Hunting Idle & Miss Fire ..... Advice Please?

[stacky]

Hi all,

Have a series 1 R33 Gtst and have a few annoying problems that i hope someone can help me with....

Problem 1: Hunting idle & High tickover.

On first start up when cold it rev's quite high (normally between 1500rpm and 2000rpm) for the first 5(ish) mins.

Then when stopped at the lights, 50% of the time it idles stable at about 800rpm, but the other 50% of the time it hunts between 500rpm and 1500 rpm.

I did a search and found the two likely causes to be the idle control valve and/or the AFM.

I took both out yesterday and cleaned them with carb cleaner but NO DIFFERENCE :-(

Problem 2: miss fire when cold.

It missfires at from 4K plus when cold (not that i drive it all that hard when cold), but after a good 20min drive no more miss firing.

Finally,

The alternator belt or water pump bearing is screeching. Not sure if this is connected to the problems but thought i should mention it.

It does seem to play with the idle a tiny bit but as it only screches for the first 30 seconds of startup from cold - its obviously not the route cause.

Any help would be much appreciated.

Cheers

[AGROV8D]

Try resoldering the AFM pins. Take out the AFM, open the box and resolder the pins going from the PCB to the loom connector.

Resolder them even if the old solder is still intact. You'll find that a lot of idle issues have been resolved simply by resoldering the connecting pins if you do a quick search (including mine, contacts were intact however I still ended up resoldering them just to rule it out and.it ended up fixing my idle issue).

Additionally, check that the AAC has been cleaned properly including mating surfaces and tightened properly when you reinstalled it. Check all the hoses going to and from the intake manifold for leaks.

Clean the throttle body and check/adjust the TPS to correct setting.

Reset the ECU and the idle once you've done all of the above. There is a step by step guide on cleaning the AAC and resetting the idle, do a quick search.

I have a feeling that your missfire issue is related to your idle problem so hopefully sorting out the idle will sort out the misfire.

Check the belts for wear, if worn, replace them. If not, check/adjust the tension, could be as simple as that.

Edited March 12, 2013 by AGROV8D

[stacky]

Thanks for the reply.

I will try re-soldering when I get a chance.

The acc was defo done correctly so I'm gona eliminate that from the possible causes list!

I'm gona wrap PVC insulation tape around the coil packs later to see if this cures the misfire (as per the sticky thread).

One thing I have not checked is the fuel filter so I'm going to change that tomorrow.

Any other opinions / suggestions?

[stacky]

Ps, how do I adjust the tps?

[AGROV8D]

Here's a couple of threads on how to adjust the TPS:

http://www.skylinesaustralia.com/forums/topic/404812-help-setting-tps-on-r33-s2/

http://www.skylinesaustralia.com/forums/topic/374524-rb25det-s2-tps-clarity/?hl=%2Badjust+%2Btps#entry5983578

[stacky]

Well, I adjusted the TPS. It was out but after adjusting correctly I still have the hinting / erratic idle issue.

Is it possible for the TPS to fail, or is that highly unlikely?

So far i have:

• Adjusted the TPS.
• Replaced the air filter,
• Cleaned the AFM with electrical solvent cleaner.
• cleaned the AAC

This weekend im going to do the following:

• Replace the lambda/o2 sensor.
• Resolder the AFM.
• Oil change,
• Fuel filter change.

I suspect however that none of that will fix the issue :-(

Anyone else have any other ideas??

PS.... currently the problems i am experiencing is:

When Cold:

• Screeching belt on cold startup for the first 30 seconds.
• Very high tick-over when cold (2000 rpm) but no hunting idle.
• Miss fire at 4500 rpm.

When Hot:

• Hunting/erratic idle (needle waves from 500rpm to 1200rpm).
• Poor fuel consumption.

Edited March 14, 2013 by stacky

[niZmO_Man]

Screeching belt... have you checked alternator belt?

Unfortunately, you'll have to track down another known working AFM to rule it out.

[stacky]

Ya, the belt is fine (its in good condition and probably less than a year old) so i figured it was just loose.

I tightened it using the adjuster on the alternator, started it up and it was screeching non stop, so then i slackened it off and it got alot better (but still screches when stone cold).

I need to budge and re-tilt the alternator bracket to slacken it off any further.

[rooney1980]

hey mate, did you resolve your prpoblem as Im currently experiencing exactly the same symptoms!