# Hot Start problems!



## leeroy_25 (Dec 19, 2006)

I have had issues with my car starting from hot pretty much since it was first built RB30/26. Seemed to be fine after one mapping session and then another mapping session later it was back. Tuner is quite a way from me so I have not had a chance to take it back.. It's been mapped by two decent tuners a few times over the course of time too. So I was trying a bit of self help! With the assistance of some experienced guys on here hopefully!
I was googling/searching the other day and found a few old threads on here describing the same problem with some suggestions but no final post of the end result.
Basically if I go for a drive and the car is warmed up then say stop for petrol.. fill up.. go pay.. when I come back to start the car sometimes it keys over a long time before it fires and when it does the rpm is real low and you have to give it a blip to clear it.. then it's fine. Rarely it will fire and then stall.. Then key over and nothing.. then key over and fire instantly and with a blip as before it's fine?
First of all I was wondering if the heat soak was setting messing the air temp settings up? as it does get hot under the bonnet quite quickly if its a warm day. And it is definitely worse on warm days.
I pulled the air temp sensor plug off to try and test the theory and it didn't seem to help? i.e it did the same thing.
I did notice that if you stop and then start the car straight back up it's perfectly fine.

I am guessing it is lack of fuel or lack of spark? just not sure why and then how to fix it..
One suggestion was a faulty FPR. not sure why this would only effect if on hot start?
I have played with the cranking settings in the ECU a bit but don't think these would normally need changing and I am not 100% sure which way to move them in honesty.. but they don't seem to make a lot of difference with what I did try.
Leaky injector was also mentioned in a post? However I would imagine this would only effect 1 cylinder an the car would start fine but run lumpy for a second?
Dodgy Battery? I noticed the voltage can drop quite low when cranking when I monitored on the commander the other day? but that was when it was cold and had been sat for a few days and although sluggish turning over it fired up no problem! Not had a chance to check it hot after a good run.

Anyway if anyone could give me some advice I would really appreciate it! its sounds like quite a few people have had this issue but cannot find anyone posted and answer to it!

Thank you
Lee


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## R32 Combat (Jan 29, 2004)

Have you tried a different cas?


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## leeroy_25 (Dec 19, 2006)

No but I am open to suggestions.. Would that cause only hot start issues? People with similar problems had all tried. CAS, Coil packs etc with no result. not saying mine will be the same..
For some reason it clearly either gets no fuel or spark. or possibly crap loads too much fuel?


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## leeroy_25 (Dec 19, 2006)

No one else got any input?

Cheers
Lee


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## mambastu (Feb 13, 2002)

Have you checked the compression at all ? My 26 was a pig to start when hot and it had low compression on every cylinder apart from one. 

Cheers

Stu


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## Natbrat300 (Mar 6, 2012)

Sounds like too much fuel to me!


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## leeroy_25 (Dec 19, 2006)

Too much you reckon?
Stu, it's been like it on and off since new built! Sometimes it's okay too?! I cannot seem to pin point it 100% but it seems like heat soaking in somewhere is the cause.

Cheers
Lee


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## R32 Combat (Jan 29, 2004)

What ECU are you running?


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## leeroy_25 (Dec 19, 2006)

Running an Apexi Power FC. Standard type running off MAF's.


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## CSB (Nov 15, 2007)

did you manage to get this sorted? Mine does this as well getting worried cause it's getting worse.

Cold start is perfect, idle perfect. Hot start and it really doesn't want to start. Have to push the accelerator then let off, then revs fall to around 400rpm then it slowly takes its time to get over the 1000rpm idle, then would sit there nicely.

Getting annoying now.


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## steve_gts4 (Nov 30, 2009)

i used to have exactly the same problems with my R32 and powerfc..
i also have a bit of a tricky clutch, so if god-forbid i stalled it in traffic, i had to get out and push.

MGT have recently locked the map on my ecu, so i cant see what the cranking settings are, now..
but, in the settings -> cranking menu, i increased the amount of injector opening time, from what I assume was the default, and I managed to completely solve the problem.

my 2 cents are, write down the starting settings, get the car hot so that it wont start, then increase the numbers at the appropriate temperature range until it starts properly.

Steve.


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## steve_gts4 (Nov 30, 2009)

further to that, i think I found where i got this advice before.. 
SAU thread Car Won't Start When Its Hot! - Skylines Australia

in particular

"Go into 'settings' then 'cranking' and have a look at the 50deg and 80 deg settings.
Change the 80deg to 9.0 and the 50deg to 10.0 and see if it starts easy for you."


