can you cause any damage,driving around with a plug egr system.
You could possibly ruin an engine. The EGR controls combustion chamber temperatures and if the engine rattles under a load then it’s possible to burn valves and/or pistons right out of the engine if the problem is bad enough and chronic.
Every situation is different so there is no one answer fits all. Some vehicles and engines motor along just fine with an inoperative EGR system; others don’t.
The EGR valve ONLY functions when the engine is operating at a steady cruising speed. It is normally closed at idle and during acceleration. I have personally disconnected hundreds of them without a single negative outcome. Cars ran without them for 70 years without any problems so I suspect your Datsun P/U will not suffer…If you can not detect any detonation or spark-knock, you are not damaging the engine…You may even see a slight improvement in fuel mileage…
It is VERY rarely that I disagree with ok4450 but on this issue I must offer a different opinion …
I’m in agreement that it’s possible no damage could be done but that also depends on any rattling, how bad that rattling is, and if the driver is prepared to take his foot off the gas when it happens rather than floor it.
There could also be a difference based on the year of the truck. If it’s a distributor equipped model, and especially if the timing has a bit much advance in it, damage could be even more of a possibility.
When my youngest son was off at college he had an EGR failure on his Camaro and had no problems at all until I repaired it during his next trip home.
On the other hand, a super clean, low miles Subaru I bought one time on the cheap had a trashed engine due to pre-ignition. This was a timing advance problem rather than EGR but the symptoms and results are the same. One piston burnt clean out and the other 3 were not far behind. It ran but had the mother of all knocks in it and was even sending chunks of piston into the catalytic converter.
Like Caddyman, this may be one of the only times that I question OK4450’s reply.
I too have disconnected literally hundreds of EGR valves. I worked in a dealership in the 70’s and every time we did a “new car prep”, we disconnected the EGR. Often we’d stuff a ball bearing in the vacuum hose and then slit the hose beyond the ball bearing to relieve any possible vacuum buildup.
This was the “modus operandi” for several years in the dealership. It likely continued after I left there.
I agree with OK that if an engine’s timing is already advanced beyond reasonable limits, a functioning EGR can help suppress detonation and be the key to preventing engine damage.
Do be aware that in the 70’s, EGR was just an added on (and poorly at that) thing to engines that were originally designed without EGR. Engines designed today counted on the EGR system being there. Some won’t work well without it, and other engines couldn’t care less if it is working or not. There’s no universal answer of it’s okay or it’s not okay. You have to go engine by engine.
Good point. Agreed.
When I disabled the EGR on my '81 Accord the MPG’s went down. Later a Weber carb, stage 2 cam, headers etc. changed the game.
When I disabled the EGR on my '88 fuel injected Accord the throttle was a little more responsive and no change in MPG, but the cruise control would hunt up and down.
I agree that more than likely no damage will be done with an inoperative EGR. The OP was asking about the possibility of damage and my opinion is that it’s entirely possible; all depending.
Pre-ignition can be fatal to an engine if it’s bad enough and if the driver does not ease up when it starts happening. Some people turn the radio up to drown out the noise… 
Not only did the Subaru I bought have a trashed engine due to pre-ignition I’ve also seen a few others in the same predicament, including a 30k miles VW Bus that blew up on the highway a few weeks after being serviced at our dealership.
They had it towed to another dealer who stated that it had 30 degrees of static timing on it which led to piston/cylinder disentegration. VW corporate got involved and they tried to hammer the tech at our dealer who serviced this Bus.
Knowing the guy well, I knew he did not screw this up. With some investigation it was discovered that the (at the time) new high tech electronic instrument that VW was having the dealers use was at fault. This unit provided all engine info and was also fitted with a magnetic timing plug. Come to find out the unit was goofy and was allowing too much timing advance while giving an entirely different reading. The VW District Rep, who also blamed the tech, was livid and downright embarassed when he was shown personally the fault was in their test equipment.
Granted, these are timing issues rather than EGR but a functioning EGR could make a difference depending on situation with this particular truck.
Much could depend on whether this EGR fault is a CEL with no obvious symptoms or whether it’s rattling like crazy on acceleration.
With respect, the EGR valve functions only under heavy load, not when idling or cruising under light load. Heavy load conditions are when cylinder temsp rise and spark knock or pinging is most liekly to occur. The EGR systems two functions are to prevent this spark knock by keeping cylinder temps down a bit and to prevent the excess NOx generation that occurs when cylinder temps elevate.
The EGR functions by allowing a bit of inert exhaust gas to join the incoming air stream to displace a bit of the oxygen. Under open throttle conditions a lot of oxygen is allowed in, and it’s like pumping a fireplace with a bellows, the fire intensifies. The EGR valve keeps the fire from roaring too much.