VT V6 sluggish, slight miss/hesitation at low revs/light throttle, at the end of it!
Hi guys, my name's Mat. I've got a VT Series II Executive, V6. Had it for a few months now.
I'm getting over this now and I've searched everywhere here and elsewhere for ideas!
A lot are close but I don't feel like I've found anything as specific as I would like. Still trying bits and pieces and I might have to invest some cash here and there, but I've spent so much money on this already and with holidays coming up, I really can't afford to keep 'guessing'. I thought I'll ask you guys since there's tonnes of Commy knowledge floating in all your heads combined!
This is very long winded so if you have the time to read it I would really appreciate it and love to hear from you!
Earlier I replaced the engine mounts, front rotors and pads (thought still vibrating and busted a siezed stud! Will have to go back to that job and check :/).
I started getting the gear change problem and code for the TPS so changed that (only a second handy but resistance tested ok), it was sluggish and hesitating when accelerating so cleaned out the plenum and throttle body (didn't take it off, just removed the lid).
After this it ran really smooth. Was really happy with it, felt like a new car!
But the after a while noticed a very faint miss/hesitation, noticed at the time fuel was very low so thought maybe had something to do with it. But over time it became more noticeable. It ended up feeling sluggish and hesitating when you just take off slowly or put light pressure on the accelerator, it was the same way at 80 to 100. The problem would go away when you put the foot down. Not necessaraly flat to the floor, but enough to get the car up and going.
It didn't miss in the obvious way, more flat/hesitating.
The reciept from the previous owner getting it serviced said they'd done the plugs (still look ok so I haven't touched them yet. But they did note to change the leads as the were original.
So what I have done so far:
Leads
O2 sensors
Checked coil pack and dfi from an old VR I had (replaced them only to find out it was the CAS so I kept them)
Fuel filter (was original- black crud came out) and Injector cleaner
After the filter (I think, I'm getting hazy now on the details) it would actually miss a beat at the start of accelerating off. Then it would just be normal problem.
After the coil pack (left original dfi) it seemed to be smoother but still sluggish, though the next day it was playing up with hesitating again.
It seems to be worse on hot days, on cooler days it seems to be better at least for a while.?.? Again memory is getting fried with all of this.
Pulled off the plenum yesterday and wiped the oil residue and checked the hoses. The one below the throttle body that goes a few inches to the tap thing just under the plenum had a split under the clamp, store was shut so I cut a piece of garden hose just for now! Squeezed the hose today and engine revs dropped a little.
It seemed to be smoother for some random reason but then changed it's mind!
Today I played around with the vac hose going into the fuel pressure regulator, no fuel around it or seemed to coming out. But I disconnected it and took it for a drive with no difference!?!?!?
Engine changed a little at the point it was unplugged/plugged in but still drove ok.
I removed the purge hose that goes under the plenum to the back firewall purge thing, engine dropped with that out.
Removed the EGR and it rattle which with my limited knowledge of that I just assumed movement was a good thing??
I tried my old dfi, no difference.
The other thing that worries me is one guy said to replace the fuel pressure regulator but it is welded to the fuel rail, I saw one post that said there's a clip but it definatley looks sealed.
After changing the filter, the way it missed changed and after today it seemed to have more power back, and only a very faint incling of a miss/flat when idling arounf at 50 60km, etc. That was after playing around with the regulator hose and other vac hoses.?.?
But after swapping the dfi and back again I'm not sure if it's falling back into old habits again, but it had been running for a while.
Noticed the last couple of days (yes I'm still going on... sorry), it would ping at the start when I tromp it (only when I floor it, doen' t keep pinging).
Also noticing the engine sounds noisier when you rev it (around 2000 to 3000 revs). Gets a rumble, deep/mid wirring, semi pulsating kind of sound, just sounds a bit rattly. And around the same revs it has a faint knocking sound appears which I'm sure I've heard on my old VR or other commy engines.
And again, not sure if I've just not noticed this before but I can hear the fuel pump humming when I'm at the lights/idling, etc.
Not that this is necessaraly fool proof but I've resistance tested the air temp sensor and unplugged the maf and checked resistance wise and by unplugging what I can but I know this doesn't necessaraly tell me anything.
I think this is about it. I am really sorry for such a massive post, but I've spent quite a bit of cash and I'm just hoping to keep as much money as I can for our holiday, but on the same token this car needs to get from Adelaide to Melbourne which it may just do. This may just be a bugging problem but not so much a major one, but still! If anyone can help me so we can have a nice ''smooth'' drive I would be greatly appreaciated. Also willing to offer a carton of beer if anyone can pop over and find the problem with me, and maybe teach me something. I love being able to fix my own car and I've done heaps so far with this car and others, but when you get stuck like this it's a little depressing!