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## CSB (Nov 15, 2007)

thanks for your reply, does seem like an option but I don't have a power fc fitted. I have got it sitting in the garage but will probably ditch that and get a link. 

If I'm running the standard ecu and the problem seems to be getting worse something must be deteriorating?


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## leeroy_25 (Dec 19, 2006)

Just seen these replies guys.. I have not fixed mine yet as been busy working on other things! I have tried playing with cranking a little. But was a bit concerned that it is not something you would normally change. That said my setup is not normal! I was planning on changing my MAFs back to factory ones and see if that helped? After that I think it can only really be one of the idle control valves maybe? One of which is a plenum off job to change and I am not sure if it would have any effect on warm starting anyway? I find mine is worse starting when warm as a pose to hot. It is an irritating problem though for sure! Post any finds please as no ther post I have read yet has a solution posted.

Cheers
Lee


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## leeroy_25 (Dec 19, 2006)

Well I changed the cranking settings the other week and have been trying to monitor if it helps at different starting temperatures. I haven't used the car a lot to be honest but it certainly seems to help. So the question is do I just keep adjusting the cranking settings until it's sweet or does this mean I need to start looking for something that is causing the issue to begin with. Or is this just a sympton of cars with big injectors, large MAF's and adjusted cam timing?!

Thank you
Lee


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## RB26 240Z (Dec 29, 2007)

Similar problems with mine turned out to be the ignitor that sits on the coil pack cover getting warm and it would drop a cylinder and be a pig to start (fine from cold) have lent another ignitor the car is so much better will be swoping mine for a new Z32 unit.


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## leeroy_25 (Dec 19, 2006)

The ignition pack thing?! Hmm? And it ran perfectly other than hard to start? Didn't break down under load at all?
You say it dropped a cylinder? was that when it finally started? When my starts it runs perfect from the go?
Is a Z32 ignition pack the same then? What's the thinking in using one of these instead of the RB26 one?

Thanks for the info.

Lee


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## RB26 240Z (Dec 29, 2007)

leeroy_25 said:


> The ignition pack thing?! Hmm? And it ran perfectly other than hard to start? Didn't break down under load at all?
> You say it dropped a cylinder? was that when it finally started? When my starts it runs perfect from the go?
> Is a Z32 ignition pack the same then? What's the thinking in using one of these instead of the RB26 one?
> 
> ...


Runs 100% from cold and starts 1st time but when it's up to temp it drops a cylinder and is a pain to start from hot, turned out to be the Ignitor on the coil pack going off when it get warm i will be using a new Z32 unit down to the cost new compared with the RB.


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## gtr-loz (Feb 10, 2006)

Mine was/is the same they require more fuel when hot starting and the crank hold needs to be longer than when cold it probably doesn't help when I have an aluminum fuel rail etc with heat soak I have tried to get a gizmo intake gasket as they are phenolic but I can't find one anywhere they seem to have ceased production I used to have exactly the same symptoms as you would run fine on cold but hot starts of left for half hour or so would take ages The. Rev low with acts of 18 or so increasing the crank hold settings and post start enrichment helped alot but has not sorted it totally but I have issues with the AAC which need sorting so I'm waiting until that's done to attempt it further


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## leeroy_25 (Dec 19, 2006)

Arrhhh. Now Loz.. I think we really do have the exact same issue. I am 90% sure I have an issue with either the idle control or AAC valve under the plenum. Just such a pain to get at I have not got around to fixing it yet! Is yours booked in to get this sorted? Would be very interested to see if this solves it Please do keep me posted.

Was not sure what this meant by the way. Mainly the first bit? 
"Rev low with acts of 18 or so increasing the crank hold settings and post start enrichment helped a lot"

If you can elaborate please?

Thank you

Regards
Lee


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## gtr-loz (Feb 10, 2006)

Sorry it should have been afrs of 18 or so crank hold and post start enrichment are some of the startup fueling controls of the ecu I have (link) I do the majority of work myself the inlet is off at the mo so far I have found evidence of air leaking past two throttle bodies and the 
Manifold itself just need to get some new water pipes (metal ones ) for below the manifold and i will start the lengthy refit procedure although I really would like to get hold of a new gizzmo gasket it seems impossible to do so


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## leeroy_25 (Dec 19, 2006)

Thanks for clearing that up. I am on the Apexi ECU and that only has cranking adjustment in milliseconds for the injectors at startup as far as I know.
Can you confirm it is the AAC valve under the plenum you are changing?

