Jump to content
SAU Community

Recommended Posts

got a really weird problem with my r33 rb25det

mods are

cooler

exhaust

walbro pump

now im using a blitz ebc and ive got stock boost setting 7psi and high which is 10psi

the plugs are gapped at .8mm copper ngk plugs and ive tapped up the coils

but the car will only miss fire either at nite(cold air) or early mornings(cold air) on way 2 work 8am.

i drove it around for about an hour today around 1-2pm and it would rev fine on 10psi all the way to 7000rpm, driving home from mates place before 8pm colder air, it would just miss fire from 4500rpm onwards wether on high/low boost

would any of you guys have any idea wot this could be? maybe AFM?

thanx

Justin

Edited by l0WRB
Link to comment
https://www.sau.com.au/forums/topic/127057-rb25det-miss-fire/
Share on other sites

it might be getting higher boost (creep) due to the cold weather and the boost cut from the stock ecu is kicking in....

hey mate, nah ive felt boost cut before and it nearly thru me thru the windscreen LOL

the boost barely spikes above 10psi ive got it set to it creeps up and just gets to 10psi

so im buggered as to wot it could be ?

There is no Map sensor.

Does it still happen if your on the low bost setting?

Sounds like the common rich and retard(search).

Well i dont know about your car but mine has a map sensor, it used to break down as it would only read up to 19psi and my car would sometimes hit 22psi when it was cold, it would miss and break down over 5000 revs. My mechanic reduced the boost and it hasnt missed since then.

There is no Map sensor.

Does it still happen if your on the low bost setting?

Sounds like the common rich and retard(search).

i can turn the ebc down as low as it can go 7psi stock and it still splutters and farts up thru top end. wont rev out cleanly

For justin- you are probably on the edge of the r & r mapping and the cold denser air is tipping you over the edge. Combined with old coils you begin to get the miss as the mixtrues are richer. Check the heat range plugs you are running too. You want a 6.

I'd put it on a dyno before doing anything though and see what your arf's are doing. It will eliminate afm's/fuel pumps/fuel filters/injectors from the list of possibles for 60 bucks. Then start looking at spark.

Taso- your's is almost certainly coils, but try gapping your plugs down to .8 before commiting to a set of splitfires or similar.

how old are the plugs that you are running? if they are getting on a bit then whack a new set in. even if they are iridiums and aren't that old (10-15,000k's) they may be dead.

does it sound like its hitting the speed limiter? i had a dead coil and when you boosted up it sounded like it was hitting the speed limiter (but would keep reving).

quote name='BHDave' date='22 Jul 2006, 08:52 AM' post='2348076']

For justin- you are probably on the edge of the r & r mapping and the cold denser air is tipping you over the edge. Combined with old coils you begin to get the miss as the mixtrues are richer. Check the heat range plugs you are running too. You want a 6.

I'd put it on a dyno before doing anything though and see what your arf's are doing. It will eliminate afm's/fuel pumps/fuel filters/injectors from the list of possibles for 60 bucks. Then start looking at spark.

Taso- your's is almost certainly coils, but try gapping your plugs down to .8 before commiting to a set of splitfires or similar.

ok mate i will give my mech a call and get him to throw it on the dyno and check those possibilities out

i know the timing is set at 15degrees advanced at 650rpm as we set it about 2 weeks ago because for some reason the timing was at 0 degrees on idle : ,fuel filter was changed when the car was complied about 8 weeks ago along with oil,i also put in a new walbro 500hp pump 3 weeks ago as stock one died on me. i wish i had a mate with a powerfc to plugin and find out but he lives 4hrs away! :( im running heat range 7 plug gapped at .8

how old are the plugs that you are running? if they are getting on a bit then whack a new set in. even if they are iridiums and aren't that old (10-15,000k's) they may be dead.

does it sound like its hitting the speed limiter? i had a dead coil and when you boosted up it sounded like it was hitting the speed limiter (but would keep reving).

plugs are only about 4 weeks old, i pulled out platinums that it came over with from japan

nah its not hitting speed limiter, ive felt that before it and its a jarring motion and basically pulls ur whole car back lol

This is IMO absolutley ECU.

To back it up.

I have a Jaycar DFA - it's a air flow voltage adjuster that works like a safc.

The DFA has a switching mechanism that turns on the voltage regulation, only atfer the car has started.

I installed it and had it tuned and my car was going well, with no misfire. It had repaired colipacks and spark gapped at 0.8mm.

Anyway, one night, my car seemed sluggish at 10psi. This was at the start of winter this year. Then on cold nights, it would pop and fart and misfire etc.

After checking things out, I found that the adjustment for the DFA to kick in after the car had started was out, and not kicking in. The original afm voltage was being put though to the ECU. After recalibrating the DFA so it would kick, the car went better than ever, all problems solved.

