Any Direct Injected 300gt / 250gt V35's?

[PN-Mad]

Whatever is happening, its obviously dumping too much fuel into the system. So, check your plugs- is one black and the rest golden? Or are all equally black?

As deep dish said- stuck injector could be the issue. Or it may be one of the temp sensors to the ECU has broken, and its sending coolant temp of -10 degrees or something to the ECU all the time, rather than the actual coolant temp.

Is the battery nice and new, and charging? this can cause some funny electronic issues.

My suggestion would be to take it to a mechanic that can log the ECU data, and look at it to determine the over fuelling fault.

[beercat]

What I"d really love is a service manual specifically for the 250 GT; engine/electrical/chassis.

The G35 ones aren't really helpful as even the ignition coil wiring colors are different.

[projects]

Hi guys, sorry to did up an old thread. I've recently purchased a VQ25dd Stagea, and having to do a few things to it i've got a warm start problem and sometimes it takes forever to start, but fires fine when cold. couple guys said to do the intake clean and egr blanking.

So i followed whats in here, ( egr bolts a terrible to get to ) and the intake was caked up along with the TB. I'm going to steam blast the covers and acid tank what i can and de-grease the rest. Couple questions i had,

With the EGR valve i want to remove it completely and run plates over the plenum and up pipe? what do i do with the egr valve plug, leave it empty?

With the resistor to wire in, i understand it needs to go into the grey 2 wire temp sensor ? can the sensor not be used as standard, why does a resistor need to be wired in?

and all the hoses that run between the egr, plenum and TB what do people do with them?

Thanks guys.

[scotty nm35]

Just blank it off with a plate between the egr and plenum, if you remove the pipe you would have to drop the exhaust manifold and weld/bung up the hole, you won't do that once you see how hard the manifold is to drop...

If you remove the EGR you would need to drop a resistor over the plug so the ECU doesn't throw a fault code. Same with the temp sensor.

You may have to remove the lower plenum and lower runners as both will have been heavily gummed up with carbon. There are butterfly valves in the lower runners to promote swirl in the chamber, make sure they are clean too. It sounds like your throttle is gummed up hence the warm start issue.

[projects]

Thanks for the prompt reply. i was going to bolt a plate over the up pipe so i didnt have to remove the pipe from the manifold, reason for removing the egr valve was because those 2 bolts that go into the plenum were hard enough to get off i didnt want to have to do them back up.

if i was to run just a plate and keep everything plugged in like factory would the ecu through out a fault code, or just open the valve and nothing happen further?

I noticed the little butterflies in the runners, wondered what they were there for. i'm going to remove them now and clean them off the motor. Yes everything was caked up in there. once im done i'll run some cleaner through the intake to try clean the remainder ports to the valves.

[scotty nm35]

I would try and clean as much as you can before you bolt the lower section back on, you really don't want all that crap in the combustion chamber. Blow it out with an airgun perhaps. Just remember one or two of the valves may be open...

It will eventually throw a code anyway I think, as the temp sensor won't be seeing hot gas go past. Perhaps you can fix this with a resistor, not sure as I have never had my DD running.

[projects]

so with the covers i steam blasted the top cover cause of the temp switch and other crap on it i didnt want to drop it in the tank over night. but the bottom cover got a tanking and ended up like this after the carbon build up.

Now i just need to remove the lower runners and steam clean them, and clean the ports out. also degrease the TB. then put it back together with a couple blanking plates and resistor.

Top cover

Bottom

[projects]

Does anyone know the wattage of the 10ohm resistor? i dont want it to small that it overheats and fry's itself, and i dont want it to large to draw to much from the ecu and damage that.

[Spong]

Does anyone know the wattage of the 10ohm resistor? i dont want it to small that it overheats and fry's itself, and i dont want it to large to draw to much from the ecu and damage that.

As an electronics technician, I can say that fitting a higher wattage resistor shouldn't cause any harm, it won't pass any more current than a low wattage one. Assuming a maximum of 13.8V on one side and earth at the other, the power would only be 1.90Watts. Chances are there will be less than this in practice. Ohms law takes care of that. As an owner of an M35 direct injected VQ25DD, I'd be very interested in seeing pictures showing the connection points of the plugs/sockets involved in this mod.

Edited April 26, 2013 by Spong

[projects]

Thanks for that. Ended up on a maxima forum this afternoon. And found they've been doing the same but using 68k ohm .25w. Closes I could find in a hurry was a 44kohm 5w. So thats wired up and hope I dont get any faults back.

[Nicko_2010]

1. 10 ohm resistor bridged temp plug of EGR cause ECU wont open valve and no errors

2. between the EGR and plenum blank it off with a plate

3. you can also cut the pipe that comes down to exhaust manifold and bend the bottom end down ( you can unscrew the pipe =EGR > exhaust= cos it has a thread on the bottom) in order to block any fumes coming up from the engine.

4. take off two rubber pipes that warm up EGR valve with coolant and attach together by any cooper pipe

Hope it will help

Edited April 26, 2013 by Nicko_2010

[scotty nm35]

Great, so it is possible with a simple resistor to trick the ecu.

Personally I would be leaving the pipe intact and simply blocking it off, just in case you need to go back. It only takes one cop to dob you in to the epa... Make sure everything looks as per stock.

[Nicko_2010]

With the pipe attached you will have to take off egr every time in order to open plenum intake. My setup allows me to open intake as quick as posible

[projects]

So yesterday I got it back running, fired up fine. Idled a little high but was a cold start. Then as it warmed up I still had warm start issues a little to the point were it wouldnt fire at all. Once I got it going the idle was around 1100. Today I'll try reset the ecu, re learn throttle pedal and idle. Hopefully it starts for the idle learning once warm.

Also still have a oil leak on the left hand side I need to source.

[projects]

ok so done the ecu clear. then done the pedal check, and also the Throtle check, then i done the idle re learn. and its now sitting at 650-700 all the time. very happy about that. but i still have the warm start problem where i think it may be fuel related. so where's the fuel filter on these? might change that to be sure and then work to injectors and hopefully not pump. also might have to do the plugs while im in there. is there any copper altenatives or do i need to fork out for the expensive ones?

[PN-Mad]

Fuel filter is wrapped around the fuel pump, located under the passenger side rear seat. Might need to go to Nissan to get a correct one, cause I don't know if DD motors run a different setup.

Iridiums are cheaper from the us. But take a while to post, if your using cheap shipping.

[scotty nm35]

If it's a DD, you are supposed to run special plugs, not sure what the difference is but you could perhaps be able to run the LFR5's with no issues. If I get time I will compare the plugs for you.

The only copper plugs I have seen for VQ's were the same price as iridiums anyway. You should be able to source a set of LFR's for around $60-$80

[0li3te]

Today Dad and I opened up my 300gt. It has 46,000 kms and there wasn't that much crud. we only took off the top half of the plenum and cleaned it out, it didn't seem worth going any deeper. There was a small amount on the throttle and we sprayed carby cleaner on it and it got rid of most of it.

It all went back together no worries, it idles fine, and started first time.

And it has reassured me that the kms are genuine.

[scotty nm35]

This jogged my memory to post up these pics of the VQ25det plug, DD plug and whatever plug the last mech installed into the 25DD I have here.

[Roachy94]

Cheers to Sam for supplying the ever reliable vq30dd for comparison