Cough While Driving At Low Rpm

[Stixbnr32]

Hello,

Will give you guys some background.

R32 GTR - built engine.

I have had this cough nothing major when cruising around the city or on the motorway at low RPM. As soon as it happens (its not even major) it is fine and you can accelerate fine.

It does happen when you start to accelerate.

Have new platinum spark plugs

new spitfire coil packs (did this after i did those before it was built)

HKS F-con pro (latest version)

HKS EBC

Forged blah blah blah.

Now I was thinking it could be the wiring harness to the coils but not 100%.

Like is said there is no miss/cough anywhere accept when you start to accelerate from low rpm and its not even major but it is there.

[zebra]

might be a tad lean or even a tad rich

need more info

is the same load point every time?

[Stixbnr32]

Yeah it is at the same load point. So you could be in 4th at 2k rpm. just put your foot down it cough/miss.

as soon as you go past it she's mint and its so brief that it just more annoying than anything.

It has Tomei Poncams in it as well as cam gears.

it still happened before the engine was built and before i had new turbos (-5's).

Did it happen before i had the computer? I couldn't tell you have had it for awhile now.

[tridentt150v]

My fuel pump would 'sneeze' more than cough, but thats what it ended up being. Not saying yours is but keep it in mind.

[Stixbnr32]

New Nismo Race pump with FPR.

[KiwiRS4T]

Ring your tuner and ask him for any ideas.

[Badgaz]

i believe this sounds like the power fc cough that has been talked about here before...wonder if its similar but with the HKS.... anyway...one of the solutions that worked for some was to fix up and make better all the grounding points in the ingnition harness and ignitor.

[Stixbnr32]

Yeah called the tuner he does think it could the ignition harness and ignitor. Ah well might have to replace after all it is 25 years old

Other than that the car is running perfect and goes hard.

Thanks for the help much appreciated.

Edited December 18, 2014 by Stixbnr32

[scotty nm35]

Sounds like a lean pop as you accelerate, could be a simple tuning issue? The Fcon can be a difficult ecu to tune if you aren't familiar with it...

[Hadouken]

I don't see how the ignition harness is letting you down at low rpm. I would understand at high rpm.

Get him to check the tune

[tridentt150v]

New Nismo Race pump with FPR.

Mine was a new 275 with new FPR! Started out Ok then over a few months started as a very quite and gentle 'choo' type sneeze then slowly got louder. Pump eventually went very noisy so I replaced it and problem solved.

[Stixbnr32]

Interesting - the tuner that did it is a native Japanese (used to work for Nismo afaik) and he is HKS certified.

He tunes big power GTR's here in NZ/Aussie (when called) and other big power cars.

It just had a retune after the rebuild and has the same little cough.

I will pop him another call get him to check.

[scotty nm35]

$130us for a WB these days, shipped. Should be pretty easy to see if there is a lean spot on acceleration with one of them mounted in the exhaust. He might not see it as well on the tailpipe wideband.

[Badgaz]

That's just for the sensor, what about the data logger? Its unlikely a lean issue will cause a cough on acceleration.

[scotty nm35]

Firstly, yes the WB comes shipped with sensor, box and display for $130us. No need to data log.

Secondly, yes, a lean throttle enrichment will cause those exact symptoms.

[Badgaz]

Got a link for it? Might buy one. Have you actually had a lean throttle enrichment do that?

[scotty nm35]

I have had all kinds of tuning 'faults', that one included. My evo does it on cold start atm, I need to fatten up the cold start map but I will just be wasting fuel I guess.

Spools the turbo extremely well though. The joys of not having to worry about knock.

WB is the brand. http://www.wide-band.com/widebandproducts. Looks like the price went up $15 since I bought mine a couple of months ago. I got the tiny display to hide behind the clock.

[Badgaz]

I get what i think is the same cough in the gtr but haven't really tried anything to fix it yet... Think we had to lean the throttle enrichment a bit might check that as well. It's quite a violent cough sometimes though... Like early rev cut. Cheers for the links.

[zebra]

I have had all kinds of tuning 'faults', that one included. My evo does it on cold start atm, I need to fatten up the cold start map but I will just be wasting fuel I guess.

Spools the turbo extremely well though. The joys of not having to worry about knock.

WB is the brand. http://www.wide-band.com/widebandproducts. Looks like the price went up $15 since I bought mine a couple of months ago. I got the tiny display to hide behind the clock.

My E85 cold start makes the 25 brap like a PP 13B for a few seconds.

Decided I'd leave it as is.

But yeah, it the car pops or coughs as soon as you press the throttle, its the throttle pump/accel enrichment