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Strange 944 Running/ No Start Issues....

 
Old 02-05-2019, 08:09 PM
  #31  
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I appreciate what you are saying about comprehensive testing and the reasoning behind replacing components but it is still a sign of desperation from not understanding the issue or issues and applying a methodical diagnosis and testing.

If you are half as frustrated as I was with my 944S2 last year when i too was chasing an over-rich mixture that failed emission checks then believe me I do understand. i'm not being critical just pointing out the facts is all.

if you are certain that your fuel pressure is stable and to spec and your leakdown test was ok and your injectors are working as they should then that has eliminated quite a lot of components so you can strike them off your list of possible culprits and concentrate on what remains.
Clearly an over-rich mixture has nothing to do with your ignition system components either.

Concentrate your search on the remaining components that control or effect the control of the fuel supply ie the ECU , DME relay, engine temperature sensor, TPS AFM and AIC valve
I'll re read your old thread see if there are any clues there . In the mean time try not to dismiss others advice and suggestion just because you do not think they are pertinent . you don't know what is causing this issue so try to keep an open mind . Remember,... we cannot see or hear your engine nor can we check anything so we are solely reliant on your description
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Old 02-05-2019, 08:47 PM
  #32  
Jacob AbuKhader
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Originally Posted by peanut View Post
I appreciate what you are saying about comprehensive testing and the reasoning behind replacing components but it is still a sign of desperation from not understanding the issue or issues and applying a methodical diagnosis and testing.

If you are half as frustrated as I was with my 944S2 last year when i too was chasing an over-rich mixture that failed emission checks then believe me I do understand. i'm not being critical just pointing out the facts is all.

if you are certain that your fuel pressure is stable and to spec and your leakdown test was ok and your injectors are working as they should then that has eliminated quite a lot of components so you can strike them off your list of possible culprits and concentrate on what remains.
Clearly an over-rich mixture has nothing to do with your ignition system components either.

Concentrate your search on the remaining components that control or effect the control of the fuel supply ie the ECU , DME relay, engine temperature sensor, TPS AFM and AIC valve
I'll re read your old thread see if there are any clues there . In the mean time try not to dismiss others advice and suggestion just because you do not think they are pertinent . you don't know what is causing this issue so try to keep an open mind . Remember,... we cannot see or hear your engine nor can we check anything so we are solely reliant on your description

Thats fair I cant argue with that. It is insanely frustrating looking at this thing in my driveway and not being able to drive it and enjoy it. I do appreciate the input very much. In the old thread when youíre skimming through be sure to watch some of the videos I posted hopefully they can provide more clues as to what may have been causing those symptoms. Hopefully you can provide more input or point me in a direction I didnít even think to look. Part of the frustration be it on the forums or talking with specialty shops/ dealer techs is I get all these great suggestions like ďhave you tried this or tested thatĒ and my answer is now ďtried that, tested that, and replaced thatĒ and then I get ďIíve never had a car do something like that beforeĒ or ďyeah thatís really strangeĒ
I will make a conscious effort to keep more of an open mind.

If it helps Iíll list every component that I can 100% confirm is working.

Fuel pump
fuel pump relay
ignition switch
ignition coil
battery
starter
fuel injectors
fuel pressure regulator
fuel pressure damper
air flow meter
throttle position sensor
coolant temperature sensor
Oxygen Sensor
Spark plugs
plug wires
Cap/rotor
altimeter sensor
alternator
fuel pump check valve

I did have an AOS seal fail that I thought was causing a big vacuum leak but after replacing that I still saw no change in how he car ran after replacing those seals.

I also smoke tested the intake/ vac hoses to look for leaks and couldnít find any. The only clues I have been relying on are the symptoms I experienced, low mpg gauge indications /fluttering/ and the car only starting without the pump fuse installed. I have a new DME unit ready to install once the new harness comes in. I will plug in both to see if thereís a change between the two. Other than testing the DME next if the issue isnít resolved I have absolutely no idea where to look. Except for that Idle air control valve that you mentioned.

