3.8l VT hesitation / misfire under light load when warm

[Kyle_au]

After I got back from the fire today, I had a few hours, so as we all know, jobs don't get done by sitting around - so to the shed..

Replaced the Throttle position sensor - no change
Replaced the Idle air control - no change
replaced the cam angle sensor - no change

Pulled the crank bolt out to change the crank angle sensor, only to realize that I don't have a tool to pull the pulley.
So put the bolt back on, only to be unable to tighten it up properly.
I don't have a torque wrench that goes to the 325nm required (mine only goes to 150nm)

Even if I did, I can't hold the pulley tight enough to stop it turning.

I've tried to use a ratchet strap down to the k-frame - no luck
i pushed my car under my hoist arm, and tried both a strap and my serpentine belt wrapped around the pulley twice with enough tension that I was lifting the car up. - it still turns when tightening.

I'm on call for the fires tonight, and on shift for tomorrows graveyard shift.
Hopefully its tight enough, but if it spins off, that will give me the answer I spose.
It throws the balancer and snaps the crank - new engine at that point, or maybe the car to the wrecker.

How on earth do you hold that balancer tight enough to put enough force to tighten that bolt?
I'm going to Perth tomorrow so I can pick up the balancer removal tool and anything else special I need.


Was doing some reading last night - my lifters are sticky/noisy , particularly when cold. Normally it clears up once warm.

Is this something that could cause my issue? Would a playing up lifter cause this? ie not opening or closing the valve properly?
Would this throw an error to the computer?
Is there any value in one of those lift treatments in a bottle? (I've always been very skeptical of 'mechanic-in-a-bottle' products.

thanks

So the way I was able to do the crank bolt was with an air gun. I asked my mechanic about how to stop the engine from turning when doing it the way you are, and he said to access the flywheel and use something to jam that to stop it from turning.
You may not have to do all this, I managed to solve my issue today by replacing the DFI module (I’ve attached a photo circled in red). It’s the plate the coils attach to.
New coils don’t mean anything if the module is bad, my car now runs like new! I really hope this helps you, you can grab a kit off eBay for around $260, as I didn’t want to wait I purchased the kit locally for $350

 

[Reuben Campbell]

Thanks Kyle_au for your info.

I went and caught up with a friend who runs a tool van and ive got a stumpy rattle gun thats good for 300nm. This, with a run up, 125psi and locktite and that should be fine. It pulled up great. I also changed the front oil seal while I was there.

Update from today.
Changed the coils and DFI plate - no change
Changed crank angle sensor - no change

After my chat with my toolshop friend (ex mechanic), he suggested that I should check the fuel trims to see what they say. He also suggested that it could be the Air Flow Meter giving a wrong reading. This wont throw a code, but make the car run high fuel. Ive already cleaned this with AFR cleaner and all the wires seem intact - compared to pictures of a new one.
I pulled the AFM plug to get the computer to use a base value, and it ran worse, so I suspect that the AFM is OK.

He also offered to remote into my laptop whilst I use my odb2 reader and live view the numbers.
Unfortunately, I'm playing fireman sam tomorrow to mop up after the bushfire here, so not much time to play with my car.

I have also chucked in a bottle of lifter cleaner as the lifters can tick a bit when cold, incase thats not helping. Now that the oil is warm due to ambient temps, they never seem to tick, just during winter and the oil is old.

Still doing the half-misfire thing / rough running thing. It seems to be every where, and not in a particular cylinder. Ill test the exhaust port temps at next chance to see if there is anything there.

Any other ideas?

 

[Reuben Campbell]

So I go to start it this morning and it wont budge. Bloody thing will fire once, then fail to hold idle.
I give up and get a lift to the fire station for todays shift. grrr..

So after todays shift on the fire ground I go back under the bonnet again - some google research suggests that its the IAC playing up.
I pull the plugs out and reinsert - success. Must have been a loose plug. Its a brand new IAC unit
Then after some more inspections of plugs, the rib belt decides to split in half and make a mess. Its only about 6 months old,
Off to my wreck out the back and fish out a second hand belt on that.

After some cursing about how the belt nearly whacked me in the face, i find a thread on a forum about how the EGR valve can get blocked and cause all sorts of weird issues.

So I pull that, and its not really blocked at all. Some black exhaust dust, and the valve is moving freely.
I scrape out as much as I can find, and put it all back

EGR valve clean - No change

Ive got a heap of cooking to do tomorrow, but im hoping to get an hour or two to lug in the scan tool and see if anything new has turned up.

 

[V6025]

So the way I was able to do the crank bolt was with an air gun. I asked my mechanic about how to stop the engine from turning when doing it the way you are, and he said to access the flywheel and use something to jam that to stop it from turning.
You may not have to do all this, I managed to solve my issue today by replacing the DFI module (I’ve attached a photo circled in red). It’s the plate the coils attach to.
New coils don’t mean anything if the module is bad, my car now runs like new! I really hope this helps you, you can grab a kit off eBay for around $260, as I didn’t want to wait I purchased the kit locally for $350

Glad you got your issue fixed. Fingers crossed. But not to be a jinx, lol. But I've replaced the DFI That was the first thing I did. It ran ok for about 2 weeks and then it was back to coughing and farting then loss of power again when kicked in the guts. I've replaced everything that you mentioned also.
No idle problems, no engine check light, no codes, it used to winge and bitch a bit after 60kms-100k after that it runs like a Swiss watch. ( Pain in the arse) and if you didn't know any better? You would bet your house on the odds that. "This car has no issues' but if you level off and cruise along on say 110kms for example it will start chugging and bitching again. But if you keep increasing your speed there is a problem. Sometimes you can get up there with no issues as long as you ease and baby the throttle but you can't just kick it. That pushes me to believing it's a fuel pressure problem and replacing the PRV Should curb it's tantrums. And to finish up with. If you want another way to lock that balancer is to have a manual like mine.lol. it will also let you wind your engine out through each gear, like I reckon it should be treated. Don't like Auto's. Good luck with your machine mate.

