Olds 307 dieseling when under load

[88olds32]

The car drives ok usually. It has new plugs, wires, fuel filter, EGR valve, and an air filter. It also has a new catalytic converter and radiator. It isn't a daily driver. Oil changes are done regularly.

I've noticed that sometimes, whenever I floor it, I can hear a dieseling sound from the engine area, and the car will not accelerate, but rather seems to want to shut off. When I hear it dieseling, I let off the gas pedal, and then slowly accelerate to gain speed. It doesn't happen regularly. It tends to happen more when I am accending. Any thoughts?

I don't know what the timing is set at, but it seems to idle well, and it passed smog a few months ago.

 

[GP403]

Do you mean "pinging" "Dieseling" is usually when the car runs on after you shut it off. I'd try running higher octane gas for a tank to see if it goes away, if it does then advance the timing slightly. You don't say if its a later electronic advance car or not...

 

[88olds32]

It may be pinging, but it really sounds like dieseling. In any case, I'll try the high octane gas to see if it makes a difference.

I don't know if it's a late advance car or not. It's a 1988 if that means anything.

 

[GP403]

I said advance, but I meant turn it back the other way just a bit. If its a stock '88 then I don't know how much you can actually mess with the timing before the computer starts not liking it. I'm not that knowledgeable about it yet (!) I'd start with the gas and see what happens.

 

[Texas82GP]

Sounds like pinging to me. Might just be carbon build up on the pistons and in the combustion chambers.

 

[88olds32]

Thanks folks. Is there any easy and effective way to reduce the carbon build up?

 

[pontiacgp]

I think it sounds like9t could be bogging and it could be the accelerator pump is weak

 

[PapaTrain]

The car drives ok usually. It has new plugs, wires, fuel filter, EGR valve, and an air filter. It also has a new catalytic converter and radiator. It isn't a daily driver. Oil changes are done regularly.

I've noticed that sometimes, whenever I floor it, I can hear a dieseling sound from the engine area, and the car will not accelerate, but rather seems to want to shut off. When I hear it dieseling, I let off the gas pedal, and then slowly accelerate to gain speed. It doesn't happen regularly. It tends to happen more when I am accending. Any thoughts?

I don't know what the timing is set at, but it seems to idle well, and it passed smog a few months ago.

I just recently bought a 87 supreme, mine acted the same way. Took the carb apart, the two larger barrels were carbon glued shut. Hadn't opened in god knows when. A spring had come a loose and half the damn thing just didn't work. My carb was "wet stacking" so to speak and even backing fuel up into the vacuum lines.

 

[airboatgreg]

Sounds like it is running out of fuel so could be a lot of things. I know you have a new fuel filter but re-check as you may have a bunch of dirt. Also, look carefully at check valve in filter to see if swelled or distorted. Secondary on carb may be sticking as previously mentioned. This is a little far reaching but I ran into a couple of quadrajets where someone was in them and did not adjust the metering rods correctly and one of them would intermittently stick in the jet causing a lean issue that would occur at times. Look at fuel pump pressure and look at fuel pump vent on top of pump. If it is wet with gas the pump is bad or if it looks cleaner then surrounding area it may be that the diaphragm is intermittently leaking. The pinging to me is probably a symptom of running out of gas and not a cause. As to removing carbon the absolute best product I have ever used is an AC Delco aerosol called X66a. You spray in throat of carb at fast idle (2000 RPM or so) After you spray in the whole can shut car off and let sit a couple hours. Start up an go for a drive. I have seen some instances where people used 10w-40 oils and had to use 2 cans.
You have a new EGR valve. Is it OEM? Temporarily disconnect and plug vacuum hose with a golf tee or such and see if problem goes away. I have seen many after market EGR valves allow to much exhaust in. Other then that swing it by and let me drive with you