Weird idle (possible electrical) problem

[Rolls]

I orginally posted this on r31skylineclub but didnt get a whole lot of response so Im going to post it here.

When my rb20det passage is started first thing in the morning (starts no worries) it starts idling at 1500 then drops to 1000 about 2secs later then starts to stall, give it a little throttle and it goes back to 1500 but then repeats itself about 5 times before it will idlle correctly at 1100. This also happens in traffic sometimes when then engine is warm and in N. It will startidling at 1500 for no reason then drop to 1100 or 700. Any ideas what could be causing this? Also when it does feel like its about to stall it feels like the engine is missing a beat now and then and gets worse as the revs drop. The car still drives great when warm and doesn't miss a beat though.

Sound like its running rich or maybe the timing is out? my mate said it blows some thin black smoke under hard acceleration.

http://forum.r31skylineclub.com/index.php?...p?topic=23816.0

Either way they said its most likely my AAS that was stuffed so I cleaned the AAS and it dind't do squat, however it was very clogged up with carbon.

Anyway when I put it back I also had a go at installing my alarm but didn't quite finish it. In the process I had my ECU unplugged for several hours and when hooked it all back up again encountered a very strange problem

The car wouldnt start, it would kick over but not start, eventually after about 5 goes it made some backfires but would not start. Went under the engine bay, unplugged the coil pack etc and sprayed conductive spray on everything, tried again, would fire on about 1 cyl and instantly stall. Tried agai, wouldn't start. This went on and off and eventually it started running on 4cyls, ran like crap, took it around the block and didn't get better, then turned it off started it again and it started perfect everytime. Any ideas?

either way Ive found out the idle problem is related to something electrical I think as when it drops from 1500 to 400 it starts misfiring, not a lot but enough to make it drop that many rpm, then as soon as I give it some throttle back up to 1500 no worries, about 5 secs later will start misfiring and go back to 400. This goes on for about a minute getting better and better and after about 3mins the car is fine. THe colder the engine the worse it is,if ive driven the car within 4 hours it starts perfect.

Edit: it also doesn't have very good throttle response in neutral, have to give it quite a bit to make it rev, although in gear it still has plenty of power and goes fine.

[race_snooze]

My 2 cents coil packs, plug gaps, air flow meter check them out clean and replace see what happens

[Rolls]

Are you sure it's got good fuel pressure? I think those old Rb20's had a fuel pump modulator controlled by the ecu so they idled at low voltage on the pump. Or if it's a later Rb20 then the ecu directly controls the pump voltage at idle.  

On idle with little or no alternator output, they can starve for fuel.  

Regards.

What would you suggest doing to fix this issue? I have a spare pump but it sounds like its not the issue, the way its getting its power is.

Also I think Im gonna check the air flow meter and maybe replace the plugs, what does a new coil pack cost?

[Rolls]

ok ran the diagnostics on the ecu

it flashed both lights on once, pause, both lights twice, pause, both lights 3 times, pause, both lights 4 times, pause, both lights 4 times, pause and then it repeated

now according to this http://wiki.r31skylineclub.com/tiki-index....age=Error+codes

That means my crank angle sensor (surely it cant be this or I would experience massive power loss?), fuel pump circuit (apparantly this isn't even stored in memory), 33 which doesn't even have a diagnostic code for it and then 44 which I think means no more faults.

any clues?

also being as I have a transistor pack and 1 coil do I even have a crank angle sensor?

Ok just reset the ecu, started the engine for about 1min and then ran diagnostics again, flashed both lights twice then 4 times twice and then went back to the pattern I initially mentioned

[Slipero]

wassup the codes that u have said is the ecu going through the 4- modes it has! its like the r32 ecu wen its up to mode three(wen it flashes 3 times) turn the dial fully anticlockwise then wait to see yr error codes! its definately electrical it looks like yr ecu has remapped itself 2 rich.

[Rolls]

wassup the codes that u have said is the ecu going through the 4- modes it has! its like the r32 ecu wen its up to mode three(wen it flashes 3 times) turn the dial fully anticlockwise then wait to see yr error codes! its definately electrical it looks like yr ecu has remapped itself 2 rich.

Yeah its definately running too rich, getting about 20l/100km on average, about 15 if I do some highway driving and thats not giving it much.

Gonna get a tune and see if it improves economy and see if in turn it fixes the idle problem.

[Rolls]

Also was using the AC today and when I turned it off sometimes the device that compensates for it and ups the idle speed didn't turn off and it would start idling at 1300

[Rolls]

Update:

Ok ive changed my plugs and gapped them to .8, changed my O2 sensor and taped up my what appears to be shagged coils (hairline cracks and scald marks) and its made the problem worse, when the engine is cold, any throttle between 1.5 - 2.5krpm causes it to missfire really bad, the more throttle the more the revs drop and the worse it is, after 5mins however its fine.

