTW). I've looked in Bentley FSM, gonna try to get a fuel pressure tester. Bentley says to check pressure with car running, of course I can't do that, but it should generate the same pressure with the key on, right? Does anybody know if an Autozone lender FP set will connect? Other ideas on what could cause this second change in behavior?

Will it run with the intake tubing removed? I don't know why it wouldn't, I see no sensors in the tubing or airbox. But I've never tried to start it that way. I did find cracks in the main intake hose, all the way thru the rubber, yikes. So that will be replaced of course, but I don't see how it could have been my problem.

Penny for your thoughts! Thanks,
Jeremy in Tucson

 

If you mean the pipe between the air filter and throttle, yes, the car will run in that condition.

Based on the fault code, I'm thinking you need a new throttle body. The 2 throttle position sensors within it must agree for the car to be happy. That code indicates they are not in agreement. I would go after that fault and see what happens.

When my car had fueling issues leading to my replacing the fuel pump and pressure regulator, it would exhibit intermittent loss of power or a stumble when accelerating. It never stalled out on me or failed to start, however. In that case, I never had a check engine light nor did I bother to check for codes because I knew both the pump and pressure regulator were original on the car, so I didn't mind replacing 20-year-old parts for what seemed to be me to be a fueling problem. Fortunately, that was exactly what my car wanted to be happy.

 

Hey Ghost, did you replace the filter on the other side also when you did your fuel pump?

I got a fuel pressure gauge kit from AutoZone and I'm not getting any pressure whatsoever. The manual says start it and idle it to take a pressure reading, but it's gotta generate some pressure when you turn the key on normally in order to start, right? I turned the key on and cranked it over and I'm getting nothing on the fuel pressure gauge.

 

It's the fuel pump! I chased that hunch, learned that FP is powered for 2 sec with key on, then continuously once the engine is turning. I got in where the FP relay; it's a standard relay, checked it out and it's fine. I also removed the FP cover. Jumpered across the main hot to the load side of the relay connector (terminals 30 to 87), and that does send power to the FP connector, but doesn't make the FP turn. Also, the FP motor has over 40k ohm resistance through it, which isn't normal for a motor.

I'll get a FP and a filter, which is buried in the other side of the tank, that should fix it.

Looks like the P1125 was a red herring. It means something about the TB/TPS system, but I'll figure that out later.

 

Is it clear now, what is happening in there?

 

All good now?

Edit: Thanks for the update.

 

As of yesterday, YES! FP was definitely the issue. Motor is burned out. The new one has half an ohm resistance, bad one is in the k ohm range. I also replaced the fuel filter, and a few other random things.

Why on God's green earth couldn't they make those ports in the top of the tank 1 inch bigger in diameter? The FP and filter housing (on the opposite side) just barely fit thru, and then there are fiddly hoses, connectors and float arms to deal with. I mean, really, what's the point of "just big enough"? There's space there for bigger ports. That said, I LOVE the access panels on both sides under the back seat (very easily removed) so the tank can stay in place.

 

Did this also solve the surging acceleration on part-throttle issue that you were having?

 

No, fraid not. That's been my companion for years now. But the FP works good!

 

Ahh that’s a shame. I was hoping my upcoming pump replacement would be the end of it.

 

Ah, yours has this "feature" as well? Lemme know if you ever figure it out!

 

Will do!