Still Having Problems With My Car

[benro2]

Hi guys,

I've had a couple of threads before with these issues but I have since fixed a couple of other problems and just wanted to get your opinions on what could be wrong here. My old threads are here and here but you probably don't need to read those as I'll be describing the problems again, plus new things that I've been noticing since then.

I have since replaced all the coilpacks with new Splitfires and my misfiring at idle problem has disappeared. I have also replaced the O2 sensor but that didn't make any difference at all, both to the engine or the readouts on my ECUtalk Consult Display. I have even replaced the ECU (as the old one supposedly had a fried part - the part which controls the valve timing) and the VVT solenoid! This made a small difference at low rpm - not as laggy and builds boost quicker below 2500 rpm.

Problem 1: between 30C and 60-70C, my engine is down on power big time, and my ignition timing is retarded by 15-20 deg or so from normal. When the engine is at these temps I would expect to be running 30-35 deg BDC on say 10-20% throttle but I'm running maybe 10-15 deg. It happens very suddenly, as soon as it hits 30C and the car feels *very* sluggish. Also, when I say "down on power", I mean just driving around normally, not WOT! Even to accelerate keeping up with traffic I would need to run a few psi boost, or 0 psi to maintain 60km/h in top gear!

Problem 2: once the car is up to temp, under high loads, such as a long hill in top gear in boost, the car "surges" like it is in R&R. It is definitely not R&R because the boost is < 5 psi. I have also noticed the timing can be down to as little as 10-15 deg BDC with ~ 5 psi boost @ 3000 rpm in top gear!

Problem 3: at high rpm the car also loses a lot of power just before it changes up (it's an auto). Sometimes it will hesitate a couple of times just before the gear change.

Problem 4: this is the most dangerous and annoying problem - after driving for say 20+ mins, the car randomly loses 50% power and runs 0 deg timing! I need to use 50+% throttle / 3-5 psi boost to even pull away normally in traffic from a stop! As revs build, say 3-4k rpm where it shifts, it's just starting to get to say 70% normal power, probably because the ignition timing is gradually building. It *seems* to be a heat issue but I cannot be sure about this. I highly doubt it was my old coilpacks because I can't see how this would affect the output of the ECU.

Problem 5: sometimes when the car is 60 - 80C the ignition timing at idle in neutral is all over the place. However, is this normal? It seems to range anywhere from 0-10 deg but if I put it in D it will settle on 20 deg. Normally in N it's settled on 15 deg. Is this just an issue with warming up? I have also noticed that occasionally, while up to temp (80+C) it will decide to do this random timing in N and when I pull away from the lights, the car feels much more responsive, ie: running the timing it should be running all the time, however this is quite rare and I'm not sure if it's related to the idling at all. I have also noticed that my idle speed is quite high, say 1000-1100rpm in N when it's normally 750 rpm, but I'm not sure if this is only when the timing is running haywire.

Possible solution: replace the cam timing sensor (or CAS / Crank Angle Sensor). One of my friends said to go for a new one however I don't think he knew they are $650 new!! I have just bid for a second hand one for $150 but won't know if I've won that until later tonight. Is it worth risking a 2nd hand one? Is it possible to open them and see any obvious problems? I don't want to do this to mine just now as it's my daily and need it to get to work It's probably best if I buy a 2nd hand one and look at that before putting it on the car! Could it be anything else?

Thanks in advance for all the help and sorry for the long post!

Edited December 12, 2010 by benro2

[SECURITY]

Check out your temperature sensors on the plenum. There are 2 next to each other on the front, a few cm from where the top radiator hose connects. Make sure there is a good connection with the plug and even look at having them replaced.

[benro2]

Thanks for the suggestion SECURITY - but I have just replaced the cam angle sensor today and it has FINALLY fixed the remainder of my problems! Very happy

Edit: now that I think of it, what's the correct operating temp for my car? It seems to hover around 80C on a relatively cool day, but can go up to >90C on a hot day, especially when idling (the thermo fan apparently turns on at 92C and off again at 87C, which I have tested for myself). However, even when cruising along the highway, on a cool day it's say 82-83C but if I hit a decent hill it will go up to 87C, maybe even higher.

Just wondering why it runs around 80C for starters - seems a little cool to me - and why it fluctuates so much? For comparison, my Supra is rock steady on 92C, no matter the temp, no matter how hard I flog it. Just a little worried that maybe my radiator is blocked or something?

Edited December 19, 2010 by benro2

[mad082]

it is common for it to fluctuate a little bit. 82 degrees is about where it should sit, but it isn't uncommon for them to get a bit higher. if you are worried about it then there are 2 things you can do. the first is get a new thermostat, and the other (which will more likely make a difference) is to take your radiator to a radiator place and get them to clean it properly. often they get a bit clogged over time and lose their effeciency. the cost of getting it properly cleaned might not be much less than getting an aftermarket alloy radiator though.

