Hi guys,

My wagon is experiencing issues of missing, jerking and loss of power under load when cold or left for several hours. Even under slight acceleration when moving, will miss, jerk forward, or lose power for a up to a second intermittently. There doesn't seem to be a significant increase in fuel consumption, according to the fuel economy readout.
It doesn't seem to be a ignition lead or spark plug as there is no pattern or consistency, and is worst when cold. Could it be a worn distributor cap and/or rotor, or ultimately a worn coil/faulty distributor?

My sedan has only started experiencing the same issue within the last day or so, which the rotor and cap was replaced 68,000km ago at 201,000km. It is not known how long the cap and rotor has been on the wagon, which has 225,000km.

I've inspected the rotor and cap this morning and provided photos, I'd appreciate some constructive opinions.

Cheers! :)

https://fbcdn-sphotos-b-a.akamaihd.net/hphotos-ak-xfp1/v/t1.0-9/1976913_10153453113158336_2032397990681391411_n.jp g?oh=d1b143a05454aa0844143247ac579cb8&oe=55FE1B18&__gda__=1442360904_596c8fabea4c2eba29aa8095ebbd01c a

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Button doesn't look great, I'd clean it up with a bit of emery or a fine file or just replace it. The cap contacts are hard to assess from the pics but probably same condition and solution.

Question: Is there a difference between very light throttle and heavy throttle? For example, with the throttle barely off idle does the motor spin up cleanly without staggering, but with a normal to wide throttle it plays up? Or is it the other way around, or does it make no difference? If the first condition is true I'd suggest coil, if the reverse (ie. staggers or stalls on light throttle but OK with a bit more welly) it may be an intake manifold leak, dodgy EGR valve/solenoid, failing MAF or any of a hundred other things.

Question: Is there a difference between very light throttle and heavy throttle? For example, with the throttle barely off idle does the motor spin up cleanly without staggering, but with a normal to wide throttle it plays up? Or is it the other way around, or does it make no difference? If the first condition is true I'd suggest coil, if the reverse (ie. staggers or stalls on light throttle but OK with a bit more welly) it may be an intake manifold leak, dodgy EGR valve/solenoid, failing MAF or any of a hundred other things.

Thanks for the reply Ensoniq, it happens under light-mid throttle only, under heavy acceleration its fine.

I have disconnected and reconnected the O2 sensor connector (so the ECU adapts a default map) to see if its a sensor fault, as advised by MCS_XI. I'll be paying close attention on the cold starts and driving to see if it has made any difference.
I think I'll then replace the cap and rotor, give the MAF and throttle body a clean and reassess from there.

Thanks for the reply Ensoniq, it happens under light-mid throttle only, under heavy acceleration its fine.

Doesn't sound like coil, maybe air leak somewhere. A small leak in the inlet manifold may not be evident at idle since the ISC will compensate, and won't make much difference at moderate to wide throttles, but at low throttle openings it can affect the mixture considerably. A loose leaky vac hose can do it, as can a stuck EGR valve (if you have one). In my case a dying MAF caused the ECU to open the EGR valve at inappropriate times, giving the same symptoms as you describe.

How did you figure out it was the MAF?

How did you figure out it was the MAF?

I didn't really, it eventually died completely throwing an error code and reverting to 'failsafe' airflow mode. Horrible economy but at least it ran and it did finally answer the question of WTF was going on. Replaced it and the issue was gone. It's worth noting that in trying to find the cause I cleaned the MAF with MAF cleaner which had no effect on the fault, so presumably this is something they can do when in their death throes and isn't necessarily the result of a dirty MAF. Assuming the EGR is clean and not gunked open it can be eliminated by removing and blocking its vac line to see if there's any difference. If the fault is gone it's a process of elimination working back from there, ensuring TB ports are clear, vac lines secure, EGR solenoid functional etc. If the fault's still there then potentially leaky vac line or plenum, split snorkel, split PCV hose, etc. etc. Any place that unmetered air could be getting to the cylinders.

I would be interested to know the result of this thread as well.

I reckon my car needs more throttle input when cold to move. It seems to feel like its heavier and more sluggish when cold, then frees up when warm but still needs large amounts of throttle to move anywhere and not drive like a grandpa LOL :D

Maybe I need more power upgrades :P

Ensoniq, my car has a bit of a rough idle and I feel it could be smoother below 2,000rpm in genera. It used to be much worse but after replacing the EGR solenoid and the fuel vapor solenoid it became much more consistent, yet still not perfect.
Any idea how these would have influenced the idle? And if anything else could be faulty taking the above into consideration?

I'd like to add that my car is experiencing a similar issue, too. On slight acceleration, or at a low, constant speed that requires say 5% throttle to maintain, the car will jerk back and forth for about a second or two. Adding or cutting the throttle stops this jerking, which occurs intermittently, but is much more pronounced with a cold engine. The car's idle when cold is also considerably high — somewhere between 1200-1900 RPM — but drops to a normal 750-800 after driving for a while.

