runs bad when hot.

[crazymat666]

right basically when the car is started its nice and smooth on idle but as soon as it gets warm after a drive it tends to be a abit bumpy on idle and the revs drop down now and then even randomly when driving along when all this is happening is seems abit hesitant .it did this before i had my standard cat on and removing that and replacing with a decat sorted it all out for a while but its happening again.the only thing i can think of is if theres a air leak or loosing boost.but from looking at the boost gauge it isnt boosting any difference from before but every now and then if i put my foot down there is a high pitched whistle which sounds to me like air escaping when under pressure.

just havent a clue how to sort this as its making the car hard work to drive as you got to watch the revs when you stop all the time.

i thought it might be due to the car not being recirced but like ive said above the decat sorted it (for a while).

sorry for the essay but i really want to get this sorted.any help would be much appreciated .

 

[maiky-s15r]

it could be some old rubber vac lines that expand after it generates some heat ...first thing i would do is go over the car and tighten all cooler clamps ect and replace some of those old rubber vac lines

 

[S15_SAM]

Well if it's running hesitantly and hunting on idle its more than likely to be air flow meter, or less likely the idle control valve. An air leak could be the cause too tho so as said above check all the vac hoses and intercooler piping!

 

[crazymat666]

ive gone over most the clamps il check the rest once the rain has decided to stop .yeah my mate said i should clean up the idle control valve but had that done before and it didnt cure it.but not 100% if it is a air leak because it wont show on the boost gauge and its boosting fine.wheres the best place to get a new air flow meter?

 

[S15_SAM]

When mine went down I got a 2nd hand one off here or try sxoc as s14 ones are the same, I was told. There about £25-40 2nd hand. New I'm not sure but Nissan or rhd Japan are popular.
Air leaks are hard to find, best way I find helps is to get brake cleaner in an aerosol can etc and spray it around the inlet manifold and vac pipes as if there's a leak it will suck the brake cleaner in and revs will rise, therefor pointing you in the right direction/area to look.

 

[crazymat666]

by the way as for checking the vacuums etc.where are they?

 

[crazymat666]

problems have started

so today i took the car out and when its cold its fine but as soon as its warmed up and drove for abit the revs drop down and sometimes it stalls when i stop and some times the revs go higher on idle then back down.but when im driving along normally without giving it any hassle il have my foot rested on the peddle cruising along so held at the same revs and itll start hesitating until you put your foot down more .i just cant figure out what this is and its making it no so enjoyable to drive has anyone had these same problems or have any idea what it could be its driving me insane

 

[sliding-r]

What dumpvalve are you running? Is it vta?

 

[crazymat666]

What dumpvalve are you running? Is it vta?

im running a hks sqqv2 bov not recirced.always thought that it would be the problem but its never been as bad as now.

 

[crazymat666]

it could be some old rubber vac lines that expand after it generates some heat ...first thing i would do is go over the car and tighten all cooler clamps ect and replace some of those old rubber vac lines

where are the vac lines too?

 

[S15_SAM]

The vac lines are all over the engine bay. They run from the intake manifold and under it to such things as boost controller, purge canister that sits by the radiator, fuel pressure regulator etc etc

As I said above when my air flow meter started to fail, it showed symptoms the same as yours. As on very little partial throttle it would hesitate until I put my foot down further! so i replaced it and hey presto. Try one or take it to a garage would be my next suggestion.

 

[crazymat666]

yeah im going get a replacement afm from my mates s14 is he can find it failing that buy a new one and replace the vac lines and see what happens.can anyone point me in the right direction where to get a silicone t-piece for my dump valve where they different outlet sizes?most sites only seem to do the different size bores thats all

 

[Max]

I have something a bit similar, in that when i come to a stop the revs sometimes drop momentarily to about 500rpm and then recover. It seems fine after that though. Im having most of my exhaust changed and having a new air filter, intercooler and BoV fitted later this month so I will see if it disappears after all that. If not maybe its the first symptom of AFM failure as has been described above, or when I had all my silicone hoses done a few months ago maybe they were not put on properly.

I have another S15 ECU if you want to borrow it if you are in the Reading area. (I have no idea if it will make any difference)

 

[crazymat666]

yeah i have a exhuast system fitted and front mount and bov on mine too but wasnt like it when i got it so it does seem like somethin has failed .im in somerset mate

 

[Max]

Im probably driving down to Devon next week, probably wed night, but I will only know on monday. If you think it might help I can come down the A303 with it.

 

[Max]

make that thursday daytime, not wed eve

 

[crazymat666]

i live a very long way from devon mate hhmmm

 

[crazymat666]

The vac lines are all over the engine bay. They run from the intake manifold and under it to such things as boost controller, purge canister that sits by the radiator, fuel pressure regulator etc etc

As I said above when my air flow meter started to fail, it showed symptoms the same as yours. As on very little partial throttle it would hesitate until I put my foot down further! so i replaced it and hey presto. Try one or take it to a garage would be my next suggestion.

so this morning i replaced the AFM thing is though the one that was on there looks literally brand new and the 2 pins have no damage but strange thing is i replaced it with another one which looks older etc and it seems to be better the revs dont die down anymore ive only driven it for a little bit but enough to get it up to temp the same as before .is it possible for the original one to look fine but still be nakerd??

 

[crazymat666]

ohh and ive got some new silicone vac lines coming some when this week which aint guna hurt to change

 

[S15_SAM]

Yeah you can't tell if an AFM is broken by looking, it's all to do with the resistance within the hot wire etc. So hopefully it will be all good for you now. Just give it a good test tonight and let us know!