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Thread: LS1 - Heavy Surging (Undriveable)

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    Registered User [TUFFVQ]'s Avatar
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    LS1 - Heavy Surging (Undriveable)

    Morning Gents!

    Recently I bought a VYII LS1 Adventra (dead stock). It had sat unused for about a year with the previous owner, I picked it up quite cheaply with the knowledge I'd need to sink some cash into it. I've driven it about 1,300km since (during which time I found the Auto is slowly losing 2nd gear, the Aircon has no gas and the ABS Module is faulty!) and had an issue a few weeks back where I was rolling into it in 2nd and it was way down on power. Trans wasn't slipping, it felt like it was running out of fuel. Had a check engine light come up, so I pulled over and power cycled it, tried the same actions and received the same result.

    Plugged an OBDII reader into it the next day, nil codes and no CEL has come up since. I drove it some more and the lack of power turned into a heavy surging and not wanting to accelerate at all. Steadily got worse to the point now I can only idle it around the driveway. It free revs fine, but as soon as you start to move it falls on its face. It feels like a lean out issue as I get the usual lean backfires/stumbles.

    I replaced the fuel pump with a new Walbro 255, replaced the fuel filter (even though it was near new). Tank was clean. No dice.
    Pulled the cat sections of the exhaust out, factory cats are still fine. I drove the car with open pipes to eliminate a muffler collapse, but with the O2 sensors connected in a short section of pipe so they functioned correctly. Same issue (just louder).
    Plugs and leads look good.
    I've ordered Oxy sensors and will put them in when they arrive as some google searching had someone with a similar issue solve it this way.

    It's got me stumped - any thoughts??

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    Registered User [TUFFVQ]'s Avatar
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    The only other thing I can think of was that I pulled the inlet piping off to check the air filter before the issue occured, wondering if I did something to disturb the MAF? But then it would affect it during free revving also so it wouldn't seem like an issue - would also throw a CEL I would think?

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    Registered User Rascasse's Avatar
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    I don't know if Commodore and Adventra LS1 ECU's and MAF Sensors are interchangeable, but if so, I'd be tracking down one of each/or swapping in known good ones to eliminate electrical related issues.

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    Registered User [TUFFVQ]'s Avatar
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    Thinking a MAF change mightn't go astray - anyone have a spare one?

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    Quote Originally Posted by [TUFFVQ] View Post
    Thinking a MAF change mightn't go astray - anyone have a spare one?
    Did you probe the existing MAF to check if the voltage signals look sensible?

    FWIW, I've run a car with the MAF signal wire cut, and it ran pretty well, just very rich.

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    On old Nissans with dead mafs they would go into limp mode and run better with it unplugged. Might be worth a try.

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    No check engine light or limp mode whilst running. Only did the CEL once, but that wasn't a limp mode condition (no trans locked or cooling fan running).

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    sack riding 10sec rx7's Avatar
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    lol at maf change... change it in the bin
    im a cunt
    and apparently i dont know shit...

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    Quote Originally Posted by 10sec rx7 View Post
    lol at maf change... change it in the bin
    I will bin it when it gets tuned, but right now I can't even get it to the tuners!

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    Well, it's not the Oxygen sensors!

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    Registered User Stix Zadinia's Avatar
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    coil packs?
    Quote Originally Posted by Smidge View Post
    Would bang. Did bang. Marrying that shit.
    SUNTORY BOSS is the boss of them all since 1992!

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    I just gave it a thorough check over on anything related to the intake (PCV, IAT, Intake hoses and all that) and no issues I could see.
    It was idling like a sewing machine. Free revved ok. Shifted into drive, no problems. Touch the throttle while in gear, fail. After that ran like a dog. Bucked around like a bronco, then stalled. Restart, still terrible.
    Kind of frustrating!

    If it was the coils, I would think they would be stuffed all the time?

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    Ellis Juan mizone's Avatar
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    Pull the MAF out and blast it front and back with a full can of MAF cleaner.

    Let dry, plug in and try that. If it comes good the MAF is fucked. I've tried this on a number of cars and found that to be a way to detect the issue.

    Also mentioned above re a broken wire. Check all your sensors are plugged in right and there aren't any burnt wires or broken plugs from a zealous tech/mechanic.

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    Ellis Juan mizone's Avatar
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    Quote Originally Posted by [TUFFVQ] View Post
    I just gave it a thorough check over on anything related to the intake (PCV, IAT, Intake hoses and all that) and no issues I could see.
    It was idling like a sewing machine. Free revved ok. Shifted into drive, no problems. Touch the throttle while in gear, fail. After that ran like a dog. Bucked around like a bronco, then stalled. Restart, still terrible.
    Kind of frustrating!

