Need help with idle/mixture problem. My fault need help

[phebbler]

My vehicle was running excellent and I had the great idea of trying to add a eaton m90 spuercharger directly over the metering plate in a blow through design. This was very simple and just used the 2nd groove on the A/C pulley and I had a plate machined to screw to the top of the manifold in the existing tapped holes and a 1/2" silicone rubber gasket that sealed on the lip of the metering plate opening.

I first installed air/fuel and boost/vac gauges to document the vehicle before attaching the super charger so I would know what I was comparing to. Everything looked spot on. I allowed the vehicle to completely warm up and the air fuel mixture read spot on with the normal lambda isolation for lean to rich when reving the engine to 2-3K. Well I attached the supercharger and it started right up with no problem. When driving the vehicle around the neighborhood it was very lean. I would drive around the neighborhood and the air fuel guage would consistantly drop until there was only one bar and fading. I never got any boost registered the couple times I got into the throttle (I was only trying to get 4-5psi)and then the mixture would take a little while to get back into the yellow (ideal mixture) so I was driving home to remove the system (it only takes about 10 minutes) and I got into the throttle again to see if i could get any boost to build and the idle would not drop below 3000 rpm. I got into the drive way and put it in park and it would still not drop. I cut the vehicle off and restarted it and again the idle was extremely high about 3000 rpm. I pulled the plug on the idle motor and the rpm dropped and when I plugged it back in it rose immediately again.

After I removed everything I once again started the motor, now even without the super charger the air fuel shows the lean side of the range and just gets worse as it idles until it finally dies. Even when holding the throttle partially open the engine starts but seems to loose more and more power until it dies. The air fuel guage starts at maybe one yellow and two red and then gradually drops until it is completely lean. Once the car was up to temp it is extremely bad and the engine won't run a few seconds before it dies. Could I have damaged the idle motor by possibly pressurizing the manifold to 1 psi? How can I test the idle motor? By thw way I am getting a little blue black smoke right before the vehicle stalls. The air fuel guage reads ultra lean but it smells rich??

By the way the co mixture adjustment hole was only covered with a plastic cap and it was displaced when I pulled into the garage. I knew this was a vacuum leak so I plugged it with a nylon screw but this didn't change anything.

The idle motor is humming...

Any suggestions would be appreciated.


Also Does anyone know of a competent service shop that can work on my delorean near orlando, lakeland or tampa? I would prefer not to drive all the way to Bonita Springs.

[DMCMW Dave]

My vehicle was running excellent

.

More likely you blew a hole in the rubber connector between the metering assembly and the throttle, and now you have a huge unmetered air leak which will cause it to run lean. Or you pushed the brass tube that connects to the idle motor out of the socket. Same result. Or blew out that o-ring. Nothing in that part of the engine is designed for any pressure. Anything you blew open is now an unmetered air leak.

Almost all supercharger/turbo setups on this engine use a pull-through design.

[David T]

There are also vacuum hoses that could have been blown off from any pressure. You need to go over the whole air induction system. A smoke machine would be handy. Adding a supercharger requires you to add fuel to enrichen the mixture. There are ways to do that but by pressurizing the way you did you overrode all of the vacuum control including the vacuum advance and the CPR enrichment. You also lose power brakes. I would also be suspicious that you could have overboosted the engine since you say you are now seeing blue smoke. I don't know how the brake booster would handle 5 lbs of boost! You may have blown the guts out of it! Block the hose off and see what happens. The A/C controls also use vacuum. Putting pressure on that system could not have done it much good either. There is a reason most of the systems that have been tried over the years used the "pull through". It preserves the function of all of the vacuum systems. Pull the spark plugs and see if you are burning oil and do a compression test and a leak-down test. I don't think the problem is the idle motor.
David Teitelbaum

[phebbler]

Thanks for the input. I never got over ~0.5 psi on the boost gauge because I had a boost leak. I will deffinately check all of the vacuum connections. The A/C works fine for as long as the vehicle will idle. It seems to idle longer when the engine is cold than when it warms up. I only saw smoke when the engine was chugging before it died.

Also I am only seeing about 10-12 psi of vacuum (that should be a clue...) when I was seeing 20 before (I recorded a 7 minute video of the car from start through warm up while monitoring both the vacuum/boost gauge and the air fuel gauge). The car, as soon as it starts, shows about 15psi of vacuum but then immediately drops back to about 10.

Also, this may be an important clue, when I use a slot head screw driver and raise up on the metering plate (closing the air gap) the idle seems to smooths out but the rpms also raise.

Can you confirm the vacuum connections on the manifold? I can see two large vacuum connections on the end of each manifold and then a small vacuum connection on the top rear of the left manifold. I have a service manual so it seems like this are the only taps into the manifold aside from the two small plugged ports at the front side of each manifold.

Also of course the rubber connection you mentioned is a big question. if I plug all of the vacuum ports to isolate any leak outside of the manifold will the vehicle still idle correctly? The vacuum to the distributor is shut off by a solenoid valve anyway at idle.

[phebbler]

One other observation from your post about the tube that feeds the idle motor. The pipe that feeds the idle motor from under the fuel districutor is a little loose. I disconnected the hose to the throttle motor to try to check the motor and the tube moved freely. Is there a oring or gasket that seals that pipe?

[TTait]

Can someone post the procedure to check the air/fuel mix with a dwell meter?

[DMCMW Dave]

Can someone post the procedure to check the air/fuel mix with a dwell meter?

DMC Service manual page D:04:15 is a good start.