Elevated Idle Problem After Injector Change

[Dale FZ1]

Here's a problem I may need opinions on, while I look for a fix.

Car: ECR33, runs Apexi PFC and FC Datalogit. High flow turbo, stock manifolding. Injector upgrade to S15 Silvia spec.

I installed the injectors yesterday, entered the correction factors via Datalogit and car started straight up, no issues with running that I could tell. Took it for a short run this morning to check for fuel/water/air leaks. All nice and tight that I can tell.

Problem came up when I stop and engage clutch. Revs drop down to about 900 (normal), and then come up to a stable 1250-1300. This happens when a/c is OFF. When a/c is ON, revs drop to about 900-950 (stable).

I'd considered a few potential causes.

Vacuum leak. Inlet manifold has to be split to access injectors, and throttle body removed. Machined faces were all cleaned up spotless prior to reassembly, I used copper spray gasket to further aid sealing, and the manifold bolts were all torqued down in sequence (and a bastard of a job it is too). There is no obvious hissing under vacuum or under boost. The car also responds to a throttle lift, so I think (hope) I can discount air leaks.

TPS adjustment. Didn't touch it. Should be operating same as before.

Idle adjustment. Didn't touch the throttle body other than use some carby cleaner around the butterfly. Didn't do any electronic adjustments via Datalogit. Should all be operating same as before.

ATM, I'm going to have a second look at the inlet manifold bolts for tension, similar for throttle body bolts.

Any ideas on where else to look?

cheers

Dale

Edited August 2, 2006 by Dale FZ1

[Dale FZ1]

BUMP

Are there any opinions or experiences amongst you? I'm looking to fix this one myself.

Many guys have reported doing injector upgrades, so have there been problems like this one?

I can't identify any loss of boost, or decreased vacuum @ idle.

I've been considering that my correction factor was incorrect, leading to a rich mixture similar to cold-start correction. Going to do a short test by altering the correction slightly.

First test I will do is alter idle speed setting in the ECU and see how that impacts things.

comments?

[Dale FZ1]

BUMP

I made a slight change to injector lag, with no effective change to idle.

Then I went into idle control, altered the FC1 / FC2 values and got a hunting idle (rolling up/down between 500-1000). Made me remember that I had used carby cleaner in the plenum to purge oily film from the PCV feed. The AAC valve was left in-situ, and I suspect it may have got a coating of the oily crap. Going to have a look at cleaning it tomorrow.

Surely someone has some idea here?

[202.3rwkw]

just by chance did you disconnect the battery? may have to do a thorough idle relearn?

u say you split the manifold? is the iac reconnected at the firewall end of the manifold?

[Dale FZ1]

Didn't disconnect battery for the job - didn't need to. And yes - I know the manual says to do so, and the potential issues with sparks when the fuel rail is disconnected. Working in a well ventilated area, and I had control over the keys at all times.

To do this job, the manifold has to be split. It is the only way to access the fuel rail and injectors.

All connections put back together and double checked for proper attachment.

Edited August 4, 2006 by Dale FZ1

[brett33]

Didn't disconnect battery for the job - didn't need to. And yes - I know the manual says to do so, and the potential issues with sparks when the fuel rail is disconnected. Working in a well ventilated area, and I had control over the keys at all times.

To do this job, the manifold has to be split. It is the only way to access the fuel rail and injectors.

All connections put back together and double checked for proper attachment.

Think it says here to let it idle for half hour to learn idle

http://members.dodo.com.au/paul/docs/power...powerfc-faq.htm

[Dale FZ1]

Thanks Brett; appreciate your thought.

Self learn idle really only applies if the ECU has been removed (my understanding). In this case, all I did was disconnect the sensors that feed info to the ECU, laid them aside, and continued with the removal of plenum and fuel rail. At the end of the procedure the plugs were reconnected.

I don't think that it (ECU memory wiped) would be the cause, because my idle is stable - it is just a couple of hundred rpm higher than previous.

[Dale FZ1]

I removed the AAC valve assembly from the plenum today. There was some carbon deposited through the air channels, but not caked in or excessive (that I could tell). Used a fair bit of carby cleaner to loosen up anything, then blew it out with compressed air. Also removed the AAC solenoid from the assembly, cleaned up everything I could realistically get to.

Result: no significant change. Given what I saw, I didn't expect much different. The idle quality DID change, but inconsistently. Coming to a halt and engaging the clutch, revs would go down to about 800, climb to 1200, then hunt for about 10-15 seconds between 500-1000. Typically this seems to be related to a crappy carboned up AAC. Not sure on that one given that I had just put a reasonable effort into cleaning it out.

Further effort put into reading the engine service manual, and I found there is a manual adjustment on the AAC. Pic below shows it circled, viewed from the drivers side:

Following the manual, a clockwise adjustment of the screw did pull the idle revs down. A test drive showed the engine would come back to an idle within spec. Will have to drive the thing for a few days and see if the fix is satisfactory.

Has anybody found this sort of fix useful/workable in the past?

[paulr33]

*nevermind, didnt read the last post*

i have this idle problem as well, im often pegged at 1500rpm for long periods, ill give it a shot

[rob82]

Are you sure you didn't bump the TPS??? What its voltage at closed throttle?

[blind_elk]

Did you re-tune to idle fuel maps? Bigger (I'm guessing S15 are higher flowing) injectors are going to deliver more fuel for the same duty cycle.

[rob82]

I removed the AAC valve assembly from the plenum today. There was some carbon deposited through the air channels, but not caked in or excessive (that I could tell). Used a fair bit of carby cleaner to loosen up anything, then blew it out with compressed air. Also removed the AAC solenoid from the assembly, cleaned up everything I could realistically get to.

