Rb20det Silvertop - Intermittent: Rough Revs & Running Rich

[E.k]

Having a bit of an issue with my Silvertop.

For the last 6 - 8 weeks, I've had an intermittent drop in revs, making the car run richer than Bill Gates & sound like a filthy Subaru on it's death bed, for no apparent reason..

It can happen while driving, at any revs & any speed, or even while stopped & idling.

On idle, it would be at 600 - 800 rpm.

Once it hits, it sticks & stays, until the car is turned off & left for 3-4 or more hours.

At first, I was able to get it to go away sometimes by putting the boot into it, making it stutter & snap out of it. Now, it just shudders along like a bitch, no matter how hard I try..

It used to be totally unpredictable & intermittent. But now it seems to always hit after 15 - 20mins, regardless of temperature, weather conditions, revs, driving style, stops/starts ect.

My first thoughts were coilpacks, spark plugs or fuel filter.. But all along, I've been leaning towards something electrical, because of the way it just happens - It can be running beautiful, then all of a sudden feel like its running on 4 or 5 cylinders.

I replaced my non-gapped Irridium plugs with standard RB30 ones. Put on a new fuel filter.

The car starts quicker & idles slightly better, but still had the problem.

Me & a mate taped up my coilpacks, to temporarily stop them arching out, if they were.

Made no difference either.

I unplugged my AFM while idling, the car stalled. Started it while still unplugged, coughed & spluttered & slowly picked up revs until it was idling smooth at about 2000 rpm. Plugged it in, revs dropped to 600 again..

Got a good condition S1 R33 AFM off another mate, (which is rediculously clean internally, compared to mine) put that in tonight.

No difference. I can still unplug it & have the revs smooth & raise up to 2000 - 2200.

I've checked the crank sensor plug, all coilpack plugs, igniter plugs & grounds, & the AFM plug itself. Wiggling & pushing ect.

I checked the ECU, getting error 55, which = No Fault or No Malfunction. Reset the system with the batt & brake pedal method, checked again, 55 still.. Although I havnt driven it since the reset or the new AFM.

I will know in the morning when I drive to work.

Anyone have any ideas?

Any help at all would be much appreciated guys.

Thanks.

[mad082]

it could be that the afm is faulty and it was only an intermittent fault, like if you hit a bump and that was enough to move a loose connection.

it could be a faulty tps (throttle position sensor)

could also possibly be an issue with the ignitor pack as well.

[E.k]

Same results this morning on the way to work.

Car started & ran fine. After about 10 mins, revs dropped & ran like crap for the rest of the 30 min trip.

Let me just add that by "running like crap" I mean an extreme lack of power & response.

It becomes very sluggish to climb speed & will continue to be sluggish no matter the speed, revs, gear ect.

And coming on boost just agrivates the whole roughness..

it could be that the afm is faulty and it was only an intermittent fault, like if you hit a bump and that was enough to move a loose connection.

it could be a faulty tps (throttle position sensor)

could also possibly be an issue with the ignitor pack as well.

The AFM has been changed, lastnight, with a known working one. Which is insanely clean inside compared to my old one.

Nothing changed at all.

Is there any way to diagnose the TPS or Ignitor? Finding RB parts to test or lend isnt easy..

[mad082]

when i was talking about the AFM i was refering to the old one since you hadn't properly driven with the new one, but now you can rule it out.

TPS would be best tested with a consult cable, however i'm not sure if they can be used in the older cars as i don't think they have the consult port. however you could test it with a multimeter.

i'm not sure how to actually test the ignitor. the general symptoms of a stuffed ignitor is that once they get hot you start to get a missfire, very similar to when the coils go. generally the symptoms get worse when you get on boost.

another possibility is that the CAS is dodgy and it is retarding the timing. to test that you really need a timing light and once it starts playing up, if it is playing up at idle, pop the bonnet, connect the timing light and see if the timing is out. might be a good idea to test the timing when the idle is fine as well so that you have an idea where it is when normal so you can easily and quickly tell if the timing is out when it is playing up.

[PUDZ 32R]

same thing happened to mine last week. changed plugs and coil packs now its sweet. i am going to test next week if it was plugs by putting my old coil packs in and see if it starts again if not i can give my mate his coil packs back!

it sounded like a subi. was running on 5 cylinders whenever it got hot sounds exactly like what was happening to yours and i knew it wasnt fuel because it backfired heavily when i let off when it was running shite. so spark was the cause! i put NGK iridiums in mine even though the book says there is no known number for the RB20 silver top. i cant remember the codes tho but they are a match to fit the RB30E with 1.1 gap i gapped down to .8.

hope this helps!

[E.k]

Good point mad082, Im gonna get a hold of a timing gun off the old man to see if the CAS is throwing the timing out.

I'll test the TPS & Igniter too. Anyone else have any more info on the testing of these? Exact readouts I should be getting?

Thanks PUDZ

I was going to replace the coilpacks, but I dont want to do that right now if it isnt going to fix the problem..

My concern is that when it happens & the car is idling like crap, unplugging the AFM (BOTH mine & a mate's known working one) instantly brings the revs up (rather high though) & takes away the rough & rich idle...

So if the problem isnt with the AFM's, then whats goin on? How can it be nearly resolved by unplugging, but not be the actual AFM's causing it since I've tried a perfectly working one?

[PUDZ 32R]

this is unlikely but have you tried unplugging your temp sensor wire that feeds the ECU? there are 2 temp sensors one for the dash and one for the ECU. it is the 2 pin plug they are right next to each other on the right radiator hose. it could be that the sensor is feeding the ecu dodgy temp info and it is running massivly rich as it is "playing it safe" as it has no f ing idea what the temp is. try changing temp sensors with a mate.

also you havent said if you left the valley cover off and went for a drive to get it playing up then unplug one coil pack at a time to see which cylinder doesnt make the missfire worse. then you know which cylinder is your problem.

[E.k]

Changed the CAS with a mate's spare GTR one.

Made no difference.

Turned out to be a coilpack..

And yeah, we unplugged them 1 by 1 until we found the one that made no difference to the idle.

I have no idea why we didnt try this first .. Someone's retarded..

So now I have to go get some YellowJackets or JJRs..

Is it causing any harm by driving the car for 2x 30 min trips, 5 days a week?

It only drops the coilpack after 15/20 mins..

I'll need a bit of time to get a hold of the new ones.

Thanks again guys, I'll definitely use all the info to make sure everything else is in order.

[mad082]

you could try to help the problem by altering the gap in the spark plug (make it smaller). also i'm too lazy to reread the thread, but have you tried taping up the coils? this may also help with the problem until you can get new coils

[E.k]

Yeah we have already taped them. It didnt work..

Im leaning towards JJRs. Simply because of the price, availability, mate's experiences & what I've heard.

I dont wanna spark (heh, get it?) an argument here or anything, but whats peoples opinions on the best value / quality coils?

[mad082]

i have heard quite a few things about the JJR coils, and not many were good. i'd go for the yellowjackets. not much more in price but seem to have a better reputation.

[040122]

hey ive had rich problems and extreme backfiring at high revs, just changed to splitfires coil packs, that got rid of the backfiring but car still runs very rich, anyone have ideas??? by the way its an r32 gtst