HELP! Stuck with a No Start w/ Alpha N

[MKovac]

Hey S14!

Need some help from the Alpha N gurus...

I will start from the beginning... I just bought a 1991 M3 that got delivered to me with a no start. It was sitting for over a year so I did the right thing:
-Drain all fuel and refill with 100 octane
-Replace fuel pickup pump (was sitting in old gas and apparently was having issues)
-Replace inline pump (due to age)
-Replace fuel filter
-Install fresh plugs
-Check all rotor and cap points
-Pulled and cleaned all injectors, bench tested with 12v
-Checked for vacuum leaks

Car has fuel, spark and compression. Right now there are some unusual symptoms. The car will crank and eventually start and hold a very rough idle but will eventually die if you give the car any throttle. The weirdest thing is that if you unplug the DME coolant temp sensor (blue) after the car is running it will jump revs up to 2k and then the car behaves normally, takes load and drives around normally with the exception of the high idle. My guess that this is forcing the car into open loop.

So far we have switched DMEs, Alpha N units, compared the Alpha N DME wiring with another car (no issues) and I am left with nothing else. At first we thought that the Alpha N unit was bad - it was sent out to G7 computer for hardware check - no faults. I even went so far as to take the existing Alpha N and pluged it into my other M3, and it behaved fine.

Help! Im stuck and really don't know where to turn!

Thanks for any help in advance.
Michael

[evommm]

Does it have a car alarm installed could be another view happened to me

[Mick]

Probably obvious, but have you replaced the blue temp sensor? Hard to believe that would cause the issue but who knows?

Does the car have an ICV? You could try unplugging it and also switching off idle control in the Maxx software.

[MKovac]

Does it have a car alarm installed could be another view happened to me

Hmmm... no alarm. I would also assume that the car would never start to begin with if that was the case.

[MKovac]

Probably obvious, but have you replaced the blue temp sensor? Hard to believe that would cause the issue but who knows?

Does the car have an ICV? You could try unplugging it and also switching off idle control in the Maxx software.

Yes - replaced the blue temp sensor for a new one.

Oh, also forgot to mention... I switched the TPS with a brand new unit. No difference.

The car does have an ICV but I think that this is more related to something else that I am not seeing. Will run to the garage and try unplugging the ICV to see if that makes any difference.

[bmwdayz]

Have you hooked up a computer to the Alpha N unit to see if the settings are correct? And if you removed the Tps you need to check on the computer again that its adjusted correctly in the Alpha N software.

[MKovac]

Have you hooked up a computer to the Alpha N unit to see if the settings are correct? And if you removed the Tps you need to check on the computer again that its adjusted correctly in the Alpha N software.

So I unplugged the ICV, no difference.

I pulled the boots off of the TPS connector- seemed like one of the pins was backing out of the plug. I took the plug out of the equation and hard wired the TPS/MAF. Started the car and boom, started like normal. Maybe a bit low on idle but definitely much better. Start goosing the throttle, was looking good. Eventually it just died and then wouldn't start again. Started messing with the TPS position... nothing.

Next Im going to have to get the car hooked up to the computer and calibrate the TPS - although it seemed to sputter out and not take load regardless of the TPS.

If anyone has any more ideas please lay them on me...

[babarabus]

try the intake temp sensor, my car got delivered to me in the same manor. It wouldnt start but you could crank it for a while, apply throttle and sometimes it would start. Other times it would start and run (rarely).

Anyway long story short it had no intake temp sensor installed so would be running open circuit. I installed a new sensor and car ran fine immediately after. Maybe check your sensor and wiring.

[evanboyle]

Check to make sure all hose clamps are tightened on ICV, breather, and brake booster (all your vacuum lines really).

Also check your throttle pedal bushings and throttle cable grommet. Throttle cable tension is extremely important due to the full range TPS.

I was having idle/lean/part throttle issues on my car with A/N and the above items fixed everything.

good luck!

[ttw18]

Check the settings using a laptop. I had a similar condition and Saw that the wide band O2 sensor wasn’t being input into the maxx controller. Fixed an intermittent grounding issue then it ran right.

[Reelizmpro]

Check the resistance of the new CTS and make sure it is within specs. I once had a new one go bad right out of the box. If resistance is too high, it will cause the DME to dump fuel into engine causing a flood condition. I too, ruled it out since it was new. That mistake caused me to go through the entire engine and harness after countless hours of trying to diagnose the issue. The engine will start cold, idle high for a while before dying, then you cannot restart it until the flood is cleared.

[MKovac]

Figure I would share what the conclusion was.

Wrong injectors!

The car was delivered with M20 injectors. Not enough lb/hr to have the car start and run right. Knew it was going to be something stupid. Thanks for all the help S14!