Failing getting to the bottom of this, anyone know a good, honest mechanic around south Adelaide?
Sorry forgot to mention, has used fuel on and off throughout this ordeal. Seems moderate now but it likes to take a dip and start counting down even though it should still have 60 70 kms in it still, etc. Then it comes back up. Could be just the VT but it may be related.?.?
Howdy mate,welcome.
Have you had the airflow meter cleaned with CO Contact cleaner?
When you checked the plugs did you look for any faint hairline cracks?
Does the car have any alterations over factory specifications.
A good honest mechanic down that way that is also very well priced labour wise is West Torrens Dyno Centre,Chris and Mike(Father and Son),weather it be a boat or dune buggy they know their stuff well.They have all the appropriate tools,scanners ect to diagnose well.
could be harmonic balancer for the reving knock which might effect cas sensor
Hi Karlos, thanks for the quick response. I haven't cleaned the MAF (this is the one yeah?). Do you just clean the fins with the cleaner? I looked at the plugs all over but hair line cracks could be missed I suppose. Worst case a new set isn't too much to try. Maybe plugs and contact cleaner are worth a shot tomorrow. The car is just stock.
A guy at sprints told me he had customers who had similar probably and it was the crank sensor. Is this possible. I thought they generally just die.?
Hmmm, wondered about the balancer. Any way to test?
Just read on another post here, they are pretty clockwork at failing at 200000kms... mines 200 and something thousand! :/
best bet is to watch it at idle, if its wobbling like a bitch its time to change.
You can buy a spray cleaner fro the MAF at places like Super Cheap. It's a delecate instrument and I think you just spray it, don't touch it with anything.Originally Posted by WoodysVT
Also have you changed the air cleaner and if cleaning the MAF does nothing check it's electrical connections.
Last edited by wortus; 09-12-2010 at 11:17 AM.
The MAF looked pretty good but I'm guessing there could be fine dirt, etc on it? Air filter was done in that last service, nice and clean. I can't remember too clearly but I though yesterday I unplugged it with no difference.? Might try that again today.
A thought on the balance, could that still be possible cause if the car seems smooth every now and again? After fiddling around with bits and pieces there were a few moments where it idled ok. But in general its rough. And if its not causing the car to be so noisy and whirry when its revived and the spot what else could do it? Actually have noticed a few times a slight muffled noise. It generally has a bit of a 'whop whop whop whop' sound you can feel under your feet too, can a balance do that too?
Little scared to ask this but any chance it being the timing chain/guide, etc?
These cars are great but they can be confusing at times! :/
Can you give it a compression check and check for any error codes? I have a friend who's VS was not running very well, similar things like a rough idle and it was the fuel pressure, he had plenty of fuel flow just not enough pressure so you could get that checked? Also there's an intank strainer that from memory needs to be replaced at around 200,000km.
Any vibrations you can feel under your feet I'd be checking the drive train for any wear stuff like uni joints etc.
No error codes unfortunately, don't have equipment for compression test, I thought and heard could be fuel, where is that strained? Is that the black filter under near the fuel filter? I might need to find someone who can help me test fuel pressure, etc. Given the filter was so grotty and changed the way it ran, could be another place to look.
'sigh'... More stuff to check. Too many options!
Just come out of the store with spark plugs.
A little confused and the guy in the store was too. What and where is the intake strainer?
It's inside the fuel tank and is part of the fuel pump/fuel gauge assembly. When I took one apart there were actually 2 of them in there. The black plastic box near the fuel filter is the charcoal cannister that collects fuel vapour from the fuel tank.
Firstly, Wow what a massive write up . haha
But I'll stop you halfway through your first sentence...
Who did your Engine mounts and How??
what has most likely happened is the wire to the Knock Sensor has been damaged my bet is on the Passenger side .
It runs very close to the Engine mount and the engine can easily damage it
Check this out. if you need Pictures of where they are let me know
ps. I have a pair of knock sensors if your sensors are actually stuffed . if you need them.
Um... I did...Firstly, Wow what a massive write up . haha
But I'll stop you halfway through your first sentence
Who did your Engine mounts and How??
what has most likely happened is the wire to the Knock Sensor has been damaged my bet is on the Passenger side .
It runs very close to the Engine mount and the engine can easily damage it
Check this out. if you need Pictures of where they are let me know
ps. I have a pair of knock sensors if your sensors are actually stuffed . if you need them.
That side was a turd and just the other day I was looking at that after reading about the sensors. Banged the drivers side and the revs jumped but that side didnt seem to. It was only at the end that it appeared to maybe jump a little but not like the other side. Spark plugs if anything made it hesitate a tad more at the start so I'll have a look underneath.
