I have had a horrible pinging problem in my 90 f-250 2wd 460cdi for several years that I was able to remedy temporarily by retarding the timing from 10 to about 7 or 8 degrees. I won't pass the inspection portion of the smog test in Ca. so I have had set it to as close to 10 as possible, filled a tank with super and limp it to the inspection station, obtain a smog cert then promptly return the timing to a setting where it would run without the pistons jumping out of the block. I finally got fed up with this arrangement and invested in a code reader so I can hunt the culprit down. The manual that came with the reader states that the code I was getting during the KOEO test, 33, indicates that my EGR valve is not closing properly. Could this explain my severe pinging issue and if so, how do I find/inspect/test/clean the unit? There is a unit mounted on the intake riser near the back of the engine compartment that has a large tube with some sort or corrugated shielding or something that disappears to the backside of the engine, is that the EGR? Any help on how to test and clean would be greatly appreciated.

 

At bare minimum, it could explain part of the pinging. The EGR closes at idle and WOT, and remains closed until the engine is warm enough to switch to closed loop control. Only then does it start modulating exhaust back into the intake to displace some of the air coming through the throttle body. This is to reduce fuel consumption/emissions, and helps the engine run a little cooler too by reducing the amount of fuel/air being used in the cylinders.

A quick test, is to block off the EGR somehow. I know nothing about the 460's emissions, but normally the valve is on the intake somewhere. Block it, and see if the pinging goes away. More than likely, it is stuck open. You should be having some rough idle issues.

If the pinging is your primary concern, check very carefully for vacuum leaks as well. Lean mix, pinging engine. That's a guarantee.

 

My scanner manual shows 33 as EGR not closing properly OR not opening.

If it's not opening, thats your pinging problem.

 

Thanks Old Paint and 87 XLT for the replies. I was fairly confident that an EGR servicing would resolve my pinging problem so I dove into it last night. After figuring out what had to be removed inorder to get access to the EGR valve, I finally was able to reach the valve, which unfortunatly is located at the back of the engine right next to the fire wall. The 1 1/16 nut that attaches the exhaust gas supply to the valve will not budge. I struggled with it several hours last night using adjustable wrenches then broke down this morning and went to Sears and bought a set of large combination wrenches that happened to be on sale and struggled with it some more. I finally had the throw in the towel and just put the whole thing back together being unable to break that nut loose. I slid under the truck to see where the other side of the tube is connected to see if I could disconnect it from that end. The bottom side which connects to the exhaust manifold is even worse to get to. So I am back to square one but at least a have a new set of wrenches to look at. If anyone has any ideas how to break that nut loose I would be interested in hearing them.

 

I dont have any sort of a manual for a 90 F-250, but there should be an EGR vacuum control solenoid that opens up at approx 2,000 RPM's and allows vacuum to go to the EGR diaphragm & pull the EGR open.

Have you checked for vacuum at the EGR?

What would REALLY be handy for this is if you had the Ford emmisions troubleshooting manual. It will have the pin point tests to perform for your code 33 and for any other codes you might get in the future.

 

go to fordfuelinjection.com and you cane get detailed info on egr's

 

pb blaster got mine loose day or two soaking came right off

 

Yea, ALBUNG, thanks for the reply. I'm not sure what PB blaster is but I'll assume it is similar to WD40. I think a little soaking, and in my case, a lot more leverage, did the trick. The Engineers mounted that in a not to easy to get a big wrench on that 1-1/16 nut place. I literally had to tie a three foot piece of white oak lumber with bailing wire to the wrench but I busted it loose. Unfortunately I found no problem with the EGR valve. Yea it was dirty, but it worked fine. I picked up a hand held vacuum pump from Harbor Freight and put the valve through its paces. It opened completely, closed completely, did not leak when closed, and the position sensor read a smooth readout when hooked to an ohm meter. I was comfortable with it so I slapped a new gasket on it and reinstalled it. I thought maybe a leaky EGR vacuum solenoid might be the source of my code 33 and severe pinging so once the engine warmed up enough to start the pinging I pulled the vacuum line off the EGR valve. Removing the vacuum line did not halt the pinging so I do not believe EGR issues are the source.