Please do keep me posted with what you find.. Might spur me on to strip mine down when I eventually get a garage sorted! I to do all my own work other than the actual mapping. Trouble is finding the time at the moment as I am working on another project! And trying to finish my custom bonnet to fit on the GTR in between!


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## Mwohaaahaahaa (Feb 19, 2010)

Have you tried replacing the cold start sensor? I am having similar issues. I find keeping my foot slightly on the accelerator when it is starting for a few seconds sort is most of the time. then take you r foot off and drive normally. The sensor itself is about 80 quid and it is easy to ift. about a 10 min job.


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## leeroy_25 (Dec 19, 2006)

Cold Start sensor?? I was not aware there was one? Col start valve that is a PIA to get at yes! no one has mentioned a sensor before.. Does it effect the hot start as well then? Please confirm what and where this is! I do have to say if I rest my foot on the throttle just slightly when starting it never seems to fail.

Hopefully GTR-LOZ can update with his progress soon.

Thank you
Lee


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## Mwohaaahaahaa (Feb 19, 2010)

To Be honest I can't tell you exactly where it is. The mechanic I go to did his as he had similar problems. And he only charged me a 5er to fit it. Like I said the part itself cost 80 quid which you can get direct from nissan. Yes the cold start sensor does effect the engine when hot. If it is not working properly then it sends signals to the ECU which confuse it and cause the issues you are seeing. I'm sure someone on here with more mechanical knowledge on skyline engines could tell you exactly where it is and what it looks like.


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## leeroy_25 (Dec 19, 2006)

Cold start sensor anyone??
Cheers
Lee


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## gtr-loz (Feb 10, 2006)

Never heard of it on a gtr they have a coolant temp sensor and the valve under the inlet which feeds air in when on cold start


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## [email protected] M/S (Feb 16, 2002)

GTR has a auxiliary air valve on the bottom of the inner plenum (long manifold) this allows extra air over what the AAC valve can pass when cold.

TBH these normally these seize open so cause a high idle , the feed pipe comes from underneath the plenum at the back ( No.6 cylinder) you can clamp it off when the car is warm to ensure it isn't stuck open.

When we tuned Loz car on Link it needed a lot more fuel on hot start added to help get pass the heat soak issues , from memory it sounded like it needed some more air via the AAC valve on cranking.

On a Power FC your are limited to what you can adjust , I would need to have a good look through the software to work out what you can adjust, I am sure you can adjust cranking added fuel thou.

GTR Loz I think those Gizzmo inlet gaskets have been dis-continued but we never saw any gain/s from them when we have used them.


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## gtr-loz (Feb 10, 2006)

Cheers mark yeah they have been stopped my manifold is stripped down at the mo as it sprung a water leak from one of the hoses under the plenum found air leaks from the inept manifold and throttle body gaskets as well as light showing past all butterflies where all special paste has worn off! Hopefully these things will rectify a lot of it! Is there anyway to check the aux valve with it off the car?


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## [email protected] M/S (Feb 16, 2002)

Your car being Map based will not have any real hassle with the small air leaks cause inlet manifolds leaks.

If it was a air flow meter based car yes they would cause rich running under boost and lean mixture while be cruised off of boost.

With regards the Auxiliary air valve , remove it , have a look through the pipes , cold it should be open a small amount, if you then 12 volts it it should close slowly.

This valve only really comes into use when the weather is very cold we find.


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## gtr-loz (Feb 10, 2006)

Thanks mark will have a go tonight I have managed to find some stuff like tomei throttle coat to apply tithe bodies to reseal them it's a dry film lubrication spray meant for engine and gearbox use


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## leeroy_25 (Dec 19, 2006)

Hi Mark.. Thanks for replying to this thread.. I would say this valve sounds like a good candidate for a lot of issues I have or have had and worked around!
Firstly the idle used to be too high when I first ran it.. Could not adjust it down enough with the idle valve so adjusted the throttle bodies to shut them slightly more.. (thought maybe cleaning the throttle bodies had caused the issue?) Then when it went really cold last winter, one day it suddenly starting fueling rich as hell cold idle.. seemed okay once warmed up.
since summer and a new map it can be a pig to start when hot although adjusting the cranking fuel settings with the FC commander has helped a lot.
Normally I have a slight lean spot pulling away under normal load and then a rich plume from the exhaust as I boost up which I have been meaning to get sorted for a while. This week suddenly it nows seems to have gone leaner on boost to the point of getting some high knock readings and minimal plume! (will check that for a fact with my AFR gauge at the weekend) Have another post on that subject too! Maybe colder air temp related?

