Throttle position sensor.

[soop]

Hi,
Another quick question guys.
I've a strange miss fire coming from my LS1. I started it today and let it warm up while idling and noticed that after a while, when it tried to return to its normal warm idle speed it almost wanted to stall. It will rev fine but when it returns to idle it really stumbles and has serious issues. After a while this went away.
This issue has been intermittent and has occurred whilst driving it. The car seems to loose all power and backfiring can be heard through the exhaust. I really feels as if its dropping a cylinder.

Has anyone else ever encountered this issue?
I'm waiting to get a scan tool so I can accurately diagnose the issue but through some research I've found a few possible culprits.
Is it possible that the TPS could be the cause?
Is it possible that either the cam or crank sensor could be causing the issues? Because to some extent its also as if the timing is horribly off (As the points in a distributor have given up, similar feeling).

For the record I've so far replaced the following:
Spark plugs.
Leads.
Both Oxygen sensors.
Whole exhaust. (leaked like a sive)
Oil pressure switch. (through an engine light, which is now rectified)
Radiator. (died a horrible death during last summer)

Any help would be greatly appreciated. As I'm really at a loss.

[GenReaper]

I would take the throttle body off and give it a good clean with carbi cleaner.
Could also be a dirty Maf or even a faulty air intake temp sensor.

[soop]

Maf is fairly clean. Faulty intake temp sensor wouldn't surprise me. I don't understand why it would do what it does, but hey its electrical it doesn't have to make sense lol.

What exactly gets dirty within the throttle body to cause the issues?

[GenReaper]

Missfire can also be faulty coil packs, have you had them tested ?

[soop]

Nah I haven't and I've been thinking about that too. Really kind of hoping its not because they're not cheap.
What's needed to test them?

That said, I took it for a drive today and when it doesn't play up it pulls like a 13yr old boy at a swim suit comp.
Leaves nice elevensies with ease.
So I'm not totally sure that its a mechanical/physical issue.

[GenReaper]

An auto electrician, lol.

Or a mate with a set laying around doing nothing.
I got spares on my old motor, but im in another state so i guess you cant borrow mine

[soop]

lol, is it as simple as check with a multimeter?

[cpbait]

throttle position sensor would throw up a code, that's what mine did anyway, you can test the leads as well with a multimeter as well to make sure its not one of them.

[soop]

Leads are all brand new.

Heck, Its even possible I've got a blocked fuel filter. It'd fit the bill. Such an annoying problem.

[soop]

Okay, Did a small test today. Put the car in gear and held my foot on the brake. It idled like an absolute dog. Did this for 30seconds?
Then all of a sudden decided to idle properly. Totally randomly.

What's the Idle solenoid on the TB called?
I'm going to give it all a clean up and see what happens but some info on it would be cool.

[GenReaper]

AIC sensor.

It wont be your problem, all it does is regulate air flow as a bypass to the throttle butterfly.
Basicaly its a stepper motor.

Im still guessing you have not tried replacing or borrowing coil packs to test it yet?

Cause you will be chasing your ass forever until you do the process of elimination and it sounds like coil packs to me for the 50th time

[soop]

lol, I haven't got any to try. So untill I run through everything else, Im not spending a fortune on them .
Why would the coil just randomly fix it self though?

Seriously, it was sitting there shaking and trying to die, It was almost like someone flipped a switch and the idle came back. Almost like turning the AC on.
Never had a coil pack issue like that before. Not to say your wrong but it just doesn't add up in my mind.

[PirateJoe]

Sounds like maf sensor issue. What happens when you got WOT under load? Would be good if you had one to swap over and try. Getting a can tool is a good move. Wish i had something more constructive to add sorry mate.

[Not_An_Abba_Fan]

Something to try, take the belt off and give the water pump a spin. Our Senator was doing something similar to that when the water pump was on the way out. A few weeks later it seized totally. It will get tight when spinning, loading up the engine and making it idle like crap. That was the problem with ours anyway.

[soop]

Hmm I might give that a crack actually. I've got a squealing pulley somewhere on my motor.

I'm getting a scan tool next week anyway, very handy bit of kit.

[NonStick Squid]

hey soop did you end up fixing this problem? If so what was it?

[Kingston_99]

my ute was missing, back fireing. felt like it was surgeing etc.

i went straight to holden. they put there scan tool on, while they had the tool on it backfired and cam up as a missfire on cylinder #2. they checked the coil and lead on visal inspection. found nothin out of the normal. then one guy looked again and noticed it was arcking out on the side of the mandafold. so he pushed the lead in and it clicked into place and the problem was all fixed.

also another one for you. i had the rough idle a couple of weeks ago. so i just changed the throttle postion sensor. cost me $280, but it fixed the problem.

*run your car in your garage in the dark and look for an arcking on the leads.