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Old 03-28-2014, 04:03 PM   #21
peashooter
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Quote:
Originally Posted by choate View Post
I just got the p0128 again. Didn't replace anything yet, just cleared code. It stayed off the first time for 5 months. The second time for a week. I'm gonna change the thermostat and see if that helps as the heat gets decently hot, but it takes is a long time so I'm hoping that's my problem. Any info is appreciated.
Assuming our cars use the same thermostat, get the motorcraft part, its been redesigned to help minimize the p0128, and test it before hand. Motorcraft part RT1193 and $36 on amazon.

Last edited by peashooter; 10-02-2014 at 10:34 AM.
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Old 10-02-2014, 12:42 AM   #22
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2004 Focus ZTS with P0128 issue

Quote:
Originally Posted by peashooter View Post
I decided to try the Mazda TSB repairs since its really the same engine I have and I've run out of "standard" options. Again I had replaced the thermostat and CHT several times, still got the p0128 code. Per the mazda tsb, I brought it into the dealer(Ford) today and had them hook it up the diagnostics machine, it didnt bring up anything I didnt already know so fortuntately they didnt charge me for that part. I told them I wanted the PCM updated to the latest flash (i'm not sure its ever been updated since the car was made). The pcm update cost me $60. So now we will see if the code comes back.

The only other thing I think it could be in my case (with a 2004 2.3) is that the new thermostats are not a proper replacement for what the car originally came with. Here is more info on that Mazda tsb and it refering to some vehicles needing to use a "modified thermostat per workshop manual section 01-12". I downloaded a version of that manual but didnt see anything mentioning a modified thermostat so I'm going to stop at a mazda dealer and see if they have some updated books that might mention what the modified thermostat consists of.....

(From Mazda tsb)"The important part to look for with this answer, is the engine type ZJ, Z6 and LF.

then there is this message: Model Years affected 2004, 2005, 2008

Some vehicles may experience Check Engine Light illumination with a trouble code indicating the thermostat is stuck open. The thermostat will need to be replaced with a modified one and there is a software update for the Powertrain Control Module."


http://engine-codes.com/uploads/mazda/2007-10-04.pdf
Peashooter: I'm having the same P0128 issue after multiple trips to the dealership. I'm curious to know if the PCM update worked for you? Any update from you would be greatly appreciated.

Thanks!
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Old 10-02-2014, 10:26 AM   #23
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Quote:
Originally Posted by rharmon618 View Post
Peashooter: I'm having the same P0128 issue after multiple trips to the dealership. I'm curious to know if the PCM update worked for you? Any update from you would be greatly appreciated.

Thanks!
Yes, I have some updates. Unfortunately the PCM update did not solve my issue as it does on some other vehicles. I do have another idea I'm going to try this weekend that I'm hopefull for and I'll explain below but here is some stuff I've learned since the last post. (I've been monitoring temps using an ultragauge).
The reason for the P0128 is that the temp sensor doesn't see 175 degrees within a calculated time period after starting up (time depends on outside temperature). For me its because I get in my car in the morning and drive to work which is 20 miles away, the first 15 minutes I'm able to drive about 55 without any slowdowns or traffic, and that's when I get my P0128. If I drive and stop someplace for gas or get stuck in traffic in that first 15 minutes or so then my car gets up to temp quick and no P0128.
First off the factory ford thermostat has changed but it hasn't changed temperature, its still an 82 degree C thermostat (180 F), so the even though the ford part number is now RT1193, it doesn't mean 193 degrees, which I've confirmed with ford and testing in water with a thermometer, mine starts to open at 177F. I tried several thermostats including some custom ones I made using higher temp units, and even taking a ford unit and bending the pin support bridge of it out so that the factory RT1193 thermostat doesn't open until 190F. Non of those helped.
I've read a lot about the P0128 code and many manufacturers have this problem we do, Mazda (as mentioned previously with the same engine), Subaru with their new 2013+ vehicles, some GM, ford, kia, and Chrystler. Subaru fixed there issues with a new water manifold "Water log" that basically has some different sized hose connections to restrict water in certain places. Chrysler had some cars getting this problem after a replacement radiator was put in because they were missing an internal restrictor. Some older fords had this issue and ford put a restrictor into the heater core hose.
What I'm going to do this weekend is put my stock unmodified RT1193 thermostat back in (currently have the modified one in) and then add a restrictor to the upper radiator hose right where it connects to the radiator. I got the idea from this post: http://jeep-xj.info/HowtoRadiatorRestrictor.htm
I cut out an aluminum disc just a little under 1.25" diameter and drilled a 1/2" hole in it. I think the car just flows too much coolant through the radiator when the thermostat IS OPEN. But even when it isn't open I think that coolant must be doing some weird mixing through the upper hose and keeping the engine below temp. I may also add an adjustable valve/restrictor to the heater hose like the Four Seasons Brand 84706. I'm pretty confident these are going to help the issues if not solve them all together now that I've learned so much from the other things I've tried..... but I wont know until I try them out this weekend. The good news is that they are cheap fixes too, but I really think the upper radiator hose restrictor might be the magic fix.
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Old 10-11-2014, 09:23 PM   #24
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Well after nearly a year of fighting the P0128 code on my 2004 2.3PZEV focus, I have finally solved the problem. Rather than go over the multitude of things I have tried up to now, I'll just say that it appears to be a flaw with some ford programming and/or the wrong temperature thermostat for cold climates (and they dont have a choice in thermostat temps).
The factory ford thermostats RT1193 are 82*C which means they start opening at 179*F. I've now tried around 4 of the Ford ones and many other aftermarket brands hoping there would be one that would open at a higher temp. I've tested them all with a digital thermometer and heating them in a pan on the stove and they all open right around 177*F. Thats a problem for some of us because if the computer doesnt see the engine get up to 175* within a certain time then it sets off the P0128 code. Even though the water temp may be around 180*f, the cylinder head doesnt get that warm for a number of reasons. There is supposed to be a 20* gap between the thermostat temp and the p0128 code but its not set that way.

So my ultimate solution was to make my own thermostat. I took a STANT 14139 thermostat that is a 188*F unit and put it into one of the RT1193 housings that I cut out. It would have been really easy except that you need to have a backer plate to hold the thermostat in or else it will just get sucked into the engine block. So I traced and cut out a backer plate from some thin stainless steel I had. I used a punch to nibble away at the inside thermostat hole area since I didnt have anything else that would cut it well without bending it up. Then I used some gray instant gasket maker to hold the thermostat to the housing, put the backer plate on, and then put some more gray gasket maker onto the back of the stainless backer plate and bolted it back onto the engine.

Final results are that the engine keeps heating up until it gets to around 181*F on a cold day or with the ac compressor running (which turns the fans on). Previously it would top out at 174 in the same scenario. So the new thermostat lets it get hot enough to avoid the p0128 code.
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Old 10-11-2014, 10:27 PM   #25
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Good Work!

An answer for those who DON'T have either part inop..

I added "P0128 solutions" to the title so more can find this in the future.
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