3ltr NA auto vl runs like rubbish
hi folks. hoping you can help me.
i have a stock standard 3ltr auto vl commodore. it's running strange. when i fire it up it runs fine for 3 mins or so, then begins to intermittently drop revs. it'll sit on 800 revs or so, then drop to half that for a few seconds, then back up to 800. as it warms up, it'll idle at somewhere between 600 and 700 rpm, but drops lower and lower. by the time it's been running for ten mins, it'll idle at 600, but drop to 100 to 200 rpm for a few seconds every half a minute or so - nearly dies, but never quite stalls. it will always jump back to normal idle speed. have replaced cas and oxygen sensor, air flow meter, checked fuel flow and spark, all seems fine. any ideas?
Another VL Driver
Sea Dogs Champion!
try cleaning out the plugs to the CAS, AFM, as well coolant temp sensor (CTS) etc etc.. r u sure the afm is fine.. this sounds like an afm problem.... unplug the afm and start the car,.. if it idles fine and as soon as u touch the throttle it stalls the afm is failing..
put a timing light on it and see if its at 15 degrees(factory setting) report back and we can walk u through other tests...
Air leaks in intake and check idle mixture on ecu.
checked wiring connections to cts, afm, o2 sensor, all seem clean and good. replaced wiring connector to cas when i replaced the cas - although i couldn't get the bearing out of the dizzy, but it looked fine, very little dust in it and no lateral movement in the distributor shaft that i could detect. took the air intake apart up to the throttle body a couple weeks ago, did find a slight leak after the afm but fixed that and it made no difference. have put a brand new afm in, reset the ecu, still no difference...
i've just unplugged the afm, and it started up but stalled again before i could even give it a few revs. after that it wouldn't fire up at all. does that suggest afm is the problem, or is that normal?
i can't check timing or fuel mix yet cos i don't have a multimeter or timing light... i'm not sure that the idle speed is set correctly, and even if i could check all this now i think i have another problem. the mechanic i have used in the past found out that somehow, the timing marks on the crankshaft pulley are nowhere near where they should be. it was suggested that this could be because the harmonic balancer hasn't been fitted correctly at some point in the past... would that make sense? he had a lot of trouble getting the timing right as a result. i've never checked the timing myself (obviously), and i got no idea how to do it without using the timing marks.
as you can tell i'm kinda learning as i go. i'll see if i can get my hands on a multimeter, tachometer and timing light, and try the rest of your suggestions asap...
oh forgot to mention, i've recently noticed the engine seems to get hot real quick too...
cheers
lach
Not sure and i cant remember but does the harmonic balancer sit in a key way?
Im not sure what your mechanic is saying.how do you tell that the marks on harmonic balancer are no where near where there sposed to be?like where are they supposed to be?
Car going into safe mode once hot?have you driven it in its current sittuation?
it was a few years ago... had a cracked head, he repaired that for me and tuned it up, and when i picked it up he told me the timing marks weren't right, and that he'd had trouble timing it as a result. in reality, i don't know. i've never timed it myself so i've never run into it. i'll definitely be trying to do so as soon as i can get the tools for it though, guess i'll find out the truth when i give it a crack... a mate suggested the harmonic balancer thing to me, but i've never been able to figure out if it was a possibility.
i have driven it once in it's current state. it was when the problem first came about. was driving for about 5 mins, pulled up to a red light, and realised it had died. took me ten mins to get it to fire up again - i figure it had just cooled down a little - got 2mins further up the road and it died again at the next set of lights. figured out that it would run as long as i kept revs in the engine, but when i took my foot off the accelerator to hit the brakes as i approached the lights it died straight away. so i turned around and managed to get it home again without it stalling by keeping at least 1000 to 1500 rpm in the engine, and braking with my left foot when necessary...
since then i've been unwilling to leave it running for too long - just to run tests on it - cos i'm worried i'll do more damage to it, especially cos it seems to heat up so quickly. i'm not sure what you mean by safe mode, i wasn't aware it had one. it's always run really well (i've had it for 8 years) - i've done heaps of roadtrips up the coast in summer, run it for hours on days where it's 30+ degrees, and the temp guage has only ever approached half way, no more. i know how easy it is to overheat a vl so i've always kept a close eye on coolant and cooling system - it's never caused any problems.
is it possible that the temp sensor has failed? i didn't think that would cause the engine to run in the way it is, but i don't know enough about the engine management system to be sure... i've also found a very thin coating of oil on the radiator cap, but the oil cap is clean as... i guess i could have a slight leak in the head gasket but again, i can't see how that would cause the engine to run like it is...
