Aloha,
Still going through this 411 and working the bugs out. Here's on I could use some feedback on. When I starts it up, it idles fine, stalls sometimes when in drive or reverse. When it warms up, the idles surges up and down with rpm a little higher. When I have it in drive idling with the brake on, the rear raises up and down with each surge and the brakes need to be on hard or else it creeps with each surge. All vaccuum lines seem tight. I did the unlit propane torch to find vaccum leaks and couldn't find any. It does have the original FI, automatic. Any ideas? Thanks
A couple of things to start with. What this is generally signaling if nothing else is wrong.......is one of two things: (1)is that your mixture is way too rich. As you start up, the auxiliary air regulator is open giving extra air and the CHT is cold giving maximum fuel. As the auxiliary air regulator closes, if either MPS settings or the CHT settings or the fuel pressure are too high....it causes there to not be enough air when the AAR is closed. With excessive fuel in the mixture sometimes you can get surging.
(2) Once everything is really warmed up...ie...the CHT has gone down to 100 ohms or less...you could be too lean. It can cause teh same issues searching for air.
Usually though when tehengine is hunting or surging like that...you have a vacuum leak. Does teh MPS hold vacuum? You can use a hand pump or suck on the fitting on the end and put your toungue over it. It must not leak vacuum at all.
Next...check that g9old colored vacuum dashpot net to the throttle body for leaks. If it leaks...it extends outward pushing the throttle. This part actually is designed to keep you from stalling when you are sitting at a light in gear. When you open the throttle...that plunger should suck back in. When you snap teh throttle closed...it should pump outward to delay the closing of the throttle ....but only for a moment and only once.
Also check teh vacuum line to teh transmission and check that modulator valve for leaks. Ray
Not dumb questions at all! The AAR...means auxiliary air regulator. That is a little round pot shaped thingy near the rearward right end of the center of the intake manifold. It has a hose going to the intake and one to teh rubber boot on the throttle body. It has aelectrically heated coil inside. When you start the car...it is effectively your choke. It is open whne cold. About 8 minutes later as teh coil heats up it closes shutting off the unnecessary air. Warm the car for 10 minutes or so. Then pull the hose from the big rubber boot on the throttle body. If there is any suction on that hose when you put your thumb on it....the valve either is stuck, has no power (check the fuse) or has a bad coil.
The CHT.....is the cylinder head temperature sensor. It is a single wire coming out of the drivers side cylinder head. It must have a PERFECT connection...and read about 2300 ohms cold and can read as low as 70 ohms when fully warmed up.
The MPS....is the heart of this monster. Usually located on teh left hand side of the engine compartment. It is about the size of your fist and looks a little like a fuel pump. It has a single vacuum line and a 4 pin plug. It must be able to hold vacuum indefinately. Ray
Thanks Ray! That cleared a lot of things up. I should be able to zero in on the problem in a day or so. I'll let you know how it progresses.
What does MPS mean? Manifold pressure sensor (Just guessing)?I was wondering what that thing was seeing there wasn't some sort of mass air sensor. Am I assumming the MPS takes the vaccuum signal to tell the ECU what the fuel mixture should be?
Yep ...you are spot on. This is a complex barometric unit that uses manifold pressure to tell the ECU what the load is. Your main fuel mixture adjustment is inside of it...but do not open it until you work a little further...and let us know. Ther are a few things you must know before you remove that plug on the back. Ray
Ok, I just finished fixing my oil leaks, fired it up to see if any drips...nothing! So now I started at the vaccuum modulater on the tranny. I pulled off the hose and some trans oil came out. Should I assume the modulator is toast? What does the modulator do anyway?
Again , I appreciate the help. I'm literally on a island by myself with this one!
Its a good possibility that the modulator is toast but may still not be your vacuum leak. The modulator is very important. It is one of the main pressure adjusters on teh hydraulic oil pressure for your shifting. It varys shift pressure according to vacuum of the engine. Do not throw the old one away yet...just in case. There is an adjustment inside of teh modulator accessable through the vacuum nipple.....with a 4mm allen wrench. Only adjust it when you use the pressure gauges described in the automatic section of teh Brown bentley type 3 manual....which is teh same transmission. Later...you should probably do that. It helps teh shifting a lot. Ray
The update...the modulator was toast. Wouldn't hold a vaccuum and it was full of trans oil. Took one off a junked Type 3 that held vaccuum and it helped some. However, it shifts nows! I dove into the timing and found it was off. It was way retarted. So I got it lined up at 3500 rpm and it's fine. Idles steady with little pressure on the brake at the stop light, it doesn't stall and it has some power again. Finally no more people looking at me like I'm an idiot jacking around with the 411 "Humping" at the stoplight.
