I'm not sure if Pinging is the right word.... My 1990 Deville 4.5L with 180K miles on it has had noisy valves for the last 10 years. Usually only happens in the summer when it's hot. Recently, they have starting making noise much more often. I run 93 Octane fuel all of the time. I found this topic which might be relevant, but I'm not sure and would appreciate if someone can confirm that I should adjust the timing? (http://www.cadillacforums.com/forums...ad.php?t=32981)
Here are the symptoms:
1) Driving at highway speeds or almost any constant speed - quiet operation
2) Medium to Hard Acceleration - quiet
3) Slight changes in acceleration - clattering valves - increase the acceleration and it goes away.
Car runs great, starts easy, no missing. Wires, cap & rotor about 4 years old. No timing adjustment since then either. Spark plugs about 1 year old. Gas mileage has steadily declined from 20 mpg to about 15 mpg over the last 10 years. Injectors all sound strong and healthy, but have not been flushed or replaced. Throttle body clean. TPS new. Timing chain - original.
I would suspect that you are hearing spark knock or detonation from what you say.
From your description it sounds like it may be caused by poor EGR flow.
For starters....hold the throttle blades wide open and look down the bores with a strong light. See the two tubes sticking up at you from the floor of the intake manifold..??? Those are the EGR delivery tubes and they are NOT supposed to be full of carbon and crud. Rod them out all the way thru to the passage below with a piece of stiff wire to remove the deposits. If the tubes are clogged the EGR flow will be reduced/shutoff and detonation will result. When you go deeper into the throttle as you describe the noise stops because the EGR is turned off at heavy throttle anyway. At part throttle and moderate accels the EGR is on and lots of spark advance is added by the PCM to compensate for all the EGR flow for good fuel economy. IF the EGR flow is deficient because of the clogged tubes the extra spark causes detonation.
Thanks. I cleaned out the rods last time I pulled the throttle body, but I probably didn't do a good enough job as I was worried about the deposits falling inside of the engine. It sounds like this is not a concern. I'll shine them up!!!
Every 6 months or so, the car will throw an EGR code, but resetting it makes it go away and stay away. I've pulled the EGR and inspected it, replaced the gasket, however, the EGR hasn't ever been replaced. Shall I just replace it as well?
Thanks for the quick reply. I'll do my homework and post a followup to the group when done.
Sounds like the EGR tubes are plugged. Clean them out all the way thru. If there are a lot of deposits then use a shop vac and tape a piece of small tubing to the nozzle to suck the debris thru the tubes as much as possible. It won't hurt anything , though. I would make sure that the EGR tubes are cleaned out completely before changing the EGR.
If the tubes are clean and the spark knock is still evident then make sure that there is vaccum to the EGR solenoid. It should have vacuum constantly supplied when the engine is running. Possibly a vacuum line is off or the EGR solenoid is failed.
Put a vaccumm gauge in the hose between the EGR solenoid and the EGR valve. Do a gently brake torque against the torque converter in drive and watch the vacuum to the valve. It should pop up as soon as you open the throttle and stay on while crowding/loading the engine in DRIVE...not neutral. If not, then possibly the vaccum supply is missing to the solenoid or the solenoid is failed.
Run the vaccuum line directly to the EGR valve bypassing the solenoid. It will idle poorly and drive like crap but nurse it up to speed and see if the noise you were hearing is gone at normal speeds and light load/light acceleration where the EGR solenoid would be turned on full time and the EGR should be supplied with vacuum. If so, then likely the EGR solenoid is not operating and needs to be replaced. If the problem dissappears at the complaint condition with known vaccuum to the valve then the vaccuum supply mechanism....i.e...the EGR solenoid...is failed.
Here's a quick update. After reading your first post, I ran outside and gave it a try. It was just before midnight, so I couldn't see the best. There are two tubes under the throttle plate: a large one and a smaller one. The large one had no obstructions. I couldn't see down the little one, but rodded it out. I drove it to and from work and it was doing much better. If I pegged yesterday's behavior as 100%, I would then call the current behavior as 10%. About a 90% reduction in the clattering. I can still get it to clatter, but I have to barely accelerate.
I'll work to clean it out better during the day. I can check the vacuum as well. I replaced all of the rubber vacuum hoses recently, so I'm probably not leaking. I'll check the solenoid as well.
How bad is detonation on the engine? Mine has been doing this every summer on really hot days. When I hear the detonation, I attempt to vary the acceleration to make it go away.
Wow! Thanks for the advice. You nailed it immediately!!!
Get some carb cleaner and spray into the tubes to soften up the carbon and clean both of them out thoroughly to make sure the EGR system can flow.
While you are in there, clean the throttle body bores and backside of the throttle plates with the carb cleaner and an old toothbrush. Get rid of all the deposits. Disconnect the negative battery cable connection for 60 seconds when you clean the throttle body to reset the idle speed learned values.
The spark knock you have been hearing is no going to hurt anything...don't worry about it at all.
Here is an easy way to check the EGR vacuum solemoid. First pull out the feeding vacuum tube from the EGR solenoid. You should hear a hiss and feel vacuum with a wet fingertip while idling. This is OK - means you get vacuum from the throttle body. Connect the vacuum hose to the EGR solenoid and check for vacuum at ouyput of the solenoid. Should be none. Now unplug the solenoid.
