new owner, have issues...

[crono35]

Hello,

Just picked up a 92 VR4 as a project car, seems the previous owner just gave up on her. Hoping to give her a new lease on life
First off, my symptoms:

- tachometer is broken.
- at what appears to be around 3000 RPM, car just begins to stumble, hesitate, and buck wildly. I can't stay on the gas at this point, car feels like it'll shake itself apart.
- seems to happen in neutral as well.
- gets better in 3/4/5th gear, I was able to drive it 30 miles home.
- ISC valve clicks nonstop, even with engine off and key in ACC position

here are the current mods, per PO:

4 Bolt Engine Block
Mitsubishi Genuine Forged Steel Crankshaft for 2nd Gen 3/S
GT PRO Piston Set 93mm for 6G27B Turbo includes Pins and Rings
GT 358-SX TurboCharger Set for 3000GT
Lifter for 3000GT
Bearing ACL Main
Bearing ACL Rod
GT PRO Big Bore Head Gaskets 93mm
+1mm+2mm Oversized Valve Package
Labor Charge (Drop to bowl blends on heads)
Engine Machine
Labor Charge(Assembly Turn Key)
Oil Pump
Engine Gasket Kit
Timing Pulley
Tensioner Pulley
Labor Charge Engine Remove and Install
Timing Belt Hydraulic Tensioner
Walbro 341 Pump
Labor Charge (Engine Dyno)
Type RS BOV
Stillen Stainless Steel Lines
Labor Charge to install fuel pump
New Oil Cooler (Custom)
Engine Timing Belt Kevlar Power Enterprises
Polished and Shaved Valve Cover
Labor Charge to paint calipers Ford Blue
NGK Iridium Spark Plugs
Greddy EB-1 Boost Controller

Clutch Masters – Stage 2 ($500)
Clutch Masters Aluminum Flywheel ($400)
Install ($486)

Manual Transmission and Transaxle Assembly – Remove and Replace with Used Japan Take out Assembly – AWD (Performed 2/10/2010) ($2,500)


What I've tried so far:

- pulled ecu. looks like they already went down this path, it appears to be brand new with no rubicon caps. Of course, this doesn't guarantee that it is good.
- disconnect ECS computer- looks like they did that already too.
- disconnect MAF, no difference
- disconnect F/R O2 sensors, no difference
- swapped plugs, NGK cheapo platinums gapped to .04, no difference

other things I have noticed:

- tach signal at ECU appears to be dead. I tapped my greddy RPM signal wire to it, and it does nothing, just like the stock gauge.
- when a timing light is hooked up to each wire, they all flash at different speeds, and all of them have an intermittent flash- it would fire a few times, stop, fire a few times etc...
- ISC valve clicks nonstop, even if the key is only on ACC position
- coil packs get strange results when measured- sometimes I can get a dodgy signal from the front and rear ones, but the center one gives a pretty consistent reading
- clutch makes a leaking noise if i press it in, and when let out in neutral i notice quite a bit of clutch chatter... hopefully that's the right term

things I have already ordered:

- new (used, tested) coil pack
- used, tested PTU
- used ISC valve

I know it's a whole lot all at once, but I'm counting on the gurus here to bring this lady back to life.

TIA everyone!

[GTOJOE]

Pull your ECU and check for leaking caps. Also I had a similar issue with the surging and bucking etc. Problem was the MAF. ran perfect with new MAF. With MAF unplugged it won't run well till the revs are up. If it runs ok'ish with high revs and no MAF then try another MAF. Can't help you with the Tacho.

http://www.stealth316.com/2-ecmremoval.htm

[TonyM]

For tach signal, you need to check the PTU wiring. I don't have a diagram in front of me but the PTU supplies the tach signal to the ECU. Check wiring and make sure it's in tact, if the PTU is trashed than a new one might take care of that problem.

[Fletch]

ECU's caps any sings of leaking near the bases?
There is a guy around Chicago named Steve that will recondition your ECU for about $100 IIRC, new caps and he can test your boards.
The ISC, I know that the ones from Rockauto are cheap and have the Mitsubishi stamp on them, I have picture of mine somewhere.

Here is a pic I pulled from a google search for leaky caps...
http://i47.photobucket.com/albums/f1...cu-damaged.jpg

[crono35]

Thanks for all the suggestions so far. The ECU looks fresh, but I'm going to try and find someone local who's willing to test it out for me. I've got PTU and coils on the way, I'll unplug the MAF tomorrow and see if it causes it to run better in the higher RPM range.

[steve]

If the ISC is making noise with the key in ACC it doesn't sound like the MPI relay is turning off. The ECU normally does this about 10 seconds after you turn the key off but the PO may have done something to the wiring to work about earlier ECU issues or this one could still be bad. You should hear the MPI relay click when it turns off. Does the car have a turbo timer or aftermarket alarm?

As mentioned, the power transistor module generates the tach signal and sends it to the ECU for checking that the coils a being charged and the gauge cluster for the tech.

The ECU can look good and still be bad, I haven't met many people that really know what they are looking at/for. Or it can just be getting bad inputs.

Thanks for the referral Fletch, I'm starting a new job on Monday and have stopped repairing ECUs to focus on it. I may start doing repairs again if it doesn't work out or I find that I have spare time.

[crono35]

Thanks for the heads up Steve. The PO did wire in a boost controller, I'll have a look at the wiring to make sure nothing stupid was done.