    If it was the coils, I would think they would be stuffed all the time?
    Oh, just read your post. Only stumbles under load? Hmmm. At idle in N is the trans fluid too high?

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    Registered User Stix Zadinia's Avatar
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    Quote Originally Posted by [TUFFVQ] View Post
    I just gave it a thorough check over on anything related to the intake (PCV, IAT, Intake hoses and all that) and no issues I could see.
    It was idling like a sewing machine. Free revved ok. Shifted into drive, no problems. Touch the throttle while in gear, fail. After that ran like a dog. Bucked around like a bronco, then stalled. Restart, still terrible.
    Kind of frustrating!

    If it was the coils, I would think they would be stuffed all the time?
    have you checked what voltage it has whilst charging and/or running too?
    Quote Originally Posted by Smidge View Post
    Would bang. Did bang. Marrying that shit.
    SUNTORY BOSS is the boss of them all since 1992!

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    Clean your injectors?

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    Hungry Hungry Hippo Tripper's Avatar
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    Perhaps take it to a vet
    you cant spell advertisements without semen between the tits

  18. #18
    sack riding 10sec rx7's Avatar
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    here is a tip.. just unplug the maf.. it will run fine
    im a cunt
    and apparently i dont know shit...

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    Quote Originally Posted by 10sec rx7 View Post
    here is a tip.. just unplug the maf.. it will run fine
    Just curious (I have an avalanche) but will it run any better, or just the same?

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    It will go onto the low octane timing table so will be a nugget

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    Registered User Milkman Don's Avatar
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    Whats the gap on the plugs? You mention you think its a lean out, what do the plugs tell you?
    Quote Originally Posted by Faux Forg View Post
    I agree with Rdyno

  22. #22
    are hairy Dogsballs's Avatar
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    Try contact cleaner in the O2 sensor plugs. In my vz I had a weird issue with O2 loom extensions but was just the plugs

    I was about to say abs unit but thats more weird electric issues
    Quote Originally Posted by 50RTD View Post
    Dave, have you uploaded the data from the carby?

  23. #23
    sack riding 10sec rx7's Avatar
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    Quote Originally Posted by mrniceguy View Post
    Just curious (I have an avalanche) but will it run any better, or just the same?
    as BPM said it will drop the low octane spark map, but in this case where something is playing up its a simple way to check if that is the problem
    im a cunt
    and apparently i dont know shit...

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    Cheers everybody

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    Thanks for the responses guys.
    Mizone - I checked the trans fluid when I bought it and seemed OK - I'll give it another check. What would this indicate?
    Stix - I checked charging voltage when I got it too as the battery was a bit lazy on start and it was OK. I'll check again.
    Niceguy - Cleaning the injectors was next on the list but I'm not confident it will do anything.
    Dale (10 sec) - Thanks for the tip re: maf - I'll try that.
    Dale (Balls) - I replaced the O2 sensors with new bosch items - Still reckon I should give it a go?

  26. #26
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    Unplug maf and o2's, use a scan tool to check that coolant temp is reading correctly, check fuel pressure at the rail, check spark plug condition, check that each coil and lead has strong spark. If all that checks out, get the injectors cleaned. If it's still no good, the computer might be fucked, but this is a fairly unlikely scenario.

    Just going off everything you've mentioned, my best GUESS would be injectors. Did you take note of how much fuel was in it when you did the pump?
    Last edited by Ben.; 11-12-17 at 10:50 AM.

  27. #27
    Registered User [TUFFVQ]'s Avatar
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    Forgot to mention, I checked plugs, they looked fairly new with nothing to indicate an issue. I did gap them back down from .055 to .040 to see if it was a weak spark issue.

    The CTS has a cracked plug but it does engage with the connector. Removing the connector sends it into limp mode so there is some sort of signal there. Dash gauge also read normally in the lead up to the issue. I'll plug my OBDII reader into it again to check coolant temp output. Eventually will replace that sensor also.

  28. #28
    Registered User [TUFFVQ]'s Avatar
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    Unplugged MAF, threw a check engine code, still surges, free revs OK.

  29. #29
    Ellis Juan mizone's Avatar
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    Quote Originally Posted by [TUFFVQ] View Post
    Mizone - I checked the trans fluid when I bought it and seemed OK - I'll give it another check. What would this indicate?
    It sounds really silly but, the shifting issue with second gear you mention above. Some people fill the trans with extra fluid thinking its low, which I've seen causing all sorts of weird things with shifting on the GM 4L autos.

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    cleaning injectors costs about $20. If the motor was sitting for a while its a cheap and easy check

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