FredR

If you unplug the sensor the brains will read infinite resistance and it will set fuel for the coldest day setting it was designed to operate in- not good on a warm engine. Thus if it made no difference the ogical inference is that the temp2 is in fact goosed. Much easier to measure the resistance and if possible, check the temperature of the coolant inside the water bridge or siml red the temeprature off the panel gauge to correlate readings.

GregBBRD

These items have fooled me, more than once, in the past. I've gotten a bit smarter, over the years.
As long as there is fuel pressure in the system, you are correct.
However, your comment that there was a smell of fuel in vacuum line, made me post my suggestion. There should not be the smell of fuel on the vacuum side.
In the case of large leaks, once the fuel pressure is gone, the vacuum lines will be sucked dry by the intake vacuum, very quickly.

A quick way to check the dampers and regulators is run the pump, with the vacuum elbows disconnected, and see if there is fuel in any of the dampers or regulator. A small allen wrench makes a terrific dipstick.

Kevin in Atlanta

I recall having a bad damper or 2 on a 91 S4 that filled the MAF elbow with fuel. Pretty scary.

Zachattack8805

Well I really appreciate all the responses. I have lots to try this weekend on the car. I plan on doing a full intake refresh as well as new valve cover gaskets. While I'm in there I am going to clean and or replace any bad electrical connectors as well as check vaccuum for leaks and check fuel pressure. While I'm at it I will check all relays pertaining to fuel and ignition. Might take me awhile but it's a high miles car so probably worth just going through and cleaning things up anyways.​​​

dr bob

Great plan. But... I'd be looking hard at getting the current issue solved BEFORE starting a major intake refurb. Else you risk fighting several issues at once as you come out of that work, and the fixing options go up exponentially with the number of things you touch.

I have a spare LH controller somewhere in a storage bin, but I'm a few hours away on the other side of the mountains from you.

Zachattack8805

I actually live in bend so we are very close!

Zachattack8805

Okay, so far I checked all dampers and the FPR and there are no signs of fuel in the vacuum lines. Also when I pull the fuel pump fuse I can get it to run albeit rough, even with all the vacuum lines off of the dampers and FPR so I think I can rule those out. I also swapped EZK and LH relays with the horn relay and neither made a difference. Unplugging the TEMP II sensor and MAF sensor made no difference. I will test my TEMP II signal to the LH sometime next week when I can get ahold of an ohm meter. I also pulled various spark plugs again and checked for spark. All of them have a fairly bright spark that I can see during daylight, also the car runs with fuel pump fuse removed so I am fairly confident it is not weak or bad spark. Also when i run the car with no fuel pump fuse i get a fair amount of white/grey smoke out of the exhaust. I am assuming that is just burning the excess fuel in the cylinders from previous flooding. If i run the car for awhile with the fuel pump fuse out, then shut the car off and pop the fuse back in when I go to start it it will fire right up and run smoothish for like 5 seconds if I keep the throttle cracked about halfway but then will die out and go back to no start. At this point I am starting to lean towards an LH failure, even though I haven't had injectors clicking issue or no power to fuel pump relay issue like others have reported it seems likely that the LH is just either timing injector pulses wrong or just leaving injectors open for way too long. I still am baffled as to why the car will continue to run for a long period of time with no fuel pump fuse but maybe I am just underestimating how much fuel remains in the lines. I am fairly certain this LH has never been replaced or rebuilt so might be worth just having it rebuilt pre-emptively anyways and if it doesn't solve this issue at least i can scratch LH failure off the list. For those of you who have had yours rebuilt, what was the turn around time and are there multiple options for who I have do it ?

FredR

If you pull the MAF and temp2 connectors off and it makes no difference that suggests to me your MAF and your temp2 are not working if we are talking about a warm motor condition. If the MAF detects something is not right it defaults to limp home mode which is basically a single operating point corresponding to somewhere around mid load and 2k rpms- at that operating point it will sort of work ok but it will be pig rich at idle and will rapidly lean out to the point it will not operate at a little above 2k rpms.

When you try to run the engine with the fuel pump fuse removed have you gone to the back of the car and checked that the pump is indeed not running or are you [quite understandably] inferring such? Gasoline is a liquid, it is therefore non compressible - no pump = no pressure = no power- the engine will die more or less instantly- the pump spinning without power will thus become a brake of sorts and stop rapidly as within a couple of seconds type of thing.

dr bob

Let me know how I can help. Have metric crescent wrench and worksop manuals. Qualifies me as a 928 expert...