missfire when boost tunrd up?

[doggydowg]

Hiya guys

Im due to take my car to get rolling roaded 2m and set up for one bar i have temporarily fitted a bleed valve to get it up to just under a bar.

Thing is in 2nd gear if i plant foot at 3k when it gets to 5-6 it slightly misfires, i have recently fitted a walbro fuel pump so fueling shouldnt be an issue it pulls strong at standard boost.

Is it still worth me doing a 120mile round trip 2m to go to rollers when this is happening?

Any sugestions as to what could be causing the stutter?

thanks in advance Paul.

 

[marcymarc]

Check all plugs before anything, bet one is frazled.

 

[fletch]

what he said^^^^

sounds like a plug to me:-D

 

[doggydowg]

ive just tried point 8 of a bar and same thing going to try standard boost in a bit and if it still happens i guess the extra power must have fookd plugs or leads

what plugs and grade should i buy for it then for a bar of boost its a pulsar not a sunny so jap spec if that changes anything i know the timing is advanced more on jap.

what sort of price are we talking for plugs?

thanks Paul.

 

[doggydowg]

found these plugs BKR8EIX for £30 so il get some of them as im probably still on standard,is 0.8mm of a gap ok for a bar recvomendations please>? what leads do i go for at a bar or will standard part co ones be up to do the job?

thanks

 

[ram5ay]

Like marcymarc said, check your plugs, if you have run lean (an uprated pump is no guarantee that you will be fuelling ok) and melted something like a plug tip, you could be doing more damage by continuing to run it.

If all is ok, take it to the rolling road on std boost and ask them to set it up at a bar and check fuelling for you, poss gap your plugs if need be. It shouldn't cost you alot extra and is worth the peace of mind over melting it on the way there in the hope of a better power figure.

found these plugs BKR8EIX

8's are a bit overkill for a bar, stick to the standard PFR7B or get BKR7EIX if you want iridium, NGK's are good tho, better than Denso / HKS IMO.

;-)

 

[doggydowg]

ive turned it back down to standard boost and it pulls like a train again no hesitiation
at all, il buy some new plugs on the way to rollers and if they say thats the problem i can fit them or if not just take it back.

if id ran lean and melted a plug tip wouldnt it still be misfiring now ive turned it back to standard boost?

thanks for replys;_)

 

[Fast Guy]

Have you tried closing the plug gap up abit? Allegedly the spark can blow out.

 

[doggydowg]

i have'nt taken the plugs out yet going to get up early 2m to checkamd buy a feeler gauge i suspect they are std plugs in there.

 

[antgtir]

Do a fault code check to make sure your not picking up any det, if you are the ecu may be retarding the ignition and putting you into a temporary safe mode.

Check all ignition parts before you map it, you want to ensure your firing as best as possible:

Plugs
Leads
Distributor Cap
Rotor Arm
Check Resistence Across Coil Pack

If no joy try these:

Change Fuel Filter
Check Fuel Pressure
Check Earth on MAF
Check Fuel Pump Earth

Just as a start:lol:

Good luck,

Ant.

 

[youngsyp]

8's are a bit overkill for a bar

Since when ?
Afaik, it has always been advisable to go to a cooler plug, when raising the peak boost levels ?! The same goes for all the things Ant mentions above.

To the OP: If you set the bleed valve to just under 1 bar, why didn't you set it to 1 bar ?! It's not a magical boost level. Any increase in peak boost level will require extra fuelling which, up to sensible levels, the stock ecu can cope with.
Unless you have some form of fuel management fitted, all the dyno place will do is retard the base timing a degree or two, if there's knocking detected. If the ignition and fuel system are in good condition, and you only use the best fuel available, the GTiR will do 1 bar all day long.

If you're getting a missfire now, there's no point going all that way to have them tell you the same thing and, if they're any good, not raise your boost level any further.
Of course, they could probably diagnose the issue but, that will cost money, not only for labour but, for any parts which, will be priced at their rate.

As above, first change your fuel filter, then re-gap your plugs to 0.7mm (change them if you don't know how old they are). Then check the dizzy cap and rotor arm, again changing them if you don't know how old they are. Whilst you're at it, give the leads a clean up.

Paul

 

[ram5ay]

Since when ?

Ok, as I said this is just my personal opinion.
Through experience I have found that the std plug heat grade (7 if ngk) copes well on the GTIR (amongst others) at this, and in many instances higher levels of tune / boost. Why fit a colder plug when it is not necessary, and risk the possibility of cold fouling and starting issues etc (depending on use). Colder plugs have disadvantages as well as advantages.

Why go to the expence of replacing plugs and a list of other parts, without starting with the basics, I would still pull out the plugs, check all is ok, and if need be gap the std ones to cope with the higher boost.

Just my tuppence worth, take it or leave it.

;-)

 

[doggydowg]

quick update

i took out plugs they are hks and when i looked closer said denso... i done a search on hear and aparently these are good enough for the boost i plan on running 1 bar.

i have turnd the boost back to std and it runs fine.

evan at 0.1 of an incrament of boost ie 0-8 from 0.7 it has the hestitation at 5k strange.

i only planned on taking the car to rollers purely for them to check the car wasnt underfueling i was going to take it to surrey rolling road, but untill i have replaced all bits or solved problem im not going to bother.

I will replace fuel filter and probably just leave it alone as i cant realy be botherd replacing aload of igntion parts on the offchance i mite cure a problem which is only there when i start upping the boost above std.

if anyone is local to me who could do a fault check on a data cable please give me a shout as this may reaveel the reel problem;_)

thanks for everyones input Paul.

 

[Jonesy]

Do a search you can do a faut code check, by bridging terminals out in the fuse box.

 

[treemonkey]

I had almost the exact same symptoms with mine. Turned out I had been gradually blowing the ringlands out of the number 4 piston. Ended up running on three pistons and getting seriously embarrassed by a boyed up Saxo. I would suggest a compression test.

 

[doggydowg]

i know about the check u can do with bridign wires where number of flashing lites indicates problem sounds a bit hit and miss to me.

dont say things like that "Turned out I had been gradually blowing the ringlands out of the number 4 piston. Ended up running on three pistons and getting seriously embarrassed by a boyed up Saxo"

i just tried gradualy upping the boost and it now seems to be fine have managed to up it to 0.9 of a bar and it now seems fine??? how strange.

im going to remove bleed valve and re plumb it all up how it should be and see about running a bar after ive replaced fuel filter and done a fault code check.

 

[antgtir]

Get yourself an electronic boost controller and set that up instead, im personally not a fan of the bleed valve option, just my opinion though.

Have you changed your fuel pump? You may not be getting the feed required if not. Check your fuel pump earth to while your there, you may not be getting the full potential from the pump you have got.

Ant.

 

[Mr GTiR]

Have you changed your fuel pump? You may not be getting the feed required if not. Check your fuel pump earth to while your there, you may not be getting the full potential from the pump you have got.

Read his very first post.....

i have recently fitted a walbro fuel pump so fueling shouldnt be an issue it pulls strong at standard boost.

 

[antgtir]

Ok, check the earth connection, its a possibility.

Ant.

 

[doggydowg]

ok mate ta im going to get a fuel filter today from nissan;_)