Hi guys, Ive once again got myself another magna. 9th one I think lol

Anyway, its a 3rd gen 3.5l, has 180k, It runs very rough. Doesnt blow any smoke. Seems to rev quite freely once its up in the rev range. Just down low is rough.

Im not getting a engine light, The light does come on when ignition is on the 'ON' position so I know it does work. Ive pulled all the plugs out and they dont seem to look that old so I cleaned them up a bit and chucked them back in (I dont wanna spend money on it unless i know the motor is ok). The rotor button had a bit of build up and the dissy cap was a bit worn. Once again I cleaned them up and put em back on (made no noticable difference).

Im quite happy to replace all servicable items when I know car will be ok, otherwise Im chucking money down the drain. Again.

Any more suggestions on narrowing down this issue?

Any help would be greatly appreciated!

Cheers,
Rob.

When looking at the Tacho, is it a smooth idle but feels like it's rough? Engine mounts could be rooted.

Does it rev freely once you go wide open throttle ? if so im guessing oxygen sensor

Nah, mounts seem ok. Can't remember what tacho looks like. I've had rooted engine mounts before and this is much worse :(

Yeah it seems to, not as good as it should but much better then down low. Would o2 sensor bring up engine light?

Na the o2 sensor doesnt bring up the engine light hence why it took me nearly a month to diagnose! but if it was the o2 sensor it would run fine when you floor it as the ECU ignores the o2 sensor

Maybe try the fuel filter ? Could have a dodgy lead but unlikely

Oxy sensor will not change the revs, idle etc so forget that before you even bother to start

Begin with standard stuff like making sure the air filter is clean, the MAF is not damaged, the TB has been cleaned out etc.

May be something simple like the above, may be dist as well as can cause these issues, may be MAF sensor needs a squirt of MAF cleaner

I always like to inspect an engine with similar problems to yours at night in total darkness....engine idling and bonnet up. Look for any high voltage leakage at idle....then try doing this with some load on the engine - for safety have an assistant place the car in reverse (so you don't get run over) with the handbrake and footbrake fully on and just bring the engine up a few hundred revs till it starts to miss/splutter whilst you eyeball the engine again looking for HV leakage....don't do this for more than 10 seconds at a time to avoid overheating the torque converter. If there appears to be no leakage, it will rule out high voltage leakage as a problem. Next I'd check the injectors which if bad should cause one or more plugs to look 'wet' or otherwise different to the others. I'd also clean the throttle body and also check every vacuum hose for splits etc.
Good Luck.

Thanks for the info.

I have cleaned out the throttle body and air filter seems ok. I unplugged the front 3 injectors 1 at a time to try and narrow down which cyl has the issue but with no luck. Rear back is obviously near impossible to get to without pulling manifold back off.

vac hoses seem ok, ill sus them out a bit better tonight and run the car in the dark to look for voltage leak.

Car runs the same with the maf plugged in and unplugged (ive been told because of this is not the maf?) I havent heard of maf cleaner before?

Thanks again for your help guys

The car runs the same with and without the MAF?

I think you have a non-functioning MAF!

When I unplug my MAF it runs like dog shit lol

well it runs like dog shit to start with! :(

I would say your MAF is completely broken dude.
Normal thing that happens is when your MAF is plugged in, you start the car and it idles smooth like normal.
Unplug it and it starts coughing and spluttering on idle.

I've done it many a time, started the car and forgetting the MAF isn't plugged in.
If your car acts the same whether your MAF is plugged in or not, I'd say your MAF is dead.

Get a new one, they're about 50 bucks.

That's my guess anyway, all the symptoms are ticked.

If you car does not run any better with maf unplugged, your maf or the wiring up to it is shagged

awesome thanks :) hope thats it.

I have to get someone I know with a magna to stop by so I can try swapping it. Though, once again, wouldnt that bring up the engine light?

Ok well I used some contact cleaner and cleaned up the maf, it seems to make a difference both pluged and unplugged. Still runs like crap though, so I'm assuming it isn't that

Either way, try to get your hands on a MAF and plug it in to see. My bet is that's your problem

Im goin to swap the maf out of my mates vrx today.

I had a look last night and couldnt see any leaks in the leads. If it was low compression either rings or valve wouldnt it blow smoke?

nope, didnt change anything :(

I had a similar problem in my old Pajero... turned out one of the pistons had a hole in it, so it was running on 5.

