GTST Wont Idle Steady

[Penitent_Spark]

I have recently purchased a 94 R33 GTST, Manual. Has a blow off valve fitted, stock ECU, turbo upgrade (I Believe). I have had it for two weeks however I noticed that after driving it for a while, the RPM at idle would start dropping from 800 slowly overtime down to 500 where it would start hunting between 500-700. So this Saturday just for a laugh I decided to disconnect the TPS when the car was idling.

After I disconnected it, the engine became a little upset and started hunting wildly, so i thought I had found the problem and as such i cleaned the AAC valve . That seemed to fix the oproblem a little bit, however it still hunts occasionally, and when you turn the Aircon on, it destabilises, behaves almost like a critically under damped sinusiod, i.e. it takes it a long time to settle, sometimes it doesn't.

Also found that the AFM has been changed on this moddel as the connecter seems to have been spliced baddly (I am a particular fan of poor workmanship) into the loom. I found that out when I pinched the connection the engine stalled, so i have re-spliced the connections to the AFM and it seems to be fine now. Though it still hunts when it feels like it.

Also when I played around with the AAC valve and readjusted the idle, there seemed to be little change in RPM, except that one position made it more stable than any other (between 750-780RPM). So is the idle screw an Idle adjust or are you adjusting the gain in a Proportional-Integral loop for idle control?

I will clean the AFM in the comming week, could it be the TPS, if so what is the quickest way to adjust the TPS?

Any help and comments would be greatly appreciated, thank you.


P.S. On a side note, does anyone have any experience in dealing with Osborne Motors in Perth? I am looking for a good mechanic in that area. I have had a look, not the most glamorous of places however they are a Nissan Certified Mechanic (can do Nissan log book services), are members of MTAWA and are autherised serv group members. When I talked to them they claim to be quiet comfortable in servicing Skylines (of course they would claim that). However I did see them reconditioning two RB25DETs. Any comments would be greatly welcomed.


Thank You all.

[TJ]

Get another tps, try it.

[Penitent_Spark]

Any Ideas where I can get another TPS from relatively cheaply, or is that a distant dream?

Failing that what are the other possibilities>

Thanks

[Penitent_Spark]

Also I should add that when I remove the TPS, it's not a steady idle either, sitting between 750-780RPM. So I am not entirely convinced that it's that either.

[TJ]

Thats standard - without a reading from it, it will idle up and down.

Perhaps a wanted add to borrow one to test offering a 6 pack or the like might get someone to help.

If you try a known working one and it solves the issue, then go buy one.

[Lump]

vac leak?
put a vac gauge on it & see whats going on.
spray every vac/boost hose & intake gasket with carby cleaner & see if idle changes

[ForgedV6]

Is this you DJ?

Hopefully someone on here can solve your issues or as TJ stated let you borrow known working parts to troubleshoot with.

[confuzion]

Mine had an epic hunting problem when warm, I cleaned the AAC valve which didn't really help, so I did it again and used gasket goo instead of re-using the old gasket and it's sorted now. It still hunts like 100rpm sometimes but it's fuck all and is probably just a little vacuum leak somewhere I havn't found yet.

I suppose what I'm getting at is if you re-used the old gasket, try re-seal it with silicon gasket stuff..

To adjust the TPS get a multimeter, with throttle shut the reading should be ~0.5v

[Penitent_Spark]

Yeah It's Dj.


O.k I will give the AAC another clean. I did use gasket goop as the old gasket was non existent. What I did find was that the previous owner had the idle screw in all the way, so he might have adjusted the throttle position instead, which is such a noob thing to do. So I will check that as well. Will also check the TPS with a Mutlimetre and clean the MAF with some CRC and the Throttle Body with some Carby Cleaner.

And will check for Vaccuum leaks.

Otherwise the car drives without a problem

This Saturday will be fun.

Thank You all for your input, greatly appreciated.

Hopefully this will sort it out.

I will keep you posted.

Anymore suggestions would be great.


Thank You all!

[TJ]

2nd gear limiter skid might help clear carbon out from the inlet path

[Penitent_Spark]

Sorry a 2nd Gear Limiter Skid is what exactly?

[Penitent_Spark]

Also I have two more questions.