[benro2]

it is common for it to fluctuate a little bit. 82 degrees is about where it should sit, but it isn't uncommon for them to get a bit higher. if you are worried about it then there are 2 things you can do. the first is get a new thermostat, and the other (which will more likely make a difference) is to take your radiator to a radiator place and get them to clean it properly. often they get a bit clogged over time and lose their effeciency. the cost of getting it properly cleaned might not be much less than getting an aftermarket alloy radiator though.

Thanks for the the advice. I think mine sounds about right then, so I think I'll just leave it unless I notice it getting *really* hot on a 40C day or something. So far I haven't had any problems. Pretty sure as soon as the thermo fan cuts in at 92C it doesn't go any/much higher.

[mad082]

yeah just keep an eye on it.

when it is the thermostat you can often tell because the car takes a while to come up to temp (should be up to temp on the dash gauge in a few mins of driving, bit longer to get to 82 degrees though). if after 10 mins the car isn't fully up to temp that the thermostat is stuffed. but skylines are old cars now, so it is common for crap to have built up in the radiator, making them work much less effeciently. there are people on here who have replaced the radiator and then had the temp never move off 82 or 83 degrees, so i'd say that yours is probably heading towards needing the cooling system checked out. just keep an eye on it over summer. the final thing that can make temps a bit irregular is the water pump. as they get old they can get a bit worn and not pump that well. this generally results in higher temps all the time though.

[benro2]

yeah just keep an eye on it.

when it is the thermostat you can often tell because the car takes a while to come up to temp (should be up to temp on the dash gauge in a few mins of driving, bit longer to get to 82 degrees though). if after 10 mins the car isn't fully up to temp that the thermostat is stuffed. but skylines are old cars now, so it is common for crap to have built up in the radiator, making them work much less effeciently. there are people on here who have replaced the radiator and then had the temp never move off 82 or 83 degrees, so i'd say that yours is probably heading towards needing the cooling system checked out. just keep an eye on it over summer. the final thing that can make temps a bit irregular is the water pump. as they get old they can get a bit worn and not pump that well. this generally results in higher temps all the time though.

Yes, all good points, thanks for the tips!

My car does reach 80C by about 5 mins of normal driving, faster in summer.

One thing that is weird is the water temp gauge. About midway is pretty much 82C, but you can see it drop noticeably by 70C, yet by 90C it's still midway?? Is this correct? It may just be calibrated like that so it doesn't worry people on a summer day or something. Just seems weird it's sensitive one way and not the other!

Another "mod" I was considering this summer is where you can tell the thermo fan to come on with the A/C compressor. This would double as keeping the engine cooler all the time, as well as giving me cooler air, faster, just after I've started the car and am rolling around a stinking hot carpark at 1km/h for a few mins. The only reservation I have with this mod is whether or not it will stop the thermo fan from still cutting in at 92C, even if the A/C is off? Realistically, I would have the A/C on for the car to reach those temps, but I'd prefer not to chance it. Also, is it possible for it to make the water temp *too* cool, or would the thermostat take care of that? If there's any way to do this mod *and* have the thermo fan cut in at 92C regardless of whether or not the A/C compressor is on, that would be the ultimate setup! Kinda weird they didn't program it that way in the first place - I know a lot of other cars do this...?

Edited December 20, 2010 by benro2

[SECURITY]

the standard water temp gauge doesnt move till around 105 degrees. kind've sucks hey?

ive got a thermo fan that im going to wire into my ECU (vipec), so when the temp hits over 90deg it turns on. other then using an aftermarket ECU, you will have to install a thermo fan controller. im unsure of the temps they kick in at or if they are adjustable but im sure there are some floating around on ebay.

worst case - get a separate gauge and install a switch.

[mad082]

people have modded the thermo fan to kick in with the aircon by using a resistor. my car never had that fan (had had front end damage) and i bought an aftermarket one and simply wired it to be triggered to come on when the AC compressor kicked in. a mate of mine who tried the resistor method and had a slight problem with that method is going to try it the way i had it and see if he can get it to work as well as having it still work as an over temp fan as well.

[benro2]

the standard water temp gauge doesnt move till around 105 degrees. kind've sucks hey?

Yeah it does! Weird they did it like that, but I spose it makes sense for people who get worried when the needle moves up 1mm when it's a couple of degrees hotter (like my granny ). It would be all over the place otherwise, so I can see why they did it.

people have modded the thermo fan to kick in with the aircon by using a resistor. my car never had that fan (had had front end damage) and i bought an aftermarket one and simply wired it to be triggered to come on when the AC compressor kicked in. a mate of mine who tried the resistor method and had a slight problem with that method is going to try it the way i had it and see if he can get it to work as well as having it still work as an over temp fan as well.

