New Problem ... HARD to start, and Rough Running Off Idle Until Fully Warmed Up

[Meteorite]

As we have a lot of cars to choose from for daily drivers, and limited funds to insure them all, we sometimes put one or more cars into "storage", i.e., take the liability insurance off them, for several months.

We did this with my wife's (bone stock) 2003 Marauder this year. I think it sat idle for 5 months. When we parked it, it did have a slight rough idle, which I attributed (possibly) to a vacuum leak I could never find.

So now, it is super hard to get it to start. It cranks fast (I kept the battery fully charged during the hibernation). But it just doesn't seem to want to catch. Too lean, maybe? I'm not hearing as many ignition events as I'd expect.

What I did: Like a numbskull, I threw some parts at it. I changed the spark plugs and the IAC Valve. I put fresh gas in the tank. No difference. I took it in to my local mechanic, and they said it need a new MAF and TPS. I replaced those. It's still the same.

More details on the symptoms: Once I get it to idle, it seems to idle fairly normally, but when you tip into the throttle, the RPMs go down to about 300, and it almost stalls, before finally catching. Once it is started, it runs fine at anything over 2000 RPM. The longer I warm it up, the better the off-idle performance, until (when fully warmed up) I can drive it normally.

Any ideas? Sometimes, when I blip the throttle off idle, it sounds like there's a pop around the air cleaner area, almost like the timing is off and it's backfiring.

[justbob]

Just for giggles, data log the IAT and compare it to the ECT. They need to be close to matching prior to firing the engine and the ECT should climb at a normal rate as the coolant warms up. If these aren’t close to the same temps it will give a terrible cold start. I’ve seen plenty of temp sensors out of range. Start with that because it’s the simplest.

Next up I’d go back to checking for vacuum leaks while cold that are either self sealing once the metal it’s touching has expanded or it is now being compensated for by the PCM once it’s warm.


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[Meteorite]

Just for giggles, data log the IAT and compare it to the ECT. They need to be close to matching prior to firing the engine and the ECT should climb at a normal rate as the coolant warms up. If these aren’t close to the same temps it will give a terrible cold start. I’ve seen plenty of temp sensors out of range. Start with that because it’s the simplest.


Well, dang. I'm betting you're right. I neglected to mention that I am getting one code: P1290 - Cylinder Head Temperature Sensor Signal Less Than Self-Test Range.

That sounds a lot lie what you're talking about. So, where is the temp sensor located?

And, thanks for your help!!

[justbob]

No problem. There is one on each side of the coolant crossover tube. One is for the PCM, the other is for the gauge. However it’s been too long now to remember which is which.. so sorry on that.

I do remember the dealer only shows a 4.6 2V when we looked up the fiche on that certain part a few years back and that was obviously incorrect. I think we ended up viewing the fiche on an ‘04 and it showed the correct 4V engine and parts. Anyways you need the PCM one.


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[Meteorite]

No problem. There is one on each side of the coolant crossover tube. One is for the PCM, the other is for the gauge. However it’s been too long now to remember which is which.. so sorry on that.

I do remember the dealer only shows a 4.6 2V when we looked up the fiche on that certain part a few years back and that was obviously incorrect. I think we ended up viewing the fiche on an ‘04 and it showed the correct 4V engine and parts. Anyways you need the PCM one.


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That's odd ... or maybe not. I put new temp sensors in both locations when I changed the crossover tube earlier in the year. So, that could've been the culprit. Maybe I got the wrong part for one of them.

But I'm confused, because (going by the description in the trouble code) I was expecting a sensor that went directly into one of the cylinder heads, not a coolant sensor.

[justbob]

That's odd ... or maybe not. I put new temp sensors in both locations when I changed the crossover tube earlier in the year. So, that could've been the culprit. Maybe I got the wrong part for one of them.

But I'm confused, because (going by the description in the trouble code) I was expecting a sensor that went directly into one of the cylinder heads, not a coolant sensor.

It’s just bad wording. It’s within a few inches of the head but not actually in it. The harness plugs aren’t interchangeable unless you went with aftermarket. Some off the aftermarket ones I have noticed are notched to receive either pigtail. Motorcraft are definitely not interchangeable. I’ve also seen my fair share of bad sensors right out of the box, just like alternators, and water pumps. Seems I get the short end of the stick more often than most LOL


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[Meteorite]

It’s just bad wording. It’s within a few inches of the head but not actually in it. The harness plugs aren’t interchangeable unless you went with aftermarket. Some off the aftermarket ones I have noticed are notched to receive either pigtail. Motorcraft are definitely not interchangeable. I’ve also seen my fair share of bad sensors right out of the box, just like alternators, and water pumps. Seems I get the short end of the stick more often than most LOL


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Thanks for all the information! You've definitely put me onto the right path.

