Brief History...Its a 94 automatic. I just purchased the car and have only driven it 10 miles. I noticed the temp. gauge started off in the middle when cold and worked its way up. I purchased a new OEM thermostat and all 3 temp.. sensors. I burped the car and perfection, temp gauge works as it should. Now, the damn thing idles at about 1500 w/o AC and 1300 with AC running. Oh yeah, while I was changing the thermostat, I cleaned the Throttle Body which was really dirty. I already unplugged and replugged the battery to erase any codes. What am I missing here?
And now yet another Gremlin.
- Thread starter El-Cojonico
- Start date
Did you remove the throttle body and clean the idle air passage and screw?
All I did was remove the throttle body, spray it with carb cleaner (brush it some) and dry it with a rag until 90% of the black gunk that was in the bore and butterfly was gone. I didn't take anything off or apart from the throttle body itself.
10 miles - so I am assuming that the car is very new to you? If so, follow [MENTION=18194]Honcho[/MENTION]'s lead. I am going to speculate that perhaps a previous owner was having idle problems because of a dirty throttle body and rather than fix the cause, treated the symptom by cranking up the base idle to compensate for the dirty throttle body. When you cleaned the throttle body, you may have removed a blockage in the idle air control circuit which is now flowing more air than before with a resultant higher idle speed. If a previous owner cranked the base idle setting up super high to compensate for a really blocked idle air control circuit, there may now be so much air flowing that it is beyond the ability of the EACV to regulate the idle speed. This may require resetting the base idle following the procedure in the service manual (Fuel section / idle control system). However, before doing this I suggest a thorough cleaning of the throttle body including cleaning of the electronic air control valve (EACV) which the ECU uses to manage idle speed. You want to make sure that the EACV / idle control circuit is sparkly clean before you go through the hassle of setting the base idle.
Also, if the ECU was reading higher than actual temperatures during & following start up the ECU would cut back on after start enrichment which could make for a rough / poor idling engine and somebody might have cranked up the base idle to compensate for that.
Also, if the ECU was reading higher than actual temperatures during & following start up the ECU would cut back on after start enrichment which could make for a rough / poor idling engine and somebody might have cranked up the base idle to compensate for that.
I will clean out the EACV tomorrow and get back to you guys. Thank you!
I would first check the TW sensor connector. The one just below the EGR valve so not easy with coolant hose, tank, etc already in place.
Kaz
Kaz
Somewhere there is a document describing the complete cleaning procedure for the early throttle body including all the little secret passages that need to be cleaned out. I have a DBW car so I have never bothered to try to find the document. Perhaps some other owner can provide the procedure to you.
Ok, cleaned the EACV and no change. Still 1500 RPM no AC 1200 RPM w/ AC. BTW no check engine light and I replaced the PCV.
This is exactly where I was going.
But, Kaz's suggestion is a good one. If the TW sensor has failed, the ECU may still think the engine is cold and thus keep idle RPM high.
I changed all three water sensor's and thermostat to eliminate any doubt regarding the erroneous temp reading. The temperature now reads perfect. I have yet to get the radiator or engine bay fan to come on though. I'm wondering if I have a vacuum leak somewhere. When I turn off the car, it makes a puffing sound in the general area of the air filter. Also, the throttle cable has some minor slack, so its not like its out of adjustment. FYI, the engine accelerates smooth with no hesitation. If it wasn't for the high idle I would say she's perfect.
If you are satisfied that the throttle body is clean, perhaps time to check the base idle setting.
However, do check the TW sensor connection as Kaz suggests(I presume that the sensor was replaced as one of the three sensors?). A bad connection equals high resistance. The sensor resistance normally increases as the temperature drops. If the connection is bad the ECU will read this as a cold engine and it is normal for the ECU to increase the idle speed for a cold engine dropping the idle as it warms up. It seems to me that 1500 RPM (or slightly less) is the idle speed for a stone cold C30 / C32.
