Missfire, popping, hesitation in low rpm R32gtr

[duz10s]

Hi Gents,

Just thought I would ask this question on here as its doing my head in, recently had the car tuned, got it back was perfect, month or so later car starts spluttering, hesitating, misfiring etc all in the low rpm/cruise, thought it was as simple as changing plugs, no

So got new plugs, gapped them the same as the tuner had them, R35 coil packs are brand new from dyno tune, month or so old.

Go for drive last night, its the same if not worse, spluttering, hesitating and popping, and one stage it nearly died, this all happens on light take-off or cruise, you can here the boost building but car isn't accelerating, if I keep my foot down once it finally climbs out of low rpm it clears up and comes good.

Look at my Haltech dash in the low rpm range afr's are like 19,20,21,22, voltage reads fine at 14

My thoughts

- maybe heat range on plugs to cold, currently are 8's?

- coil pack faulty? they are like month old thou?

- fuel pump starting to die, but then why would it be ok in higher rpm with boost?

- injectors need cleaning?

 

Given the AFR's im seeing something tells me the fuel isn't getting ignited?

Any help would be great.

[Duncan]

Very, very rich AFRs are normal when a car is misfiring because the whole cylinder of fuel gets dumped out the exhaust instead of burning.

Given you've recently had work done, the most likely is that you've got an air leak somewhere.  stick your head under the bonnet while running and listen around all of the vacuum lines for air hissing. Also check all of the intake / intercooler piping is not leaking

[duz10s]

12 minutes ago, Duncan said:

Very, very rich AFRs are normal when a car is misfiring because the whole cylinder of fuel gets dumped out the exhaust instead of burning.

Given you've recently had work done, the most likely is that you've got an air leak somewhere.  stick your head under the bonnet while running and listen around all of the vacuum lines for air hissing. Also check all of the intake / intercooler piping is not leaking

Those AFR's I have quoted are not rich they are lean

You are right thou possibly could be an air leak which I will have to double check but unlikely from what I remember when listening

[Mick]

i have similar problem, i used to only get it if i used a 91 octane fuel but not it even happens on 95, it barely happens on 98, i know that it got bad where it was doing it even on 98 until i changed the plugs and it was better but not fixed totally, the ceramics on the plugs look overheated and had brown heat marks on them, im talking about the caramic base not the tip

[duz10s]

It turned out to be that it was running to lean in the lower rpm/ off boost area of the fuel map, we are still not sure why but 5% extra added in that part of the map and problem fixed, not sure if the Haltech had a spaz out or something is a miss, fuel pump and pressure fine, injectors fine, only thing I haven't checked is fuel filter but highly unlikely.

[Mick]

im glad you sorted it out mate, i just sorted mine out as well accidently, it was cos my oil was so old, who knew that could make an engine hesitate and pop pop pop when taking off lol, i do need to get my air fuel ratio adjusted tho, but i have the old safc and i dont wana spend any money upgrading so i gota find someone that can tune a safc