Spetz, the most common cause of rough idle is a dirty throttle body, and they don't take much to get fouled up. In theory the ISC should compensate for any minor leaks and your idle shouldn't be affected by a bad MAF. Having said that, if one or more of the vac ports on top of the TB are blocked it could cause the EGR valve to open (assuming you have one, older 3rd Gens don't) when it shouldn't, since from memory the solenoid effectively controls when the vac that opens the valve is relieved via one of the other ports (ie. EGR is opened by high manifold vac during deceleration and would be open at cruise and idle if not for the ECU-controlled solenoid that over-rides it. I think!). If your TB is clean it could be the EGR valve itself, it might be gunked up and not closing properly.

I'd also check that your PCV system is clear and not leaking. Simple check is to remove the PCV valve from the front cover and place your finger over the grommet, then remove the PCV inlet pipe from the snorkel and blow in it. With your finger over the grommet you shouldn't be able to blow through the engine (once pressure has built up) and with your finger off the grommet you should be able to blow through with a bit of resistance. If you can't blow through you could have a blocked hose (usually front-to-back cover hose, replace with genuine) or blocked valve cover baffles (remove and soak in degreaser or something). Your PCV valve might also be buggered, it's a bit complicated to test properly (simple test is that it should rattle when shaken) so if it's old it's worth replacing ($15-ish from Repco, $95-ish OEM. Your call!). Obvious other checks are that all vac lines are intact and gripping at the ends.

Hyphen, hard to say but it does sound similar to what I had. Maybe your MAF is starting to fail and isn't reading properly at low air-flow rates, but I have no idea if they fail often or if my case was in any way 'unusual'. It's worth squirting some MAF cleaner through it in case it's just grotty (only use MAF cleaner, not degreaser or anything else). Also make sure there's no splits in the snorkel and that the expansion chamber(s) aren't leaking or anything (sometimes there's two, one above and one below the snorkel). If there's any air getting to the cylinders other than through the MAF it'll cause lean running at low throttle openings which could be what you're experiencing.

Ensoniq, I tested my PCV the way you described and it works.
With the EGR, I blocked off the EGR intake (the one that goes from the exhaust manifold to the intake manifold) and there was no noticeable change in idle so I assume this would mean that the EGR should be functioning fine?

The TB has been cleaned, and the idle rpm is spot on (as tested by a diagnostic tool).
Not even sure if a mechanic can find the source of the poor idle or not?

I don't think many 3rd Gens idle totally smoothly, at least none I've been in. There are so many things that only need to be a little bit out to have a noticeable effect on idle. Mine's never been smooth, though it's much less noticeable with the new engine mount (cheers Mits-Fix!). So long as it doesn't stall, race, or shake the lenses out of my glasses I'm not particularly fussed. Let me know if you ever do find the cause, I reckon there'd be a few members who'd love to know.

Re the OP, I initially thought diz cap button.

The description by hyphen is very much like symptoms my ts had. They cleared up completely with a cleaned set of injectors.

(which was just the latest in a series of things I've done all of which had some effect. Rebuilding the TB, cleaning the PCV and hoses, breather pipes, flushing the trans and replacing the thermostat, plugs and leads being the ones that had the most noticable effects of them to how the engine/car runs but none of them like the quite amazing lasting change to idle, throttle response that clean injectors had. Now it starts instantly, settles at 750 rpm straight away and stays there with no hickups when lightly or firmly pressing the accelerator. (I've also changed the maf, o2 sensor, cat, fuel pump, fuel pressure regulator, fuel/air filters, distributor cap, coil, vac hoses, cleaned contacts all mver and lubricated cables. I suspect the injectors had been in need doing for the last 200 000k's tho more so lately. As I now have a working injector testing rig and an ultrasonic cleaner I'll make changing them a regular maintenance thing now with a spare set always ready to go.))

I've been in a couple that idled pretty smooth, and on a very rare occasion mine also idles really smooth.
When it is running and I put my hand on the motor there is an obvious repetitive miss, so there must be something wrong.
If I could find a good mechanic to test things rather than replace things I would be fairly happy, especially as I've replaced "the usual suspects" already.

Update:

After unplugging the oxygen sensor plug, the issue disappeared for 2-3 weeks, and then started missing/jerking again. What I deduce from this is that the ECU adopted a default map, then returned to the values based on the oxygen sensor's signal over a period of a fortnight - suggesting that the oxygen sensor is faulty.

I replaced the distributor cap and rotor last weekend as a matter of maintenance, and replaced the oxygen sensor with a direct fit, non-genuine one this morning. Early signs are good so far with no missing/jerking and no decrease in fuel economy - but the proof will lie in cold start conditions, which I have yet to test with the new sensor.
At 226,000km it was probably due for replacement anyway, and at $68 even if it doesn't work I'm not going to lose sleep over it.
I will monitor closely and reassess after a fortnight or so.