When unplugged it should open completely and you should feel some vacuum (aproximately half or the third of what you got from the throttle body). If you get much less than that your solenoid is leaking vacuum and cannot drive the EGR valve properly if at all.
Enter diagnostics with the engine idling.ECM output E004. ECM will cycle the voltage on the EGR solenoid and yo shoul feel vacuum at the output of the solenoid cycling. These are simple test you can perform without having someone else power braking the car. Looks like rather the EGR solenoid is the weak link in 4.* engines than the EGR valve. And the tubes inside the TB fail first of course.
Thanks Adalla. I've cleaned thoroughly the carbon EGR tubes and throttle body, however, I'm still having a problem. After some more driving, I'm less optimistic that I've nailed the entire problem. I'd say I'm about 50% there.
I did your checks and found great input suction, but I'd say very little to the EGR valve, about 1/3 of input. Is this really enough to move a crusty old EGR? I pulled the power to the solenoid and got vacuum, but the idle changed very little. I thought with the EGR open, it would idle very rough. So, then I put the vacuum directly to the EGR and no change in idle. Seems like good solenoid and bad EGR valve?
However, back to my original problem. Driving 45 mph with foot off of accelerator: quiet. Slight acceleration to maintain 45: clattering. Medium acceleration to reach 50 mph: quiet. Would the EGR make a difference here?
When you cleaned the EGR tubes you went all the way down thru them to the passage below?? The carbon that you clean out just blows thru the engine the next time the EGR flows and doesn't hurt anything at all.
Reach under the EGR valve hat with your fingertips and feel the vaccum diaphragm. Pull up on it with your finger tips gently to manually open the valve. Do this with the engine idling. The EGR flow manaully induced should cause the engine to run rough and/or stall. That will indicate that at least the EGR system is capable of flowing.
If the valve is getting vacuum from the solenoid when you open the throttle it should function.
You can check this by feeling the vaccum diaphragm of the EGR valve with your fingertips while a helper does a LIGHT crowd of the throttle with the car in drive. Hold the brakes firmly and gently open the throttle to load the engine against the trans. This will actuate the EGR as the engine has to be warm, off idle and in drive for the EGR to function. If you reach under the valve and feel the vacuum diaphragm with your fingertips you can feel it quiver and start to open if it is working correctly. If the valve is opening and the EGR tubes are clean then the system is working correctly.
If the EGR checks out and you are running good gas all the time then I would check the distributor reference setting...the timing. It should be 10 degrees BTD when in the fixed timing mode. If it is above, bump it back just enough to stop the spark knock. It should be nice and quiet at 10 but you can pick up a little power by running it above 10 so 11 or 12 degrees is fine is it is quiet. You'll just have to adjust and drive it and see.
Thanks bbob. I think I did a good job of cleaning out the tube. I confirmed that there is flow by pushing up on the EGR diaphram. The engine started running rough as expected. I noticed that the diaphram was quite a bit hard to push up, which matches with full vacuum not being able to open it as well. It seemed to travel ok and return to the closed position.
Next, I did the in-drive and engine crowd test and it did not move at all. I pushed it open while the accelerator was open and it did not change the sound/feel of the engine. Appeared to be OK with EGR open.
The last person to time the engine was a mechanic, but that was about 4 years ago, so I don't know what it's set at. I'll have to get a light to check it.
I guess if the EGR was to fail, the closed position is the best way to go. :-) I guess I've got a mpg increase on the way with a new EGR valve.
hmmm.....those EGR valves are as close to bulletproof as anything around and they seldom really fail. When they do they usually fail such that they open fully all the time causing driveability problems not the problem you describe. Not that it can't happen, understand, but that is not what I would expect.
Try bypassing the EGR solenoid with the vaccum line. Take the vaccum line that goes to the EGR solenoid off....it should have pretty strong vacuum all the time the engine is running....and put it directly onto the EGR valve. Drive the car for awhile like that. If the detonation stops then I would suspect that the EGR solenoid is failed, not the valve. The car will probably idle poor and not drive away off idle very well with the EGR plumbed directly to vacuum but don't pay any attention to that for the moment. That would indicate that the valve is working OK which is a good thing in any case. Pay more attention to the spark knock under the conditions that you noticed it before and if it is OK then replace the EGR solenoid instead.
I can try that, however, I did already try bypassing the solenoid and going directly to the EGR valve. It did not make the car idle rough, that's why I'm thinking that the valve is bad. However, here's what I didn't think of. Does the car pull more vacuum when the throttle is open? If so, I failed to test to see if the EGR opened with direct vacuum and throttle. I'll try that tomorrow and/or the solenoid bypass while driving.
Well, I did the bypass thing, however, I'm not pulling the EGR open. At idle, the car ran no differently. I drove it at least 30 minutes this morning, so it did get a chance to warm up.
I don't think I have a vacuum leak, but won't swear to it (I do have all new vacuum tubing - preventative maintenance last year). Pulling the vacuum on and off of the EGR, I noticed a change in idle speed when the system was disconnected (leaking) and the vacuum seems strong.
I have got results which are very close to yours. Replaced the solenoid - same thing , so the solenoid seems to be ok. I have just removed the EGR valve (it is not that easy) to inspect clean etc. I'll post the results in a couple of hours.