Slight misfire

[evo3john]

Hi all

I'm after some advice on where to go next. My car has a slight misfire at 6.5k, this happens consistently, and at all throttle percentages 1% - 100%.

I have changed the crank/cam sensor thinking that was the fault but had no change

I have also changed from spark leads to cop kit thinking the spark may be getting blown out

injector have been checked for flow rates twice

The car is running a haltech, which I have tried with another and still the mis remains.

When the mis occurs the afr don't change, we have logged the fuel map and its stays perfect to where is tuned. Air temp is good.

I feel like I have checked everything that could cause the mis but can't find anything wrong.

Does anyone have anymore ideas to try?

 

[Dave_GSR1.8]

You don't mention it, have you done anything about the spark plugs ?

 

[evo3john]

Yep tried new plugs, check gaps on both sets

 

[Dave_GSR1.8]

Did you gap them down ? Most people suggest 0.7mm, even less. Also what plugs have you got? As this thread

http://www.4gtuner.com/topic/4035-the-spark-plug-thread/page-2

says just use NGK BKR6E at 0.8mm or as you up the boost go to some BKR7ES gapped to 0.6mm (as per EVL20T's advice in post 28 of that thread).

I had a bad miss due to bad (expensive) plugs, went to some BKR6E's and problems went away.

 

[evo3john]

Yer plugs were gapped, can't remember the exact gap but was lower then 0.8

I'm using BPK8ES. I've got a new set of 6's that I may try tomorrow morning on the way to work.

 

[evo-gsr]

I would be swapping them for the BKR as mentioned above

 

[blackvr]

What is the rev limiter set at ? It is highly unlikely you will get an electrical misfire at very low throttle settings due to hardly any load on the engine. Check the rev limiter settings. If it is at 700o rpm, you may just be approaching the start of the soft rev limiting ??

 

[evo3john]

Limit is set at 8500, even full throttle happens at the same rpm

 

[ENGINR]

Check to see if you're getting temporary fuel starvation. Mine would behave like it was missing but it was the fuel sloshing away from the pickup in the tank and temporarily starving the surge pot.

 

[MDK87]

You would see that on the AFR though, and he says it is in line with the maps.

I hate these slight misfire problems.
The fact that it does it consistently at 6.5k under any load whilst maintaining AFR makes it a tricky one.
I hope you find the cause, be sure to let us know what it is.

Helped a friend with an RVR with a dirty inductive CAS pickup last night, causing what would feel like soft rev limit. Cleaned it and it was ok.

 

[evo-gsr]

Change the plugs to the ones mentioned above.
If not..try changing the ignitor?

 

[BYBY5L]

Engines earth straps all good?

 

[evo3john]

Ok sorry I taken a little while to respond.
I've checked both the 6's and 7's and the plugs made no difference.

I'm also not running the factor igniter anymore as I have a cop kit that uses the individual igniters on the coils.

The earth that is on there currently is good. I have some extra cable that I'll add another earth and see how it goes.

Check the voltage at idle which sits at a constant 14.5.

 

[4piknup]

Its very interesting.. being that afr dont change, i think a plug miss would make afr change (leaner because of extra air in exhaust). Also that its independant of throttle position suggests its not spark.
you need to find out if its one cylinder or varying. I assume you are saying it will miss in driveway with no load?

You said in post 1 that you logged fuel map and its perfect. Is that- you logged fuel pressure or logged fuel and map.
ie, does the manifold pressure/vacuum flutter at miss?
And just verifying, it will miss at cruise ie driving at 6500 in 3rd showing vacuum on map?

As you have seperate ignitors, can you run it up to the miss and rotate the cylinders off to try to find what cylinder is missing?

I take it the timing is solid at the miss- thinking maybe a vibration is phantom knock and its pulling timing.
maybe vibration shaking bov or wg open (this prolly shows in map log tho)

Maybe move the intake cam, maybe its some wierd pulsing of the intake air like harmonics but in the intake charge.

 

[4piknup]

Are you sd?

 

[evo3john]

What do you mean by sd?

 

[4piknup]

Do you run a maf?
I dont think so on haltech. Just a map and air temp. Sd-speed density.

If you had a maf, it measures air volume directly. So wondering if anything in the airflow log at the miss area.

 

[BYBY5L]

What cams and springs are ya running? Possible valve float?? Or even a burnt valve

 

[khubner1]

Ahh now the details come out using toyota coils? I suspect ittl be a coil itself i have a pile of dead denso coils

 

[evo-gsr]

Ok sorry I taken a little while to respond.
I've checked both the 6's and 7's and the plugs made no difference.
I'm also not running the factor igniter anymore as I have a cop kit that uses the individual igniters on the coils.
The earth that is on there currently is good. I have some extra cable that I'll add another earth and see how it goes.
Check the voltage at idle which sits at a constant 14.5.

The plugs need to be BKR not BPK