Would you be able to let me know how this turns out? I would be very interested. I'm sure it's possible, I think it shouldn't be to hard for an auto electrician. I'll ask mine when he comes round next time and let you know.

[benro2]

OK, a small update for those who are interested (probably nobody )...

First of all, the CAS (*cam* angle sensor, *not* crank) FINALLY fixed most of my problems - at least the major ones! As soon as I put that in the car was MUCH more responsive, just like it's supposed to be! I haven't reset the ECU but I will do this shortly when I think of it. Seems fine anyway.

Secondly, I am having slight misfire problems at idle when I try to lower the idle speed to 650 rpm. I am thinking this is probably to do with incorrect spark plug gapping and/or fouled plugs from running too much boost in winter, plus from my aforementioned problems. The plugs probably haven't done any more than 5000 km, and they're just regular plugs, nothing like platinum or anything. I can't remember the gapping, but if I'm planning on running 10 psi boost in the near future, what should I gap them to?

So, when the idle speed is set to 850-900 rpm or so, the misfiring problem goes away, however when I put the car in D the revs have a long way to drop, and they actually drop to nearly 500 rpm for a second before climbing back to 700-750 rpm, and it's pretty rough and kinda annoying. When I tried idling at 650 rpm in N, when I put it back into D it was a smoother transition, probably because the revs didn't have as far to drop? Also, idle speed in D was pretty low, probably 550-600 rpm, so I had to adjust it back up to 850-900 rpm in N. At these revs, the timing is usually sitting at either dead on 0 deg BTDC or somewhere jumping between 0 and 10 deg. When I lower it to 650 rpm the timing is dead on 15 deg, and in D it's always dead on 20 deg. Do all these things point to the plugs or could there be something else?

Also, one thing that was new to me that's quite interesting regarding the thermo fan "mod" I was going to do in summer: it's not just an overheat protection fan, it *does* come on when the A/C compressor comes on, but only when needed! I'm guessing it's some kind of pressure switch, as on a fairly cool day it would take ~30 secs for the thermo fan to switch on (engine temp was ~60C which I how I knew it's not just an overheat fan) after the A/C compressor turned on, versus a 38C day where it took closer to 20 secs. So, no need to do this mod anymore! Would Nissan have done this for fuel savings or something?

Anyway, overall I'm now very happy with how the car is running - just need to get this idling problem ironed out and then I'll be able to rest

[GTR-N1]

Good to hear.

It's always difficult when there are 2 or more simultaneous issues eh Ben?

So now you're investigating IAC valve & ECU settings perhaps?

[SECURITY]

idle speed is good at 650rpm. i'd be looking at the AAC valve for the revs dropping too low.

also, the timing for an auto is 20deg btdc. check it with a timing light.

Edited January 8, 2011 by SECURITY

[benro2]

Good to hear.

It's always difficult when there are 2 or more simultaneous issues eh Ben?

So now you're investigating IAC valve & ECU settings perhaps?

Thanks for the tip, I guess I will be BTW, is the IAC valve the same thing as the AAC valve?

ECU should be fine as it's just been replaced (2nd hand of course). STILL haven't reset it, keep on forgetting! Will have to do that next weekend.

idle speed is good at 650rpm. i'd be looking at the AAC valve for the revs dropping too low.

also, the timing for an auto is 20deg btdc. check it with a timing light.

I've checked the timing and it was dead on. The sticker inside my bonnet says 15 deg BTDC - which I presume is for when it's in N - and I can see that the timing increases by 5 deg when it's in D. When I drop idle revs in N to 650 rpm I do get 15 deg BTDC, and in D it goes up to 20 deg.

Sounds like I'll have to check this AAC valve though! I remember reading aaages ago that the AAC valve may be blocked if the car picks up and drops revs, kind of like when the steering wheel is turned when stopped. It doesn't really seem to do this, and come to think of it, last time I had it in the garage I *think* the mechanic said he cleaned the AAC valve - will have to check this too.

Anyone agree that it may be the plugs still? Will have to check both though by the sounds of it...

[benro2]

OK, this post is more for when people do a search and curse when the problem's been fixed with no solution provided!

So yep, my car is FINALLY running back to normal now!!

These were all the things I had to fix, in the order I fixed them in, and what the symptoms were:

- VVT solenoid blown: replaced, picked up a small amount of torque below say 2000 - 2500 rpm. Almost undetectable if you didn't know any better.

- Replaced ECU: strangely, just the part that controls the VVT solenoid was fried. Had to replace the whole ECU. Done at the same time as VVT solenoid so I guess this is really what made the bottom end torque reappear.

- Splitfire coilpacks: stopped misfiring at idle and at high revs. Tried a second set of OEMs, but these had the same problems as my originals - spark must have been escaping out the sides. Tried siliconing up the gaps and tried every combination of coils between cylinders, no difference. Only solution here was new coils and Splitfires were availabe for < $500 shipped from Nengun.

