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1986 Olds 307 EGR

Started by Scot Minesinger, June 02, 2016, 09:06:31 AM

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Scot Minesinger

Working on the 307 V-8 engine Olds made and GM installed in Cadillac and other cars.  It is carbureted and uses an EGR valve.  The EGR valve completely failed, vacuum actuator ruptured.  Car ran smooth but way too hot and had no power after well warmed up.  Guessing the exhaust gas is being re-introduced into intake when it should not (or in greater quantity) and with less gas to burn and more heat, this is the problem.

I'm going to replace the EGR, they have high quality a/c Delco units available still - great. 

Is there anything else I need to be aware of? 

The heat riser on exhaust is operational, but vacuum line is disconnected, so presuming no vacuum is open position.  Snorkel damper too is disconnected so it stays in already warmed up position.  I'm Ok with the already warmed up positions of exhaust and air intake valves/dampers. 

The car is in very good repair and has 81k miles (OK it is a 1985 Buick Riviera, but figured you could help me) and I went thru every vacuum hose, found just one bad vacuum hose and replaced it.  The car originally came to me for a compressor replacement, dash controller switch of heat and cool cable work, and tires.  The car ran well a few weeks ago, and I guess the EGR just failed recently.

Last time I worked on one of these engines was in my 20's.  I do have the shop manuals, looking for experience here.  It may well be a replacement of just EGR valve and I'm good, just making sure.
Fairfax Station, VA  22039 (Washington DC Sub)
1970 Cadillac DeVille Convertible
1970 Cadillac Sedan DeVille
1970 four door Convertible w/Cadillac Warranty

TJ Hopland

EGR takes vacuum to open so in theory just like the other stuff you mention broken or unhooked puts it in the normal operation mode.  Engines that came with egr tended to be tuned on the lean side to start with and not having a working egr tends to make them go even more lean.   Lean tends to make more heat.   If all that other stuff is working I would hook it back up.   You are dealing with a computer controlled system and the computer is expecting that stuff to be working.   If its not working you may be forcing the computer to try and make other adjustments to compensate and it could be getting confused in the process. 

Has this got an electric or air heated choke?   A lot of the 307's had air chokes which don't tend to work well with age which usually leaves the choke at least partially on which makes em run rich which then plugs up the cat which then makes em run really hot and kinda flat on power.   Plugged cat could happen for other reasons so that is worth exploring that possibility even if the choke seems to be working at the moment. 
StPaul/Mpls, MN USA

73 Eldo convert w/FiTech EFI
80 Eldo Diesel
90 CDV
And other assorted stuff I keep buying for some reason

Scot Minesinger

The EGR is hooked up and was operating as factory designed.  The EGR failed (diaphragm) and would not hold vacuum, so it was also a vacuum leak.  Plan to replace EGR and have it operating as factory intended.

Will check choke to be sure it is operational, just flashing back in memory, I think it was - will check.

Just to restate:

1.  EGR valve factory operation once replaced
2.  Will check choke for proper operation - thanks TJ Hopland.
3.  This is a summer car and going to leave snorkel damper and exhaust heat riser open to already warmed up position.

BTW this car starts super nice (when cold) and idles extremely smoothly (at all times) even with and without functioning EGR.

Anything else need to watch for?
Fairfax Station, VA  22039 (Washington DC Sub)
1970 Cadillac DeVille Convertible
1970 Cadillac Sedan DeVille
1970 four door Convertible w/Cadillac Warranty

TJ Hopland

Non working chokes and plugged cats were about 90% of the issues I ever saw on 307's.    All the other issues common to the era would cause hard starting or poor idle/running which apparently are not an issue with this one so no reason to go there.

The plugged cat will result in no power at all but perfectly smooth running.  The first time I ran into that I was working in the dark at night,  came back from a test drive and dropped the shop light which broke the bulb.   I could then see the orange glow from under the car without even bending down to look close.   Popped the hood and both manifolds were also glowing.

If you are going to leave the other stuff disconnected just make sure the vac lines are all capped so you don't get leaks.   Leave the solenoids plugged in, computer may get angry if it can't at least talk to them. 

The electric vs air chokes went back and fourth on the Olds for some reason.   I think 85 or 86 was when they went back to the air chokes which I never understood.   Everything else was electric and computer controlled so why did they go back to the 60's with the choke technology?    Was good for me when I was into the full size wagons tho,  bought 3 of them over the years real cheap that had 'bad' engines.    A cat, choke, and usually spark plugs and they ran great.   If someone ran em a log time that way they did tend to consume oil presumably because they ran hot and glazed the cylinders and lost some tension in the rings.         
StPaul/Mpls, MN USA

73 Eldo convert w/FiTech EFI
80 Eldo Diesel
90 CDV
And other assorted stuff I keep buying for some reason