Would bad knock sensors cause it to ping and be sluggish. Pinging when you put the foot down. After plugs the idle is rough again but when I checked the idler valve it popped out and had to be threaded back on! Seems every time I go near the plenum area it changes! I was told also if the syrainer was part of the pump you would have to do the whole pump, correct??Firstly, Wow what a massive write up . haha
But I'll stop you halfway through your first sentence
Who did your Engine mounts and How??
what has most likely happened is the wire to the Knock Sensor has been damaged my bet is on the Passenger side .
It runs very close to the Engine mount and the engine can easily damage it
Check this out. if you need Pictures of where they are let me know
ps. I have a pair of knock sensors if your sensors are actually stuffed . if you need them.
Anyway will check knock sensors tomorrow.
I'm trying to remember back when i had trouble with my Knock Sensors... Best way to describe it is at a certain rev ( happened @ 2000 RPM with my car ) it will hesitate and "hold back" then it will jump up in revs and take off ( Mainly maybe because i would force the acceleration thinking wtf ? why havent i got power?).
I read up on it and its a Fail Safe the BCM or ECU does... it detects a fault with the Knock Sensor and "thinks" its Knocking/Pinging and it will Retard the engine to try and protect it.
Check them out, They are right by the Engine Mounts on either side abit to the Rear of the car from the Mounts i think .
Let us know how you go, Hope I can and have helped you out .
It is generally sluggish and 'holding back' below the 2000 mark. And reving on the spot at 2000 she sounds pretty rough as far as engine noise and that little knocking sound.
Sorry I keep replying with more winded details every time someone helps out!
Just really keen to get to the bottom of it. Thanks again to everyone for all the support! It's great how everyone jumps in to help.
I'll save it now for tomorrow after I've fiddled some more.
I cleaned the MAF with MAF cleaner, replaced the rocker covers (they were gone) and checked the knock sensors underneath. Sensors had the wire intact, didn't appear to have any damage on them, I wasn't sure how to test them other wise.
Now the car seems to be much smoother (colder weather though so we'll see in hot weather), still not quite what it was for that brief moment after the plenum clean but much better, power is ok too. The engine still revs noisy though at stand still. There's almost what sounds like a little motorbike idling under my bonnet when just idling - one of those little bikes with those deeper sounding bubbly/worble sounding pipes (that's not a word but best I can think of
I'm thinking if budget looks ok I might just inquire about a mechanic hooking it up and seeing if it just needs a tune and for peace of mind just make sure nothings going to fall off! :P
Think I need to see a mechanic. Sounding chuggy when you put the foot down when its cold and even a bit when its warm. Feels like its running very low revs at 60 and at 100 it has this oscillating king of shudder, very low sounding vibration. The kind that goes through the whole car and in your head! Plus a little helicopter in the front as that driveline sound comes through. The revs are better but not like it was in its brief behaved period.
I'm weighing up between two options now. Try to get into a mechanic before we have to leave for Melbourne (waiting to hear back from one), or spend what I might end up spending with the mechanic on a heap of parts and hopefully knock the problem on the head!?!?!?
So I'm trying to get a list of what I might need after everything I have replaced up till now. I thought I'd check first though if anyone in Adelaide has these items or knows someone or somewhere with a great price on any of these items...
Crank angle sensor
Harmonic Balancer (maybe, at 209000kms might be worth a try anyway)
Cam sensor??? (Haven't seen much about these having problems)
Fuel pump
MAF sensor (cleaned it and could be ok but maybe after replacing other stuff could give it a go)
Injectors or somewhere to test and clean
Centre bearing (getting low rumbles at around 100kms)
Maybe uni joints while at it
Not sure about this but wondering if could be getting air in the intake so maybe intake gasket and pcv valve??
Again, appreciate anybody who would have these parts to sell or know of great prices anywhere in Adelaide. Also if anyone knows of parts worth doing that I may have missed.
Noticed it being a hotter day today the problem (which has been a bit smoother after changing the current parts) was worse and more like it was.
And if anyone with the knowledge of these who might have the time to come and have a look, or know a good mechanic who might have time before Christmas...
Willing to pay of course.
I don't mean to be a nusance with all my posts but I'd love to get the car running smoother before we go to Melbourne.
And I forgot to mention I did the bang on the side check near the knock sensors and got a jump in revs, is this an accurate test?
Last edited by WoodysVT; 14-12-2010 at 10:00 PM. Reason: Forgot some info (hard to believe???) :P
did you replace the purge hose or did you just take it off while car was running? and go nuh not that
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