Rob delta

1983 Delta 88 307
Hello All,
I'm in need of some advice. I seem to be getting a slight pinging at part throttle. I've only really noticed it for maybe a month. It's very subtle and not really noticable unless I'm listening for it. But it's there and I know it wasn't in the past. Anyway, I rechecked the timing, it's still at 20 degrees since I set it a year ago. The EGR valve is about a year old or so. I check it by pushing up underneath to open the valve, the idle slowed down as it should. Then i revved the engine a few times and could feel the valve open and close as i did so. So I think the valve is fine but I've heard there could be carbon build up blocking the passages in the intake and that it could cause pinging also. Is there anything else I should check before removing the carburetor and trying to clean out the carbon build-up? I don't have any error codes but could a sensor still be malfuntioning? Any advice is appreciated.

Thanks,
-Rob

Rickman48

20 degrees initial is a bit much! Where'd ya get that number?
If mid-range or premium makes it go-away, try turning it back 4 degrees.
Also try a different brand of gas, as it might be like Budweiser - watered down!

Rob delta

20 degrees is what the emission label calls for. It's computer controlled so i'm sure that has to do with having such advanced initial timing.
My concern is it was fine and I've noticed this now in the last month or so. It didn't do it before that with regular gas so i'm not sure thats the problem either. Any other thoughts on what it could be?

Allan R

My money's on the gas. I had that problem with my 83 Ninety Eight Regency Brougham. That heart pounding pavement ripping 307....ah it brings back memories. Anyway I found when I was using a lower grade gas (usually around town because it was a little hard on gas) and had to then use it on highway? Quick acceleration would definitely hear the pinging. So I switched to a different brand of gas with mid grade octane and the problem went away. No change needed to any timing.

pogo69

does that engine have a knock sensor?

Allan R

I didn't think 83's came with that but I just looked it up and some of them did. Mine didn't. The OP says it's computer controlled so likely he does have one. Wouldn't the KS also show up as sluggish acceleration and rough performance starting at WOT?

Might also be a good idea to check the KS wire to make sure it's making good contact.

pavemobile

I have an 86 that is currently a garage queen while I resurrect a 350 and take care of some much needed TLC. 307's are notorious for EGR sensitivity, check the EGR tubes under the primary throttle bores carefully. They look open but down low they are either fully or near fully plugged with some of the hardest carbon you'll ever see. I had my intake manifold cleaned at a local machine shop and he alum. oxide blasted the EGR tubes out. When I got everything home I cutoff the tubes flush with the nut on top & deburred just to free up some airflow. Worked like a champ, the ECM is programmed for that EGR flow and after the manifold and tubes get plugged the motor gives you feedback like pinging. It is a major pain pulling the intake with all that vacuum & smog stuff but you'll be glad you did. Really the only way to get all the passages clean.

Rob delta

Thanks for the responses. It doesn't have a knock sensor, so there's nothing to retard the timing if pinging occurs. The pinging is light is so a higher grade gas might stop it. However, I have a feeling those EGR passages are clogged to some extent. After 30 years it must have some build-up.

Any suggestions on trying to clean it by just removing the carb and the egr valve itself? Not sure exactly what I'm looking for as far as where this carbon build up would be. what do I use to clean the bores on the intake under carb? Also, I've read something else about using a stiff wire to push through and open passages under the valve. If anyone has experience with this and can explain it in more detail I would appreciate it.
Again, thanks for the help.

DoubleV

When you take the carb off, you will see 2 tubes sticking out of the floor of the intake. You can't miss them. Just remove them with a deepwell socket ( they are 2 different sizes btw ). Those tubes probably have carbon buildup. No need to clean them or cut them down though. Just toss em. If the problem persists, you may have carbon buildup in the intake passage that goes from the EGR to under where those tubes were. In that case, you may be able to remove the EGR valve and chisel out some of the carbon with a long piece of stiff wire.

What temp does your engine run at? If it's running a bit hot, that could be contributing to the problem too.

Rob delta

I have a 180 degree thermostat in there and I don't believe it's running hotter than usual. It's been in there for a while and has been fine so far. No temp gauge so I don't know exact temp.
As far as the egr tubes, I've read different things. Some say no need for those tubes so just remove them and put carb back. Others say they're needed for even flow of gases so clean them and put them back in.
I think if I go as far as removing the carb I might as well push a wire through the passage and try to clean that out while i'm at it too.

Rob delta

So I removed the carb today revealing the egr tubes. The tubes were not too bad, just slight carbon build-up towards the bottom. That cleaned up quickly. Then I removed the EGR valve and pushed a stiff wire through the passage. Without actually seeing in there I figured pushing the wire in and out I would have a better chance of loosening carbon along the walls of the passage. Every few passes I blew air through and was suprised at how much dust and actual small chunks of carbon came out. I repeated this until no more dust came out. Then I reinstalled the egr valve and the carb with a new fuel filter. After the engine was started and warmed up, I pushed up on the egr valve to open it. This time the engine stumbled and stalled out. It previously only slowed the idle. So I think I must have more exhaust flow through the passages after cleaning whatever amount of carbon I was able to get out. I'll go for a drive tomorrow and I'm hopeful this helps out.

pogo69

Nice fix, good luck