To find out if you've got a mis firing cyl without getting a compression test (as it can be a shit to get to the rear plugs), open your bonnet with the car idleing, put some gloves on, get a pair of vice grips or something similar and pull 1 lead from the dissy (it will make the car run like crap.. this is a good sign) replace the lead and go to the next one until you get to a lead that doesn't affect the idle... that will be your bung cyl.... then your up for an engine dismantle (assuming the ignition system isn't the fault)
If all leads worsen the idle look elsewhere

ps. This is the old way of doing it, don't zap yourself either!

I had a simillar problem when i swapped to a flowed throttle body. Turns out my problem was both a poorly set Throttle position sensor and the absence of the air fuel mix screw in the front of the throttle body (i may have the wrong name or function of teh screw but basically its a tube like potrusion from the front of the throttle body from memory with a largish screw inside of it) When it was running rough it would start up with the check engine light for a little while then go normal as i got it closer to correct it stopped appearing.

So yeah PERHAPS it's just poorly setup (or missing a screw entirely) if you can remember where it started off try fidling with those two things and maybe it will run a bit better.
If i'm probably wrong but hey it's another solution that wont cost you anything (just remember changing the way the two are setup will change the revs while your car is idling)

Yes if the throttle position sensor is not right, or not detecting the car is at idle it can cause it to run off the O2 sensors as they cycle lean/rich/lean/rich causing unstable idle, I had this in my Feroza, which had a pretty primitive TPS but once adjusted problem solved.

This only caused unstable idle, not lack of power issues etc. I would be looking at either TPS, faulty or clogged Idle Speed Control (not adjusting idle properly, or letting the wrong amount of air in) or missing or perished hose (which can cause the idle to wander a whole heap but be fine higher up)

I always like to inspect an engine with similar problems to yours at night in total darkness....engine idling and bonnet up. Look for any high voltage leakage at idle....then try doing this with some load on the engine - for safety have an assistant place the car in reverse (so you don't get run over) with the handbrake and footbrake fully on and just bring the engine up a few hundred revs till it starts to miss/splutter whilst you eyeball the engine again looking for HV leakage....don't do this for more than 10 seconds at a time to avoid overheating the torque converter. If there appears to be no leakage, it will rule out high voltage leakage as a problem. Next I'd check the injectors which if bad should cause one or more plugs to look 'wet' or otherwise different to the others. I'd also clean the throttle body and also check every vacuum hose for splits etc.
Good Luck.

Does this also work in neutral or park, or do you need load on the engine?

if the maf is faulty it should throw a fault. you can check for fault codes easily, there is a writeup on here somewhere.
otherwise, i would double check the vac hoses and upper plennum gaskets, (shouldnt be the prob.) check the fuel filter and fuel itself.

how does the car feel to drive? is it sluggish or normal. also, does having the ac on affect the idle?

The car is a bitch to drive, no power and is pretty rough untill you get going. Put it this way, my missus would rather drive a 88' Pintara I have lol.

I dont think it would be the TPS, That would probably only make it idle poorly.

I put a half tank of 98 octane and injector cleaner though (not that they work anyway). Not sure about the filter

Did you find out which cylinder had the misfire? you should be able to pull the leads off the dist cap one by one to check (i think, there's access)... BUT make sure you use some non-conductive lead pliers (ie wooden or similar) or you'll get a nasty surprise :P. Once you find out which cyl is missing, it'll be alot easier to diagnose the fault.

The car is a bitch to drive, no power and is pretty rough untill you get going. Put it this way, my missus would rather drive a 88' Pintara I have lol.

I dont think it would be the TPS, That would probably only make it idle poorly.

I put a half tank of 98 octane and injector cleaner though (not that they work anyway). Not sure about the filter

Speaking of which, I'd love an R31 Skyline lol

Speaking of which, I'd love an R31 Skyline lol

Want a r31 pintara? I'll be selling mine cheap in about 2 weeks :) very clean car with rego

lol I always say it but having two cars isn't a good idea for a 20 year old on an average wage (inb4 TUFFTR), how much would you sell it for anyway.

Probably put 500 on it mate and see how i go. Lol, I know what thats like, ive got 5 cars!

Just an update: Narrowed it down to one cyl. Its not plug or lead, they get spark fine. Im thinking it might be big end bearing on that one rod because it makes a bit of noise when engine starts. (keep in mind, car doesnt blow any smoke)

Solution: Im chasing up a low k motor for it now. Anyone got one? :) It will be easier to just chuck another engine in then try to fix.

