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Discussion Starter #1
Not quite sure how to explain this. My Bro-In-Law has a 1997 Suzuki Sidekick, which just had the head removed for a freeze plug leak (water in the oil). Also found was a timing belt gear, wobble. Machine shop repaired this. OHC of course...

After driving it, we opened the hood, and I was looking for oil, and water leaks, then we started hearing a sort of poof of air sound then the idle dropped in unison with this poof noise, sounds like the beat of a drum. My first thought was a vacuum leak, causing this noise, and idle speed drop. Turned on the airconditioner, then the engine dies, also I'm thinking a vacuum problem or maybe the EGR valve failure. This wasn't happening before the repair. Idle is good until it makes that poofing sound. This symptom appears to be near the rear of the engine, by the throttle body area. Very hard to isolate. Engine is running very smooth other than this nagging issue.

Not sure it they adjusted the valves either. I was also thinking maybe the valves out of adjustment would create a sort of back pressure in an engine causing this noise and problem. EGR valve...?? Thanks for any assistance you can give...

RB in Cebu City, PH
 

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Sounds like a miss, first step, compression test

Post results.... Philip
 

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Discussion Starter #3 (Edited)
Actually it purrs like a kitten. Normally a compression issue would be gradual. Wasn't doing this before the head was pulled, nor was the engine qutting after turning on the air conditioner. The engine runs out good on the road, solid, no miss...Only at idle when the puff of air happens. Almost sounds like a very low bass drum.

Thanks

Oh, just another note, it almost seems like a back pressure sound, like when you put your hand over the exhaust pipe and it sort of sucks and pushes your hand like the old muscle cars.
 

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No, compression loss does not have to be gradual - any jump in the timing belt will be immediate. It is difficult to diagnose unless you have the foundation of good engine and ignition timing. It would be best for you to do the compression test and post your results.
Idle is not a problem in itself, but a symptom of a problem - you advise that your car stalls when the A/C is turned on. Normally, the idle speed solenoid would be regulating idle when you put a load on the engine, and keep the idle up. This is the sensor that is connected via a small air hose from the air pipe at the air filter to the sensor itself. Is there a hole in this hose?? Without the A/C on, if you pinch this hose with a pliers, what does the idle do??
 

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Discussion Starter #5
That's at least been my experience in my 45 years of troubleshooting, but when posting that I did realize there could be exceptions. I have a compression tester in my shop here I may do that. But I just found out that my Brother-In-Law is taking it to the Suzuki dealership tomorrow have it diagnosed on their analyzer for P2,500 about $55.00US so maybe we'll see what it is then.

I don't think there is any problems with the compression, (piston rings, etc.) at least there never was before they pulled the head last week. Been running too good for that. If I had a dead cylinder in a 4-cylider engine I would definitely know it...Running just as good now, very fast good acceleration, not missing a lick. It's just at idle RPM...


No, compression loss does not have to be gradual - any jump in the timing belt will be immediate. It is difficult to diagnose unless you have the foundation of good engine and ignition timing. It would be best for you to do the compression test and post your results.
Idle is not a problem in itself, but a symptom of a problem - you advise that your car stalls when the A/C is turned on. Normally, the idle speed solenoid would be regulating idle when you put a load on the engine, and keep the idle up. This is the sensor that is connected via a small air hose from the air pipe at the air filter to the sensor itself. Is there a hole in this hose?? Without the A/C on, if you pinch this hose with a pliers, what does the idle do??
 

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cebudude,

The suggestion for a compression test is not necessarily to see if you have a dead cylinder. It is a method to check the mechanical timing of your engine. With mechanical timing incorrect, compression would be low across the board.

With the scenario you described of "Been running too good for that", then after head work you are having issues, the mechanical timing becomes very suspect. The timing components were definitely altered during a head removal and whatever was done to repair the timing gear wobble.
 
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