50 replies to this topic

[Zefy]

Tried a few different things that i searched for on here but nothing has solved the problem.

The car DID run before.

after starting up, the engine would rev up fairly quickly to about 2500rpm then it would stall out quickly. Just cuts out. I can rev it up fine during these few seconds and it sounds fine.

nothing i do stops it from stalling. i have changed the maf sensor and checked my vacuum lines going to the TB. Read in another thread that the large vacuum line going to the IAC can cause this but it is hooked up and seemingly not leaking.

any help would be appreciated.

[Zefy]

i pulled the iac off and cleaned it out. at the same time i also closed it by hand. now it doesn't rev up after it starts but it still stalls out.

i think there is something wrong with my IAC. I have a spare, but it is a hitachi one. The one i have on there right now is JECS i believe. The difference being JECS has 3 wires and the hitachi as 2. Would this still work or do i have to rewire it?

other thoughts not IAC related?

[Gloyale]

the two wire one is for a 90 manual trans engine. The 3 wire is for 90 auto and virtually every EJ after til 99.

They aren't really interchangeable.

I don't think you're problem is the IAC.

Sounds more like a MAF sensor, Cam sensor or perhaps a Coolant Temp sensor issue.

Try unplugging the Cam sensor.....see if it runs that way. Sounds crazy but it works, and will tell you if the Cam sensor(or the wiring) is sending a bad signal.

[silverhelme]

What Gloyale said also check the wires going into the maf. I had one that was broken just as it went into the plug under the rubber weather seal.

[Zefy]

i checked continuity between the pins on the ecu and the pins on the plug yesterday. They were fine but the maf has 5 wires and there are only 3 or 4 on the ecu. Not to sure where the other wires go and if it can affect the function of the maf.

I will check the cam sensor tonight. Whats the theory behind the cam sensor? The pickup isn't getting any signal from the cam gear? On startup it doesn't use the cam sensor...? I will unplug it but won't this give me the same result...?

Either way, i'm giving it a whirl.

I also borrowed a buddies legacy last night and tried swapping the ecu. I forgot how much of a pain it is to get the ecu out of a legacy compared to an impreza...

Ran smoother, but no change in the problem.

[Gloyale]

One of the 5 MAF wires is a shield hooked to ground.

As for the CAM sensor.....I've seen bad connections at the CAM sensor cause all kinds of rough running issues.

With it entirely unplugged, the ECU defaults to a basic timing map and runs the engine pretty well.

Don't get too hung up on the idea....it's just a guess.

Honestly it really seems like an unmetered air leak. Either MAF screwing up or there is a leak in the system.

Got all the PCV hoses hooked up? Both valve covers and the one on the back of the block? Vacuum line to the brae booster?

[Mr. Brat]

What about fuel? Mine did the same thing, the put couldnt keep up with the demand of the motor. Would charge the line, enough to start and rev then just die. I cycled my key a couple times and it could run a little longer.
Just my 2 cents...

[Zefy]

it has a walbro pump and SS lines going to the motor. oddly enough, this is the only thing that has changed since i started it last. Just tested the fuel pressure. primes to about 40-45psi then runs at around 35psi. That is pleanty to run this motor is it not? Pressure holes strong right up till the pump stops after it dies. I don't think this is the problem.


i disconnected the cam sensor and the engine wouldn't start. not even a puff... just cranking and cranking. I made a video of it starting just to kinda show what is actually happening. Kinda hard to hear, but you get the idea.





it DID run before... over a year ago...

[Pooparu]

Sounds like the same problem I had and it was the IAC unit. Also check all your fuel lines and filters to make sure you're getting a good flow of fuel. Also make sure you don't have any vacuum leaks & try swapping out the Fuel Pump Relay.

Good luck and I hope to see the BRAT at the show.

[Zefy]

Sounds like the same problem I had and it was the IAC unit. Also check all your fuel lines and filters to make sure you're getting a good flow of fuel. Also make sure you don't have any vacuum leaks & try swapping out the Fuel Pump Relay.

Good luck and I hope to see the BRAT at the show.