[blazen71]

Motorcraft DY-1144 is the passenger side.

Motorcraft SW-5174 is the drivers side. This one is for the radiator fan.

[Meteorite]

Motorcraft DY-1144 is the passenger side.

Motorcraft SW-5174 is the drivers side. This one is for the radiator fan.

Thanks! This is very helpful.

[justbob]

Motorcraft DY-1144 is the passenger side.

Motorcraft SW-5174 is the drivers side. This one is for the radiator fan.

Awesome. This is honestly sometimes a hard one to pin down and remember!

I know you already know this Dave but I figured it might help others to understand the importance of the process.

The PCM controls the fan based of the output value of the 5174, which also is used to monitor engine temp and adjust fuel and timing. In cold open loop mode the PCM relies on correct IAT and ECT readings until the o2’s have warmed up enough to take over. The PCM pretty much acts like a choke during this time.

There is several other PCM inputs that control the fan such as A/C and trans (I believe a handful more). My fan never turned off and I finally found the trans temp in the manual tune wasn’t turned off or adjusted. I must’ve tied the Vref and return together down by the trans when I made the harness for some reason?

Funny story is that I now have a tiny LED light tapped into the trans temp wire right before the PCM to trick it to a lower value and not trigger the fan at start up. It only took 5 years of digging before the light bulb in my head lit up dimly enough to make the connection..


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[Meteorite]

No problem. There is one on each side of the coolant crossover tube. One is for the PCM, the other is for the gauge. However it’s been too long now to remember which is which.. so sorry on that.
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Motorcraft DY-1144 is the passenger side.

Motorcraft SW-5174 is the drivers side. This one is for the radiator fan.

So, after reading these two messages and trying to reconcile them, plus a little fiddling under the hood, I think:

DY-1144 (passenger side) is the one that goes to the PCM? Did I get that right?

[blazen71]

https://www.mercurymarauder.net/forums/images/misc/quote_icon.png Originally Posted by blazen71 https://www.mercurymarauder.net/forums/images/buttons/viewpost-right.png (https://www.mercurymarauder.net/forums/showthread.php?p=1594801#post1 594801)
Motorcraft DY-1144 is the passenger side.

Motorcraft SW-5174 is the drivers side. This one is for the radiator fan.



Awesome. This is honestly sometimes a hard one to pin down and remember!


I recently had to replace one and it took me an hour of google to figure this out.

[justbob]

So, after reading these two messages and trying to reconcile them, plus a little fiddling under the hood, I think:

DY-1144 (passenger side) is the one that goes to the PCM? Did I get that right?

I’m assuming Dave is correct here. With that assumption then no, the passenger side is only for the gauge on the dash. Drivers side sends the info to the PCM.

Easiest way to confirm would be to unhook one while reading the data on your Xcal (it should read close to ambient temp). If it drops to zero then that’s your sensor.


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[Meteorite]

I’m assuming Dave is correct here. With that assumption then no, the passenger side is only for the gauge on the dash. Drivers side sends the info to the PCM.

Easiest way to confirm would be to unhook one while reading the data on your Xcal (it should read close to ambient temp). If it drops to zero then that’s your sensor.


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Hmmm ... that's odd. On my car, the Driver's side is the one that messes with the gauge if I unhook it.

[justbob]

I just went back on a lot of MM.net Google searches around the time I had to replace one for the PCM and everything I found says it’s the passenger side and it needs to have a cone head vs a flat head. (The side that’s submerged) Sorry for the confusion.


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[Meteorite]

I just went back on a lot of MM.net Google searches around the time I had to replace one for the PCM and everything I found says it’s the passenger side and it needs to have a cone head vs a flat head. (The side that’s submerged) Sorry for the confusion.


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Thanks for taking the trouble to do that!

What you just wrote does make sense to me; thanks!

[Meteorite]

I replaced my Passenger Side sensor with the Motorcraft DY-1144 part, and that fixed it.

Thanks, guys!!

[justbob]

I replaced my Passenger Side sensor with the Motorcraft DY-1144 part, and that fixed it.

Thanks, guys!!

Sweet! I was thinking it might take a cycle or two but I guess that it wouldn’t as long as it reads correct.

Good to hear, keep the shiny side up!


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[blazen71]

I love it when a plan comes together

[justbob]

I love it when a plan comes together

Showing your age Dave? [emoji16]
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[SilverPhoenix]

C'mon JB, quit livin' so far back in the past...


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