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Old 02-05-2019, 09:01 PM
  #33  
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You haven't tried the other DME yet? I'd say the odds of DME fault are getting much higher...
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Old 02-05-2019, 09:40 PM
  #34  
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Originally Posted by Dan Martinic View Post
You haven't tried the other DME yet? I'd say the odds of DME fault are getting much higher...
Yeah Iíd agree especially after hearing about your fix. The DME was the next thing I was going to test before I got stuck dealing with this wiring harness mess I got myself into. Since I had the intake off and so many people were asking about the speed/ ref sensors I saw just how bad those wires were. So I decided to replace the sensors and of course of one of them broke forcing me to cut the bracket and replace the new one and I tried to repair the harness myself and without the proper insulation and connectors that went south fast, so I went back to the dealer and ordered what Iím hoping was the correct harness. (When I ordered the other harness from them a few weeks ago it ended up being the one for the interior and the upper fuse block instead of the engine bay harness) which is why Iíve been so dormant on here. Still waiting on the harness to come in and I need to readjust that bracket to make 100% sure itís installed correctly. A few weeks ago when I put the intake back together after reinstalling the old harness I tried starting the car and had no tach bounce and no oil pressure reading and no MPG gauge swing which was all caused by me screwing up the harness. Rather than trying short cut some sort of fix with the issues I may have caused I went for the safer option of a brand new harness. So once that comes in and that bracket is correctly adjusted Iíll be able to finally reconnect everything and try jump starting the car. Iím praying to lord all mighty that it starts. Iíll have to wait and go from there.
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Old 02-05-2019, 09:46 PM
  #35  
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BTW my experimemts with those two sensors taught me the gap doesn't have to be soooooo precise; there's quite a margin for error.

Put the new harness in... start it up... and I'm betting you'll be back to square one. Then a DME swap fixes it! Because if it doesn't, oh my
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Old 02-05-2019, 09:50 PM
  #36  
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Originally Posted by Dan Martinic View Post
BTW my experimemts with those two sensors taught me the gap doesn't have to be soooooo precise; there's quite a margin for error.

Put the new harness in... start it up... and I'm betting you'll be back to square one. Then a DME swap fixes it! Because if it doesn't, oh my
Donít even get me started I will actually physically pull chunks of my hair out hahahaha. Porsche can rape my wallet I donít care I will make it their problem lol.
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Old 02-06-2019, 08:13 AM
  #37  
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I read all your previous thread and watched the videos until 1am this morning so I think I now have a better picture of what has been going on ..its quite a saga isn't it.!

When the car first failed I think the likelihood is that it was just the DME relay. it certainly wasn't several components of the ignition and fuel delivery system all failing simultaneously !

DME relays are extremely crude and poor in construction and the contacts oxidize if the car is used infrequently . I had a DME relay fail at 70mph a few years ago when entering a motorway . the car ran over something in the road there was a bump and the engine cut out dead. Luckily I always carry a 3x wire bypass with me and it started right up .

This is why I suggested that you use a 3x wire bypass in place of your DME relay all the time you test and run your engine until the problem is solved.

Using a 3x wire bypass means that you can absolutely dismiss the DME relay or the ECU power supply or the fuel pump as being an issue....... because they are on permanently .!
.
The problem with substituting components in order to fix a problem is it is a very expensive and ineffective method . it doesn't address the cause of the issue and if you don't cure the problem you are left with a huge bill and still none the wiser as to the issue .

I know that you say that all the components in that list have been tested and are ok but if I were to ask you at what temperature your engine temperature sensor switches on and off I bet you wouldn't be able to tell me ? !
Its one of several critical components the ECU uses to manage the engines 14.7:1 stoichiometric fuel and air ratio for efficient fuel combustion and the operation of the IAC for cold starts .All you need to do is to dunk it in a glass with a thermometer and attach a multimeter set to continuity and test it properly. Check the manual to see if it is switching at the right temperature. Many temperature sensors are sold for the wrong climatic conditions for the Country they are sold in . Coolant fan sensors are a typical case in point.
If any of the sensors are sending the ECU a false message the ECU alters the short and long term fuel maps to compensate for a perceived change and you end up with a over-lean or over-rich mixture .

You also had a severe crankcase vacuum and oil leak issue with engine oil entering the inlet and air filter .the oil would have coated your AFM possibly causing the ECU to receive false air flow .and compensating by increasing injector flow. it would be worth substituting a good AFM or restoring the one you have.

lastly I think you need to have your injectors tested for spray pattern and leaking ...its a good investment especially as you seem to be getting a lot of fuel in the crankcase since this problem began

Last edited by peanut; 02-06-2019 at 09:47 AM.
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Old 02-06-2019, 07:49 PM
  #38  
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Originally Posted by peanut View Post
I read all your previous thread and watched the videos until 1am this morning so I think I now have a better picture of what has been going on ..its quite a saga isn't it.!

When the car first failed I think the likelihood is that it was just the DME relay. it certainly wasn't several components of the ignition and fuel delivery system all failing simultaneously !

DME relays are extremely crude and poor in construction and the contacts oxidize if the car is used infrequently . I had a DME relay fail at 70mph a few years ago when entering a motorway . the car ran over something in the road there was a bump and the engine cut out dead. Luckily I always carry a 3x wire bypass with me and it started right up .

This is why I suggested that you use a 3x wire bypass in place of your DME relay all the time you test and run your engine until the problem is solved.

