2004 vy spac ecotec 3.8 rough idle

[Juniorvsv6ute]

Hi
I have a 2004 vy spac ecotec 3.8 it is running rough I’ve checked all the normal things found out to be the fuel injectors well number 3 and number 5 if I unplugged them it would still run rough with out getting any worse bu if I unplugged any of the others it would run worse. So I just change all the fuel injector’s and took it for a spin around the block and it run like new again but then for some reason it started raining rough again and doing the same thing number 3 and 5 injector. I’m stumped at why only those two

 

[Grimes]

Tricky one.

Check for fault codes first.

Check plugs and leads, and coils by moving them around to see if the problem moves with them.

Replace the fuel filter if that hasn’t been done in a while.

Check the fuel pressure regulator vacuum line for splits, check the regulator for fuel leaking into the vacuum side.

Check the metal contacts in the injector harness connectors and make sure they haven’t been crushed. If the connector goes on at an angle they can get squashed and need to be straightened out with a needle or micro screwdriver.

Check the inlet manifold bolt torques especially in the rear corner where 3 and 5 are or any other signs the LIM gasket is letting air in.

Do a compression check. This one’s a bit out there but with 5 and 3 being next to each other it rules out a head gasket issue (compression loss) between them.

 

[krusing]

Hmm, It does sort sound like a vac leak,
A smoke test maybe a good idea to eliminate that if you can get one done.
and/or
a Live scan.

There would possibly be a DTC its created, but may not of triggered the MIL.

 

[Juniorvsv6ute]

Hi
I have a 2004 vy spac ecotec 3.8 it is running rough I’ve checked all the normal things found out to be the fuel injectors well number 3 and number 5 if I unplugged them it would still run rough with out getting any worse bu if I unplugged any of the others it would run worse. So I just change all the fuel injector’s and took it for a spin around the block and it run like new again but then for some reason it started raining rough again and doing the same thing number 3 and 5 injector. I’m stumped at why only those two

Sorry it’s actually 1 and 4 when I unplug earlier one or both it doesn’t make the car run any worse but unplug any of the other it runs worse. It’s got me rattled I’ve gone over everything. I need to get hold of a scan reader or one I can download for the laptop and try doing a smoke test

 

[Lex]

Sorry it’s actually 1 and 4 when I unplug earlier one or both it doesn’t make the car run any worse but unplug any of the other it runs worse. It’s got me rattled I’ve gone over everything. I need to get hold of a scan reader or one I can download for the laptop and try doing a smoke test

DFI or coil pack for 1 & 4.

 

[Pollushon]

Great troubleshooting. If it's not the fuel it's the spark. As above either two plugs, coils or the DFI. It's funny because I just went through the same issue with the exact same coils on Sunday, except it was 6 and 2. Fault diagnosed as two crappy GOSS packs. Resolved by wrecker OEM

 

[Juniorvsv6ute]

It’s still getting spark coils are all good as are plugs and leads and just changed all the injector’s. Runs rough at idle a big flat spot when you take off and every time you put your foot down. It runs rough the hole time, when i hold it at 50kmh the hole car shakes hold it at any Constant speed the hole car shakes. Also running really really rich

 

[Juniorvsv6ute]

Just to add as well the traction control turns it self off every now and then and have not had any engine error’s show up. Oh and the air bag light was always coming up so have just taken the fuse out

 

[lout]

It’s still getting spark coils are all good as are plugs and leads and just changed all the injector’s. Runs rough at idle a big flat spot when you take off and every time you put your foot down. It runs rough the hole time, when i hold it at 50kmh the hole car shakes hold it at any Constant speed the hole car shakes. Also running really really rich

how are you testing coils under load
new does not mean good

 

[Juniorvsv6ute]

how are you testing coils under load
new does not mean good

With a spark tester and unplugged each lead at a time, each time one got unplugged it would run worse then it already dose