Discussion:
Missing at idle

Ok here is the deal. I have been working on a lift for a while now. It has the Gm motor and it runs and accelerates great but it has a miss at idle. It had a blown intake gasket which I replaced. Runs better but still misses at idle. I have tuned it up wires and plugs. All cool pack are good. Replaced the mass air flow and cam shaft sensors. Replaced all 4 fuel injectors and it has a new vaporizer on it. I have no other vacuum leaks. It's throwing the camshaft code but it's fine all my voltage check are in specs. Anyone have any clue what to do next?
  • Posted 13 Jul 2016 00:49
  • By justin_h
  • joined 8 Jan'14 - 13 messages
  • Tennessee, United States
Showing items 1 - 9 of 9 results.
Sorry guys I have been tied up. I am going to look further into it tomorrow and I will let y'all know. I appreciate all the help!
  • Posted 28 Jul 2016 01:54
  • By justin_h
  • joined 8 Jan'14 - 13 messages
  • Tennessee, United States
sorry guys that was my mistake on that camshaft code, i was working on some cat stuff at the time when i posted that and had cat /nissan codes on the brain. Should of been a 723 or 522752 code.
sorry bout that
but i am wondering where justin is in all this now?
  • Posted 28 Jul 2016 00:55
  • Modified 28 Jul 2016 00:56 by poster
  • By swoop223
  • joined 23 Mar'12 - 3,691 messages
  • North Carolina, United States
You've been swooped!
swoop223@gmail.com
That is why I asked if it is still displaying a can sensor code. Might be mis-triggering at idle.
  • Posted 27 Jul 2016 22:38
  • By BREWSKI
  • joined 10 Jan'12 - 1,699 messages
  • Nebraska, United States
This is a hyster correct? Swoops last post makes me think no but the thread is under hyster ft.
Regardless I had something similar on a gm powered Yale recently. Coil pack cured it. Not saying this is what your problem is but it was for me. I know you say it's good but just saw this thread and thought I should chime in.
When you can't find a problem, fix what you know is bad. As swoop said the cam sensor can do strange things.
Edit: I had no codes displayed.
  • Posted 27 Jul 2016 21:10
  • Modified 27 Jul 2016 21:22 by poster
  • By stam
  • joined 12 Aug'12 - 779 messages
  • Ontario, Canada
well brewski he did origionally say

Replaced the mass air flow and cam shaft sensors. Replaced all 4 fuel injectors and it has a new vaporizer on it. I have no other vacuum leaks. It's throwing the camshaft code but it's fine all my voltage check are in specs.


but he didn't actually specifiy the code number so we can only assume it is the E28 code.
Now in some cases i've witnessed that even though the sensor is replaced the code is persistant till it is cleared via the diagnostic program or possibly can be cleared by using the 'pedal dance' or disconnecting the battery for a period of time.
In either case the engine will still run with a bad sensor, it will just be put into limp mode and turn on the MIL light once the code is picked up after a preset period of time when the ECM checks the circuit.
Now the only question that remains in my mind is did he use an aftermarket sensor? TVH?
I've had bad luck with these in the past and the only viable replacement is an OEM sensor.
Could this cause a miss? I personally have never seen it but i suppose it is possible given the function of this sensor.
  • Posted 27 Jul 2016 00:26
  • By swoop223
  • joined 23 Mar'12 - 3,691 messages
  • North Carolina, United States
You've been swooped!
swoop223@gmail.com
What code is it throwing? If there is a active code, you need to address this first.
  • Posted 26 Jul 2016 22:47
  • By BREWSKI
  • joined 10 Jan'12 - 1,699 messages
  • Nebraska, United States
ok since all that checks out\
i was reading in the troubleshooting guide and there is a 'cause' section about EMI (electromagnetic interference)
how are the secondary wires from the ignition ran?
it says to check those wires and check the ground, either one can be a cause of engine missing.
  • Posted 26 Jul 2016 00:41
  • By swoop223
  • joined 23 Mar'12 - 3,691 messages
  • North Carolina, United States
You've been swooped!
swoop223@gmail.com
What should the fuel setting be? The compression checked out and there were no vacuum leaks found.
  • Posted 25 Jul 2016 23:29
  • By justin_h
  • joined 8 Jan'14 - 13 messages
  • Tennessee, United States
run a compression check on all cylinders
could have a bad valve

also check all your vac lines, make sure there are no vac leaks.

if compresson checks ok then i'd look at the fuel system settings, could just be out of adjustment causing the miss.
  • Posted 25 Jul 2016 03:01
  • By swoop223
  • joined 23 Mar'12 - 3,691 messages
  • North Carolina, United States
You've been swooped!
swoop223@gmail.com

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