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79 Eldorado 350 EFI Running Lean at 15 MPG

Started by Jaks79Britz, June 21, 2022, 07:48:05 PM

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Jaks79Britz

Almost there! I know it's been a few months, but I thought it would be good to give an update on my 79 Biarritz lean condition.  I sent by ECU to Bruce Roe to get tested and it turned out it was running good, but about 15% too rich. Having had that tested, I was able to re-focus on items that would cause the high NO levels.  I replaced the CAT, tested and cleaned the EGR valve, and had the smog pump rebuilt.

On the latest smog test, all emission levels came down and all passed except for NO at 15 mph.  As you can see below, at 25 mpg the measurement came in well below AVG and MAX.

Why would levels at 15 mph be so much higher than at 25 mpg?
 
Also, today I found out today that I have an exhaust manifold leak on the passenger side.  Could this be the final piece to fix?  I don't want to mess around with too much and then regress my progress
79 Eldorado Biarritz
79 Coupe Deville

Dave Shepherd

If you mean nox,high cylinder temps cause this, it is the function of a correctly operating  egr system to cool the cylinders. A lean condition,or improper timing are some of the common issues that can cause this, the egr valve may be ok, but if the exhaust passage is restricted  to the egr, that would definitely  cause high nox.

V63

You can remove the EGR and start the car (It's going to be loud) and rev it a bit you should see chunks of carbon blowing  out

Jaks79Britz

It has to be the EGR.  I've checked the vacuum line and have done the EGR test according to service manual. It's the original EGR and appears to be working, but I've ordered a new to see if I get a different result. I'll try idling without the EGR installed to see if that helps too. 

79 Eldorado Biarritz
79 Coupe Deville

bcroe

Make sure the EGR passages in the manifold are clear, most I check are completely plugged. They were mostly created with a long drill, I clear them the same way.  Bruce Roe

Jaks79Britz

Quote from: bcroe on June 22, 2022, 11:53:34 AMMake sure the EGR passages in the manifold are clear, most I check are completely plugged. They were mostly created with a long drill, I clear them the same way.  Bruce Roe

Thanks Bruce.  I cleaned the passages with compressed air, but didn't think to get inside with a long drill.  I'll try that and report back. 
79 Eldorado Biarritz
79 Coupe Deville

bcroe

A couple other things come to mind.  The OEM timing
chain set for these cars fails of old age, even at
lower miles.  Slack the cam can bounce forward and
back, generally emissions go down with retarded spark. 

And then there is the ESS, see if it is working and
giving propoer spark timing. 

If an engine is not stressed much, there is more
tendency for carbon buildup in cylinders.  Sometimes
removed by running some water mist through the engine. 
good luck, Bruce Roe

Jaks79Britz

Thanks Bruce.  I haven't looked at the ESS on this car yet, so I'll read up on that.  As for the timing chain, I can't imagine this has ever been changed before.  I hope I can get passed smog before diving into this work.
79 Eldorado Biarritz
79 Coupe Deville

Jaks79Britz

#8
 Update on the 79 Biarritz. 

I drove the car this past Sunday to downtown LA, a 50-mile round trip.  This is was after I installed a new EGR and cleaning out all the passages into the manifold.  She ran good through out the trip and even climbed some hills to the top of Chavez Ravine where Dodgers Stadium sits.  Everything was going well.  Turned the car off, parked it, came back started right up no problem.  It was only until I exited the highway at the end of my trip just a few blocks from home the car turned off as I came to a stop.  I turned the car turned on after a few tries only just cranking by pressing on the accelerator a little to get her home.  Then next morning, I couldn't get the car started without forcing it on white the accelerator only to turn off when I shifted to reverse.  Even though the fast idle valve had been functioning properly, I checked into it and found that the plunger had broken piece at the bottom I replaced it along with a new heater valve (an NOS I found on eBay), installed it and still having the same issue.  Car turns off when shifting R or D.    I feel like the car took three steps back after that drive.

Here's a list of items that I think I need to look into:

Fast Idle Valve: Even with the new NOS heater installed, I'm not hearing the high idle on a cold start and then hear the idle drop after it warms up like I used to.

ESS:  I haven't looked into this at all, so I'll need to read the service manual to figure out how to test.

Timing Chain:  I had the timing adjusted last month.  If the sprockets are worn, as Bruce mentioned these cars have the tendency of doing, then I think that my timing is getting thrown off.

Has anyone experienced car turning off when going to gear?  Any feedback or suggestions would be appreciated.
79 Eldorado Biarritz
79 Coupe Deville

Dave Shepherd

How did you adjust the timing chain, that's a first for me?

bcroe

Sounds like it was fine until something broke, but what?  Could be timing or mixture, check temp sensors.  More than 2 deg slack in timing is bad.  Sometimes MAP internal connection breaks, you can check that in the car per my PHOTOBUCKET.  Bruce Roe

Jaks79Britz

Quote from: Dave Shepherd on July 01, 2022, 08:51:08 AMHow did you adjust the timing chain, that's a first for me?

After reading again sounds like I'm saying the timing chain was adjusted.   I meant that the timing was adjusted and that the timing chain could have slack and needs to be replaced.
79 Eldorado Biarritz
79 Coupe Deville