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Discussion Starter · #1 ·
My 89 740 turbo is having idle speed problems and is failing hydro carbon test required in this part of BC CA. I have checked and changed several items but it still is there. ??? Does the EGR valve affect the idle speed??? Car passed all other tests and is running well but my ability to get any idle speed adjustment = zero. It is idling at 750rpm as it should but whenever I come to a stop it dives to 500rpm before recovery. Any suggestions? Any help would be really appreciated.

Look forward to talking with you guys. I'm a lonnnnnnnng time volvo freak. Since 1961. Have had a few but rerally am satisfied with this one except for this nuisance problem.

Later

Corny
 

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You might want to have a shop clean the throttle body and idle motor and adjust the tps on the throttle body.If you have a adjustable mass flow sensor it might need to be adjusted.You either need the proper equiptment or have a shop that specializes in Volvo's work on it.Sounds like the common dirty throttle body and idle motor.But you should have the other things looked at also.
 

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Discussion Starter · #3 ·
Tech

Did all that as well as change both fuel pumps in the last year; fuel filter 2 months ago; pressure regulator 2 months ago; new plugs and plug wires 2 months ago; changed air mass meter with same 007 series 1 month ago; complete exhaust replacement including the catalyc 1 year ago but still it seems to be running rich. That is why I was inquiring about the egr valve and would also like to know if 1 of the injuctors could be misfiring and cause this hydrocarbon idle problem? I know that the Air Care shops have the equipment to analyze this but they often want your first born child just for the analysis. I was hoping that someone else may have had the same problem so I could just buy the part and resolve the problem my self. Thanks for the info.
 

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It is possible that the Egr valve could be bad.You have checked good for a Vaccum like haven't you?It could be possible that an injector might be stuck open or something like that.The only other thing I could think of would be either the thermostat or coolant temp sensor.
 

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Discussion Starter · #5 ·
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Temp and thermostat have been checked and are good. Replaced several vacuums due to their age. I'm going to look further into egr valve and throttle switch. If they don't improve the idle speed and hydrocarbon problem then I guess I shall be forced to have an analysis done with all the emission equipment. My only concern when this is done is often when you correct one problem like too rich a mixture you end up creating other emission problems which they don't repair but only replace at top $$$. I'll keep on researching. If I do find out the problem, I'll let you know so you can aid others.

Corny
 

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Thanks for the feedback.Im thinking it is some thing like the tps sensor or something like that.Was your mass flow adjustable?
 

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One other thing I just thought of have you made sure your flame trap isn't clogged.I have seen people fail emmissions and just change the oil and then pass with flying colors.If the flame trap is clogged it will hold the contaminants with in the engine and might make it run to rich.Also make sure that your fuel pressure regulator isn't bad and leaking into the intake through the vaccum line on the back side of the regulator.
 

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Discussion Starter · #8 ·
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I do believe I found the problem. I took off the throttle swirch and cleaned it then reset it and reinstalled it. I then made sure that throttle cable was in proper place. Restarted car and full control over idle returned. I was able to use idle screw with results again; I was able to reset throttle adjustment screw; and I was able to reset timing to its proper values. Seems to be back to full operation again. I will drive it for a couple of days and then return to air care and hopefully it will pass the hydrocarbon problem. Now that the air fuel mixture is again responding, I am hopeful it should pass as before the flapper valve in the throttle valve would just remain in the closed position at idle = too rich a mixture as little or no air entering the mixture. What is your take on this minor tweaking I've done?

Corny
 

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That might have taken care of your problem.If you have full responce and you adjusted timing you might be where you need to be.Another thing you can do is put some denatured alcohol in your gas tank before you go for emmission that will help it run cleaner also.
 

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Discussion Starter · #10 ·
Yes I use methal hydrate coupled with high octane fuel 91 or 94 grade. Thanks so much for your wise advice
Corny
 

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Discussion Starter · #12 ·
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Me again. I know there is a site where I can get the diagnostic codes for 89 740 turbo. Do you know where it is? As well where is the diagnostic control located on the 740? I shall let you know air care results when I return to them.

Corny
 

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The diag control is located under the hood it is a little black box with a wire that sits in the cover.Then you stick the wire in the proper hole then read codes.I attached the link to the site that will help explain how to do it.

http://www.troublecodes.net/Volvo/

This should help you do what you need to do to get it done.
 

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Discussion Starter · #14 ·
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I'll have a look tomorrow for the diag control and check out some of the results. Should confirm whether I've solved the idle speed problem and if not should point out problem areas. I printed a copy of the codes. These could really be a bonus. Thanks for the advice once again.

Corny
 
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