Marika Posted March 12, 2006 Report Share Posted March 12, 2006 I have been driving around for a few weeks now noticing a strange rattling noise in my engine. It's particularly noticable under light acceleration and while going up hill. Finally had the car to the mechanic yesterday for an oil change and tire rotation and I told him to take the car for a test drive and to tell me what that sound is that I'm hearing. He comes back about 1/2 hour later and asks me what type of gas I'm using. I said, I've been using Amoco Ultimate 93 for the past few weeks. He said, the gas is bad, change to something else. What you are hearing is the engine knock. I was surprised but then again, I know I read in the newspaper that a lot of local gas station were getting caught pumping illegal fuel while the pump would say 93 octane, what was coming from the nozzle was much lower. The gas station owners depend on the fact that modern cars have anti-knock sensors that will adjust the engine timing and the owner won't be able to tell if the engine is knocking. Well, the old 4.9 litre caddy engine doesn't have an anti-knock sensor, if you feed this baby bad gas, she rats you out in a heartbeat. The tank indicator was at the half way mark so I decided to fill it with something else. So I tried Hess. Seems that the car is not only knocking less but my gas mileage has climbed now and the car suddenly is getting at least some of its peppiness back. I think in a few tanks hopefully the knocking sound will disappear and I'll get better than 10 miles to the gallon mileage which is what I was getting on Amoco 93. I'm going to report the guy who owns that Amoco station. Let the State check his tank of 93 and see if it really is 93 in there or if he's selling something lower than 90 for $2.43/gallon. If you really want to make people safe drivers again then simply remove all the safety features from cars. No more seat belts, ABS brakes, traction control, air bags or stability control. No more anything. You'll see how quickly people will slow down and once again learn to drive like "normal" humans. Link to comment Share on other sites More sharing options...
Marika Posted March 12, 2006 Author Report Share Posted March 12, 2006 I just called the Bergen County division of the Bureau of Weights and Measures for New Jersey. They are responsible for testing octane rating of fuels in addition to making sure the pumps are putting out the amount of gas they claim they are. I reported this gas station to them. If you really want to make people safe drivers again then simply remove all the safety features from cars. No more seat belts, ABS brakes, traction control, air bags or stability control. No more anything. You'll see how quickly people will slow down and once again learn to drive like "normal" humans. Link to comment Share on other sites More sharing options...
BodybyFisher Posted March 12, 2006 Report Share Posted March 12, 2006 Is it a light pedal noise? It could be detonation and not related to octane but related to EGR flow which the 4.9 is famous for. Pre-1995 - DTC codes OBD1 >> 1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/ Cadillac History & Specifications Year by Year http://www.motorera.com/cadillac/index.htm Link to comment Share on other sites More sharing options...
Marika Posted March 12, 2006 Author Report Share Posted March 12, 2006 Mechanic says it's engine knock and it's the gas. That's all I know at this point. Let the guys at weights and measures check out the gas station I was using to determine if it is in fact the gas. Otherwise, I'll look further into the problem. If you really want to make people safe drivers again then simply remove all the safety features from cars. No more seat belts, ABS brakes, traction control, air bags or stability control. No more anything. You'll see how quickly people will slow down and once again learn to drive like "normal" humans. Link to comment Share on other sites More sharing options...
BodybyFisher Posted March 12, 2006 Report Share Posted March 12, 2006 I beg to differ but, your mechanic is wrong, if you do some research you will see that I personally confronted the guru stating that it was related to octane and that it was PINGING or Preignition..... It was NOT and the guru was right, it was DETONATION, and related to poor EGR flow. Have him rod out the two EGR ports you see when you open the throttle blades in the thottle body and check the egr system. The LIGHT pedal detonation is the key, octane related problems with show it self on HEAVY pedal or overheating conditions. Don't go the route of assuming its the gas and looking to blame the station and getting weights and measures involved, its not related to octane, its related poor EGR flow. Do a search on it (pinging, detonation on 4.9, etc), here is an article on Preignition and Detonation: http://www.contactmagazine.com/Issue54/EngineBasics.html This is a WELL documented problem and the search archives will bare me out Pre-1995 - DTC codes OBD1 >> 1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/ Cadillac History & Specifications Year by Year http://www.motorera.com/cadillac/index.htm Link to comment Share on other sites More sharing options...
Marika Posted March 12, 2006 Author Report Share Posted March 12, 2006 I beg to differ but, your mechanic is wrong, if you do some research you will see that I personally confronted the guru stating that it was related to octane and that it was PINGING or Preignition..... It was NOT and the guru was right, it was DETONATION, and related to poor EGR flow. Have him rod out the two EGR ports you see when you open the throttle blades in the thottle body and check the egr system. The LIGHT pedal detonation is the key, octane related problems with show it self on HEAVY pedal or overheating conditions. Don't go the route of assuming its the gas and looking to blame the station and getting weights and measures involved, its not related to octane, its related poor EGR flow. Do a search on it (pinging, detonation on 4.9, etc), here is an article on Preignition and Detonation: http://www.contactmagazine.com/Issue54/EngineBasics.html He MIGHT be wrong, you might be right. Let's see what a few tank fillups of a different gasoline will do before I start rodding out engine parts, etc. The other reason I suspect it's the gas is because Amoco Ultimate 93 is supposed to be crystal clear if I recall, yet when the attendant spilled some gas on the side of my car one day, I used a rag to soak it up and it was NOT clear, it was a light honey color. That also aroused my suspicions. If you really want to make people safe drivers again then simply remove all the safety features from cars. No more seat belts, ABS brakes, traction control, air bags or stability control. No more anything. You'll see how quickly people will slow down and once again learn to drive like "normal" humans. Link to comment Share on other sites More sharing options...