Does anyone know if a bad O2 sensor could cause severe pinging? The truck has about 140K on it and I have never replaced the O2 sensor. I pulled it out this weekend just to get the numbers off it to see how much a replacement costs. I know there is a test procedure using a propane torch but I was not in the mood to mess with it so I put it back in. Many auto part sites recommend replacing it every 60K.

 

Code 33 in my actron manual shows EGR not fully closing OR not opening.

If your sure it's getting vacuum & that it IS opening as it should, you might want to take a look at this link.

http://draco.acs.uci.edu/explorer/ping.html

I kinda like the post from bob m about feeding the engine a glass of water.

Yours probably has a MAP not a MAF, so disregard the cleaning the MAF stuff.

Edit
BTW, the only reason that I swapped out the factory O-2 on my 87 2.9 was because it had 180K miles on it.

It was running fine on the old O-2 & changing it made no difference.

 

If you are sure that you checked out the valve and EVP completely, which it sounds like you did, then the EGR solenoid is most likely at fault. The EGR doesn't get full engine vacuum, it gets it from a solenoid. If the solenoid isn't giving the EGR valve the correct vacuum, it won't work right. The solenoid is on the other end of the vacuum line to the EGR.

Although this implies that this will fix the code but not the pinging.

I'd be interested to see if once the code clears the pinging problem will go away.

 

The article has some good information from people with problems who fixed them. I had the upper and lower intake flush done with a chemical designed for this which also burned a lot of the carbon off the top of the pistons . There was a definate improvement in performance. Sound like the water trick is another approach.

 

Yeah, the water trick is kinda slick. It turns to steam in the hot combustion chamber & does a great job of removing the carbon build up.

 

OK, maybe someone can clarify something for me. I am of the understanding that the EGR valve is just an emission device that expedites the engine reaching full operating temperature and thereby minimizing the time the engine has to operate in a rich condition. Once the engine is warm, an EGR valve that fails to open should cause no major anomalies. As the way I see it, the only harm that can come from a EGR not functioning properly is when the valve will not close and thereby causing hot exhaust gases to enter the intake system when they are not wanted and lean out the intake charge. How would a EGR that fails to open cause pining. Am I confused?



Once again, thanks to all those who reply!

 

The EGR is primarily used to reduce NOx emissions, which are caused by high combustion temperatures. The exhaust gas is inert (won't burn) and are just along for the ride, so to speak, which reduces the amount of oxygen available for combustion, thus lowering the combustion temperatures and NOx emissions, but decreasing performance. This is why the EGR valve isn't opened at idle or wide open throttle situations. Since the computer only knows valve position, not actual recirculation rate, if the computer reads the valve to be open, it thinks the exhaust gases are present, and will lean the fuel trim accordingly. The combination of hotter combustion and the computer leaning the mixture slightly causes the pinging.

I had a code 33 for a while, along with some severe pinging. The valve is stuck shut -- it won't open even with straight manifold vacuum. I've unplugged the EGR position sensor, which triggered the check engine light, but it has greatly improved driveability, power, and fuel economy. I suppose I should replace the EGR valve and position sensor, but I can't afford to spend the ~$150 to replace it all.

Try unplugging the position sensor and see if it makes any difference, then take the proper steps to fix the problem and get the system working normally again.

 

Since EGR cools the flame front during normal operation, NO EGR usually results in Pinging. Make sure that the EGR passages are clear of carbon buildup. If the EGR works properly, but the passages are plugged, the ECM will lean the mixture on the assumption of normal EGR flow, hence pinging! Plugged passages are the result of the engine never reaching normal operating temperature due to short trips in cold weather or a stuck or wrong range thermostat.