1.)The car came with a Turbo Timer that reads the A/F mixutres of the O2 sensor. However it bounces around all over the place and sometimes sits at 20!! This can't be the case can it? It would detonate itself 6 ways to sunday? I am thinking that it's just a standard O2 sensor that it uses and not a wide band one and this is were the problem is.

2.) Also the temperature gauge never gets up to full heat, it stays maybe a quarter notch or so below middle. Could this impact Idle?

Thank you to all who have and do reply to this.


Thank You

[TJ]

Youtube is blocked at work, ill post a guide when I get home.

[Lump]

Also I have two more questions.

1.)The car came with a Turbo Timer that reads the A/F mixutres of the O2 sensor. However it bounces around all over the place and sometimes sits at 20!! This can't be the case can it? It would detonate itself 6 ways to sunday? I am thinking that it's just a standard O2 sensor that it uses and not a wide band one and this is were the problem is.

2.) Also the temperature gauge never gets up to full heat, it stays maybe a quarter notch or so below middle. Could this impact Idle?

Thank you to all who have and do reply to this.


Thank You
1. - its narrow band so practcally useless if using stock 02 sensor

2. - sounds like normal operating temp. lol at full heat.

[SSICK]

Sorry a 2nd Gear Limiter Skid is what exactly?

jump in the drivers seat, ignition on, start car......drive to a nice straight bit of road, clutch in, select 2nd gear, dial in about 7000rpm and clutch out, then steer as it bounces off the rev limit until you gain traction again. repeat if necessary.

[TJ]

<iframe width="480" height="390" src="http://www.youtube.com/embed/gZBRDobcMMM" frameborder="0" allowfullscreen></iframe>

[Penitent_Spark]

Right Well I might leave that until I have this thing figured out.

Had some time to clean the MAF today and no real change, so it might not be the MAF. Next I am going to check the TPS when I have sometime. Simple multimetre test.

Couple of Questions still.

1.) Anyone know where I can get a new TPS from and roughly how much they are?

2.) The best way to check for Vacuum Leaks.


Thank You

[Lump]

for 2. see post #6

[sam5709]

I don't know if series 1 and series 2 rb25det throttle position sensors are the same but iv got a series 2 one you can try from my old motor, if it fixes the problem you can have it because I'm not putting a 25 back in my car

[mitchy]

Series 2 is different.

If you get really stuck I have one, but the car is not easily accessible.

[UK-Rushy]

blow off valve leaking at idle maybe?

What sort of blow off valve have you got?

[Penitent_Spark]

I believe it is a series one R33 as it is a 93 E-ECR33.

If any one has a TPS that would be awesome, willing to pay or buy beer, I am not sure if that's the problem, but it would greatly help.

I do have an aftermarket blow off Valve, it's a HKS, i am not the biggest fan of it. One of these days I will go and find myself a non atmospheric one. If the Bow of Valve is leaking, is there a quick fix for that. Do I just tighten the screw at the back?

[Penitent_Spark]

Just a quick update to anyone that's reading this.

I have checked the TPS connection from the ECU and it is providing a very happy 5.45V to the TPS. So I can rule out a bad connection to the TPS.

I will try and source a new TPS in the next two days and try that, as well as clean the AAC valve again.

Any thoughts and suggestion are greatly appreciated.

[Lump]

did you check for vac leaks?

[Penitent_Spark]

I have performed a quick check and I can't seem to find one, there a a couple of hoses that seem to be cracking but I am not entirely convinced that it is them, I will have another attempt this Saturday afternoon.

I will also clean the AAC again, and be less frugal with the Gasket Goop, I wasn't very liberal with it to be honest.

I might check the blow of valve as well.

Any suggestion on what lines I should have a look at most?

Thanks

[Penitent_Spark]

I have also noticed that it hunts when warm.

Does this rule out or single out anything?

Thanks

[Penitent_Spark]

Sorry the above was supposed to be when cold, though less so.

Though I guess that still doesn't rule out vacuum leak or TPS.

[GhostFc3s]

Vacuum leaks and dodgy afm (MAF) are the usual issues with a idle hunter.

[Penitent_Spark]

I am not sure that it is my MAF. The trouble really started when I disconnected the TPS, the engine really started to Hunt Idle. So I cleaned the AAC valve but I am afraid that I haven't put the appropriate ammount of gasket on.


What leads me to think that it is the TPS is that once I removed it the engine started playing up, even when I reconnected it. Also if I apply light throttle sometime it will go back to idling around 750 RPM.

