Flat Spots In Rb25De Neo

[shaunconnors34]

Okay so Ive got my 1999 r34 rb25de neo non turbo and lately I've been having some problems with taking off slowly at the lights without the car wanting to stall and also when sitting at a constant speed (cruising) it'll have a flat spot every now and then. Since having the problem I have done...

The iac valve has been cleaned

Maf cleaned

New coilpacks

New spark plugs

New fuel pressure regulator

Injectors cleaned

Ran awesome for about 2 weeks and now having the same problem. Searched many forums and websites but cant seem to get any decent information. Any ideas would be great full thanks.

[niZmO_Man]

Changed fuel filter?

[shaunconnors34]

Fuel filter was done only around 5000kms ago. I thought it was that when it first started to happen but because it wasnt throughout the rev range only cruising. Didnt think it made a difference

[shaunconnors34]

Well didnt make a difference after changing it at all. Which led me to changing the coilpacks etc.

[Mr Roux]

I've got the same problem in my r32 rb25de, happens when it's cold but when it warms up abit it's not there/ hardly noticeable. I'm leading towards an over fueling issue

Wonder if anybody else has had this problem

[shaunconnors34]

Ahh okay thats interesting I rarely get it when the car is cold but when it heats up it does it a lot more. I purchased a genuine sard fuel pressure regulator yesterday and still no luck.

[NeilC]

Throttle Body? Varnish and sludge build up can cause odd idling problems as well.

[shaunconnors34]

So I found out yesterday that the wrong plugs have been fitted to my car. Bkr5eix were fitted and the new mechanic said he is going to fit the iriway-7 (ngk) so hopefully this fixes my problem. Only thing is, is that the problem was happening before the plugs were changed but it will get a dyno done tuesday and will post the results. I thought about the throttle body but it was cleaned when the aicv was cleaned which sucks. Thanks for the feedback

[mad082]

The bkr plugs should be fine for your car. If the 7 on the end of the ones you are fitting refers to the heat range then they are too cold for your engine.

There isn't really a right and wrong plug for your car so to speak. There are ones that fit and ones that don't. And then some that will perform better than others.

[shaunconnors34]

Ahh okay fair enough makes sense. The guys down at signiture performance said that they were the wrong plugs and out of all of them they tested they seemed to work the best for the n/a's. Being that the plugs in it are designed for jap fuel or something?

[NeilC]

Correct NGK plugs for RB25DE Neo N/A are PFR5G-11 Platinum or BKR5EIX-11 Iridium. Putting the wrong plugs in will make things worse. The 5 in both of these plugs is its heat range and shouldn't be changed unless you are running LPG.

[shaunconnors34]

Interesting, thanks for that because well I have the BKR5EIX-11 Iridium in the car at the moment, the guys said to change it to that iriway-7 which I've honestly never heard of....

[NeilC]

Shaun. Iriway-7 are NGK racing plugs. Unless you have done a lot of work on your engine I dont for the life of me see why you would need them. Also a 7 is two stages hotter in heat range something I defo wouldnt do if it were me. If your running a stock Neo engine you could try decreasing the gap on your plugs to 0.8mm and see if it makes any difference. Those Iriways wouldnt be cheap either I will bet. Also just read your first thread again and am thinking you are confusing flat spot with a miss. Flat spot is when you accelerate away either from rest or through the gears and the engine dies then takes off. A miss when at a constant speed is as if you momentarily lose power sorta like if someone turned your ignition off then on really quick.

[NeilC]

BTW the Iriways retail at about 38.00 or so each. They use them in the turbo versions so I guess they cant hurt. I would be checking every vacuum hose on your engine as well. It only takes a small split to upset everything.

[shaunconnors34]

Yeah car is still pretty basic at the moment. Well been a n/a anyway. I get what you mean I was just saying what I was told thats all haha. But I will take that on board and I dont really want to be wasting my money on stuff I dont need. And yeah with the plugs they were a tad too cheap especially for a n/a. From what you hsve said there I have both a flat spot snd a miss. Taking off from a stand still the car will want to die before it takes off. And at a constant speed the car will feel like its starving for fuel or something causing it to lose power. Im just running out of money very quickly on mechanics saying different things that are wrong with the car and it not working if you get what I mean haha:-/ but thanks for the feedback Neil its good talking to a real person that doesn't treat you like a 5 year old haha:-)

[NeilC]

Hmmm looking through what you have replaced leans me towards fuel being the problem and not overfuelling but rather the opposite. Have you had the fuel pressure itself checked? How much mileage on the car? I would have your fuel pump checked if I were you. Also your O2 sender. Is it using more fuel than before? Also what fuel are you running?

[shaunconnors34]

Not exactly checked I've had the fuel pressure set because I've got the fuel pressure regulator. But I haven't had anyone actually check the fuel pressure... cars done 107000kms roughly and speaking yo a guy today said my cat could be stuffed or something similar. No actually its using probably the same amount of fuel as before and I only use 98 from bp or caltex. Haven't gone yo 7/11 or shell because I've had friends have major problems using their fuel.

[niZmO_Man]

BCPR6ES (spark plugs) is what you want to run, about $4 each.

Have you tried another AFM? Solder fix might fix the issue.

[NeilC]

@ Ravi those are the standard version of the platinum and iridium plugs. They would be fine except that they dont last as long. Main reason for using the others I reckon is because its such a bitch to change the plugs on a neo engine. Magna V6 engines have platinum plugs on the rear bank for the same reason . You have to dismantle half the engine just to change them.

[mad082]

Yeah the magna v6 requires the plenum to be removed to get to the rear bank (been there, done that).

Copper plugs still last pretty well. In the long run they can actually work out more cost effective than irridium or platinum plugs. From memory I got about 50,000kms out of the ones in my Commodore, and only replaced them because I was chasing a misfire (that new plugs didn't fix)