Using a 3x wire bypass means that you can absolutely dismiss the DME relay or the ECU power supply or the fuel pump as being an issue....... because they are on permanently .!
.
The problem with substituting components in order to fix a problem is it is a very expensive and ineffective method . it doesn't address the cause of the issue and if you don't cure the problem you are left with a huge bill and still none the wiser as to the issue .

I know that you say that all the components in that list have been tested and are ok but if I were to ask you at what temperature your engine temperature sensor switches on and off I bet you wouldn't be able to tell me ? !
Its one of several critical components the ECU uses to manage the engines 14.7:1 stoichiometric fuel and air ratio for efficient fuel combustion and the operation of the IAC for cold starts .All you need to do is to dunk it in a glass with a thermometer and attach a multimeter set to continuity and test it properly. Check the manual to see if it is switching at the right temperature. Many temperature sensors are sold for the wrong climatic conditions for the Country they are sold in . Coolant fan sensors are a typical case in point.
If any of the sensors are sending the ECU a false message the ECU alters the short and long term fuel maps to compensate for a perceived change and you end up with a over-lean or over-rich mixture .

You also had a severe crankcase vacuum and oil leak issue with engine oil entering the inlet and air filter .the oil would have coated your AFM possibly causing the ECU to receive false air flow .and compensating by increasing injector flow. it would be worth substituting a good AFM or restoring the one you have.

lastly I think you need to have your injectors tested for spray pattern and leaking ...its a good investment especially as you seem to be getting a lot of fuel in the crankcase since this problem began

Iíll have to pull the new coolant temp sensor and test per your suggestion. Not sure if it matters but before this my car was my daily. No matter what time of year in AZ so ambient temperatures ranging from 38F to 120F on average my cooling fans would come on once my coolant temp reached about 96F and would shut back off at around 83F and cycle regularly at this. After this issue started the fans still cycled correctly if the car was running long enough to come to temp.

In colder temps i would notice idle smoothed out at about 80 degrees so if your asking at what temperature the coolant temp sensor switches off leaning out the mixture then my answer to you would be when the coolant reaches about 80degF

Like I have been saying, I jumpered the pump and tried starting the car and nothing changed, still crank/ no start flooding. When I pull he fuse and the car starts, If I try to replace the fuse while the car was running or jumper the pump it dies immediately. This is when I went back and tested pressure and ultimately why I installed that fp gauge in the car so I can no see what itís at all the time.

I replaced my old AFM with a new tested one already because I was worried the oil had dirtied it up. (I couldnít find anyone willing to swap so I had no choice but to buy one)
still made no change and did not solve my issue.

I already sent my fuel injectors out to be tested, thatís when I was told that one was dumping fuel, one was spraying the correct amount, and two werenít spraying enough. So I replaced all of them with units that were flow tested before even going in the car, still no change. But the spray pattern and flow is perfect on the new injectors.


We could probably go back and forth all day about replacing those things compared to not replacing them but at the end of the day, this car is coming up on 36 years old and I want to continue to drive it without more issues like this coming up so for me personally Iím more in the mindset of, okay I know this can contribute to a failure similar to what Iím seeing, ill replace this now for peace of mind and if it fixes the car great, if not I can check it off the list.


Anyways that aspect of this thread is irrelevant at this point anyways because Iíve already replaced majority of those components and Iím still experiencing the same issues.

The thing thatís really throwing me for a loop are things like in that video where the car runs fine... misfire for 10 seconds, runs fine for another few seconds, then misfire is back.

Or where when the car smokes and runs poorly like in one of those later videos as soon as soon as I kill the fuel pump suddenly all 4 cylinders come back, the smoking ceases, and the car runs normally until it burns up the fuel. Something is just really screwing with my mixture and I donít know what it is because save for the DME itself Iíve replaced everything that corresponds to the mixture. Unless thereís something else that Iím missing.

Last edited by Jacob AbuKhader; 02-06-2019 at 08:14 PM.
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Old 02-06-2019, 08:19 PM
  #39  
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Originally Posted by Jacob AbuKhader View Post



Iíll have to pull the new coolant temp sensor and test per your suggestion. Not sure if it matters but before this my car was my daily. No matter what time of year in AZ so ambient temperatures ranging from 38F to 120F on average my cooling fans would come on once my coolant temp reached about 96F and would shut back off at around 83F and cycle regularly at this. After this issue started the fans still cycled correctly if the car was running long enough to come to temp.

In colder temps i would notice idle smoothed out at about 80 degrees so if your asking at what temperature the coolant temp sensor switches off leaning out the mixture then my answer to you would be when the coolant reaches about 80degF

Like I have been saying, I jumpered the pump and tried starting the car and nothing changed, still crank/ no start flooding. When I pull he fuse and the car starts, If I try to replace the fuse while the car was running or jumper the pump it dies immediately. This is when I went back and tested pressure and ultimately why I installed that fp gauge in the car so I can no see what itís at all the time.