However, the fact that your problem emerged after cleaning the TB still leads me to favor a mal adjusted base idle setting - unless you didn't get the connector on the TW sensor seated properly after you replaced the sensor.
I'm heading out to work soon but, will re-check Monday. My wife has forbid me to work on the car on Mother's day. Thanks for the info. If anyone else has a suggestion please chime in. Another note. The car never comes of 1500 rpm, even when the temp gauge hits just below middle.
That is entirely possible. The gauge temperature sensor is separate from the sensor that the ECU uses to measure temperature, so the gauge could be telling you that the engine is nice and warm and a bad connection on the ECU sensor could make that ECU treat the engine like it is a stone cold rock. I would still put my money on the throttle body being the root cause of the problem; but, it is always good to be aware that the root problem could be elsewhere. Nothing is ever 'for sure'.
If TW sensor connector permanently disconnected, it will trigger CEL but not if partially locked or intermittent.
By the way, No CEL (or no warning lights) doesn't mean you don't have error code stored.
Some failure modes require two consecutive detection or even two drive cycles before triggering the CEL. For example, some of the O2 sensor related codes.
I always have CEL code #36 stored on ECU as I disabled TCS by disconnecting the TCS controller.
It won’t trigger CEL because for code #36 , it needs to be detected twice per cycle but since there is no TCS controller connected, it can only be detected once per IGSW reset.
Hence, code stored but no CEL.
I don't know if it's possible to mix up and install TW (black connector) and rad fan sensor (brown) by mistake (diameter, thread) or even connect the mating connector properly (extra key on the connector).
Even if it was possible, your rad fan would be spinning fast even when the engine is still cold so very unlikely to be the case.
Hope you used the OEM sensors.
Since it's thermistor, you can just measure the resistance at the ECU connector once eng fully warmed up.
No need starting the engine or even the IGSW.
This will tell whether the ECU is getting correct temperature info or not.
Check paint lock on the idle air adjust screw of the TH body.
It's grey from the factory so not easy to distinguish.
This will tell whether someone touched it or not.
Doesn't mean it was re-adjusted wrongly but at least, removes the headache of cleaning all that hardened lock paint inside the small screw hole before new screw installation.
You will have hard time doing it while preventing the piece of paint dropping inside without removing the TH body....
Kaz
By the way, No CEL (or no warning lights) doesn't mean you don't have error code stored.
Some failure modes require two consecutive detection or even two drive cycles before triggering the CEL. For example, some of the O2 sensor related codes.
I always have CEL code #36 stored on ECU as I disabled TCS by disconnecting the TCS controller.
It won’t trigger CEL because for code #36 , it needs to be detected twice per cycle but since there is no TCS controller connected, it can only be detected once per IGSW reset.
Hence, code stored but no CEL.
I don't know if it's possible to mix up and install TW (black connector) and rad fan sensor (brown) by mistake (diameter, thread) or even connect the mating connector properly (extra key on the connector).
Even if it was possible, your rad fan would be spinning fast even when the engine is still cold so very unlikely to be the case.
Hope you used the OEM sensors.
Since it's thermistor, you can just measure the resistance at the ECU connector once eng fully warmed up.
No need starting the engine or even the IGSW.
This will tell whether the ECU is getting correct temperature info or not.
Check paint lock on the idle air adjust screw of the TH body.
It's grey from the factory so not easy to distinguish.
This will tell whether someone touched it or not.
Doesn't mean it was re-adjusted wrongly but at least, removes the headache of cleaning all that hardened lock paint inside the small screw hole before new screw installation.
You will have hard time doing it while preventing the piece of paint dropping inside without removing the TH body....
Kaz
Minor update. The idle adjust screw has not been messed with. Also my battery is really dead. It must have just barely started the last couple times. I confirmed its old. I ordered an Optima. Should be here Wednesday.