Result: no significant change. Given what I saw, I didn't expect much different. The idle quality DID change, but inconsistently. Coming to a halt and engaging the clutch, revs would go down to about 800, climb to 1200, then hunt for about 10-15 seconds between 500-1000. Typically this seems to be related to a crappy carboned up AAC. Not sure on that one given that I had just put a reasonable effort into cleaning it out.

Further effort put into reading the engine service manual, and I found there is a manual adjustment on the AAC. Pic below shows it circled, viewed from the drivers side:

Following the manual, a clockwise adjustment of the screw did pull the idle revs down. A test drive showed the engine would come back to an idle within spec. Will have to drive the thing for a few days and see if the fix is satisfactory.

Has anybody found this sort of fix useful/workable in the past?

Its not the right fix - your only masking the problem.

[Cubes]

Dale,

When I dropped my larger injectors in I initially had a few issues with idle.

I'm thinking I stuffed up the learnt values within the pfc upon the initial start as I forgot to connect the carbon canistors vacuum feed, resulting in a high idle.

Once connected the idle was all over the place and wasn't going to settle down, init and idle reset was the only thing that fixed it.

The ONLY solution in my case, get the pfc to relearn idle:

Disconnect the aac plug and reset idle to as close but not over the target set within the pfc, I then had to init the pfc and let it do its idle thing.

My PFC won't do the idle relearn if I disconnect the battery etc, it's still niggly with the high idle etc, but once done the above it was perfectly fine.

At a later date my carbon canistor crapped it, I could hear an ever so slight whistle from the carbon canistor, upon replacement it once again stuffed the idle required an idle reset.

If left untouched it does idle ok and learns a little but still has the odd high idle and hunt which gets under myskin, once an idle reset (manual adjustment + init then learn) it idles 100% perfect all the time)

[R31 POWER]

If i have the hand controller plugged in i get all sorts of shit idle, like idling high sometimes. With it unplugged it's great Maybe dissconnect the commander and see how it goes?

[paulr33]

yeah ive heard of that problem too

hanving the hand controller unplugged helps wierd problems

the hand controller sucks off 5v to run itself, maybe you have a voltage problem ?

[Dale FZ1]

Rob - didn't touch/adjust/bump the TPS. I will check my throttle closed voltage to be sure though. And yes, I am concerned that giving the AAC a thorough cleanout and adjustment is only a gloss over whatever the real problem is. At least it seemed to work.

Blind Elk - yes, as per original thread starter, I entered appropriate correction factors for the larger squirters. If not, it would be richer everywhere by a factor of about 18%

Cubes - although it was only the vacuum ports, AAC and TPS that were effectively disconnected, I will have a go at a full idle reset / ECU re-learn. I find it odd because there was no mechanical changes done other than installing bigger injectors, and no electronic changes other than specifying the injector correction factors. The ECU was not disconnected or power source removed. I will firstly run it for a few days with the current AAC clean/adjust, then have a go at full idle reset and post up any results during the week.

Paul - the hand controller has been disconnected at all times other than for a short run to see the difference in duty cycle. As expected, it was reduced by a factor of slightly less than 1/5 for similar running as with the original injectors.

The whole situation has been a bit odd but I reckon not something that has to be tolerated.

Thanks guys, the input/feedback has been helpful.

cheers

Edited August 6, 2006 by Dale FZ1

[The Mafia]

I'm keeping an eye on this thread - COuld be useful.

Sorry I didn't reply to your SMS Dale, been out most of the weekend.

[Dale FZ1]

Looks like I have fixed it. Got a couple of pics for posterity too.

I'm going to run it for another day, then post up the outcome. Looks like it was related to attention to detail rather than any glitches.

[Dale FZ1]

After checking out the amount of adjustment I needed to make in the air bypass, I was satisfied there must have been an air leak somewhere/somehow. Note that there was NO noticeable loss of boost, or any hissing to indicate such, nor was the vacuum at idle lower than normal, nor was the idle rough.

Suggested method of tracing an air leak is to run the engine, then get a fine misting spray bottle of water to mist water around the manifold and injectors. If the engine stumbles while doing this, it's a fair indicator of a leak. Alternative is to spray some ether (sold as Aerostart or Start Ya Bastard) in the same areas, and watch for the idle speed to lift higher. Be careful using ether because it ignites easily. No good having an engine bay fire.

I re-split the manifold, and though the gasket seal looked perfect, I did find something:

The circled areas show where the inside bolts go. Note that one has a rubberised locator/isolator missing? It came out with the bolt upon disassembly. When I had originally put it in, things had not gone "home" properly. I must have been in a little rush just to finish the job and failed to see this. Then when I went to check the tension on all bolts, I gave it a little tweak with the spanner and felt it suddenly seat home. I presumed the seating was in fact yours truly stripping the thread and got very cranky. I had expected to need a thread repair job while redoing my work. (thankfully there seems to be steel thread inserts used by Nissan, so it would take one hell of a lot of tension to strip things out).

When I reassembled the manifold, I did it with perfect daylight, checking things 3 times.

Result: final adjustment of the AAC ultimately returned the bypass screw close to where it had originally been. Stable idle, about 700rpm at operating temp, about 900 - 950 from stone cold. Also I haven't gained any additional boost or vacuum. That leak must have been very very small.

There has been a lesson in this one, shows why some of us are mechanics and some aren't.

cheers

Dale

[jnr32r]

Are you using an original gasket or something like loctite gasket maker?