I can hear the fuel drain back into the tank so i know i'm getting enough flow and pressure. I just cleaned all my distribution blocks, connectors, and battery to see if it made a change. it ran smoother but still the same problem.

I was talking to somebody about the IAC and he was saying it should close or open on its own because it's spring loaded. (he couldn't remember which it was...)

When i cleaned mine out i could turn it by hand but it would stay in either position as if it wasn't spring loaded.

thoughts on the IAC? i also checked for visible vac leaks (unplugged) and the only thing i could find was the crank case vent (the big one) had a crack going down the side but only at the bottom. This would be such a minor leak (if at all...?) but probably safe to fix it just to rule it out as a cause...

I hope i can get it to the show too!

[Zefy]

so i threw on the wrong IAC. I used the two wire vs. the 3 wire. It could still start, but it wouldn't really run. still stalled like normal.

after a couple check it seems that the main relay is dropping during and after cranking leaving my ecu with nothing to run on. I'm thinking this is the problem but i won't know for sure until my battery is completely charged and ready for another try.

will see tomorrow after work... maybe tomorrow morning if i'm ultra ambitious...?

[Mr. Brat]

Have you checked you MAFS? Bad or dirty?

[Gloyale]

IIRC, the main relay is powered from the same circuit that is reference voltage for the ALT. (yellow wire with diode, becoming green before it goes to ECU)

Perhaps this wire is the problem. Did you leave the diode in it? I wonder if somehow the voltage is being driven low while?

The more I think about it....it does sound like a power supply to the relay issue.

[Zefy]

yes the diode is in tact and functioning. I'm going to have to confirm my theory tonight. It might have been a simple supply issue as my battery had started the car multiple times before i decided to test.

I will also have to throw on the original IAC. It was spitting codes with the 'new' one on. The door on the IAC (green rotating thingy) on the manifold side does not open or close via spring. It only moves when i use a finger or screwdriver. The flapper on the vacuum line side is spring loaded and very springy. Is this the proper function of the IAC?

I cleaned it out a bunch with brake cleaner and it still functions the same way.

I might just put a jumper on the main relay and bypass it to see if it works.

Mr. brat - the maf was the first thing to get changed. Got pulled from a running car, same results with the original or new maf.

[Yo'J]

Wait..isnt it magnetic? The IAC?

[Zefy]

Wait..isnt it magnetic? The IAC?

maybe...?

I guess that would make sense... Either way, the original one was not being 'springy' in that i had to force the tumbler open and closed with a screwdriver/finger...

I put another one on from a 98 impreza 2.2. It seems to function fine although the wiring appeared messed up. I had to fiddle with it a bit to make it function correctly.

So now it starts up fine, with a wee bit of a high idle like a good motor should. it then continues to turn off ~5 freaking seconds later...

I'm going bonkers with this piece of S***...

I bypassed the main relay to ensure it was indeed giving good current and to confirm i swapped it out for another unit. Did the same for the FP relay...

i then proceeded to test voltages all over the place. Seems as though my power issues i was noticing yesterday were due to a dieing battery. Starting a car a dozen times can do that to one... So i charged it up last night and threw on an extra jumper battery just to be safe.

ECU was getting a modest ~13.5v during priming, drops to ~12 during cranking, then up to about 14~ while running. This was the same on 4 power wires for the ecu. I also checked the main relay, FP relay, TPS, injector, coil, etc etc all getting about the same thing. At least i know my alternator is working...

I also pulled a plug wire and tested to see if the engine stopping was perhaps due to a cutting out of... something... Anyways, the sparks continued right to the bitter end... The engine must be cutting fuel? I know it is getting air because the IAC was stuck open before, and i know it's getting spark so WTF...?

Runs really smooth with all these new bits on it and all the electrical grounds and powers cleaned up... but only for 5 bloody seconds... SAAAAAVE me...:-\

[Gloyale]

gonna sound dumb, but.......

do you have the fuel lines reversed?