- Replaced Cam Angle Sensor (CAS): this was responsible for strange behaviour when the car was warming up. As described in some of my other posts, when the water temp reached 30C the car would suddenly lose about half power (on a light throttle) and timing would retard severely. Timing would pick up again at around 70C. Obviously had to check timing after replacing but was already dead on. Picked this up for about $130 2nd hand off Ebay, but I'd make sure you have a DOA warranty and don't buy 2nd hand off a private buyer, as you cannot fix the CAS (AFAIK) and I really tried to pull it apart but it just wouldn't New are around $650 (!) so I figured I could buy 5 or 6 2nd hand ones for the price of that, and *surely* one would be OK! Luckily, the first one I bought was fine

- Cleaned AAC valve: before I cleaned this, the car was sometimes hard to start (particularly in cold weather) and was dropping too many revs when changing the gear lever from "N" to "D" (it's an auto!), so the car would "shudder" for a second while the revs dropped to ~500 rpm. Generally wasn't behaving normally around idle and when I tried to drop the idle speed to 650 rpm the car would misfire badly. As soon as I cleaned this, the idle speed picked up a couple of hundred rpm and the car shudders a lot less when changing from "N" to "D", although it still does happen slightly - but I think that possibly the car may have done this even when new. Either that or I didn't clean the AAC valve well enough I'm satisfied with it for now, although idle revs are hanging around 750-800rpm and I can't seem to get them to drop any lower, but I'm not too worried about that for now.

- Cleaned AFM and replaced K&N panel filter with paper filter: at this point I still had some slight "surging" on and off power under 5+ psi boost up a steep hill in top gear, much like R&R. Found out that you can NEVER run any kind of filter that requires oiling to be cleaned when you're running a hotwire AFM (ie: stock Skyline AFM) as the oil will eventually coat the wire and cause false signal readings. This happens even when it's been oiled properly (ie: not drenched in oil as once happened to me which required another 2nd hand AFM!). Cleaned the AFM with some AFM cleaner (yes, I was shocked that they actually *make* cleaners specifically for this too!) and went back to a paper filter to ensure it doesn't happen again. Apparently there are aftermarket panel filters (non-paper) that don't require oiling but usually these are harder to come by and much more expensive, so I didn't bother. I have not noticed one tiny loss of power at all.

- Reset ECU: this was the final touch. I noticed that the timing *appeared* to pick up slightly under a lot of light throttle situations and the car felt more responsive. I say "appeared" because it's quite hard to watch the timing under particular conditions and drive at the same time However, I can tell that resetting the ECU definitely changed the way the car drove from the seat-of-the-pants feel.

Only two remaining problems but I can live with them for now:

1. Idle speed is 150-200 rpm too high and cannot seem to lower it. Could be a split air hose, and I've heard that the ECU has an idle fine tuner on it, although I've also heard that the series 2 AFM's don't have this anymore. Haven't had a look on mine yet. I doubt this will help as I think it only has a max range of 250 rpm or so.

2. Slight misfiring at idle still. Could be dirty plugs and/or incorrect gapping, although I'm sure my gapping is correct as I made sure I researched this properly before replacing the plugs last time. Seems to happen when the A/C compressor turns on after idling for a few seconds after rolling to a stop. Only happens once every 30 secs or so on average.

(3. This may not be a problem, but timing is quite low at 50%+ throttle under 3000rpm. This is quite possibly just how the stock ECU behaves. I've seen it drop to as little as 8 deg BTDC @ 3000rpm in top gear @ 5-7 psi. However, the car seems to feel like it used to (when it wasn't broken!) under the same conditions, so I'm not going to call this a problem just yet, unless someone can confirm the correct timing under these conditions!)

Hope this is of help to someone! It's taken me a LONG time to diagnose and the car is a LOT better to drive than before. Overall I'd say it's using about 20-25% less fuel than before I started replacing parts too. I keep close tabs on fuel consumption via my ECUTalk box and after I replaced the VVT solenoid and ECU I was using about 10-15% less. Replacing the CAS accounted for the other 10-15%. The AAC valve, cleaned AFM and reset ECU didn't really make any detectable difference. The car is MUCH more responsive on light throttle and doesn't feel sluggish like it used to. I also noticed a slight change in engine note too, slightly more "growly", I suspect from running more advanced timing.

Interestingly, I had replaced the O2 sensor prior to the first item on this list thinking that it would solve all my problems and it didn't make one tiny bit of difference! At that stage the car had done roughly 130k km, and I bought the car at 49k km. Supposedly they're only good for 60k and I'd done 80k at that stage. The readout on the ECUTalk didn't change at all, and fuel consumption didn't change at all. It was a bit of a pain to do so I'd leave this one until last!

Edited March 11, 2011 by benro2