Mysterious Engine Problem

[hermit-dragon]

Ok, I haven't posted in a long time... anyone who read my post about "dead ECU" may remember. Now.. here's the thing... I have had this problem since I got the car, and it's driving me bat crap crazy! I now have 2 MT ECUs (thinking that was the problem originally) as well as a second AFM... Also NOT the problem. I have data scanned it with Consult as well as bringing it to a dealer.. no fault codes ever. I also have an AT ECU from the previous owner who got it from a shady shop that told him that was the problem.

Initially, the car would run perfectly then suddenly just die and not start again. Switch ECUs and it would run. now it won't even do that half the time! but still.. no fault codes at all. I even replaced the engine temp sensor for good measure. I've ordered a new fuel filter just in case, because when the car dies, it almost sounds like someone switched off the ignition... Blocked fuel filter? After it dies, the car will not start at all for a while, except occasionally when switching ECUs... this leads me to believe it's NOT a fuel problem, but an electrical one. The other day I washed the car, moving it to a different bay in my car park from where I park it... started and ran fine till I went to drive it back to my spot... dead... switched to AT ECU, and drove fine.

I have a funny feeling its a bad wire somewhere, but as there is literally hundreds of meters of wiring in this car, I'm reluctant to pull the harnesses out and inspect them all. I have recently installed a Apex'i electronic boost gauge, and Apex'i Full auto turbo timer and an HKS electronic boost controller (haven't hooked up the vacuum lines yet) all of which I tapped to the ignition switch for switched power. They all work fine (except the boost controller because the stepper motor is not plugged in yet)

One other strange problem that I found recently, when I changed the bulbs in my left tail light, the dash lights would come on when I pressed the brake pedal! WTF?! then when I wiggled the wires to the bulb in the tail light, the dash lights stopped coming on with the brake pedal again.

I will try to take a video of the problem and maybe one of you will have a clue... I am at my wit's end trying to figure out this problem.. I have never come across a car problem I couldn't figure out until now. I hope someone here can help.

Thanks Mates

[hermit-dragon]

ok.. a little update.. hopefully it might help figure this weird problem out. I couldn't get the car started with the MT ECU tonight, and with the AT ECU, it's chugged and bogged and stalled like a bee with an itch until it finally settled down into a nice idle. I decided to let it get up to operating temp (almost half way on the gauge) and then switched back to the MT computer... lo and behold, the car fired right up and kept a nice steady idle for at least 10 minutes until I decided to shut it off.

It started no problem on the MT ECU 3 more times through the night while I puttered around doing some other stuff. The point is, it was still hot from running up to temp from the first time... soo.. maybe the cold start valve? or AAC? I'm in Hong Kong, and the temp is about 27C, so I can't see it being too cold...

Anyway, that was my findings for tonight. Thoughts?

OH! I checked the voltage and resistance to the fuel pump with a multimeter, and that came up good, so it's not the pump. I read in the FSM that a clogged Catalytic converter might stall the engine like this... anyone think THAT might be it?

[GTSBoy]

Have you swapped the ECCS relay with a known god one to make sure it is not that that is pulling the power from the ECU?

[portaz]

The dash light is easy, u have the wrong bulb in the wrong place as in as in a single element instead of double I've seen it before, in terms of the engine issue have u removed fuel pump? Sometimes there can be an intermittent issue with the wiring degrading. Also have u done compression test ? Low compression engines can be hard to start when hot also. Good luck

Scott

[TurboMick]

Sounds to me like it's an intermittant bad earth somewhere.

I'd check the harness very closely at the plug for the ECU, and as far along as you can access. It could be a simple case of pulling/twisting the wire into the correct position (out of contact with the chassis or something like that) when you change computers, so it seems like the computer's to blame. Just a thought.

Goodluck.

[jattsta]

I think your right TurboMick .. Check all the groundings. ensure there isn't any wires broken around the ecu plug. check to see what voltage you get at the pump during the whole stop - start ignition process. clean the afm and TPS (might not be a direct problem but will help)

do you have any other wirings? Sub/Amp/Capacitor hooked up wrong? Is the apexi boost controller etc all wired correctly?

i highly doubt the ecu alone is to blame.

[hermit-dragon]

no sub, amp or cap.. I even yanked the aftermarket alarm and all i's components and fixed the wires it was tapped into to eliminate hat. the TT is brand new and wired correctly, and I know that's not the problem cus the car did this before the Apex'i TT was even there. the fuel pump gets full voltage even when the car refuses to start... but it's nowhere NEAR as loud as my old R32 was when the pump was priming... is this due to the R34 having a plastic tank that has that bizarre shape as opposed to the metal box of the 32?

My mate has agreed to let me swap-borrow parts from his GTT to find my problem. I'm starting with the CAS as many ppl have said that is suspect. any other suggestions if the CAS turns out ok?

[hermit-dragon]

ok.. so I cleaned the IAC valve the other night and took it for a test tonight.. ran like a champ even when beating on the loud pedal... no even the slightest hesitation or flutter! now, the Idle set screw is fugged.. some cracker stripped it before I got the car and I could only get the idle down to about 1000 RPM, but I can live with that for now. I also noticed when I took the IAC off, the hose going to the intake was split near the intake end. I taped it up with electrical tape for now... maybe this split in the hose was my problem all along?

[GTSBoy]

Could well have been.

[DVS JEZ]

1000 is te perfect idle

[hermit-dragon]

1000 is te perfect idle

I thought it was supposed to be 600-700?

[bish33]

600-700 is too low I think 900 is perfect just below the 1 on tacho

[GTSBoy]

Nah. Stock idle will depend on temperature, but will variously sit in the range 650 - 800. You only have to look at the settings in Nistune to see what they are supposed to be for any given motor. They tend to idle high when the IAC is all gummed up (read that as stuck open).

My Neo is a bit like that at the moment (mostly when the weather is cold - I suspect the coolant connection at the IAC is blocked and so it doesn't warm up properly). Bloody annoying. When it was warmer it would idle 150-200rpm lower, which was smoother and less thrashy.

[hermit-dragon]

it's been a few days and I've stared and ran the car several times with zero problem... I'm starting to feel like an *** for letting something as simple as an intake leak stump me for so long... but in my defense, the previous owner took the car to a shop and was told it was a bad ECU, so I was working from that trying to hunt down some electrical problem. I'm glad I did in a way tho... there were so many bad wiring hacks and whatnot that couldn't be HELPING the situation!

So now I'm tentatively thinking the problem is finally solved, but time will tell. If there is no issues within a month, I think I can confidently say it's fixed.

Actually, it makes a strange kind of sense now.. I replaced the leaking valve cover gaskets, and that's about when this problem got really bad. I took that hose off to remove the valve covers, it must have split more then? Well, just goes to show, the simple problems can sometimes be the hardest to track down