If the idle screw has not been tampered with, then the base idle has not been adjusted and high idle is not the result of somebody adjusting the idle up to compensate for a dirty throttle body. Since the high idle speed appeared after you did your maintenance, I suggest three possibilities:
1) As Kaz suggests you have a bad connection at the coolant temperature sensor. My 2000 na2 has an air pump that runs on start up to fire up the catalyst fast, so the start up sequence is not exactly the same as your na1; however, this morning I noticed that cold idle was around 1500 RPM and then tapers down.
2) When you were working on the throttle body, you created an intake leak downstream of the throttle plate. Downstream air leaks into the manifold look just like idle by-pass air to the ECU and will result in high idle speed
3) When you were working on the throttle body, you did something to the throttle cable / throttle plate mechanism which is not allowing the throttle plate to return to its normal closed position.
Have you checked for any stored error codes in the ECU. There might be something there that provides useful information.
1) As Kaz suggests you have a bad connection at the coolant temperature sensor. My 2000 na2 has an air pump that runs on start up to fire up the catalyst fast, so the start up sequence is not exactly the same as your na1; however, this morning I noticed that cold idle was around 1500 RPM and then tapers down.
2) When you were working on the throttle body, you created an intake leak downstream of the throttle plate. Downstream air leaks into the manifold look just like idle by-pass air to the ECU and will result in high idle speed
3) When you were working on the throttle body, you did something to the throttle cable / throttle plate mechanism which is not allowing the throttle plate to return to its normal closed position.
Have you checked for any stored error codes in the ECU. There might be something there that provides useful information.
Another small update. Battery came in and I installed it.....Car continues to idle high with no end in sight, the good news is that the radiator fan came on. The engine bay fan has not. I will be checking for stored codes tomorrow.
Ok, kinda threw in the towel and ordered an SOS throttle body upgrade......I know I know it doesn't make a significant update, but at least I know I'm starting with a fresh throttle body. SOS also informed me they are back logged about 2 weeks. So for now I will be replacing my belts and crank shaft pulley (remember I have 133k miles on it). and I also will replace the rear engine mount which is shot. Thanks guys. I'll update after I swap everything out.
Oh damn. I'll check that as well. Also.....can anyone advise is the Crankshaft bolt, righty tighty...lefty lucy?
Success, I got an SOS Throttle Body today and put it right in. The car idles perfect (although it did stumble once and shut off). So grateful for all the info you guys gave me. The front radiator fan comes on and the temp holds perfect. One question...Does anyone know when the engine bay fan kicks on, I have yet to see it run, even though I know it works. Thanks again! Now I can attend the Pembroke Pines meet next Sunday.
The 1991 service manual description of the fan control is rather minimal. As best as I can read between the lines, the service manual implies that the engine compartment fan does not operate until the fan control unit switches from low speed to high speed on the radiator fans. The switch from low speed to high speed operation occurs when the temperature hits 90 C and it switches back to low speed when the temperature drops to 84 C. If your coolant temp never exceeds 90 C then the fan will never operate and if the temperature drops to 84 C before you check the fan it will shut off. Based upon the service manual description if your radiator fan is running on high speed when you check I think your engine compartment fan should be running. If the rad fans are on low speed then the engine compartment fan should not be running.
In addition to control by the fan control unit, the engine compartment fan relay also has a direct connection to the ECU, presumably to allow the ECU to switch the fan on independent of what the coolant temperature is. The ECU is interconnected with the automatic transmission control unit so perhaps there are some 'automatic transmission conditions' that can trigger operation of the engine compartment fan.
In addition to control by the fan control unit, the engine compartment fan relay also has a direct connection to the ECU, presumably to allow the ECU to switch the fan on independent of what the coolant temperature is. The ECU is interconnected with the automatic transmission control unit so perhaps there are some 'automatic transmission conditions' that can trigger operation of the engine compartment fan.
Thanks for the info. These cars are so complicated sometimes. Since I have no desire to race it, weight loss isn't my thing. It will stay there for now. So happy she's running great.
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