It's annoying, any thoughts?

Today I will be going past KYP, as I have sometime in the Morning and will see if they have a MAF that I can quickly swap out and test. Also they are quoting really cheap prices for TPS so I might get one in case. Failing that does anyone here have a MAF (R33) that they are willing to let me Test out?

Thank You to anyone who Replies

[Orange_33]

got a pink label series 2 AFM u can try if that helps

[Penitent_Spark]

Will that work on a series one RB25DET?

I have just obtained a TPS and an O2 sensor (I thought that might be the culprit, maybe not) and will post the results tomorrrow.

I will keep this updated as I go and hopefully this can be used in the future as I have read that many R33 users have this problem and they have been solved to varying degrees of success.

[Orange_33]

unfortunately no... u need the green label one... which im sure is the same as the rb20 AFMs

[GhostFc3s]

the idle hunts when u unplug the tps because it goes into limp home mode which makes the idle hunt

[Penitent_Spark]

O.k so,

Replaced O2 sensor and TPS, still hunts occasionally.

Though I have noticed that during hunting, the Blow of Valve seems to be operating, very slightly, but there is a gas venting noise coming from that area, exactly around the blow of valve.

Is this a symptom or the cause??

Any Ideas??

[Penitent_Spark]

Also anyone know what the best way is to adjust the Blow of Valve.


Thank You

[Orange_33]

factory or aftermarket? either way u should just block it off so you can eliminate the list of causes of ur idle hunting

[Penitent_Spark]

I am still not sure about the BOV though, I can't make it if thats a symptom or the cause.

Also It is intermittent, sometimes when I apply light throttle and bring it down, it wont hunt idle. Also it doesn't always idle hunt, just sometimes.


This any of this pin point anything in particular?


Thank You

[Penitent_Spark]

Aftermarket, HKS


What's the best way to block it off?

[Penitent_Spark]

I just thought of something

The car has a boost gauge installed that is not functioning.

Could this be the source of the Vacuum Leak?

I will investigate,


Anyone, offer any thoughts on if a non functioning boost gauge can cause a vacuum leak?


Help?

[Penitent_Spark]

I have found a hissing noise around the intake plenum area.

To the right of the throttle position sensor, I would have attached a picture however still figuring out how to do that.

Though when I spray the area with carburetor cleaner there is no change in idle.

I need someone who is more familiar with RB25DETs in order to figure out what all the pipes are and where to get replacements.

Thank You

[Penitent_Spark]

I am just going to keep posting in the hopes that the symptoms present will let someone on here figure out what's going on.

Apologies for the insanely long posts and this thread, however this is more cost effective than giving my money to a mechanic who will essentially do the same thing, except charge me $75 an hour.

I don't hate my money that much.

(it's also A way to keep record of the things i have done and the things poeple have suggested i do.)

Replaced the O2 sensor this weekend. Upon replacing it i noticed that the tip of the O2 sensor was stained white, from obviously a too lean mixture.

1.)Could a faulty MAF cause a too lean mixture?

2.)Or is the Fuel Pump on its way out?

3.) I am not too sure it's a leak because sometime the car starts low in idle around 500rpm stay there for a few second then it will automatically jump to 1200RPM when the cold start valve opens.


Any thoughts on the above?

[ForgedV6]

I can’t help you with most of your posts DJ, but i can offer some information on the O2 sensor discolouration.

White sensor doesn’t necessarily mean its running lean, it could also be from fuel additives, sealants (exhaust mostly). bad fuel or in some cases coolant leak.

Check your spark plugs mate and see what they are like.

If I use octane booster I get a orange tinge on my plugs and I can’t confirm but would guess it would be the same on the O2 sensors.

[Penitent_Spark]

Yeah I thought of that.

I did when I first got the car fill it with 91 octane fuel, when I hadn't thought about it, so it could be from that.

The spark plugs are hard to get to but it is something that I am going to have a look at.

It's not the coolant leaking becuase I have been checking the fluids almost every second day and I have not lost any fluid anywhere, the coolant is still a vibrant green.

It could be running leanish due to a faulty MAF or a Vacuum leak as well.

Does anyone here reading this have a MAF for a series one R33 that i could borrow to check the MAF.

