Hi. I have a 1988 pontiac firebird with a 5l v8 305 chevy small block engine. It has 172k miles on it.
Doesn't matter if in idle or in drive there is this weird deep pulsating rumble/vibration throughout the car. Its not violent, but definitely noticable. Interval is about 2 seconds. It kind of comes on slower, gets more intense and fades out. Repeats every 2s or so. I think it gets faster when i accelerate hard.
Not sure if related but i did the paperclip trick and it gave me an error code 32 which would indicate EGR system issue. It also barely got past emissions test earlier this month. They said i need to check it out.
I have noticed it has slightly less power than before. New spark plugs didn't really do anything I guess the old ones weren't bad.
Should i just try replacing the EGR? Could this cause the vibration too or is it engine mounts? Visually I don't see they are bad at all.
How did your old spark plugs look when you changed them? Were any of them carbon or oil fouled? Is compression reasonably even across all cylinders? What is the condition of those decades-old fuel injectors?
OBD1 code 32 is a circuit fault in your EGR system which apparently is electronically controlled and employs a solenoid to operate the valve. It's likely that the solenoid has failed or there is a wiring problem. Check the connector and wiring.
Check your engine mounts more closely. If original it's not likely they're much good after 34 years. Even if they look OK the rubber has probably gotten hard as a rock over time and lost its ability to absorb vibration.
Plugs looked fine, no oil just a little white from heat. I tested each one with multimeter and they are functional I guess previous owner changed them.
Mine has a carburetor which looks clean and nice.
I haven't tested the compression, but I am planning on doing it shortly. Might as well recheck the mounts while I'm down there, thanks.
Carb may well be plugged up internally and needing an overhaul, especially if that has not been done since ethanol-contaminated fuel became mainstream.