99 cr-v surging idle and overheats with ac on
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From: Arizona
99 cr-v surging idle and overheats with ac on
Hi everyone! My 99 cr-v symptoms: surging idle and overheats with ac on. I've replaced the radiator, water pump and last week replaced the timing belt. 2 days later idle starts surging again, ac starts blowing hot air then overheats. When I turn the ac off the temp drops back to normal. What else could it be?
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Re: 99 cr-v surging idle and overheats with ac on
Ok.
is the idle surge present with AC OFF . This includes DEF AND DEF/HEAT OFF as choosing def or def/ heat mix will cycle the AC compressor. So is it present with climate controls off?
Engine idle control on this engine is run by the ECM via the idle air control motor and also, during warm up, controlled by the fast idle valve which is basically a thermal sensitive valve that operates in the same fasion as a engine coolant thermostat. It uses coolant and a wax pellet. It can cause an idle surge but usually during warm up of a cold engine.
The ECM will command the Idle Air Control (IAC) motor will adjust engine idle during loads such as alternator output, P/N switch selection and/or AC compressor operation. If the AC compressor is loading the engine ( overpressure from blocked line/accumulator) the engine idle will stall out then surge and if the refrigerant pressure is high enough, the ECM will release the compressor clutch and the engine will surge then drop to idle. This cycle can repeat multiple times until the AC is manually disengaged. I have seen the pressure high enough to load an engine heavy were the IAC can keep the engine idling but you can tell its maxed out in its ability to do so from the perceived engine load. This in itself won't cause an overheat, unless the coolant/condenser fans are not cycling when requested by the ECM for cooling the radiator or during AC operation. Keep in mind that while traveling at a preset road speed the fans operation is switched off as the ECM understands how fast your traveling and the fans operation isn't needed as there is sufficient airflow via vehicle travel speeds.
At idle and low speeds, the fans should be cycling regularly, given time see above operating coolant temp and/or during AC compressor operation. The signal for coolant temperature is via a coolant temp sensor switch in the radiator. Its important to verify these fans operation.
The ignition timing should be verified and set properly by putting the ignition system in service mode and setting the base timing.
Also....
verify the coolant is all still in the cooling system and there is no chance of low coolant or a loss of coolant from a gasket leaking ( water pump, head gasket and/ hose clamp)
is the idle surge present with AC OFF . This includes DEF AND DEF/HEAT OFF as choosing def or def/ heat mix will cycle the AC compressor. So is it present with climate controls off?
Engine idle control on this engine is run by the ECM via the idle air control motor and also, during warm up, controlled by the fast idle valve which is basically a thermal sensitive valve that operates in the same fasion as a engine coolant thermostat. It uses coolant and a wax pellet. It can cause an idle surge but usually during warm up of a cold engine.
The ECM will command the Idle Air Control (IAC) motor will adjust engine idle during loads such as alternator output, P/N switch selection and/or AC compressor operation. If the AC compressor is loading the engine ( overpressure from blocked line/accumulator) the engine idle will stall out then surge and if the refrigerant pressure is high enough, the ECM will release the compressor clutch and the engine will surge then drop to idle. This cycle can repeat multiple times until the AC is manually disengaged. I have seen the pressure high enough to load an engine heavy were the IAC can keep the engine idling but you can tell its maxed out in its ability to do so from the perceived engine load. This in itself won't cause an overheat, unless the coolant/condenser fans are not cycling when requested by the ECM for cooling the radiator or during AC operation. Keep in mind that while traveling at a preset road speed the fans operation is switched off as the ECM understands how fast your traveling and the fans operation isn't needed as there is sufficient airflow via vehicle travel speeds.
At idle and low speeds, the fans should be cycling regularly, given time see above operating coolant temp and/or during AC compressor operation. The signal for coolant temperature is via a coolant temp sensor switch in the radiator. Its important to verify these fans operation.
The ignition timing should be verified and set properly by putting the ignition system in service mode and setting the base timing.
Also....
verify the coolant is all still in the cooling system and there is no chance of low coolant or a loss of coolant from a gasket leaking ( water pump, head gasket and/ hose clamp)
Last edited by Davey7847; Jun 5, 2021 at 09:37 PM. Reason: Also....
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Re: 99 cr-v surging idle and overheats with ac on
I found a link to download 1997-2000 crv serv man in PDF or kindle etc. I did download it and copied the fan circuits for you but here's the link. There is good troubleshoot of the Heat and Air Conditioning.
i reccomend having a repair manal for any older car and Hondas are easiest to repair in my experience and the manuals make it way easier.
https://archive.org/details/HondaCRV19972000/page/n947/mode/2up
Last edited by Davey7847; Jun 5, 2021 at 10:22 PM. Reason: Attachment missed
Thread Starter
Honda-Tech Member
Joined: Sep 2020
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From: Arizona
Re: 99 cr-v surging idle and overheats with ac on
Ok.
is the idle surge present with AC OFF . This includes DEF AND DEF/HEAT OFF as choosing def or def/ heat mix will cycle the AC compressor. So is it present with climate controls off?
Engine idle control on this engine is run by the ECM via the idle air control motor and also, during warm up, controlled by the fast idle valve which is basically a thermal sensitive valve that operates in the same fasion as a engine coolant thermostat. It uses coolant and a wax pellet. It can cause an idle surge but usually during warm up of a cold engine.