Thank You

[TJ]

I dare say with all the dramas etc it is giving you, you might be just best of going to a workshop that posses the OBD scanning tool for Nissans and getting them to run the codes.

[Lump]

Aftermarket, HKS


What's the best way to block it off?
remove it and block off the hole with something that will seal the hole.

put a vac gauge on what does the needle do?

block up any open vac lines - especially ones that might have been connected to a boost gauge.

[Penitent_Spark]

Thanks I will keep trouble shooting and seeing what it does, I am determined to get to the bottom of it.

I want to try and exhaust all my options before I go down the route of getting a mechanic to do it for me. So I am still waiting on somoneone with a MAF sensor. Hopefull someone somewhere will show up (here's to hoping!).

I enjoy trouble shooting and fixing things and I really want to find this out myself because I am sure it's something simple I have missed and I just need someone elses input who is not so invested in this and can see the forest from the trees. So please spread the word to anyone with a series one R33 I am in want of a MAF sensor for a series 1.

Please!

[Lump]

i think its going to be a vac leak, not an electronic issue

[Penitent_Spark]

CrankY I think you are problably right,

But I will check just to be sure.

[turael]

Hey mate, you can check your AFM with a multimeter just like you did with the TPS. instructions are in the R33 service manual. If the AFM is bonkers you would probably have issues revving it as well.

From what you said it sounds like a vac leak.
I've done the following for testing how sealed my RB25DETs buggys intake system was:

- block up the air filter side. I took off my pod and AFM and used a heap of duct tape to seal up the intake pipe. Not sure if your car has any other pipes on the intake side of the turbo to block up.
- your intake system should be relatively sealed now. Turbo, intercooler, pipework, BOV
- Using a vac line that goes into the intake system somewhere (think I used the one on the turbo when I did it, unplugged from wastegate actuator), use an air compressor gun with the thin nozzle type to shoot air into the system. The thin nozzle should fit nicely in the vac line.
- after blowing in some air quickly clamp the vac line you're using else the air will just go back through the gun.
- listen for hissing. When I did this I found about 5 leaks. If this technique works for you it's really easy to find leaks, as the car is off and all you hear is air hissing out of your dodgy pipework (in my case).

I haven't actually worked on a skyline before, so not 100% sure if this will seal up the system enough to work. I imagine it should work tho

[Penitent_Spark]

No Issues reving it at all.

Only problem being that I don't have a compressor anywhere on hand. Otherwise I would have checked it.

O.k, so my next objective is to find a compressor and be able to check this as well.

Hopefully I can do this sometime soon. It does point to a vacuum leak somwhere, although would a vacuum leak cause a dodgy start sometime?

I might see if I have can find someone with a compressor. Anyone have a compressor and willing to give a hand?

Failing that I will look for someone with a compressor on hand somewhere.

Thanks for the hints.

[turael]

Where abouts are you? I could possibly help you out, I'm SOR. Don't actually have an air gun for my compressor though, unless it's hidden away somewhere.

Vac leaks cause all sorts of gremlins, it's a good idea to make sure there's no leaks before going onto the next bit.

As for checking AFM, it's in the R33 service manual (find it online somewhere). You measure the voltage going through one of the pins at idle, on start and on throttle. I can't remember which pin or what values you should be looking at... but if the cars revving the AFM is probably OK anyway. My RB had a faulty AFM, it was reading about 1/10th what it was supposed to. It would start, and stay running but very smokey with some throttle love, but refuse to rev and would stall itself if left to its own devices.

[Penitent_Spark]

I am actually NOR, near the city, but I am willing to drive. If you would help me that would be awesome, will gladly throw in a six pack or two.

Please let me know if you can help, I would really appreciate it. It's slowly driving me insane.


Thank You

[turael]

Aight man I'm just doing some paving this weekend and next, if you still need help then I can help you.

In the meantime check your AFM voltages
and run a nissan diag test by shorting a pin and watching the light (instructions in manual!), will tell you if something's wrong with a sensor.

[turael]

Aight man I'm just doing some paving this weekend and next, if you still need help then I can help you.

In the meantime check your AFM voltages
and run a nissan diag test by shorting a pin and watching the light (instructions in manual!), will tell you if something's wrong with a sensor.

[Penitent_Spark]

Excellent!

I have checked the AFM, and I doubt it's that, there are no other signs that it is the AFM.

