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  #1  
Old 06-26-2003, 08:07 PM
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maximvsv maximvsv is offline
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Throttle response problem, aggravated by air conditioning

Even since I got my SVX, if I have the climate control in Auto or Defrost modes, and the system activates the air conditioning, I have a massive throttle response lag. Here's another twist to it...it is especially bad from (1) a standing start or (2) a sharp turn.

I have been reading about the "surge" symptoms threads, and I don't think this is an aspect of the same thing (though I do get little surges when the car's idling in gear at stoplights and such).

When the climate control is off or on Vent, the lag is not gone, but is diminished to where it is no longer a danger to entering traffic areas.

Does anyone know if there is a way an impaired A/C compressor could schiz the throttle position sensor or a vacuum line in a way that would keep the throttle from opening even when the pedal is well and truly floored?
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Old 07-25-2003, 08:59 AM
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I haven't gotten a response on this. Anyone got something similar?
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Old 07-25-2003, 01:45 PM
gl1674 gl1674 is offline
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Apparently you are on your own - this seem to be an unusual problem to have.

Throttle linkage is purely mechanical, if you pedal goes to the floor, the throttle is opened. No, steel cables do not stretch.

Any trouble codes in ECU? What is your fuel economy like?
Can you plug voltmeter to throttle position sensor and MAF to see
if the signal they output is OK?
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Old 07-25-2003, 05:02 PM
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Hard one to assist on a remote basis and regret difficult to research properly using wiring diagrams and the manual but :-

Checking in the area of the water temperature sensor would be a good bet as this appears to have several duties. Check wiring connections and the actual unit. Do you have any, cold verses hot engine, drivng symptoms ?

Not likely to be the problem but you should check out the TPS so as to be able to rule this out of the equation. Go to the how to locker where there is instructions re setting and cleaning. This is not a big job and worth doing in any event.

Good luck with this rather curly one.
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Old 07-26-2003, 12:43 AM
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gl1674: I'll see what I can do, but I never much trusted my volt meter. Also, I'll have to figure out where to make the connections.

trevor: No temperature difference issues, though I have not tried to get the a/c to run in winter. The a/c is the biggest magnifier in the situation, but I don't think it is increasing the under-hood temperature enough to generate a temperature-based problem. Besides, the moment I shut the a/c off again, the throttle response lag is reduced (but not eliminated).

Does the a/c have any direct connection to either the fuel delivery or the air intake setup? What about vacuum lines? Are any connected to the compressor in a way that may affect fuel delivery or air?
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Old 07-26-2003, 12:48 AM
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[QUOTE]Originally posted by gl1674
...Any trouble codes in ECU?[QUOTE] No codes are indicated. I haven't tried to induce any, though.
Quote:
...What is your fuel economy like?
I haven't studied it, but from the comment's I've read, when my low gas level warning light comes on, I still have 30-40 miles of gas. So, I figure it's about the standard. I'll check it out, though.
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  #7  
Old 07-26-2003, 12:59 AM
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Hmm... It may not related but I thought I'd share my story. I stopped by one of those quick oil change garage. I haven't changed my oil in the last 5 months. The mechanics went over a couple of things and convinced me to do fuel injector service, because he noticed rough idle when he was pulling in the car. He removed the plastic pipe leading to the throttle body, added someting to the gas tank, replaced the fuel filter, and hooked up some kind of cleaning agent to the gas line going in to the fuel filter. Using cotton swap and cleaning spray, he hand cleaned the inside throttle body before firing up the engine. Slowly the cleaning agent went in a little by little, and the engine rumbled like a caged chicken. About twenty minutes later, it was done, and when he reconnected the gas line to the fuel filter and started the engine again, I couldn't believe how smooth it sounded; I was occasionally expriencing fluctuating idle and sudden surge of RPM out of no reason. And it's all gone now! As a matter of fact, I'm going to take my finance's car tomorrow to get the same service done. Up until today, I simply thought I'd need major tune up done to my car, but it only needed to be cleaned thoroughly. Maybe that's all your car need too. I'm sorry this was rather long but hope this helps.
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  #8  
Old 07-26-2003, 08:29 AM
alacrity024
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the only thing i can think is that something in the a/c system is a little sticky.. e.g. it isn't spinning as freely as it should be and is ribbing the engine of a little extra power..

just a thought..

-adam
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Old 07-27-2003, 05:26 PM
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Quote:
Originally posted by maximvsv
gl1674: I'll see what I can do, but I never much trusted my volt meter. Also, I'll have to figure out where to make the connections.

trevor: No temperature difference issues, though I have not tried to get the a/c to run in winter. The a/c is the biggest magnifier in the situation, but I don't think it is increasing the under-hood temperature enough to generate a temperature-based problem. Besides, the moment I shut the a/c off again, the throttle response lag is reduced (but not eliminated).

Does the a/c have any direct connection to either the fuel delivery or the air intake setup? What about vacuum lines? Are any connected to the compressor in a way that may affect fuel delivery or air?
Max

I suspect Trevor is asking if the problem only happens when the engine is cold, and not when hot, or vice versa. I don't think he is suggesting it is caused by strange or excessive underhood temps.

Regards your last paragraph, there is a connection, and I am not sure it can cause the problem you have but who knows?
When the car is accelerating hard, the electronics can cut out the electromagnetic clutch which turns the a/c compressor. This is to ensure the engine gives all of the available power to overtaking safely, the very opposite of what you are getting. I think this cutting out of the a/c compressor can happen in stages, but someone may confirm or deny this. For sure, when you stop accelerating, it lets the a/c back on again [you see no indication of this on the dials, it merely stops the compressor from turning]

Now if there was something wrong with this circuit in your car, it could be working wrong, or the opposite to how it should, and be adding a load at the wrong time. Do the diagnostic for the a/c, maybe there is an electrical fault.

Also, if your a/c compressor was hard to turn because of a tight or nearly seized bearing, it would surely create a load. Would not expect it to do this for long, though, without seizing up and burning off your aircon drive belt. You should check it out, though.

Joe
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  #10  
Old 07-27-2003, 06:16 PM
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What I am pointing out is that the water temperature sensor appears to provide signals for the management of both the engine and the air conditioning. If this is so a fault in the sensing and or a/c circuit when activated could possibly effect the ECU and engine.

Hence my reference to hot verses cold engine performance issues as possibly providing a clue as it is said that the fault is to some extent always present but exasparated when the a/c is activated. I can not see how load applied by the a/c could induce the symptoms described.

This is a suggestion only as I am unable to confirm the exact arrangement from the wiring diagrams I have. Beav would be the one to check with to confirm or reject the idea.
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Last edited by Trevor; 07-27-2003 at 06:25 PM.
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