Big end shouldn't really cause problems with misfiring, unless knock sensor is picking up noise. Done a compression test on suspect cylinder?

Nah havent done a compression test. I know im getting spark to that cyl, and its the only one that doesnt change when lead is unplugged. Unless its a injector issue?

Unfortunately I dont have a compression tester to use :(

Sounds like it could be the injector on that cylinder, can you get to it easily?

No, i dont think they are easy to get to. Ill check it out tonight

100% sure its not a plug? Check for vacuum leaks around that cylinder. If you suspect an injector, try swapping it to a known good cylinder and see if the problem moves with it. It's hard to say for sure without a comp test gauge. A rough guide would be to d/c the coil and get somebody to crank the car, while you listen/feel the compression at that cylinder through the spark plug hole. Or turn the engine over by hand with your finger over the spark plug hole to see if it has any sort of compression.
It's very rare for an injector itself to cause a completely dead cylinder.

To be honest i havent actually checked the plug. I pulled it out and cleaned it up a bit. I might pul the manifold back off, remove the plug with the lead, replace the manifold and crank it over to check it that way.

See how i go

Step 1... check the damn plug! :P lol. You can't just 'assume' it has good spark at the electrode. ;)

Also, to make life easier you don't need to replace the manifold if you're only doing a quick crank to check spark.

just swapped the plug with another one and the same cyl did the same thing, nothing when it was unplugged.

Dont discount your injector mate, move it to the front bank while the manifold is off, I have had many of these just stop working. Another reason why regular cleanign is a good idea lol

Also check that the injector is plugged in correctly as well and the pins have not pushed back into the plug

Ok, Ill rip the manifold off again tonight and try that. thanks :)

On a side note, im getting bloody good at removing the intake manifold haha

Na the o2 sensor doesnt bring up the engine light hence why it took me nearly a month to diagnose! but if it was the o2 sensor it would run fine when you floor it as the ECU ignores the o2 sensor

Maybe try the fuel filter ? Could have a dodgy lead but unlikely

I had a similar problem once. The engine's power feels "stepped" not smooth, and its intermittent. But once past 3000rpm its takes off like a rocket?

I know Madmagna says it cant be the O2 sensor, but disconnecting mine fixed the issue. I had a mechanic describe this to me as "a lazy O2 sensor". Its an easy thing to try, before you start either spending wads of cash or disassembling the engine/sensors etc.

Having said all of that I also had a trashed TPS, but that issue was throttle position sensitive - just as intermittent though.

Grab a can of contact cleaner and throttle body cleaner. Clean all electrical connections - start by checking your battery terminals. Then clean the throttle body and idle speed motor/idle circuit.

After that it could be vacuum leaks - one of the hoses leading from the throttle body.

i dont know if it would be any of the above due to the fact I know 1 cyl isnt firing, or no compression.

Previously I did spray contact cleaner in most plugs etc, didnt do anything :(

Im going to try this injector swapping thing tonight if its not too hot (42 out here today!), If that doesnt work im going to have to get a compression tester.

cheers

OK, Update!

Ripped the manifold back off and swapped the injector on the dead cyl with one from front bank. Once back together and running I unplugged the front cyl only to find out that one now wasnt working. So i swapped the injector with another one from the front bank, the issue moved with the injector.

I Unplugged the initial problem cyl injector plug and the revs dropped!, So there was a rooted injector. I pulled the "rooted" Injector from the front bank and soaked it inside out, back to front in contact cleaner. Chucked it back in.

WOOOOO!!!!! good as new :)... except the fuel rail bolt i stripped in the process. Now for the tap and dye set!

Thanks heaps for your help guys, Saved me a new motor!

Cheers
Rob.

Always good when there is a positive result, you may find this will die again fairly soon so a new injector may be a good idea asap, I have plenty of secondhand ones here

Out of curiosity what would a couple of them be worth? I was going to chase some up tomorrow

Glad you found the problem !!!

i think carby cleaner eats o rings , so remove them before soaking the injectors. i saw a U tube clip of a guy doing his own with a 9v battery and ultrasonic cleaner , dont know how well it worked.

Ill put new o rings on them when i fix the fuel rail bolt tonight anyway. I sprayed it in the injector avoiding the O ring.

Injectors are $25 each.