matt Posted May 29, 2007 Report Share Posted May 29, 2007 I have a compression tester and have used it before but I don't know the right way to use it on this motor. I have the upper intake off so I can change the plugs again. I want to do a compression check while I am at it. The book says to check comp. with the engine at operating temp. How can I do that on the rear bank and would it really make a difference? Will the water pump, pump water out of the lower intake with the plenum off? Will I get accurate results with the plenum off and the engine cool? The car sputters,sounds like popcorn popping in the exhaust, when I give it gas. The exhaust smells like gas. The plugs (ACdelco) are black but dry and they are only 2 weeks old. It also has a hesitation. I have no idea what to check next . It has a new ICM, coilpacks, pvc, plugs, wires, intake gaskets,valve cover gaskets,air and fuel filter. All injectors have 12.3 ohms. I also gutted the cat to see if it would help. No codes or SES light. Idels OK and starts good. Low on power, shudders when tc locks up. The car ran like this when I bought it a month ago. ANY suggestions would be greatly apprecciated! Quote Link to comment Share on other sites More sharing options...
19Cutlass94 Posted May 29, 2007 Report Share Posted May 29, 2007 the engine needs to be running at operating temp to do a compression test. Everything has gotta be put back on. If its popping in the exhaust, your timing is off. You need to check the timing/have it timed. Quote Link to comment Share on other sites More sharing options...
matt Posted May 29, 2007 Author Report Share Posted May 29, 2007 That sucks. How do I get the compression tester hooked up in the back with the plenum on? The timing belt is riding to passenger side of the cogs. The belt is worn down (in width) about a 1/16" or more on the pass. side. The teeth are are still there in that 1/16" but the top is worn off. Other than that it looks good! So I guess it's time to change it. I still want to check the compression and timing first. Quote Link to comment Share on other sites More sharing options...
matt Posted May 29, 2007 Author Report Share Posted May 29, 2007 Would the timing cause the raw fuel smell and fouled plugs? Quote Link to comment Share on other sites More sharing options...
19Cutlass94 Posted May 29, 2007 Report Share Posted May 29, 2007 For the rear plugs, I duno, be creative! I honestly dont know cause Im unsure of how much room there actually is. If its riding the passenger side of the cogs, and is worn, time to replace it. There should be timing marks on the cogs themselves. These marks need to be lined up. if you dont wanna mess with the timing ( which is HUGE on these engines ) Id bring it somewhere that can do the timing job. Quote Link to comment Share on other sites More sharing options...
matt Posted May 30, 2007 Author Report Share Posted May 30, 2007 I'm not to worried about trying to change the belt and timing myself. But I am going to check with a mechanic I know that works at a GM dealership. I can get his labor for around 1/2 price of the dealer plus beer. I might just save myself some time and trouble by having him do it depending on the price. I have to start shopping around for the timing belt,tesioner and the 2 idlers plus what ever else. Quote Link to comment Share on other sites More sharing options...
matt Posted May 30, 2007 Author Report Share Posted May 30, 2007 I got the timing belt covers off and I see the timing belt has been changed before. The idlers and tensioner can't be very old. The idlers are dayco brand. I asume it was all replaced with that brand judging by the fresh looking bolts and the green seals (or what ever they are) inside the idler. There was alot of dust and the belt even wore a grove in the top front cover. I had a feeling some one had been in there recently when I took off the surp belt, it was still like new. Maybe it was done a long time ago. Could the belt be bad already from a poor job? I'm worried now that something else is bad causing the belt to fail early. The car has 154,000 miles on it now. Would a car fax report be detailed enough to tell if the car had timing belt changed at a shop? Quote Link to comment Share on other sites More sharing options...
19Cutlass94 Posted May 30, 2007 Report Share Posted May 30, 2007 I dont think a car fax would show that kinda work. the belt could have 'walked' over there or was simply not aligned right when it was put on. But if theres that much dust and it was rubbing, you deff need a new one. Quote Link to comment Share on other sites More sharing options...
badassoldspower Posted May 30, 2007 Report Share Posted May 30, 2007 Actually there are an array of tests you can perform with the car not running, for example a static compression test, cylinder leakdown test, and a few others, the common misconseption is that a car has to be running for a compression test, this is innacuarate as running compression test can actually be harder to diagnose a blown head gasket, or excessive ring/piston gap due to the fast cycles of the bore being tested. And I am not just spouting off shit, I am actually in the GM ASEP program, and just graduated drivability, no offense to anyone concerned, just here to inform. Kenny Quote Link to comment Share on other sites More sharing options...
1990lumina Posted May 30, 2007 Report Share Posted May 30, 2007 Actually there are an array of tests you can perform with the car not running, for example a static compression test, cylinder leakdown test, and a few others, the common misconseption is that a car has to be running for a compression test, this is innacuarate as running compression test can actually be harder to diagnose a blown head gasket, or excessive ring/piston gap due to the fast cycles of the bore being tested. And I am not just spouting off shit, I am actually in the GM ASEP program, and just graduated drivability, no offense to anyone concerned, just here to inform. Kenny I get to be in that program in a few months - I can't wait!!! Quote Link to comment Share on other sites More sharing options...
19Cutlass94 Posted May 30, 2007 Report Share Posted May 30, 2007 Actually there are an array of tests you can perform with the car not running, for example a static compression test, cylinder leakdown test, and a few others, the common misconseption is that a car has to be running for a compression test, this is innacuarate as running compression test can actually be harder to diagnose a blown head gasket, or excessive ring/piston gap due to the fast cycles of the bore being tested. And I am not just spouting off shit, I am actually in the GM ASEP program, and just graduated drivability, no offense to anyone concerned, just here to inform. Kenny This is true. However when you do a running compression test, you can find out what the pressures are in each cylinder. Quote Link to comment Share on other sites More sharing options...
badassoldspower Posted May 30, 2007 Report Share Posted May 30, 2007 Same goes for a static compression test, either one is going to show which cylinder has the problem, on a static compression test, you can crank the engine over, providing there is no fuel you can see the pressure in each cylinder at a slower rate and will more likely notice a piston that has a small, yet performance affecting characteristic, and also, if you do a leakdown test, you test each piston at TDC and see the pattern in how much leakage each cylinder has in a certain amount of time, the one that leaks down fastest is the one with the problem. All need to be within 10% of eachother according to GM spec. You are always going to have the same pressure in the cylinder, due to your set compression ratio, and if the vehicle is running, and the spark plug is out, you have no combustion to make that compression gauge read any different, compression is: (Volume of cylinder at BDC+Volume of combustion chamber) / (Volume of combustion chamber) hence how this value will not change on either test, yielding both test should show the same result. Quote Link to comment Share on other sites More sharing options...
matt Posted May 30, 2007 Author Report Share Posted May 30, 2007 So I can do a compression check cold to get some idea of any problems. Since I removed the surp belt there should be any trouble with coolant pumping out of the lower intake. I pulled fuel pump fuse and I will pull the fuse for the ICM. I think I will try it. The only idea I have for doing it warm is running the car up to temp and then pulling the plenum and testing the back 3 before it cools down. Quote Link to comment Share on other sites More sharing options...
badassoldspower Posted May 30, 2007 Report Share Posted May 30, 2007 I would Honestly do the check with the engine cold, thats when all your gaps are at their maximums, and you will have better results IMO. Quote Link to comment Share on other sites More sharing options...
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