 

[Reuben Campbell]

V5025 - thanks - yep got the harmonic balancer back on - issue sorted.

But the real problem is still finding ways to confound me.

Its now even harder to start than before - so its gotten worse.
At least before it started easy enough, so it struggles to start, and i've got to hold the throttle down about 1/4 to stop it stalling and then it finally idles and settles.

Checked my scan tool on today and now its throwing a
#49 cam/crank signal error, and
#47 18x input missing of grounded

Both of these are associated with the crank sensor - from what i read.

Chatting to a friend - he seems to think that Goss and Fuelmiser branded sensors are terrible and are known to have issues from the box.
Everything I bought was either goss or fuelmiser - thats not a great start.

 

[V6025]

V5025 - thanks - yep got the harmonic balancer back on - issue sorted.

But the real problem is still finding ways to confound me.

Its now even harder to start than before - so its gotten worse.
At least before it started easy enough, so it struggles to start, and i've got to hold the throttle down about 1/4 to stop it stalling and then it finally idles and settles.

Checked my scan tool on today and now its throwing a
#49 cam/crank signal error, and
#47 18x input missing of grounded

Both of these are associated with the crank sensor - from what i read.

Chatting to a friend - he seems to think that Goss and Fuelmiser branded sensors are terrible and are known to have issues from the box.
Everything I bought was either goss or fuelmiser - thats not a great start.

With cam/crk codes try disconnecting the battery completely for about 10 mins always making sure that the ignition switch isn't in the on position when connecting or diss-connecting battery to make sure you don't fry anything. (We have to minimise all probabilities of adding to our problems. Lol.)
Then check codes again. As you can see iv'e attached my own write-up on the DFI Harness and what wires go where.
Especially from the cam/crk wires.
You probably already know? But if you don't? Notice. Crk has two timings,
C=18x and H=3x also the Grounds.
I can't remember but I think you said that you replaced the DFI Plate?
Just check the harness connection is tight. About a 7mm socket from memory. Give it a bit of a wiggle this may fix bad crk 18x ground and clear code also. Filling that you can test with a multimeter by back pinning harness wires. Hope this helps somewhat???
I tried to attatch a picture of some notes I took and it gave me some Bullshit about it being to large for the server. Dont know what that crap is about? Anyway.
I have plenty of success fixing cars but can't fly these god damm phones to save my life. Ha!Ha!
Looks like I'll have to do it old school.
DFI HARNESS WIRE CONFIGURATION.
HOW YOU SEE IT WITH (A)
BEING FIREWALL END.

A= EST(ICM CONTROL)
B= BYPASS (5v)
C= 18x(ICM>PCM
D= 3xREF HI
E= TACHO (GAUGE)
F= CMP SIGNAL ICM >PCM
G= CKP SIGNAL (18x) (CKP>ICM)

§ = HARNESS CONNECTING BOLT:

H= 3x CKP SIGNAL/SYNC
J= CMP SIGNAL CMP >ICM
K= GROUND
L= PCM (-)
M= ICM (-)
N= ICM (+10v)
P= IGN (+)

 

[V6025]

V5025 - thanks - yep got the harmonic balancer back on - issue sorted.

But the real problem is still finding ways to confound me.

Its now even harder to start than before - so its gotten worse.
At least before it started easy enough, so it struggles to start, and i've got to hold the throttle down about 1/4 to stop it stalling and then it finally idles and settles.

Checked my scan tool on today and now its throwing a
#49 cam/crank signal error, and
#47 18x input missing of grounded

Both of these are associated with the crank sensor - from what i read.

Chatting to a friend - he seems to think that Goss and Fuelmiser branded sensors are terrible and are known to have issues from the box.
Everything I bought was either goss or fuelmiser - thats not a great start.

V5025 - thanks - yep got the harmonic balancer back on - issue sorted.

But the real problem is still finding ways to confound me.

Its now even harder to start than before - so its gotten worse.
At least before it started easy enough, so it struggles to start, and i've got to hold the throttle down about 1/4 to stop it stalling and then it finally idles and settles.

Checked my scan tool on today and now its throwing a
#49 cam/crank signal error, and
#47 18x input missing of grounded

Both of these are associated with the crank sensor - from what i read.

Chatting to a friend - he seems to think that Goss and Fuelmiser branded sensors are terrible and are known to have issues from the box.
Everything I bought was either goss or fuelmiser - thats not a great start.

 

[Reuben Campbell]

So I have finally got off shift and now have time to look at this again
Pulled the dfi plug and found the second wire (white with black trace) has been pushed back. (N= ICM (+10v))

So managed to push the pin back in, but it seems the little locking tabs inside are worn - so I think the pin keeps getting pushed back out every time I put it back.

Not sure how to confirm that the pin is seated correctly once the plug is on.

This is the best lead ive had yet on this mystery.... arggh.

 

[Lex]

So I have finally got off shift and now have time to look at this again
Pulled the dfi plug and found the second wire (white with black trace) has been pushed back. (N= ICM (+10v))

So managed to push the pin back in, but it seems the little locking tabs inside are worn - so I think the pin keeps getting pushed back out every time I put it back.

Not sure how to confirm that the pin is seated correctly once the plug is on.

This is the best lead ive had yet on this mystery.... arggh.

Replace the dfi plug with a good one from the wreckers.

Just looked up new. I wouldn't worry about new? Expensive very!

 

[ephect]

Just push it in via the back when the plug is on. You can check the depth of the other pins so you know roughly how far it needs to go in