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HELP - engine wont idle


smijay

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Hi, I have an 04 plate 350z with the DE engine.

 

Installed a pop charger and changed my spark plugs yesterday, changed both serpantine and A/C belts today.

 

After doing each change i started the car up and tested that it idled and revved fine,

 

So... i though i'd give it a run down to halfrauds today after the belts where changed to pick up some much needed clay.

 

The car started better than ever and got me all the way there with no problems whatsoever down the 5 mile dual carrigeway... it was upon returning to the car that i noticed a problem.

 

It appears that when i start the car from warm the engine fires fine but then dies as if its not getting enough gas or air while trying to idle.

 

I tried starting the car and immediately applying gas and this started the car fine and DID then idle fine and got me all the way home with no problems.

 

I've tried resetting the ECU with the pedal procedure and it appeared to reset fine but the problem still persists!

 

Any help would be appreciated! (Sorry if this is in the wrong category etc)

 

Jay

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Thanks for the suggestions, i was really careful to check all wires and make sure they all went back in, just had another check now and everything that i've taken out is back in properly.

 

Zeus could you suggest anything that i could clean the MAF with?

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Update: Ok so i took the pop charger off and cleaned the MAF with some WD40 and a cotton bud, put it all back together and it started first time! (engine had been standing for an hour so had cooled)

 

Took it for a good 15 minute drive so everything warmed up, got it back home turned off / on the engine and the same thing happened again -.- the engine fires but just wont idle!

 

Ill try the old air box back in tomorrow and see how that is...

 

Any other suggestions in the mean time?

 

:)

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Installed the old air box and the same problem is happening, the engine wont idle when it's started from warm unless i apply some accelarator then it idles fine -.-

 

Booked in at my garage on monday for them to have a look.

 

I've got a sneaky suspicion that its an ignition coil from the research i've done so far and maybe iv damaged one when i've been changing the plugs?

 

Will update on monday!

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I'll stick my neck out here - before I supercharged mine, it used to have the *hot start, idle die unless some pedal input, often at petrol stations* problem. I initially thought crank position sensor, but after I cleaned my throttle body - which had crust on it's butterfly plate inside surface and around the edges - I've never had a problem. If you are sure there are no odd vacc leaks etc, it is an easyish thing to try (cleaning). I imagine the butterfly has physical difficulty returning to the right spot (or the small gaps when almost closed are clogged) at hot idle position.

 

Of course, whilst supercharging, I touched a billion other things, but hey - could just be a grubby butterfly :)

 

If you fancy it, disconnect battery, wait 30 sec before disconnecting the TB connector, take the TB off (bolts are F tight) and clean the back and surrounds of the butterfly using STP carb cleaner. Do not do this in situ with the cable still connected. :thumbs:

 

Edit: no-way :lol: ^^ beat me to it

Edited by ChrisB
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Thanks for the ideas! :D

 

Got a plenum spacer from wazzo to fit so may as well fit that while im working in that area anyway...

 

When i took the air intake hose off the throttle body i did notice a black sooty build up but thought nothing of it!

 

Just strange how this would happen literally a day after changing all sorts -.-

 

Whats the best thing to clean the throttle body with?

 

Thanks again :)

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Disconnect the battery before cleaning as moving the butterfly valve in the throttle body can corrupt the ECU meaning you need to send it off to be re-programmed. Crazy stuff.

Edited by Hooch
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Disconnect the battery before cleaning as moving the butterfly valve in the throttle body can corrupt the ECU meaning you need to send it off to be re-programmed. Crazy stuff.

 

Not saying that is bad advice as every precaution to not do damage should be taken, however as far as I'm aware the ECU corruption thing happens on the HR engine not the DE.

 

The problem is not disconnecting the ECU as well as the battery - on an HR even if the battery is disconnected you can apparently damage the ECU and it is not an easy repair.

 

However always be careful when cleaning throttle bodies and/or MAF's on any model :thumbs:

 

I am quite happy to be corrected on that if anyone knows otherwise :)

Edited by Keyser
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Aaaaaaand the points go to...

 

Gudzy and ChrisB!

 

Disconnected negative terminal from battery

 

Removed throttle body (PITA but doable)

 

Ceaned the throttle body with wynn's carb and intake cleaner (the back side of the TB was wayy worse than the front!)

 

I gave it a good scrub with a micro firbe cloth and carefully moved the butterfly valve to clean the carbon from around where the butterfly sits when closed

 

Cleaned the inside of where the throttle body sits on the actual plenum

 

Binned microfibre cloths (they where BLACK)

 

Gave the TB 15 mins to dry naturally and then put it all back together

 

Performed every single pedal dance that i could find out there!

 

Went for a good 15 minute drive so the car warmed up, got it home, turned engine off... tyrned engine on... IT LIVES!

 

Started first time and idled around 1k RPM (I believe this is normal while the ECU is in learning mode)

 

I've tested it a few times from hot and looking good so far!

 

Thanks again everyone for your input! :D

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Nice job :thumbs: All precautions taken, had a good clean out of the TB off the car (rather than just squirting stuff up there ;) ) ..sorted :#1:

 

Wasso spacer, exhaust and UpRev next? You have just broken the seal on a very steep and slippery modding slope :lol::welcome:

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Haha yeah, based on what i saw on the back side of the TB I would NOT recommend just squirting the stuff up there, anyone thinking about doing this... do it properly by taking the TB off!

 

Berk high flow cats courtesy of TORQUEN sat in the garage next to the wasso plenum spacer both waiting to be installed! Cobra sport y pipe and cat back should be delivered tomorrow! :D

 

Rang TDI north west to get booked in for the uprev, they said the earliest slot they had was at the very end of august and i hate waiting for stuff! -.-

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