???
Harmonic balancer is eliminated as its on a key way im 99% sure
run a diagnostics test on ecu and get back to us with what numbers the ecu is flashing.im sure theres a technical section explaining it.
Could be a sensor.the ecu goes into safe mode or limp mode if theres a problem in the vl if i remember corect....
Dont touch timing.if its been all good for eight years and you havent touched it i dont think your problem lies there.
oh i should also mention... for a couple years it's had a strange, very infrequent thing going on. very rarely, after driving at normal temp, i'd stop the car, try to start it again 5mins later, and it'd turn over fine but just wouldn't fire up. i'd always have to leave it for 10 mins or so, and then it would fire up perfectly normally and drive normally, no problems. it's only happened maybe 8 times in a couple years. but i'm now wondering if maybe it was the start of the problem i've got at the moment...
My VTEC ate your V8 ;-)
could be a crack in the fuel / main relay .. when its hot the break in the relay expands there fore not letting the car start and when it cools down shrinks back to make it start.Originally Posted by lachmack
KONY puts the meaning of "INFANT" to "INFANTRY"
yeah i've run the ecu diagnostics a few times, it always gives me the all clear. might go and check it again anyway.
timing wise, i'm not sure that i've got the distributor back in exactly the same position as it was before i started. it can't be more than a millimetre out, but i don't have enough experience to know how fine that adjustment is... i'm guessing less than a millimetre isn't going to cause any problems. nevertheless, i will try to check the timing accurately when i get the chance... but perhaps in the meantime i should check the mixture on the assumption that timing is reasonably good...
oh i've swapped various relays around and they all seem fine too - no changes to the way the engine was running...
dizzy 180 out?did you take whole distributor out?it could be one tooth out.....
timing should only be adjusted if you really know what to do.you should be able to get it near spot on by sound or near enough
yeah i took the dizzy out entirely. but i marked where it sat beforehand so i could get it back in the same spot, and yes, i did take account for the fact that it rotates slightly as it goes back in... timing sounds pretty good.
wish it wasn't pissing with rain! or that i had a garage...
hey i was just playing around with the idle speed and found that when i disconnected the aac valve it seems to run better - quite smoothly. could the aac valve be faulty? or would that indicate a related problem with something else?
on another question entirely, you know that ticking noise a lot of vls have? i've been told that's a tappet noise, is that true? it seems to have gradually gotten worse over the last 12 months or so...
Did you take notice of where and mark where royor arm was facing?
absolutely, marked rotor position as well, went back in the same way it came out too. i guess the cas i got could be dodgy... it's brand new, from aca, but people tell me you still occasionally find dodgy new ones...
ok, got an update. just pulled the aac valve out and it was coated thick with carbon. so i've cleaned it thoroughly with throttle body cleaner, as well as the housing it sits in. also cleaned the throttle body just for the hell of it. now the car seems to idle very nicely in park or neutral. however, when i put it in drive and took it to the end of my street, as soon as i took my foot off the gas it started dropping revs again. left it in drive for a little with the brakes on, just idling, and it still does the same - still drops to 100 rpm every 15 seconds or so when it's warm, then back to normal idle speed.
anyone got any idea why it would do this only under load?
cheers
I had similar problems. I cleaned my iac & acc valve twice, it got better every time but still not right. After trying other things i came back to the acc valve took it apart again and really really cleaned it. Used a cotton bud and completely cleaned the sensor behind the spring. Runs mint now. Unbelievable difference
ah. thanks mate, i'll try that again. i did clean the aac very thoroughly but not the iac. think i'll take the entire housing that contains those two parts and the fidc off the plenum chamber entirely so i can do it properly. also going to clean out the air regulator and check a few other components i have doubts about too.
thanks for all the suggestions folks, i'll let you know how it goes for future reference.
cheers
lach
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