Anymore updates?

i had the same problem the other week, i was guessing that it would've been the plugs+leads etc. As i thought the Oxygen Sensor wouldn't come into action in cold start as the ECU would be in a closed loop till engine hits a certain temp. Can anyone verify this? I'm only stating from my previous cars

The ECU only starts using the oxygen sensor signal when it enters closed loop mode, which is usually once the coolant temp reaches 36-37 °C (according to ECU scaling). Prior to that it is in open loop, but will use learned fuel trims. Resetting fuel trims normally requires power supply interruption to the ECU (e.g. battery disconnection) but it is not impossible that running the engine with the oxygen sensor disconnected may achieve the same effect.

Further update:

After replacing the oxygen sensor over three weeks ago; I replaced the spark plugs and ignition leads, as a matter of maintenance, the weekend before last. I also replaced the ISC motor as I had one lying around.
I can say that the car is running the smoothest since I bought it.

Over 1000km since the oxygen sensor was replaced, the jerkiness and missing under load when cold hasn't returned, and fuel economy has stabilised to a decent 9.9L/100km mixed cycle of 50/50 suburban and motorway.

Chiefly, I put the rectification of the missing and jerkiness down to the replacement of the oxygen sensor; but replacing the worn ignition components such as the rotor, distributor cap, spark plugs, leads and ISC also have contributed to the smoother idle and better fuel economy.
While the idle isn't completely free of misses - as Ensoniq said, you'll never get a third gen to run completely smooth - its a marked improvement from before the replacement of the ignition components.

Components replaced

Distributor rotor (Standard Motor Products - JR194)
Distributor cap (Bosch - 03419)
Oxygen sensor (PEC/Walker - 250-24232)
Spark plugs (Champion Double Platinum - RC10PYP4)
Spark plug leads (Genuine)
Idle speed control unit (Genuine)
Idle speed control o-ring (Genuine)

While it may look like I threw a bucket of money at this problem, the only things I actually purchased for fixing the issue was the rotor, cap, oxygen sensor and spark plugs, totalling about $150. The leads and ISC were gathering dust in the shed among my Magna parts stash.

What do you think is preventing it from idling completely smooth?
And what is the part number for the ISC o-ring?

What do you think is preventing it from idling completely smooth?

Don't know. Its been an inherent issue of varying degrees with third gens in general.


And what is the part number for the ISC o-ring?

MD614417

They are capable of idling smooth, but it seems very few do.
Mine idles a lot smoother than it did before, and I believe the change is attributed to replacing the EGR solenoid.
it still doesn't idle perfectly, but not horribly either. In fact there are moments where it does idle really smooth (rare moments though)

I have to say the 3.5 is less smooth than the 3.0. the 3.8 is equal to the 3.5.

However, my with my KH XI, I had a new (relatively as it had low klms) 3.8, and new mounts all round. The seals for the intake were new, and the battery was replaced. The battery and the mounts were the biggest thing. It was super smooth.

The mounts are hydraulic too. Fluid is affected by static temp, so......some of you may be chasing a ghost.

Mike

I have to say the 3.5 is less smooth than the 3.0. the 3.8 is equal to the 3.5.

However, my with my KH XI, I had a new (relatively as it had low klms) 3.8, and new mounts all round. The seals for the intake were new, and the battery was replaced. The battery and the mounts were the biggest thing. It was super smooth.

The mounts are hydraulic too. Fluid is affected by static temp, so......some of you may be chasing a ghost.

Mike

How very odd, my brother had a similar issue earlier this week. He had all 6 of his spark plugs replaced last week and since then there has been a misfire on cold or hot idle, and under slight - mid loads.

I replaced the leads with a known 2nd hand working set that I had laying around and it's now bulletproof, no misfire and it runs smooth as. I tested all his old leads and they all seem to be fine...

I have to say the 3.5 is less smooth than the 3.0. the 3.8 is equal to the 3.5.

However, my with my KH XI, I had a new (relatively as it had low klms) 3.8, and new mounts all round. The seals for the intake were new, and the battery was replaced. The battery and the mounts were the biggest thing. It was super smooth.

The mounts are hydraulic too. Fluid is affected by static temp, so......some of you may be chasing a ghost.

Mike

Generally the bigger the cylinder the rougher the engine. The 3.0 also has a really good R/S ratio.

From what I understand it is a misconception that the engine mounts are hydraulic.

And, what would the battery have to do with smoothness?

How very odd, my brother had a similar issue earlier this week. He had all 6 of his spark plugs replaced last week and since then there has been a misfire on cold or hot idle, and under slight - mid loads.

I replaced the leads with a known 2nd hand working set that I had laying around and it's now bulletproof, no misfire and it runs smooth as. I tested all his old leads and they all seem to be fine...

I had a similar issue once, turned out to be that the spark plug gapping was incorrect causing misfire.

Was only slightly noticeable with old leads, but once I had brand new leads fixed it became even worse (obviously better connection etc highlighted the issue). Regapped spark plugs and was all good. (this wasnt on a magna so a lot easier access plugs mind you..)