It would seem that on cold nights, the air is denser ^whatBHDavesaid^ and your ecu dumps heaps of fuel in making the mixture rich. This will cause misfire. It's like a protection mode. Seems to happen with engines fitted with pods and intercoolers more frequently.

Now your colis might not be good enough, but I would think that if your colis are stuffed, you would get the misfire all of the time, and not just when cold.

So your solution IMO is to get an apexi Power FC Computer, or an apexi SACF2 , or build a Jaycard DFA. Then get whatever you pick tuned.

I also netted a 20kw or more gain with the DFA. If I get more money, (and I don't sell the skyline) I will be buying a Power FC from a group buy from the forum.

Chriso

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now


  • Similar Content

  • Latest Posts

    • Surely somebody has one in VIC. Have you asked at any shops?  Is this the yearly inspection or did you get a canary?
    • This is where I share pain with you, @Duncan. The move to change so many cooling system pieces to plastic is a killer! Plastic end tanks and a few plastic hose flanges on my car's fail after so little time.  Curious about the need for a bigger rad, is that just for long sessions in the summer or because the car generally needs more cooling?
    • So, that is it! It is a pretty expensive process with the ATF costing 50-100 per 5 litres, and a mechanic will probably charge plenty because they don't want to do it. Still, considering how dirty my fluid was at 120,000klm I think it would be worth doing more like every 80,000 to keep the trans happy, they are very expensive to replace. The job is not that hard if you have the specialist tools so you can save a bit of money and do it yourself!
    • OK, onto filling. So I don't really have any pics, but will describe the process as best I can. The USDM workshop manual also covers it from TM-285 onwards. First, make sure the drain plug (17mm) is snug. Not too tight yet because it is coming off again. Note it does have a copper washer that you could replace or anneal (heat up with a blow torch) to seal nicely. Remove the fill plug, which has an inhex (I think it was 6mm but didn't check). Then, screw in the fill fitting, making sure it has a suitable o-ring (mine came without but I think it is meant to be supplied). It is important that you only screw it in hand tight. I didn't get a good pic of it, but the fill plug leads to a tube about 70mm long inside the transmission. This sets the factory level for fluid in the trans (above the join line for the pan!) and will take about 3l to fill. You then need to connect your fluid pump to the fitting via a hose, and pump in whatever amount of fluid you removed (maybe 3 litres, in my case 7 litres). If you put in more than 3l, it will spill out when you remove the fitting, so do quickly and with a drain pan underneath. Once you have pumped in the required amount of clean ATF, you start the engine and run it for 3 minutes to let the fluid circulate. Don't run it longer and if possible check the fluid temp is under 40oC (Ecutek shows Auto Trans Fluid temp now, or you could use an infrared temp gun on the bottom of the pan). The manual stresses the bit about fluid temperature because it expands when hot an might result in an underfil. So from here, the factory manual says to do the "spill and fill" again, and I did. That is, put an oil pan under the drain plug and undo it with a 17mm spanner, then watch your expensive fluid fall back out again, you should get about 3 litres.  Then, put the drain plug back in, pump 3 litres back in through the fill plug with the fitting and pump, disconnect the fill fitting and replace the fill plug, start the car and run for another 3 minutes (making sure the temp is still under 40oC). The manual then asks for a 3rd "spill and fill" just like above. I also did that and so had put 13l in by now.  This time they want you to keep the engine running and run the transmission through R and D (I hope the wheels are still off the ground!) for a while, and allow the trans temp to get to 40oC, then engine off. Finally, back under the car and undo the fill plug to let the overfill drain out; it will stop running when fluid is at the top of the levelling tube. According to the factory, that is job done! Post that, I reconnected the fill fitting and pumped in an extra 0.5l. AMS says 1.5l overfill is safe, but I started with less to see how it goes, I will add another 1.0 litres later if I'm still not happy with the hot shifts.
    • OK, so regardless of whether you did Step 1 - Spill Step 2 - Trans pan removal Step 3 - TCM removal we are on to the clean and refill. First, have a good look at the oil pan. While you might see dirty oil and some carbony build up (I did), what you don't want to see is any metal particles on the magnets, or sparkles in the oil (thankfully not). Give it all a good clean, particularly the magnets, and put the new gasket on if you have one (or, just cross your fingers) Replacement of the Valve body (if you removed it) is the "reverse of assembly". Thread the electrical socket back up through the trans case, hold the valve body up and put in the bolts you removed, with the correct lengths in the correct locations Torque for the bolts in 8Nm only so I hope you have that torque wrench handy (it feels really loose). Plug the output speed sensor back in and clip the wiring into the 2 clips, replace the spring clip on the TCM socket and plug it back into the car loom. For the pan, the workshop manual states the following order: Again, the torque is 8Nm only.
×
×
  • Create New...