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Old 11-13-2002, 06:46 PM
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Post Seeking advice on rough idle; "Y" code 307..

Okey dokey, I've noticed lately that I've had problems with engine idle in my 84' "Y" Code 307 (Q-Jet). It's been rough, loud, noisy and crappy. For the longest I'd thought it might've been the carb; the sound it's been making is liken to that of worn or loose belts. Hoping the ol' 4 barrel wasn't tired and in need of replacement (and failing to check the usual suspect of "loose and worn belts"), I ran a bottle of carb cleaner through to clean the darn thing out, even replaced gaskets, nothing. I looked over the carb thoroughly, and checked distributor and EGR valve for carbon and exaust deposits, found none whatsoever. Then, as a last resort (having it in the back of my old, senile mind that it just might be worn or loose belts), I replaced the belts and cleaned the pulleys, and abra-friggin-cadabra it did the trick. I've experienced the quiet, smooth idle the 307 is famous for for about 2 months following the belt replacement, until about a month ago the rough idle returned for yet another round of joust!

This time, the FIRST thing I checked was the belt system, yet to my suprise the belts were in relatively new condition. Now this has really had me on my toes, because than I began to suspect it might be the carb, but fortunately, no it wasn't the carb; neither was it the distributor, rotors, cat. or other emissions equippment....so, what was the culprit of this "idling nightmare"??...
Low and behold folks, to my bewilderment it was belt dressing! Yes, belt dressing! That was all that was needed, a few shots of belt dressing...Man did I feel like a moron than!!

But, now that I've shared my little mini soap-opera with you, this is were I actually askt the question. Unfortunately for yours truly, the soap opera continues; the noisy rough idle has returned. Now at this point, I'm at the end of my wits. I doused those belts up well with plenty of belt dressing, and days later I'm now experiencing this same da*n noise! The question is, what might possibly be causing this noise? The noise of worn or loose belts/lack of belt dressing? Any suggestions are most appreciated.

(Btw, one more question. I don't have too much experience with emissions equipment, as most of the engines I've built in my day either weren't equipped with them, or I simply built them without them. My 907 is an 84, which means internal EGR as opposed to 73-79 cars with external EGR. I need to check the EGR tubes for buildup, how do I go about doing this? Removing the EGR valve, as I suspected?)

Thanks for the input,
~John~

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Old 11-14-2002, 12:25 AM
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[quote]I'm now experiencing this same da*n noise! The question is, what might possibly be causing this noise? The noise of worn or loose belts/lack of belt dressing? Any suggestions are most appreciated.<hr></blockquote>

Cleaning the pulleys on initial belt replacement was correct. Did you also check the pulleys for wear and/or glaze? If a pulley has a heat glaze, it needs to be replaced, as it will glaze the new belt(s) in short order.

Did you use a good brand of belt...AC/DELCO or GATES? Usually, belt dressing causes more harm than good. If you suspect glazed pulleys/belts, hit the belts with engine idling with a spray bottle of water and if the noise subsides, you know it is a drive belt/pulley problem and not an accessory problem.

You may also have an accessory that has a bad bearing, causing drag on a drive belt. Check all driven accessories for drag or roughness of operation.

[quote](Btw, one more question. I don't have too much experience with emissions equipment, as most of the engines I've built in my day either weren't equipped with them, or I simply built them without them. My 907 is an 84, which means internal EGR as opposed to 73-79 cars with external EGR. I need to check the EGR tubes for buildup, how do I go about doing this? Removing the EGR valve, as I suspected?)<hr></blockquote>

The easiest way is to remove the valve, verify that it is operational with a vacuum tool, clean and/or replace as necessary (broken diaphram or pintle will not close completely).

Look down the channel below the valve and see if it is carboned up. A coat hanger will be needed if it is. Be sure to reassemble with new gasket and ascertain that the vacuum supply to the valve is operational.
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