No I am not sure, but it is very possible.

It's very simple to find out. Just pull off the black plastic cover. You'll find blobs of glue and caulk that mark the factory settings. If they've been disturbed, you'll be able to see it. You'll also be able to tweak the mechanism with your finger to see if you're running lean or rich. It's no big deal reattaching the cover. You just need a thin bead of caulk in the groove. You can hold the cover on temporarily with rubber bands or small bungie cords (or maybe tape?) until you're finished diagnosing/fixing/tweaking the system.

My fuel pump always runs with the key in the on position. I know it shouldn't but it does. Also I do have an aftermarket fuel pump. I am still looking for vacuum leaks, perhaps It's time for yogurt (I don't really like yogurt).

Mine did this as well. The oil pump sending unit was the culprit. It was leaking, and when I replaced it, the fuel pump cutoff started working again. Our year 280 has the fuel pump safety cut off activated by lack of oil pressure.

yes it looks tampered with. Sorry about the crappy cell phone photo (my camera is at my girlfriends house). You can see that 2 screws have been glued with gobs of silicone.

Two more updates with my engine warmed up, I am guessing a little over 130 deg my resistance is 1.85 this seems a bit high. time for a new temp sensor?? also I have gotten my vacuum up to 15 in Hg. by replacing one small hose and the biggest difference seemed to come from tightening the valve cover bolts they were all loose, I did not tighten them much just snug. I would never had guessed this but after seeing what effect taking off the oil filler cap I was surprised. I know 15 is still low but it is an improvement. tomorrow may be yogurt for supper. I am thinking of just replaceing all the vacuum lines and perhaps replacing the valve cover gasket.

oops testing wrong connectors between 13 and ground I get .068 engine is probably 120 deg now.

But I did notice all resistance readings and temperatures should measure the same for air and water temp sensors so if they differ from one to the other, one or both may be suspect. I cleaned the contacts and will test again tomorrow.

Edited July 1, 201114 yr by grantf

The resistance should not read the same unless the engine is completely cooled down, like overnight. The air sensor is in the AFM and reads air coming in to the engine. The water sensor is in the thermostat housing and reads how hot the engine is.

It looks like you're making progress though. All of these small things will add up.

That is a crappy photo, but the AFM does look pretty normal. A dab of silicone is put on the screws at the factory. If it's broken it's been tampered with, if not, maybe not.

Have you checked the cold start valve? Besides the six injectors, it is the only other place for fuel to be pumped out of the gas tank. Since it's summer-time, you could just remove the fuel line to the CSV and plug it. Don't just stick a threaded bolt in the hose, there's 40 psi behind it. If it has been leaking, you'll see a change. Or you could pull the valve and see if it leaks.

10 mpg is way low. There's something big going on. Are you sure that your odometer is working?

Maybe you mean .68 kOhms between 13 and ground? A reading of .068 would be quite low and would result in very lean running. You'd best double check that one.

Asolutely change out all the vacuum lines! It's quick and cheap. You'd be surprised how many little splits and breaks the average old car has in its vacuum tubing. I'm guessing you'll find at least 3. And yes, do the valve cover gasket too, if it looks as though it needs it. Be certain everything is tight. (And let's hope you don't have an intake manifold gasket leak like I did.)

The silicone caulk blobs in the AFM might be factory. I'd need a better picture to tell, but they did use silicone glue/caulk. Mine was sort of a translucent milky white -- not as clear as yours.

Now that you've got the cover off, warm up your engine, and then turn the mechanism just a bit while the engine idles. Try to find the highest idle, and read your vacuum there. Then guesstimate how far CW or CCW you've rotated the thing from where it normally wants to rest. That will give us some idea how rich or lean your mix is.

As zed suggested, the glob of silicon could be normal. They did that from the factory. If it's a bunch though it could have been previously broken, then someone adjusted it, then put more silicon back down. You will have to look and use your own judgement to see if it has been tampered with. Was the seal for the black cover broken ?

If you are up to it and want to rule out tampering of the AFM, on Blues website there is a way to "test" or calibrate your AFM. You could follow those directions with the weight, very carefully and see if the AFM is where it should be from the factory. I did this, and his method had my AFM spot on. I am doubting your AFM has been adjusted to the point that you are running that rich though. You are using almost twice as much fuel as you should be.

Zed has a good tip on checking the cold start valve.

And yes, the WTS and the Air sensor should not read the same. The Air temp sensor only changes the fueling at a certain tempature cut off, I cant remember what it is but it's like 62 degrees or something. Above 62, it leans out the mixture slowly. Below 62 it adds a bit of fuel to the curve. Thats it.

Also, if this is a california car, perform the check on the altitude switch.

Here is a helpful page on blues website about vacuum

http://www.atlanticz.ca/zclub/techtips/vacuum/

Nice hot day (around 70 deg here in Seattle). Drove my car home, dash temp gauge is right in the middle, so about 180 deg (if that is accurate at all). measured between 13 and ground and got .045 k, this is with my meter set to the 2k range. double checked it with my other meter (a greenlee) it read 046. air temp measures .99, I understand that they should not be the same I am just testing both.

Also I pulled the cold start injector, plugged to hole and ran the engine for about 1 min no gas came out. For shits and giggles I connected a 9 volt battery to the injector and gas squirted out. I am ruling out the cold start injector. Good to know though.

Edited July 1, 201114 yr by grantf

Grant, your air temp reads a bit warm -- around 120F. Your engine compartment might have been a bit warm. It would be better to take a reading when your engine cools off. Park your car in the shade, so that the air temp sensor would be approx the temp of the outside air. If you get another "hot" day of 70F , then you should get a reading of about 2.25 to 2.75k.

Something is definitely off with your coolant temp sensor reading. At 180F you should get a reading around .29 - .36k. After remeasuring your air temp sensor on a cool engine in the shade, I'd do the same with the CTS. You should get that same 2.25 - 2.75k measurement.

Assuming you're really getting that low a CTS resistance, I'd pull the connector off of the CTS and see if you get the same reading between the two pins. You should get the same resistance. Then with the CTS connector unplugged, re-measure from 13 to ground at the ECU connector. You SHOULD get an infinite resistance, but it's possible you have a short. Anyway if you've got a 13-to-ground resistance of 46 ohms when warm, your engine should be running pretty lean. Either your sensor needs replacing, your wiring needs attention, or both.

Edited July 1, 201114 yr by FastWoman

Here's something from left field - is it possible that someone from the past installed turbo injectors or some other higher flow injector? That would lead to lots of extra gas being squirted, even though everything is right on. I believe that there are ways to tell them apart but I don't know what they are.

And are you sure about the mileage? The inside of your tail pipe should be all black and sooty with that much gas going through there. Mine has a light coating, still running slightly rich, at ~20 mpg.

Here's something from left field - is it possible that someone from the past installed turbo injectors or some other higher flow injector? That would lead to lots of extra gas being squirted, even though everything is right on. I believe that there are ways to tell them apart but I don't know what they are.

And are you sure about the mileage? The inside of your tail pipe should be all black and sooty with that much gas going through there. Mine has a light coating, still running slightly rich, at ~20 mpg.

I really doubt that the injectors have ever been replaced. And my mileage really sucks, how accurate my odometer is? I do not know for certain but I am pretty sure it is close to accurate. I put 5 gall in yesterday and after a little driving around today I am on empty.

about my tail pipe, it is coated in black sh!t. I can even see residue forming on the bumper and rear valance (pics soon). The funny thing is the car runs pretty good, no backfiring steady idle and pretty good power, no knocking. With the windows down I get the common exhaust fumes but they smell of gas.