Also I disconnected the non functioning boost gauge and left the Tee Piece disconnected abnd fount it had no noticeable change or impact on Idle Stability. Which would tell me that there is / are bigger vacuum leaks around the engine bay, except I can't hear them over the engine running, ( I can hear a hissing sound near the intake plenum, though it's not the intake plenum, but I can't pinpoint it more than that.)

Tureal: If I can't find anyone within the next two weeks with a compressor or who knows their way around the RB25 vacuum system, if you could give me a hand, that would be invaluable.

Is there anyone else SOR or NOR with compressor or knows what they are looking or that is willing to give me a hand?

Thank You

[Penitent_Spark]

Excellent!

I have checked the AFM, and I doubt it's that, there are no other signs that it is the AFM.

Also I disconnected the non functioning boost gauge and left the Tee Piece disconnected abnd fount it had no noticeable change or impact on Idle Stability. Which would tell me that there is / are bigger vacuum leaks around the engine bay, except I can't hear them over the engine running, ( I can hear a hissing sound near the intake plenum, though it's not the intake plenum, but I can't pinpoint it more than that.)

Tureal: If I can't find anyone within the next two weeks with a compressor or who knows their way around the RB25 vacuum system, if you could give me a hand, that would be invaluable.

Is there anyone else SOR or NOR with compressor or knows what they are looking or that is willing to give me a hand?

Thank You

[Penitent_Spark]

Excellent!

I have checked the AFM, and I doubt it's that, there are no other signs that it is the AFM.

Also I disconnected the non functioning boost gauge and left the Tee Piece disconnected abnd fount it had no noticeable change or impact on Idle Stability. Which would tell me that there is / are bigger vacuum leaks around the engine bay, except I can't hear them over the engine running, ( I can hear a hissing sound near the intake plenum, though it's not the intake plenum, but I can't pinpoint it more than that.)

Tureal: If I can't find anyone within the next two weeks with a compressor or who knows their way around the RB25 vacuum system, if you could give me a hand, that would be invaluable.

Is there anyone else SOR or NOR with compressor or knows what they are looking or that is willing to give me a hand?

Thank You

[Turbo2.6L]

Might be worth buying a cheap compressor from Supercheap yourself? Sure, it wont lay down a flawless paint job but i'm sure it will come in useful later down the track, after it performs this leak-down test??

[mitchy]

there is a vacuum hose on the front of the plenum, that goes to the fuel rail.

then there is one off the throttle body, and another one about 6" further back low on the plenum, both of those run under the cross over pipe to the catch can, you can block them off to test if they are leaking.

there is another one on the back of the plenum that goes to the electronic sensor for the boost guage in the factory dash, again you can block that off.
there is also the big fucker from the BOV that returns to the plenum, you can block that to test too.

there will be another one off your cooler piping/turbo housing for your boost controller/factroy boost solenoid too, you can block that off to test for a leak.

that's it off the top of my head...

[mitchy]

oh, and the brake booster at the rear, and rocker cover breather/PCV in the front side.

[turael]

Thanks for that, will come in handy if I have to help him out, lol.

Shouldn't need to block anything on the other side of the butterfly though?

[Lump]

just buy a vac gauge ffs, autopro inaloo.

[daedalusjc]

where abouts NOR are you? Im near Carramar if you want to stop past on the weekend and have another set of eyes over it. Pissed about with alot of AFM'd cars and the up and downfalls of them aswell as diagnosis. Send thru a PM if your keen

[Penitent_Spark]

So an update on this issue.

I have found a vacuum leak, the oil breather hose was cracked on the right hand side. I have also replaced all the vacuum hoses in the car. I have replaced the oil breather hose with a $4 second hand one, no cracks, does not leak. I will order a new one from Nissan tomorrow, and I have budgeted for only one kidney to be removed.

I have also done the following;

Injector Clean,
Coolant Flush,
Power Steering Flush,
Cleaned Throttle Body,
New Oil + Oil Filter,
New Spark Plugs - Irridium.

The car still hunts idle, only very slightly so, about 50 - 100 rpm, it does not stall at the lighst anymore (which is good, unfortunately what this also means is that my Heel-Toe lessons are over as well). Do RBs have such an unsteady Idle naturally? Or is something else going on that I am not privy to?


Thanks all who have helped with this Issue.

[Orange_33]

use copper plugs.... cheaper, are adjustable (gap wise),