Does this all sound like symptons of the air bypass valve or something else? It does seem to be very sensitive to changes in ambient air temp and a little irratic!

I am running Q45 MAF's should that make any difference. Car is smooth as you like and goes like a train otherwise!

Is there anything I can do to test the valve function without stripping all the plenum off with a power FC? Can it be done away with entirely on a power FC or will I get cold start problems?

Cheers
Lee


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## [email protected] M/S (Feb 16, 2002)

Sounds to me the cold start calibrations isn't very good , when it is cold maybe to rich on the fueling in relation to the amount of air @ cold start.

hot start issues is normally not rich enough for long enough when the car is started hot.

The Q45 AFM curve will require extensive work to make he car run nicely , this takes a huge amount of time on the tune.

To test the auxiliary air valve pinch the pipe that feeds the valve when you start the car cold and see if the idle speed drops off.

Mark


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## gtr-loz (Feb 10, 2006)

You would be better swopping to z32 mafs as there is a calibration profile in the powerfc for them


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## [email protected] M/S (Feb 16, 2002)

That isnt very good either thou Loz.


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## leeroy_25 (Dec 19, 2006)

The Q45 MAF's have had a fair bit of work on the dyno and I have no complaints other than the few little odd tweaks that are needed that may or may not be due to the MAF's I find it a bit strange the car should suddenly lean out on it's own?
When you say cold start calibration I presume you mean the water temp adjustment settings. I have played with these to make it happy last year. won't know how it acts until it gets real cold this year. Fine at the mo though.. i.e not too rich. Set it up using an AFR gauge.

Can you actually get at the feed pipe to clamp it off?! If I recall there is one pipe going into the back of the valve and one from the front that connect into stubs coming from the chamber under the inner plenum bit? That the pipes you mean?

Cheers
Lee


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## [email protected] M/S (Feb 16, 2002)

If the car has leaned out 1st thing I would check would be fuel pressure , if the fuel
pressure has dropped the car will run leaner.

Cold start calibration will mean cranking fuel water temp fueling idle speed etc etc.


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## leeroy_25 (Dec 19, 2006)

I was also wondering fuel pressure. What should it be on idle. I have standard fuel rail and regulator. Strangley when I drove it yesterday with the afr gauge connect it seemed perfect. Would injector duty not go up if pressure had dropped? Or is does the map just pulse the injector assuming has the correct pressure always?
I will play with the othersettings as I need to for cold start. For the hot start is it quite comkon to have to adjust the cranking settings up or is that just covering up an underlying problem with a sensor or something that needs checking?

What are your thoughts on rb25 mafs. I do have a pair I toyed with using if I keep getting random issues. Need to get filters for them though or make adapters for my apexi ones.

Cheers
Lee


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## gtr-loz (Feb 10, 2006)

If the ecu can't see the fuel pressure then it can't adjust for it so just assumes its correct its 3 bar at idle with the vacuum to it disconnected and blocked off


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## [email protected] M/S (Feb 16, 2002)

> For the hot start is it quite comkon to have to adjust the cranking settings up or is that just covering up an underlying problem with a sensor or something that needs checking?


No you normally have to adjust this on every calibration.


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## Faris (7 mo ago)

RB26 240Z said:


> Similar problems with mine turned out to be the ignitor that sits on the coil pack cover getting warm and it would drop a cylinder and be a pig to start (fine from cold) have lent another ignitor the car is so much better will be swoping mine for a new Z32 unit.


Hi 
I have same problem like 
When my car get warm i feel there is a drop cylinder and will not star until it become cold 

plz help if you have soled urissue


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## naaltu61 (7 mo ago)

Have you checked the compression at all ? My 26 was a pig to start when hot and it had low compression on every cylinder apart from one. 
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## Faris (7 mo ago)

naaltu61 said:


> Have you checked the compression at all ? My 26 was a pig to start when hot and it had low compression on every cylinder apart from one.


Yes i have checked already the compression and its 130 for all 6 Cylinders


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