Hot Film Sensor, quirky AC, ABS and windshield fluid light?
12-13-2009, 02:39 AM
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1988 300E
Hot Film Sensor, quirky AC, ABS and windshield fluid light?
Year: 1988
Model: 300E
After replacing both fuel pumps (one was completely shot, the other would seize unpredictably) I took my vehicle to my local Autohaus for inspection. The reasons being: 1. The idle seems a bit high at start up (around 1,000 rpm) but settles at around 8-600 after a minute or two) 2. I can smell my car is running rich 3. the ABS light is still on despite having put a brand new OVP in maybe 2-3 months ago (I've checked the voltage and fuses and it's operating properly). Anyhow, the diagnosis was "Hot film sensor in throttle housing damaged - This will keep fuel management system from working correctly (may run rich.) Now, I've heard the term "Hot film sensor" before, but it's not ringing any bells when it comes to part association. Is that tech talk for a part that may be more commonly known by another name? Where is this part located? Is it actually inside the throttle housing (ie. underneath it) or am I misunderstanding? Do you think this may be the cause for the ABS light being back on again (it went over when I replaced the bad OVP but is back again unfortunately). A link to a photo of where this piece is would be fantastic.
Next..
This one has baffled me for a few months now. I'm not sure if it's due to a failing wiring harness or what, but my AC on/off switch seems to have a mind of it's own. A lot of times, when I'm accelerating or I break a bit hard, it will just click on by itself. I have to really dig on the "0/off" button for it to stay off, otherwise the blower motor keeps going on and off, on and off. Not only is it annoying but it's robbing me of fuel economy as I can tell the car runs a bit heavier when the blower engages. Any help trouble shooting this one would be greatly appreciated.
and.. last but not least..
Why does the fluid sensor light come on only when I'm in Reverse or turn the Fog lights on. Any ideas? My front left headlight wiper is non-functioning at the moment, but I don't think that's the cause of it. My windshield fluid is a little low at the moment, but it's been that low before and never set the sensor off in this manner.
TIA,
G.Francesco
Model: 300E
After replacing both fuel pumps (one was completely shot, the other would seize unpredictably) I took my vehicle to my local Autohaus for inspection. The reasons being: 1. The idle seems a bit high at start up (around 1,000 rpm) but settles at around 8-600 after a minute or two) 2. I can smell my car is running rich 3. the ABS light is still on despite having put a brand new OVP in maybe 2-3 months ago (I've checked the voltage and fuses and it's operating properly). Anyhow, the diagnosis was "Hot film sensor in throttle housing damaged - This will keep fuel management system from working correctly (may run rich.) Now, I've heard the term "Hot film sensor" before, but it's not ringing any bells when it comes to part association. Is that tech talk for a part that may be more commonly known by another name? Where is this part located? Is it actually inside the throttle housing (ie. underneath it) or am I misunderstanding? Do you think this may be the cause for the ABS light being back on again (it went over when I replaced the bad OVP but is back again unfortunately). A link to a photo of where this piece is would be fantastic.
Next..
This one has baffled me for a few months now. I'm not sure if it's due to a failing wiring harness or what, but my AC on/off switch seems to have a mind of it's own. A lot of times, when I'm accelerating or I break a bit hard, it will just click on by itself. I have to really dig on the "0/off" button for it to stay off, otherwise the blower motor keeps going on and off, on and off. Not only is it annoying but it's robbing me of fuel economy as I can tell the car runs a bit heavier when the blower engages. Any help trouble shooting this one would be greatly appreciated.
and.. last but not least..
Why does the fluid sensor light come on only when I'm in Reverse or turn the Fog lights on. Any ideas? My front left headlight wiper is non-functioning at the moment, but I don't think that's the cause of it. My windshield fluid is a little low at the moment, but it's been that low before and never set the sensor off in this manner.
TIA,
G.Francesco
12-13-2009, 10:31 AM
#2
I have never heard of this hot film sensor either...The only "sensor" in the throttle on the Bosch KE-Jetronic system is the potentiometer. This is our airflow sensor.
As for the high idle, I have "heard" of a bad connector for the OVP that required resoldering on a thread a while back @ peachparts. The guy had the same issue and after quite some deliberation noticed the connector looked a little odd so took it apart and resoldered it all and it fixed his issues.
1000rpm is correct at cold startup. My 300TE does as well. As long as it only does it when the engine is cold you have nothing to worry about. If you still think its a tad high, I would pull off the idle control valve and make sure its clean using carb cleaner. Get all dirt and crap out of there to make sure its not getting suck open slightly. But the 1000rpm doesn't seem wrong as long as it drops after a minute.
Your model does not have the wiring harness issues, so I would look elsewhere...Could be a bad climate control unit...
As for the high idle, I have "heard" of a bad connector for the OVP that required resoldering on a thread a while back @ peachparts. The guy had the same issue and after quite some deliberation noticed the connector looked a little odd so took it apart and resoldered it all and it fixed his issues.
1000rpm is correct at cold startup. My 300TE does as well. As long as it only does it when the engine is cold you have nothing to worry about. If you still think its a tad high, I would pull off the idle control valve and make sure its clean using carb cleaner. Get all dirt and crap out of there to make sure its not getting suck open slightly. But the 1000rpm doesn't seem wrong as long as it drops after a minute.
Your model does not have the wiring harness issues, so I would look elsewhere...Could be a bad climate control unit...
Last edited by ps2cho; 12-13-2009 at 10:35 AM.
12-17-2009, 05:13 PM
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1988 300E
ps2cho:
Oh, okay. Yes, it's been quite cold here (19-40 degrees F) and have noticed that the idle never goes above 1,000, and only for a short period of time before returning to 8-600'ish depending on how warm the engine is.
Where is the ICV located exactly?
I'm still feeling like I'm getting robbed of power at acceleration from 1st to 2nd gear. When I punch the pedal from 0.. it's not very peppy. It slowly climbs. However, if I shift down to second from stop sign or stop light for example, and then accelerate, it's much peppier. It almost seems like it's best for me to drive my automatic so to speak, then to simply leave it in D. I can't imagine with 177 hp this is the way a 300E was designed to run (mind you my engine has 249k miles on it). Do you think the Air Mass Meter sensor (found inside the throttle housing) is causing that? Perhaps something else?
Also, I drained my washer resoivor to check something and noticed that the check washer fluid light only comes when the high beams are on or I'm in reverse. Odd..
Last but not least, the OVP sensor is good, do you think the Air Mass is causing the ABS light or something else? I ordered a code reader today, should be here next week.
Oh, okay. Yes, it's been quite cold here (19-40 degrees F) and have noticed that the idle never goes above 1,000, and only for a short period of time before returning to 8-600'ish depending on how warm the engine is.
Where is the ICV located exactly?
I'm still feeling like I'm getting robbed of power at acceleration from 1st to 2nd gear. When I punch the pedal from 0.. it's not very peppy. It slowly climbs. However, if I shift down to second from stop sign or stop light for example, and then accelerate, it's much peppier. It almost seems like it's best for me to drive my automatic so to speak, then to simply leave it in D. I can't imagine with 177 hp this is the way a 300E was designed to run (mind you my engine has 249k miles on it). Do you think the Air Mass Meter sensor (found inside the throttle housing) is causing that? Perhaps something else?
Also, I drained my washer resoivor to check something and noticed that the check washer fluid light only comes when the high beams are on or I'm in reverse. Odd..
Last but not least, the OVP sensor is good, do you think the Air Mass is causing the ABS light or something else? I ordered a code reader today, should be here next week.
