Not your Typical Stalling issue, thoughts please

[GSLENK]

Recently my car started doing something absolutely annoying to say the least.

It stalls. It is not from boost leak, venting bov etc...

You can skip the description between the asterics if you want, its long...
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This doesn't happen all the time, but it has occurred almost at least once a day for about 1-2 weeks now. And is very irritating.

The first sign of trouble was when I started a 2nd gear pull (for logging). I built full boost 20 psi. and then at around 4500 or 5000rpm, at WOT my BOV went off very quickly, the car lurched and then continued. No knock, on the dash or in the log. Immediately built boost again and did fine. Lost full pressure. THe log revealed I did go into vacuum somehow.

This didn't feel like spark blow-out since I have been tuning slowly and the last time spark blowout happened was on autozone recommended oem style plugs. I have since switched to NGK BR7es (non-protruded), and change them at least every 12 months or so. Also I recently 7 months did NGK blue plug wires.

Soon after, maybe the next day or two something else started happening. Now it occurs just about every other time I drive the car. The car will stall in deceleration in gear, or under low rpm high load/gear example, 5th gear at 1500, anything that causes the motor to shake. This wont always induce a stall but it appears to be the most frequent.

Then one day I took the car out, and it stalled 100 ft from my house and wouldn't start. I had ECMlink on and running so I checked a few things, Car builds fuel pressure just fine (turned on fuel pump, checked the AFPR gauge, pressure was fine)

My battery voltage is fine. Car will crank for days. But the cranks sounded different than a dry crank. I could hear the exhaust puff with it, like it was about start. but no start at all as soon as I release the starter, it stops. No sputtering at all. Just stops.

I popped the hood, played with the TPS connector, the CAS connector, and the Ingnition transistor connector. All were on there although the CAS ant TPS are missing the wire clip parts. They have been this way forever and never caused an issue. My ECU is currently hanging out in the passenger footwell since I was doing some wire splicing and was too lazy to put it back just yet. I checked its plugs and they were tight. Tried to start, no good.

I then pushed the car across the street so I could further investigate. I then tried to start it just for kicks, it fired right up like nothing happened drove it around the block just fine. Drove it for 30 miles just fine. Did some pulls near a friends house just fine, drove home.

Next I drive to classes and it stalls in 1st gear while I'm lingering in low rpm 1st gear in parking lot traffic trying to avoid using the clutch (laziness) I start to roll on, then roll off then it stalls. I try to start while in motion, no go. I pull over with my momentum, wait and try 2 more times. 3rd time is a charm and I park my car. I pop the hood and touch only the TPS and CAS plugs since I suspect its the CAS (though with only minimal knowledge only knowing that it has to work to start the car...). I close it all up (didnt try starting) and go to class. I come back 9 hours later, gets me home just fine.
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Sometimes I get the decel or low rpm stall, almost daily now. I don't usually get the no start situation.


I first thought plugs, but the car runs fine otherwise. My WBo2 is a year old if that. my plugs are a year old.

Are there any connections to the engine (electrical) that are absolutely essential to operation besides the CAS causing the car not to start?

I haven't done much recently. The last thing I did was drop the firewall wiring harness down a bit, to begin my wire tuck project in the future. nothing was cut or resoldered.

Any ideas are greatly appreciated.

 

[chris00326]

Just a wild hunch but you said your bov went off loudly and u logged going into vacuume. check the bov. maybe its bad and you are venting to atmosphere without realizing it.

 

[GSLENK]

I dont think a faulty bov would hold boost, or show vacuum Think about it.

for those that dont want to look at my profile for mods... 20g turbo, fic 1050cc, stock ignition, Link v3 full, LC-1 WBo2, Speed density.

What other sensors have to be connected and working properly for the car to start/run.

I know the TPS disconnected allows a start. But the CAS unplugged wont start.

I also know the obvious ones, ignition related, and injectors... I don't think there are any others right?

 

[athlete3344]

Have you checked your timing to make sure you didnt jump a tooth? And checking the BOV wouldnt hurt since you said it did go off while boosting.

 

[GSLENK]

I doubt it jumped a tooth, even if so, It would act funny permanently. This is like an on/off switch.

Car runs and pulls just fine ( just don't want to pull and have this happen during one)

I recently had my injectors flow tested, just because I wanted individual deadtimes in my tune.

I also dropped the engine harness off the firewall, but I didn't change any connectors, or the fuel rail harness. Just dropped it down.

I think it is an electrical issue, I just don't know where to look. one injector feels like it is pulsing less than the others, but when it idles fine. When I pull the suspect injectors lead, the idle gets all lumpy and stumbly (still "idles").

It is really random and I am about to lose my S on this.

 

[GSLENK]

Heres some logs. Again for summary... I can drive just fine, park the car and come back later, no start. Try cranking a few times, fiddle with any connectors I can find, no start. Wait a little longer, it fires right up.

Here's a log of one such instance. It started 5 minutes later after I fiddled aimlessly around the engine bay (not after playing with any connectors in particular).

It may also stall while driving for no apparent reason. It typically happens after a closed throttle. Sometimes I can feel it stumble first. Then it goes max lean and no power (from obviously no longer firing).

Here it happened at highway speed. You can see me playing with throttle positions, then trying to pop-clutch-start it. Then almost last resort to starting using the starter, then when I almost run out of momentum, a pop-start works. It very well could have rolled to a stop, tried to crank a few times, then fire right up and drive fine.

Here's a log of such an occurrence.

I would really appreciate any insight on what could cause something like this.

 

[tharrison365]

mine had a problem like this and my injector was crushed

 

[GSLENK]

mine had a problem like this and my injector was crushed

What do you mean by crushed? and was the car unable to start or stall because of it? and what did you do to fix it?

 

[pauleyman]

Check the power transistor during a no start. I have seen them intermittently fail when hot. Car cools down and fires right up. Connection wil do it too. If you have a spare you can swap it out at no start and then swap back to confirm. One posibility. Grounds are another.

 

[kchaazz]

GSLENK, this is going to sound funny, but what if your bov didnt go off during that pull and in fact you blew a hole in one of your intercooler couplers or a coupler has slipped enough to leak? It will sound much like the bov when this happens, and the resulting vac and boost leak will cause hard starts, no starts and tons of random stalling. I really believe this to be your problem after reading your description, especially since you were on the gas when the bov supposedly released, and I would do a boost leak test to confirm. Generally, if a critical sensor is intermittantly malfunctioning, you will see a CEL. Do you happen to get a CEL at idle that goes away when you blip the throttle? A large enough vac leak will bypass enough air at idle that the maf doesnt read and the ECU will throw a code for a bad maf. Definitely check your intake tract as soon as ya can, its worth a look trust me.