I'm just throwing out guesses

[Zefy]

i actually had somebody else ask the same thing and seriously, i don't know! I matched it to my impreza which is:

top: high pressure feed line (pump)
middle: return line (tank)
bottom: vent (nowhere...)

did they change it ever?

anyways..

tried a few other things like bypass the fuel pump relay and main relay giving them both their own battery. so i know everything is getting power.

tried unplugging the maf and tps while in these states and nothing happened.

i also found a pin that is a 'california identifier' pin on the ecu. this is not supposed to be grounded but it was. This, now that i'm thinking about it, doesn't make sense because it is routed right to a ground from the get go meaning it was grounded in the old legacy it was in for the first ~18 years of its life... Anyways... didn't make a difference...

Also sounded like the fuel pump was struggling a bit while it was pumping (because i bypassed the relay i didn't prime anymore, just on all the time) so i put another 5 liters in it and it smoothed right out. wouldn't it be nice if it turned out i just didn't have enough gas? well it wasn't that easy i guess because it stayed the same. My fuel pressures are a little more smooth now but i still see the same results.

what the hell is going on...? i've got it running SUPER smooth then it's like somebody is jacking my keys 5 seconds later.

[Zefy]

i just picked up a full set of FSM's for the 1990 legacy.

Very detailed diagnostics in those books.

I am going to start checking all my sensors tomorrow and see what i can see...

[KootenayJK]

So, whatever happened with this? Did you get it sorted out?

[Zefy]

No i have not solved the issues yet.

I did some tests a while back before i got extremely busy with school. I found two things.

First, I determined that I am getting full spark all the way until it dies. 2nd. The motor is not being choked out by the throttle or the IAC. The ECU is cutting fuel. I determined this by reading the injector duty cycle through the priming, starting, and running. it distinctly drops to zero then a moment later (fractions of a second...) the motor stops.

So somewhere the ecu is being told to cut fuel. The only sensor that i could find that was 'off' was the MAF. The sensor itself is fine however the wiring is incorrect. This is all from memory so forgive me if the details are incorrect but one of the 5 wires going from the maf to the ecu is not getting a proper signal. One of them is supposed to be receiving something like 0.3-0.5v while the car is in the 'on' position but not yet started. it was receiving 12.1v though. odd? yes... I need to retrace my wiring... Possibly remove it from the car and clean everything up. I don't want to further clean the wiring if it doesn't run though as i could be making the problem worse or untraceable.

Either way, I'm not sure when i will be able to work on it. it's starting to get cold outside with rain pretty much every day. School is getting crazy to but hopefully i'll be able to figure it out and possibly driving it sometime this decade...

Edited by Zefy, 28 October 2010 - 08:56 PM.

[Zefy]

ok so i know nobody has peaked back here since my last post in this thread.

But here is the scoop... It won't really run at all now... WHAT THE HELL IS WRONG WITH THIS THING?

I'm seriously going bonkers trying to diagnose this problem.

I retraced my steps and started looking at the maf wiring again. I cleaned up the wiring and got rid of the tangles for the maf. And now (not sure if was ever a real problem) the maf is receiving the correct 'pre start' voltages.

However one of the tests covered in the FSM is resistance WRT the body. And these are totally bonkers.

connects (on the maf) 1,2,4 should be >1Mohm while 3(ground) should be getting ~0ohms.

well connecter 2 is at 2ohms... Not sure why it's grounded...
1 and 4 are only in the Kohm range...

I'm debating scrapping this harness and trying again. Maybe a standalone... Possibly even a different motor. SWAP REDO!

SAAAAAAVE ME... I wanna go to WCSS with my BRAT!!!

[Gloyale]

Check the connection of the crank and cam sensor wires. Make sure none of those wires are getting twisted or ferayed near the connector end.

Cuttinng out fuel seems like it could be the Cam sensor.

[Zefy]

hmmm... I will have to check that. Probably sunday. I was under the impression it wouldn't run at all without the cam/crank sensors though.

[Gloyale]

hmmm... I will have to check that. Probably sunday. I was under the impression it wouldn't run at all without the cam/crank sensors though.

May be hanging by just a strand or two of wire.

And actually they will run if it's only one of the 3 wires one each sensor that breaks. (+, -, Shield)