2011 SV6 Series 2 VE - Slow crank after being driven for a while ( wont start)

[wetherow]

Hi guys,
Just after some advice as im kinda stumped.

I have a SV6 VE commodore sedan series II which has an LLT engine in it. about 6 months ago it developed a bad misfire on bank 2 affecting all B2 cylinders - turned out to be a blocked/damaged cat which I have had brand new high-flow cats installed which fixed the issue. During this time i have had the timing chains done with heavy duty chains/new tensioners and guides as well as new spark plugs and ignition coils.

After having the new cats installed - the car now has this issue of slow cranking only when its warmed up or after being driven for a while (approx and hour of hwy driving) like its got a flat battery and essentially wont start. I have replaced the battery, alternator, and starter motor as well as checked the earth points and the wiring loom for resistance and voltage with a multimeter which have all been well within parameters. but it still has the slow crank when warm issue. I have also checked the fuse relays and they're all solid.

I have hooked it up to an ECU reader and it is showing codes for cat system below threshold on B1 and 2 which i presume is due to the high flow cats but it also have codes for running too rich fuel/air mix P0172 and P0175. I have checked the O2 sensors while connected to the scanner and the voltages are within normal ranges on live scanner data as well as long term.

Any ideas?

 

[krusing]

You mentioned when it gets hot,

I’m tipping it’s the Starter motor,
My LY7 had the same issue, cranked really slowly when hot,
Then sometimes would not turn over and wouldn’t fire,
Waited 10 min, and would start ok.
Purchased a starter motor off eBay from a reputable seller,
Replaced the starter motor,
Starts perfectly now either hot of cold,
The rest is history.

 

[Lex]

I’m tipping it’s the Starter motor,

I have replaced the battery, alternator, and starter motor as well as checked the earth points

 

[krusing]

Was the Starter motor new,
or secondhand ?

Battery terminal/lead on the starter motor tight ? as they have a tendence to come lose due to the exposure to heat from the exhaust manifold
Cranking relay ? [under the bonnet]

 

[krusing]

I read that,
but some people prefer to purchase S/H starter motors to save $20 > $30, and causes more/other issues they then need to sort out, and creates a can of worms

Items that should always be bought new if, and when needed -
Battery, [just replace them]
Starter motor, [just replace them]
Alternator, [or recondition them if you have a the tools]
[Not in that order]

As mentioned, I replaced the Starter motor in my LY7 with a new one, as I didn't want to buy someone else's faulty Starter Motor
Were it cost me $90 inc postage for a new one, [from a reputable eBay seller], with a 12 month warranty
and some sellers on eBay and Marketplace are trying to sell S/H one's for $60 > $90.

 

[wetherow]

Was the Starter motor new,
or secondhand ?

Battery terminal/lead on the starter motor tight ? as they have a tendence to come lose due to the exposure to heat from the exhaust manifold
Cranking relay ? [under the bonnet]

the starter motor was second hand from the auto wreckers. but theres no difference between the old and "new" one in terms of the issue.

i did the battery terminal lead up tight - anymore probably would have threaded the bolt haha.
the cranking relay im not sure where that is exactly if its seperate to the fuse box under the hood.

 

[wetherow]

I read that,
but some people prefer to purchase S/H starter motors to save $20 > $30, and causes more/other issues they then need to sort out, and creates a can of worms

Items that should always be bought new if, and when needed -
Battery, [just replace them]
Starter motor, [just replace them]
Alternator, [or recondition them if you have a the tools]
[Not in that order]

As mentioned, I replaced the Starter motor in my LY7 with a new one, as I didn't want to buy someone else's faulty Starter Motor
Were it cost me $90 inc postage for a new one, [from a reputable eBay seller], with a 12 month warranty
and some sellers on eBay and Marketplace are trying to sell S/H one's for $60 > $90.

i get ya point there, ive never had any issues with parts from the wrecker i buy from though - i mean theres always a first time haha but still. i bought a second hand SM as i couldnt afford the $400 for a brand new one.

 

[uglyoldfatbastard]

You had better hope it's something electrical because I just did a ECU for a guy to go from LLT to LFX and his was doing the same thing would barely turn over or start when hot and used to cut out sometimes and it turned out to be the crankshaft bearings had metal in them and it was fudged.
As soon as it cooled down it fired right up free and easy.

 

[wetherow]

You had better hope it's something electrical because I just did a ECU for a guy to go from LLT to LFX and his was doing the same thing would barely turn over or start when hot and used to cut out sometimes and it turned out to be the crankshaft bearings had metal in them and it was fudged.
As soon as it cooled down it fired right up free and easy.

Im hoping its not that, if it is = ill donate it to SES for RCR

 

[rambunctious]

the starter motor was second hand from the auto wreckers. but theres no difference between the old and "new" one in terms of the issue.

i did the battery terminal lead up tight - anymore probably would have threaded the bolt haha.
the cranking relay im not sure where that is exactly if its seperate to the fuse box under the hood.

The terminals and inside the battery clamps need to be cleaned with either a battery cleaning tool or at the least, emery cloth and or a file.
They should be shiny like a new pin before fitting.
As should be any connections that are removed and refitted.
Doing them up tight is only a small part of the battle.