KHE Posted March 12, 2006 Report Share Posted March 12, 2006 It may be the gas but why not remove the intake duct, hold the throttle blades wide open and look at the EGR tubes??? I am going to bet they are restricted with carbon. A quick rodding out with a coathanger wire will restore the EGR flow and most likely eliminate the "noise" Kevin '93 Fleetwood Brougham '05 Deville '04 Deville 2013 Silverado Z71 Link to comment Share on other sites More sharing options...
Marika Posted March 12, 2006 Author Report Share Posted March 12, 2006 It may be the gas but why not remove the intake duct, hold the throttle blades wide open and look at the EGR tubes??? I am going to bet they are restricted with carbon. A quick rodding out with a coathanger wire will restore the EGR flow and most likely eliminate the "noise" Coathanger wire? I take it they are very small openings? If you really want to make people safe drivers again then simply remove all the safety features from cars. No more seat belts, ABS brakes, traction control, air bags or stability control. No more anything. You'll see how quickly people will slow down and once again learn to drive like "normal" humans. Link to comment Share on other sites More sharing options...
KHE Posted March 12, 2006 Report Share Posted March 12, 2006 It may be the gas but why not remove the intake duct, hold the throttle blades wide open and look at the EGR tubes??? I am going to bet they are restricted with carbon. A quick rodding out with a coathanger wire will restore the EGR flow and most likely eliminate the "noise" Coathanger wire? I take it they are very small openings? Nope - They're 1/2 to 9/16" in diameter. The coathanger makes it easy to rod them out. Don't worry about getting them spotless - just remove most of the crud. Kevin '93 Fleetwood Brougham '05 Deville '04 Deville 2013 Silverado Z71 Link to comment Share on other sites More sharing options...
Marika Posted March 12, 2006 Author Report Share Posted March 12, 2006 It may be the gas but why not remove the intake duct, hold the throttle blades wide open and look at the EGR tubes??? I am going to bet they are restricted with carbon. A quick rodding out with a coathanger wire will restore the EGR flow and most likely eliminate the "noise" Coathanger wire? I take it they are very small openings? Nope - They're 1/2 to 9/16" in diameter. The coathanger makes it easy to rod them out. Don't worry about getting them spotless - just remove most of the crud. how about my gun cleaning rod with a brass brush on it for a 9mm barrel? will that work or be too big? If you really want to make people safe drivers again then simply remove all the safety features from cars. No more seat belts, ABS brakes, traction control, air bags or stability control. No more anything. You'll see how quickly people will slow down and once again learn to drive like "normal" humans. Link to comment Share on other sites More sharing options...
Ranger Posted March 12, 2006 Report Share Posted March 12, 2006 Skip the brass brush. You just need something stiff to break up the carbon if there is any in there. Being sure that the EGR tubes are clear and flowing will take them out of the equation. Link to comment Share on other sites More sharing options...
Marika Posted March 12, 2006 Author Report Share Posted March 12, 2006 Skip the brass brush. You just need something stiff to break up the carbon if there is any in there. Being sure that the EGR tubes are clear and flowing will take them out of the equation. What about the carbon that might fall into the engine? harmless I assume? If you really want to make people safe drivers again then simply remove all the safety features from cars. No more seat belts, ABS brakes, traction control, air bags or stability control. No more anything. You'll see how quickly people will slow down and once again learn to drive like "normal" humans. Link to comment Share on other sites More sharing options...
Ranger Posted March 12, 2006 Report Share Posted March 12, 2006 You could vacuum it out as you are cleaning the carbon if you are so enclined or really worried about it but it will just be injested, burned and go out the exhaust. Won't hurt anything. Link to comment Share on other sites More sharing options...
Marika Posted March 12, 2006 Author Report Share Posted March 12, 2006 You could vacuum it out as you are cleaning the carbon if you are so enclined or really worried about it but it will just be injested, burned and go out the exhaust. Won't hurt anything. I'll give it a try when it stops raining outside... If you really want to make people safe drivers again then simply remove all the safety features from cars. No more seat belts, ABS brakes, traction control, air bags or stability control. No more anything. You'll see how quickly people will slow down and once again learn to drive like "normal" humans. Link to comment Share on other sites More sharing options...
adallak Posted March 12, 2006 Report Share Posted March 12, 2006 You could vacuum it out as you are cleaning the carbon if you are so enclined or really worried about it but it will just be injested, burned and go out the exhaust. Won't hurt anything. I'll give it a try when it stops raining outside... I would be sure 100% that the EGR system is not the culprit only when all related components such as vacuum tubes, EGR solenoid and EGR valve are replaced. Cleaning the EGR tubes might be not enough. The saddest thing in life is wasted talent Link to comment Share on other sites More sharing options...
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