You may or may not know that I have a VQ30 in my S13. I've had my fair share of problems getting it going consistantly but I've been taking them one step at a time. My newest problem is quite perplexing to me.

When I first did the swap she ran great for a while. All six cylinders firing. Missing a little timing due to dead knock sensor but still pulling strong in the 2100lbs car.

Friday night I got my latest fuel delivery problem dealt with and decided to go out cruising. I could tell from the get go that I wasn't at full power or even good power. My buddy was rolling with me. I got a sharp kick in the groin when I raced him. I used to easily beat him by 5 cars. Friday night I could barely beat him. We roll around for a while and head back home. On the way back home the tone of the motor changes significantly. It goes from a high toned roar to a sort choaking much deeper sound. I knew something was messed. Get back to the shop and start browsing around.

I start unplugging coils only to find that when the coil for Cylinder 3(Middle Right bank) is unplugged nothing changes in the motors running characteristics. RPM, exhaust tone, Vibration; nothing changes. It was late and I figured I'd let the ECU reset itself over night to see what happens.

Next day I start it up and can imediately tell that its only on five cylinders. Cut 'er off and do all the normal tests.

Compression. My motor is fairly old now. Probably somewhere north of 140K so I wasn't suprised by the numbers. Most cylinders have compression in the mid 180's. Cylinder three has 180 flat. Not too significantly different. I attribute the lost compression to the fact that the cylinder is probably flooded from not firing at all.

I swap the coils. Bad cylinder stays on three. I swap the plugs. Same results. I bust out the multimeter to find that all coils are getting 14.1 volts during charging and 12.5 volts at static. Then I test for the signal. I don't have oscilliscope so I can't see the individual spikes but my multimeter averages the signals sent from the ECU. All of the averages on all cylinders are between .29v and .35v at idle. They all raise at the same rate as RPM's are increased.

Then I check the oil. As I suspected there is gas in the oil from leakdown on cylinder three. So from this I know that its getting fuel. I pull the manifold and check the voltages to the injectors anyway. All are getting equal voltages. As I said previously I don't have an oscilliscope so I can't see the injectors actually opening. Are there any other checks I can do for the injection with the equipment I have? I change the oil and continue.

The list of tests goes on and on. I pull the plug and coil. The plug fires like non other out of the head. While its out fuel is spurting out of the plug hole as I'd expect.

WTF is going on with my motor and ECU?

The only thing I can think of at this point is that for some crazy reason only cylinder three is firing at the totally wrong time. Like BDC and thus doing nothing. But even if it were firing then I'd still expect it burn all the fuel and stop the leakdown.

I'm going to swap ECU's with a spare tonight. If that doesn't help I have absolutely no ideas left. Please, any insight is more than welcome.

 

Have you checked for a leaking/sticking open injector?

 

perhaps when you reconnect it it's creating an open in the circuit?

 

If it's leaking(externally that is) wouldn't you possibly smell fuel in the engine bay? It sounds like that cylinder is running rich due to an open injector.. I think Dandy has a good idea to check that...

What's a good way to check the injector sticking?

 

Stephenmax wrote up a GREAT way to test injectors.... I'll try and find it

 

Dandy, I have not checked that. Thats a great idea. Actually that kinda makes since because i just pulled out all my injectors for some rail modification.

Tav, when I reconnect what?

Actually the stuck open theory makes more and more since every minute. With the cylinder 3 injector and coil unplugged the right bank is still rich. So rich that it pops and backfires on every throttle lift even with base FP in the high 30's. Definitely could be due to stuck injector. Is there a way to unstuck them or do I have to replace it. I have spares. I'm not worried about that. Just that I don't really wanna have to pull the LIM.

I changed the oil yesterday and drove it for about an hour with them unplugged. I'll check the oil for gas contamination tonight. If there is then we know the culprit.

BTW, slightly off topic but I'm curious. Yesterday I swapped out my 95 Auto ECU with my buddies 95 MT ECU and it wouldn't start. Very curious as to why. I would hope that nissan would've made all the pins in the same location on each ECU.

 

You guys nailed it on the head. Pulled out my rails last night and put in a spare injector. I could imediately tell on startup that they were all firing. Thanks guys. Once again saving the day.

I spent at least an hour last night wagging the tail around in third. Oh god its great when she goes. Now I just need a new knock sensor.

 

Glad you got it taken care of.

 

That's wierd... My bro has a 96 Auto ECU mated to a 95 5-speed engine wiring harness. Looking at all the pins on the 95 FSM, there's really nothing that could make a different in startup between Auto and Manual.

I've switched from my 95 MT ECU to his 96 Auto ECU several times in his car now and it makes absolutely ZERO difference in how it starts or even runs.

 

Very weird. You're telling me. But I don't really care now. Problem solved.

Oh yeah, got a new knock sensor in and I've been waxing everything with wheels all weekend long(Without a tach). Track times coming on October 8th hopefully. Hoping for 13.0 with sub 2.0 60' and 110 traps. I'm really a novice drag racer. Seem like reasonable goals?

 

I really have no idea what you should expect. Nobody has tracked a VQ'ed S13 yet. Totally new setup.