Why Wont My New Engine Idle?

[DRFT 14]

I disappointingly had to tow my car back from my auto sparky while under the impression that I was finally going to drive it home. The setup- S14 Silvia, NEO RB25DET, big turbo with all related bolt on’s and Link Plus ecu. Ive also gone with a wasted spark setup as the motor didn’t come with coilpacks and R34 ones proved very hard to source. My sparky seems to think that the reason it turns over but doesn’t start or hold idle is related to the shabby ignition leads (loose fitting). I rechecked the leads last night and had another go but it still wouldn’t quiet start. Its defiantly firing and sounds like its going to start but doesn’t quiet make it. I managed to start it once but only kept it alive by constantly holding the throttle. As soon as I took my foot off the accelerator it died instantly. Does that hint at anything?

Also, would a shabby tune on the second hand LinkPlus stop the car from idling? It was originally on an R33 spec RB25DET so surely the tune can’t be the reason why it won’t even start?

[paulr33]

airflow meter or map sensor?

do you have a stock ecu you can try (and then do onboard diag to see whats broken)

[666DAN]

The RB25 from the GTT has a few more inputs/outputs than previous models it could be a 1000 & 1 possibilities, including the traction control throttle body on top of the engine remaining closed.

If you're chasing a set of R34 coil packs, I've got a full set currently in the for sale section.

[DRFT 14]

LinkPlus utilizes a map sensor. Theres no way i can use a stock ecu. The loom was made up from scratch for the linkplus, so the plug is different etc. And we modified the plenum to face forward and totally removed the traction control in the process so that cant be the problem.

I managed to get it to start today, albeit only with my foot constantly on the throttle. It sounded like crap, missfiring badly, similar sound you would hear if you had got a couple of faulty coilpacks which again leads me to think the leads might need replacing- i did re-check them however. I kept revving it out but it died as soon as i let off the throttle. Any ideas guys?

[rob82]

LinkPlus utilizes a map sensor. Theres no way i can use a stock ecu. The loom was made up from scratch for the linkplus, so the plug is different etc. And we modified the plenum to face forward and totally removed the traction control in the process so that cant be the problem.

I managed to get it to start today, albeit only with my foot constantly on the throttle. It sounded like crap, missfiring badly, similar sound you would hear if you had got a couple of faulty coilpacks which again leads me to think the leads might need replacing- i did re-check them however. I kept revving it out but it died as soon as i let off the throttle. Any ideas guys?

Not sure on the setup with the link as I have never tuned one but is it setup for the rb trigger input? First thing's first check that you have injector pulse and spark to all cylinders. Then check its in the right spot by removing all plug leads, unscrew no1 spark plug and with it connect to the coil turn over the motor by hand with ignition on and check the spark is some where near TDC. This is just a start as its been said there are about a thousand different things it could be.

[copycutter]

If its gurgling and playing up and sounding crappy when you rev the engine then check your intercooler. As elementary as it sounds I just helped put a ca18 into a onevia and the engine was blowing smoke and carrying on. Once we mounted the intercooler properly then she was good.

For you it might be a little different though.... rb25's are great when they run good aren't they (i got problems too )

[race_snooze]

so you have spark/ fuel/ and fuel pressure?? does the link ecu have a base tune?? if not dont you have to set up some kind of idle base turn?? Also fouled plugs will cause the same thing, either due to sitting and being turned over and not heating up. (covered in black fuel shit)

Edited April 5, 2006 by race_snooze

[DRFT 14]

Ok, i went out and bought some brand new spark plugs today and fitted them. I checked the spark on all cylinder's and all were firing. Injector pulse is fine. IC piping is fine. Still no go . Im trying to avoid towing the car to a workshop and saying "take it off my hands and get it running and tuned properly" as im not keen on getting stuck with a couple of grands worth of bills. But it seems like this is the right option, id hate to put another frustration-caused dent on my bonnet!...

[copycutter]

hmmm this is a toughie you got on your hands.

Maybe the link computer with the r33 mapping has somehow reset itself?

I also heard that the NEO rb25 passes about 25% more exhaust flow than a normal rb25 due to the differences in variable valve timing. I was told the r33 model runs like a switch - on and off at certain points, whereas the r34 model is variable at all times, based on what the computer is sensing.

I'd first of all go to a performance shop/tuner that you know and ask some questions first. If you give them the impression you'll come back or bring the car in for their help they should be able to give you a few ideas on where to start looking - just to eliminate the simple stuff first.

Its either compression, ignition, or fuel related mate - the 3 elementary parts of the engine to make it go..

Best of luck anyway mate

[33SOM]

I had a link and a front facing plenum. car wouldnt idle until it was full temp cause of no aac thingie. So maybe its something in the tune?? Just a thought...

Edited April 5, 2006 by 33SOM

[MerlinTheHapyPig]

do you have software to tune the ECU?

if so, hook it up to a laptop and check what size injectors it's set to. This can cause problems so check this and see if it makes any difference. Tuning software can probably display sensor readings from the engine, so you may also be able to check if anything's not working.

[Triskillion]

dont know if this could have anything to do with it, i just quick read over this post.

but i was reading in a car mag the other day and they couldnt get the car to idle properly with aftermarket ecu (power fc) so they had to use the stock ecu to run idle and piggy back a diff ecu to control the rest (piggy back is the right term i think)

but if all else fails mayb that might help! good luck

[burnfest]

My r33 wouldnt idle with maps from 2 other cars, I got lucky with the 3rd. I have a wolf 3d with MAP sensor. Like you I just wanted to get the car running, then drive it to get tuned and not get ripped off. I think the problem is that all the base timing, tps open and shut values, etc must get programmed in from your car. Aftermarket computers cant adapt like a stocker ecu can.

Dont know if this helps...

Alex.