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Nick Mann
31-01-2004, 10:22 PM
Found a private test track today.... Car pulled fine until about 5500-6000 rpm in 4th, when it kangarood rather dramatically. :stunned: Has anyone had this? I tried a further few times, and the same happens. If I ease off, it is fine and if I force it into 5th it is fine. The car pulls very well to the red line in 1st and 2nd, and well enough in 3rd.

Where do I start looking for problems??

:huh:

haydar
01-02-2004, 12:01 AM
It doesn't sound like a misfire because the car would misfire under load even in the first three gears too. If the 'misfire' is quite violent then it could be overboost???

Does your car have a boost controller? If so try setting the boost pressure lower and see if you still get the problem.

Question: Have you replaced (a) tyre(s) recently? Are all the tyres on your car the same type with the same about of tread? The reason for the question is that it could be your traction control that is causing the problem; if there is a drastic difference between the tyres. At lower speeds the difference in the tyres would not be great but at higher speeds the difference becomes more pronounced and hence confuses the car's computer. This is not as crazy as you might think and my brothers BMW suffered from exactly this problem and it was rectified by matching the tyres.

Hope this helps.

Kieran
01-02-2004, 12:19 AM
Hmmmm.... This isn't the 4th gear/5th gear torque convertor lockup problem is it?

You see, on the GLS (ok, it's missing a cog compared to yours, but bear with me), when you go full throttle in first or second and keep full GLS power engaged through 3rd, the mechanical lock will operate before it changes into 4th - *IF* it's in Auto mode. In Tip mode, it doesn't (I imagine this is to assist a fast and smooth gearchange, because it can't predict when the signal to shift will come). I'm wondering if when your box is in auto mode, it's engaging the lock-up mecanism in 4th, then when the box goes into 5th, it's shunting a bit?

Big Ian
01-02-2004, 12:25 AM
is your fuel pump OK ?or even the filter,also my orion turbo i had did something like your's and it was the coil,it was OK till it got a bit of stick and would missfire?

haydar
01-02-2004, 01:24 AM
Hmmmm.... This isn't the 4th gear/5th gear torque convertor lockup problem is it?

You see, on the GLS (ok, it's missing a cog compared to yours, but bear with me), when you go full throttle in first or second and keep full GLS power engaged through 3rd, the mechanical lock will operate before it changes into 4th - *IF* it's in Auto mode. In Tip mode, it doesn't (I imagine this is to assist a fast and smooth gearchange, because it can't predict when the signal to shift will come). I'm wondering if when your box is in auto mode, it's engaging the lock-up mecanism in 4th, then when the box goes into 5th, it's shunting a bit?

It shouldn't be the torque convertor problem since if you are giving the car a bit of stick it shouldn't be trying to look-up. Though if it's malfunctioning it might be possible. This theory is consistant with the fact that gears 1,2 and 3 don't have lockup.

Nick Mann
01-02-2004, 01:24 PM
Only change since I bought it in october is a back box courtesy of Derek. I have a de-cat pipe but haven't put it on yet. The tyres were almost new when I bought the car, they are the same all round (BF Goodrich) with near enought the same amount of tread.

Next time I can use the private test track, I will try in tiptronic to see what happens.

The car has only done 24,000 and has full MSH, so surely the fuel system should be okay? I could try to locate the filter, I suppose. If it were the pump I think I would have the problem at those revs in any gear.

The ignition is all electronic, isn't it? So what traditional parts of the ignition do I have?

Thanks for all your suggestions so far - has given me a couple of things to test.

Freddy
07-02-2004, 07:10 AM
I wonder if the fuel cut defender is doing its job?

Nick Mann
07-02-2004, 05:51 PM
Don't understand that comment... Sorry.

Is that part of the speed limiter device that jap cars have? As mine is a UK supplied, I don't think it should have that.

Only other thing I have thought of since is that 5 miles later I put 55 litres of fuel in. Maybe the fuel level was getting low and the pickup couldn't cope? A cavitating effect from the pump maybe? It was kangarooing the way only a learner driver in first gear can do, but in fourth and at around 120 mph!