The ECM will command the Idle Air Control (IAC) motor will adjust engine idle during loads such as alternator output, P/N switch selection and/or AC compressor operation. If the AC compressor is loading the engine ( overpressure from blocked line/accumulator) the engine idle will stall out then surge and if the refrigerant pressure is high enough, the ECM will release the compressor clutch and the engine will surge then drop to idle. This cycle can repeat multiple times until the AC is manually disengaged. I have seen the pressure high enough to load an engine heavy were the IAC can keep the engine idling but you can tell its maxed out in its ability to do so from the perceived engine load. This in itself won't cause an overheat, unless the coolant/condenser fans are not cycling when requested by the ECM for cooling the radiator or during AC operation. Keep in mind that while traveling at a preset road speed the fans operation is switched off as the ECM understands how fast your traveling and the fans operation isn't needed as there is sufficient airflow via vehicle travel speeds.
At idle and low speeds, the fans should be cycling regularly, given time see above operating coolant temp and/or during AC compressor operation. The signal for coolant temperature is via a coolant temp sensor switch in the radiator. Its important to verify these fans operation.
The ignition timing should be verified and set properly by putting the ignition system in service mode and setting the base timing.
Also....
verify the coolant is all still in the cooling system and there is no chance of low coolant or a loss of coolant from a gasket leaking ( water pump, head gasket and/ hose clamp)
is the idle surge present with AC OFF . This includes DEF AND DEF/HEAT OFF as choosing def or def/ heat mix will cycle the AC compressor. So is it present with climate controls off?
Engine idle control on this engine is run by the ECM via the idle air control motor and also, during warm up, controlled by the fast idle valve which is basically a thermal sensitive valve that operates in the same fasion as a engine coolant thermostat. It uses coolant and a wax pellet. It can cause an idle surge but usually during warm up of a cold engine.
The ECM will command the Idle Air Control (IAC) motor will adjust engine idle during loads such as alternator output, P/N switch selection and/or AC compressor operation. If the AC compressor is loading the engine ( overpressure from blocked line/accumulator) the engine idle will stall out then surge and if the refrigerant pressure is high enough, the ECM will release the compressor clutch and the engine will surge then drop to idle. This cycle can repeat multiple times until the AC is manually disengaged. I have seen the pressure high enough to load an engine heavy were the IAC can keep the engine idling but you can tell its maxed out in its ability to do so from the perceived engine load. This in itself won't cause an overheat, unless the coolant/condenser fans are not cycling when requested by the ECM for cooling the radiator or during AC operation. Keep in mind that while traveling at a preset road speed the fans operation is switched off as the ECM understands how fast your traveling and the fans operation isn't needed as there is sufficient airflow via vehicle travel speeds.
At idle and low speeds, the fans should be cycling regularly, given time see above operating coolant temp and/or during AC compressor operation. The signal for coolant temperature is via a coolant temp sensor switch in the radiator. Its important to verify these fans operation.
The ignition timing should be verified and set properly by putting the ignition system in service mode and setting the base timing.
Also....
verify the coolant is all still in the cooling system and there is no chance of low coolant or a loss of coolant from a gasket leaking ( water pump, head gasket and/ hose clamp)
Just had new timing belt and water pump replaced a month ago. Went through 2 water pumps before I figured out the 2 were related.
The surging when AC is on is rhythmic and constant. Very different from morning warm up surging. I think I understand about speed and cooling...if I'm on the freeway at a constant speed with no stopping the AC stays cold, no surging, no overheating, unless I have to slow down to much or stop. On surface streets it overheats at stop sighns, red lights...pretty much whenever I'm going too slow or I'm idle. I turn AC off and temp drops down to normal within 2 minutes. I do A LOT of desert city driving so I'm constantly turning AC on and off. Gonna check if condenser fan turns on with AC.
Coolant is at normal level and where it should be...no leaks.
I do have the complete manual which is extremely helpful, but it gets confusing sometimes without guidance while I'm actually making repairs and I get stuck...and I definitely don't understand the wiring charts.
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Joined: Nov 2020
Posts: 263
Likes: 40
Re: 99 cr-v surging idle and overheats with ac on
No surging when AC is off.
Just had new timing belt and water pump replaced a month ago. Went through 2 water pumps before I figured out the 2 were related.
The surging when AC is on is rhythmic and constant. Very different from morning warm up surging. I think I understand about speed and cooling...if I'm on the freeway at a constant speed with no stopping the AC stays cold, no surging, no overheating, unless I have to slow down to much or stop. On surface streets it overheats at stop sighns, red lights...pretty much whenever I'm going too slow or I'm idle. I turn AC off and temp drops down to normal within 2 minutes. I do A LOT of desert city driving so I'm constantly turning AC on and off. Gonna check if condenser fan turns on with AC.
Coolant is at normal level and where it should be...no leaks.
I do have the complete manual which is extremely helpful, but it gets confusing sometimes without guidance while I'm actually making repairs and I get stuck...and I definitely don't understand the wiring charts.
Just had new timing belt and water pump replaced a month ago. Went through 2 water pumps before I figured out the 2 were related.
The surging when AC is on is rhythmic and constant. Very different from morning warm up surging. I think I understand about speed and cooling...if I'm on the freeway at a constant speed with no stopping the AC stays cold, no surging, no overheating, unless I have to slow down to much or stop. On surface streets it overheats at stop sighns, red lights...pretty much whenever I'm going too slow or I'm idle. I turn AC off and temp drops down to normal within 2 minutes. I do A LOT of desert city driving so I'm constantly turning AC on and off. Gonna check if condenser fan turns on with AC.
Coolant is at normal level and where it should be...no leaks.
I do have the complete manual which is extremely helpful, but it gets confusing sometimes without guidance while I'm actually making repairs and I get stuck...and I definitely don't understand the wiring charts.
Both fans should run when the compressor is cycling. The condenser needs the cooling air to pull the heat out of the refrigerant after it leaves the evaporator in the dash.
if the car idle surges when the compressor is called for ( idle drop and recovery) the pressure my be high in the line making the compressor bog down the engine.
Are the fans cycling with the compressor?
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