FNG with missing problem under load.

I think I'm about to waste everybody's time because I don't know much about this VR-4. First let me pull on your heart strings . . .

My dad died earlier this year, and #368 (if memory serves me right) was his car. He split time between that and his NSX. He wasn't driving it lately because under boost the car would miss, and he had an NSX to drive.

Here's what I know: The car was supposed to be tuned to about 280 hp at 19 lbs of boost by someone years ago. It was a rocketship. I started driving it after he died, and the most boost I could pull out of it is 5 lbs at about 4k rpm, and then it would start to miss. The limit changes based on temp and rpm. I have a stochiometric meter fed by a narrow band O2 sensor which is half way into rich when this happens.

Not knowing any better, I replaced the plugs with NGK BPR6ES gapped at .028", and the problem still exists, although to a lesser extent. On the HWY at 4k it will pull about 8 lbs with no hesistation, although it happens when cold and at lower rpm. And lets face it, 8 isn't lot, although the boost controller is turned down. The plugs I pulled out were BPR7ES gapped at .030-.032", and they didnt look bad.

My money is on bad timing, although my brother who was looked into this more thinks it not enough fuel pressure. I don't think that is likely with the meter readings.

Any ideas and more importantly warnings are greatly appreciated. My inclination is that if a little is good, than a lot is better. Can I do harm by going back to a heat range 7 and gap them at .025"? What timing ranges are beyond reasonable?

Thanks for your help

 

[TRBODSM]

Do ignition timing and see if it is 5 btdc. My ignition timing was off and i had the same problem. It would feel like fuel cut but not that bad.

 

[toybreaker]

Very nice first post!

Many times, missing under load is about a problem in the ignition secondary.

Since you've addressed the plugs, the only thing left is the coils and plug wires.

A quick visual inspection of the wires where they go into the coils may show an issue inside the coil towers. They can corrode, and give a bad contact to the wire, reducing the energy that reaches the plugs.

The wires themselves can also go bad and give the symptoms you're describing.

This is especially true if dielectric grease wasn't used on the terminal ends, and plug boots. Just the simple act of pulling them on and off the plugs can stress them to the failure point, and that's why the grease is a good idea. It lets them "snap" onto the plug tops, and will make future removal/service a breeze.

Many times, weak wires can be identified by running the engine with the hood up in a dark garage. You'll see little lightning bolts jumping from the wires to ground. You can also lightly spritz them with water from a spray bottle, and if the insulation is weak, the motor will stumble.

A logger would be a very handy tool to have in your inventory. It will allow you to check all the imputs the ecu "sees", and may help you to pinpoint the problem.

Again, welcome to the board. /ubbthreads/images/graemlins/smile.gif

 

[curtis]

Man you sound like an old guy and not a new guy. Sorry to hear about you dad looks like you hung around in the shop with him and he did a good job while around. As for toybreaker pay attention to him except for this


"in a dark garage. You'll see little lightning bolts jumping"

Man we got to get you off the top of that mountain and out of the cold, your not seeing ignition problems its orbs man orbs. What is that number for TAPS anyway. /ubbthreads/images/graemlins/grin.gif


TRY THE DARK TRICK HE'S MORE THAN LIKELY FOUND THE PROBLEM.

 

[Hertz]

Does it have the original intercooler piping? (rubber, nylon wrapped)

 

I want to thank everyone for their help. I never even thought about cracked IC tubing. I got finals starting tomorrow, so I won't be able to tinker with it until Saturday, but it sounds like everything should be easy to do. New plugs (with the right heat range gapped at .026-.028"), check timing, check for clean spark plug wire leads, and the IC tubes and joints.

The spark plug wires are Magnecore, so that should be good. If the actions above don't fix it, I'll look into to wires.

Anyone suspect fuel??? I believe the injectors, fuel pressure regulator, and fuel pump are stock. I don't know when the fuel filter was replaced last. I don't think fuel is the issue because of the gauge, but I'd love for someone to teach me why I'm wrong.

 

[Muskrat]

Those blinky light narrow band a/f gauges are almost worthless. I wouldn't trust it. Do the above, if that doesn't work hook a fuel pressure gauge up and see what it reads. +1 on the logger. It's an invaluable tool. I think someone's selling a set-up for $55 right now.

Welcome to the board, and yeah, definately the best "newbie" post I've seen in a while.