Ive bought some 2nd hand coils and Im going to properly cover them in araldite and do a few layers and replace them, if this doesn't fix it what would you suggest? CAS ? my idle vac is about -11 so im thinking maybe I have a mild vacuum leak, can't hear anything however.

Also took it for a spin tonight and it misfired really badly like when hitting the limiter at around 4.5-5.5k

did a few launches however and it seems to go away, still not happy.

I might look at my temp sensor and AFM next week on my day off, they are really the only other things aside from my timing being out I can think off. Im gonna put the money on the coils though as they are shagged.

[Rolls]

Just ran a bottle of injector cleaner through the car, the misfire at low revs under load is almost completely gone and ive only used 1/4 of the tank.

However the small hesitation at low revs when cold is still there, and the idle still hunts and goes up and down.

Still gonna replace the coils as it loses power and pops at high revs occasionally.

[Rolls]

update for anyone whos interested and reading.

I just replaced my coil packs and plugs to no help.

Anyway left it idling with my head under the bonnet, as soon as it starts misfiring I head a zzzst kind of like electrical shorting coming from the injectors, I tried the screwdriver to the ear trick but I couldn't get the one in the middle which is where it sounded like it was coming from, tried bashing it with the screwdriver but no luck.

Also I found a not the best way to cure the problem, after starting the car if I stab the throttle to 90% and rev it to 2.5-3k (I know bad on a cold engine) it idles almost perfectly.

Im thinking maybe somethings leaking or somehow clogging one of the injectors or possibly one of the igniters just needs a decent voltage through it to make it work correctly. I dont really know as Im not the most mechanically minded person.

[b1lly]

I dont have a Skyline yet, waiting for compliance .. but if Skylines have a MAP sensor it could be your MAP sensor has shit itself especially if you get really black smoke coming out of your exhaust when you give it a little rev.

[vas_95]

update for anyone whos interested and reading.

I just replaced my coil packs and plugs to no help.

Anyway left it idling with my head under the bonnet, as soon as it starts misfiring I head a zzzst kind of like electrical shorting coming from the injectors, I tried the screwdriver to the ear trick but I couldn't get the one in the middle which is where it sounded like it was coming from, tried bashing it with the screwdriver but no luck.

Also I found a not the best way to cure the problem, after starting the car if I stab the throttle to 90% and rev it to 2.5-3k (I know bad on a cold engine) it idles almost perfectly.

Im thinking maybe somethings leaking or somehow clogging one of the injectors or possibly one of the igniters just needs a decent voltage through it to make it work correctly. I dont really know as Im not the most mechanically minded person.

check the voltage across the battery with no accessories on it should be over 13 volts you can get it checked at bateryworld. It sounds like maybe your car isn't geting enough voltage since you have changed coils etc

checking the voltage will also tell you whether the alternator needs changing

[treo]

check to see if your fuel pumps stays on when the car stalls, listen for it with your head next to it. Change your fuel filter also and is your cat in good condition, could be blocked a bit

[Rolls]

Thats a good idea vas_95, will check later on. Had a similar idea myself a day back but havent had a chance to check it.

Basically when driving at night with lights on everytime it misfires all the lights in the cabin dim, and if I use my indicators the stereo cuts out for a few seconds, sometimes the misfire also causes this.

Im also thinking maybe theres a bad connection to one of the coil packs shorting to the chassis as that would explain the zapping noise I hear and the diming of the lights dude to the short.

Also my fuel pump changes tone somtimes during the misfire as well, only once the revs get real low.

I check it with a multimeter tonight and report back, cheers guys.

[wishaw]

well then it sounds like it could be your battery or your altenator. Get a trusty multimetre and check the voltage across the termainals when running with no acc's on the turn onlights etc. You should still have a voltage above 13v. If you don't then try reading the voltage as someone starts the car for you. If it drops below 8v then you most likely have a shagged battery. If the voltage doesn't drop heaps then it is most likely a problem with the altenator.

Either way you should get is tested by some battery people.

Another thing that can't hurt is some extra grounding wires near the injectors + spark plugs + coils. Get some decent 4 gauge audio cable and gold conectors and run them either to a quality grounding point on the body of your car or to a single point then run a wire from there to the battery. This should help to eliminate and voltage drop caused by bad grounding and could be a temp fix untill you find the problem.

[scott]

Try cleaning your throttle body if you put injecta clean in your tank

and you have noticed an improvemant i belive if you clean your throttle body

you will be a happy camper.

Goodluck.

[Rolls]

Battery voltage is at a constant 14v So im thinking alternator or shorting somewhere