I replaced my old AFM with a new tested one already because I was worried the oil had dirtied it up. (I couldnít find anyone willing to swap so I had no choice but to buy one)
still made no change and did not solve my issue.

I already sent my fuel injectors out to be tested, thatís when I was told that one was dumping fuel, one was spraying the correct amount, and two werenít spraying enough. So I replaced all of them with units that were flow tested before even going in the car, still no change. But the spray pattern and flow is perfect on the new injectors.
this is getting complicated .....
When I refer to the engine temperature sensor I mean the one screwed into the cylinder head not the water coolant temperature sensor which should be in your radiator ok ?

You cannot gauge the temperature when this sensor switches on and off by the coolant temperature gauge or when the fans switch on and off .
This sensor is wired directly to the ECU and is how the ECU knows when to spray extra fuel and air into the engine when its cold or at WOT.

I need to find a electrical schematic for the pre 85 cars as I have only owned post 85 944 and there are alot of differences in how the fuel injection and ignition systems are controlled

Good news about the injectors being tested . Now that they are hopefully not leaking that eliminates another cause possibilty .

Are you certain that the AFM you fitted is an early one and not a post 85 version ? check the part number if you can find it.

You have altered so many settings and changed so many components now that it is almost impossible to know how many issues you have .

If you have access to a spare ECU to substitute it sure could help pinpoint where the problem lies .



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Old 02-06-2019, 08:44 PM
  #40  
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Regarding the AFM it came from a running 84. I matched part numbers PN 0280202028


The reading I got was within spec as expected because itís a brand new sensor.


We are on same page about the coolant temp sensor.



The reason I canít plug in the new DME is because this is the current state of my wiring harness. The wires attached to the crank/ speed sensors were so corroded and frayed I needed to address this. Thereís nothing to plug the sensors into or the DME into. I am still waiting on the new harness.


Just as Dan said, Iíll install the new harness, plug in the DME and see what happens. If the car starts with the old DME then the crank sensors/ wiring to the crank sensors were the issue. If the car doesnít start then that eliminates the the crank sensors and wiring. Because itís brand new.

At that point if the car doesnít start with the old DME I will switch it for the new DME. If the car starts with a new DME then the old DME was the issue the whole time. If the car doesnít start with the new DME that eliminates the DME from being the culprit and itís on to whatever else causes mixture issues.



Last edited by Jacob AbuKhader; 02-06-2019 at 09:01 PM.
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Old 02-06-2019, 09:39 PM
  #41  
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Just two things.
You have said that your injectors were cleaned/flow tested on the test bench, but have you tested with noid lights to see if they are getting a firing signal while installed in the car?
Secondly, I went through all of the frustrations that you are experiencing on my '84 two years ago while bringing it out of seven years storage. I Cleaned/coated the fuel tank replaced fuel pump lines, filters, regulators, both sensors and had the injectors cleaned/tested and the ECU professionally retested. It still wouldn't start and I was to the point of calling a wrecker and selling it for scrap several times. Finally, while trying to crank it one day, I tightened the smaller-gauge wire that takes off of the positive battery terminal and it started up immediately and has run great ever since. It wasn't visibly loose but I guess that it was loose enough that the ECU was getting an intermittent voltage supply. I really don't know why it worked, I only know that it did. I just thought I'd mention this because it is easy to check and might help you.

edit: one more thing, does it have a factory alarm system and did you bypass the alarm module behind the radio per the Clarks Garage instructions?
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Old 02-06-2019, 10:04 PM
  #42  
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I have not tested with a noid light but Iíll make sure to do so once the new harness is in.

What a lucky fix! Glad it wasnít something crazy! Hahaha
Iíll be sure to make sure that battery connection is nice and secure.

Once upon a time this car did have an alarm system that was tied into the old radio but that was long since removed well before I bought the car. I have heard of how those can cause no starts but yeah at least thatís one headache I havenít had to worry about in this car.
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Old 02-06-2019, 10:06 PM
  #43  
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Spring44 that's a great tip! The more of these "not-by-the-book" solutions I read about, the better my chances of keeping it running and away from the junkyard lol
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Old 02-06-2019, 10:09 PM
  #44  
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Originally Posted by Dan Martinic View Post
Spring44 that's a great tip! The more of these "not-by-the-book" solutions I read about, the better my chances of keeping it running and away from the junkyard lol
Amen to that!
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Old 02-07-2019, 01:19 AM
  #45  
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Thanks, guys. I've made my share of trial and error mistakes fixing cars and making "dumb luck" fixes. No reason for everyone to have to repeat them.
I was so happy to see that car finally start that I didn't even care why it started.
I bought the car new and it was my daily driver for 25 years with no trouble. Driving it still puts a big grin on my face and I'm happy that it is running good again.
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