QuestionBill,
Thanks again for the wealth of information ...
I am interested in what you said about "Soaking the Cylinders overnight" ... It seems to be a good idea ... Can you send me the exact steps of how to do that as I need to follow some guidelines from an expert like you who knows what he is talking about ...
Also if you can point for me where is the "Knock Sensor" located and how much does it cost ?
Looking forward to your response ...
Reda Hanna
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Followup To
Question -
Bill,
Thanks for your response ... You are a Real Expert ...
Do you think that changing the EGR Valve might help in that situation ?
I have read in a previous article of yours that engine pinging & knocking are related to the EGR Valve ...
Appreciate your comments ...
Reda Hanna
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Followup To
Question -
Bill,
I purchased a Cadillac Deville 96 with 145K Miles on it ...
Since I bought it, and I can listen to a noticeable engine knocking especially when I am going up hill ... It also happened a couple of times as I was driving on the freeway with the A/C on and running at 75~80 mph ...
Currently I am using 87 grade Gas from Costco or Chevron as I cannot afford the 91 grade ...
Appreciate your recommendation on what to do ...
Thanks for your help ...
Reda Hanna
Answer -
Hi Reda, The northstar engine is unfortuneately designed to run on premium gas. If the knocking only occurs under heavy acceration then what you are hearing might be due to the lower octane gas. Some suggestions would be to switch brands of gas and see if that helps. You could have some carbon build up inside the cylinders that pouring in 3-4oz of top engine cleaner into each cylinder and then letting it soak overnight. Then crank the engine over with the coils disabled so there isn't any spark to remove what is left in the cylinders and then installing the plugs and driving the car until the smoke clears. Then change the oil and filter. This would be best done by a shop. If that doesn't stop it then the only choice is to use a higher grade gas or don't drive the way you do because you are damaging the engine. It might be best to sell the car and get a vehicle that is designed to run on 87 octane. Good luck. Bill
Answer -
Hi Reda, Thanks for the vote of confidence. I guess most times with the NS engine it is carbon build up but you are right an EGR valve that isn't opening when it should could cause pinging but most times the service engine light turns on and a code is stored. The valve is rather expensive...around $175...so installing one without testing its operation first might not help the ping. Some other things to check are is the engine running hotter than normal...is the vacuum motor that allows hot air into the air cleaner housing from the exhaust manifold sticking so hot air is in the air fiter all the time...if the engine isn't getting the correct fuel mixture like running lean due to a faulty injector or out of calibration map sensor. And if you had a distributor the timing could be set too far advanced. However the computor or PCM controls timing so hooking up a scan tool to check that it is in the correct range. A faulty knock sensor might retard timing and cause the knock. As you can see there are other things to check and by far the easiest thing to do would be to run 2-3 tankfulls of premium gas in the tank and see if that clears up the problem and then remove all the sparkplugs and soak the cylinders overnight. And that helps in alot of cases according to a bulletin published and tested by GM engineers. What fixes one car might fix the next but sometimes you come across one that is alittle out of the ordinary and takes awhile to solve. Maybe this one needs the EGR valve. Bill
AnswerHi Reda, The knock sensor is located under the intake manifold and might be best to have a shop change it as it is kind of tough to disassemble the upper engine to get to. The part might cost around $40...This is the procedure that I would use to soak the cylinders. Park the car outside. Remove all the sparkplugs with the engine at room temerature so you don't strip the threads in the head. Removeing the coil pack from the rear valve cover will make it easier to get at the rear plugs. Then useing a funnel with a 2 foot hose on it so the hose can go into the sparkplug hole measure 4oz of top engine cleaner(GM name) or Sea Foam brand cleaner and pour it into the funnel so it goes into the cylinder. Let it soak for at least 8 hours or preferably overnight. Then with the coil module electrical connectors disconnected place towels or shop rags over the engine and sparkplug holes to soak up the solvent that comes out when cranking the engine over for 10-15 seconds... If that stuff gets on the paint wash it off immediately with soap and water or as recommended on the can or it could damage the paint...Then reinstall the sparkplugs and the coils making sure that the sparkplug wires are at least 2" from the blower motor at the rear of the rear valve cover. Now comes the fun part especially if you like smoke shows. Start up the engine and drive in 2nd gear at 30 to 40 mph until the smoke clears out. It may take 10 to 15 minuits from the time the engine starts to do this and will create quite a cloud. You may have to hold the accellerator pedal to the floor before the engine starts or it may start normally. Then once the smoke clears change the oil and filter to get rid of and cleaner that found its way down to the oil pan. Hope that makes sense. Bill