I have not had the opportunity to test since. It seems fine on the Queens highway at approriate speeds!

enigma
07-02-2004, 06:06 PM
Nick, you will get fuel cut if the mass of air flowing in to your engine exceeds a preset limit. This manifests itself as a lurch of the car as all of the fuel injectors are turned off and all power is lost......power then comes back and you have a little lurch!

This is generally only a problem with cold dense air and a heavy right foot! You recent increased exhaust capability may have just allowed the car to flow a little better.

Nick Mann
07-02-2004, 06:10 PM
Too much air? So I need to talk the car into inserting more fuel? How do I do that?

enigma
07-02-2004, 06:23 PM
Too much air? So I need to talk the car into inserting more fuel? How do I do that?

Well........not quite! You need to get the engine controller to believe that there is less than its limit of air going in!

You can do that by a full engine remap, or by adjusting the MAF signal to fool the controller. I have done the latter and just hope the O2 sensor sorts the shortfall in fuel out! :)

EXACTLY how did the misfire feel?

Nick Mann
07-02-2004, 06:40 PM
It felt like going from full throttle to no throttle several times a second. It did the cycle three times before I took my foot off the throttle! I slowed down a bit, tried gentle throttle, no probs. Put my foot back down and it happened again at near enough the same speed and revs.

enigma
07-02-2004, 06:52 PM
Hmmmm......that sounds more like the rev limiter!!!! When I have experienced fuel cut it normally lasts a little longer, maybe once a second is more normal.

Keep an eye on it, and if it happens again make a note of the RPM, Speed, Gear, and outside temperature!

I get it most in 3rd 4th and 5th accelerating from low revs (2000) with the foot on the floor. It kicks in betweek 3 and 4000rpm. My HKS FCD has almost eliminated it though :) Accelerating hard through the gears is not a problem, just booting it from a moderate pace!

Nick Mann
07-02-2004, 07:05 PM
Will do. It hasn't happened at any other speed in any other gear so far. The only time it has happened was last weekend. I shall put it down to a mixture of conditions and not worry until it happens again, at which point I will write down every parameter I can think of!!

haydar
07-02-2004, 07:43 PM
Nick, you will get fuel cut if the mass of air flowing in to your engine exceeds a preset limit. This manifests itself as a lurch of the car as all of the fuel injectors are turned off and all power is lost......power then comes back and you have a little lurch!

This is generally only a problem with cold dense air and a heavy right foot! You recent increased exhaust capability may have just allowed the car to flow a little better.

Dave

Would you expect cut-off to happen that high in the rev range and at the speed? Whenever I've had this it's been lower down the rev range?

zedy1
07-02-2004, 10:06 PM
i think dave right nick cus ive been having this problem when the temp outside is cold. happened again today s ive adjusted the boost controller to 0.5 bar with the solonoid duty @50%. is that all right to do dave?

enigma
07-02-2004, 10:21 PM
I have had it anywhere between 2000 and about 4500 rpm.....after this the turbos cant force enough air in!! :D

Freddy
08-02-2004, 01:30 AM
Nick, have you fitted a boost controller (adjusts turbo boost) If you have then you must also fit a fuel cut defender. This stops fuel cut out when making larger amounts of boost than standard. I ask because what your describing sounds like a big lack of fuel.

Nick Mann
08-02-2004, 12:25 PM
It felt like lack of fuel/lack of ignition in sudden jolts. No mods to my car except a fujibutso back box.

It was a cold windy day at high speed, so thinking about what BDA has said, there could be a problem wiht too much air going in and the ECU cutting fuel to stop the mixture leaning out.

Not happened since. Will post again if it does. Thanks all for your help and info.

pjjohnson
09-02-2004, 12:02 PM
Have you discounted the speed limiter theory ?

I thought mine was delimited when I bought it, but wouldn't go above about an indicated 120mph, it turned out it still had the limiter on. They way you've described the problem is like I remember the speed limiter cutting in.

Nick Mann
09-02-2004, 02:19 PM
Definiteley not the speed limiter. AFAIK I haven't got one, but in any case, I have seen the red line in 4th gear before. (About 130 mph if I remember correctly.) This time I was 1000 rpm short of that.