with my 96 Chevy truck. It has a 5.0l engine with the OBD II diagnostic stuff. What it is doing is it acts like it has a miss at low RPM under load or steady throttle. Faster engine speeds alieveiate this. It idles fune(No miss at idle) and it has not turned on the SES light.


Sunce I know -0- abuout OBD II, hopefully someone that does can tell me where to start looking......

 

TTT

 

F4,

OBDII should diagnose any misfires. You might not get a MIL lamp, but the DTCs are probably set in the PCM memory.

It sounds like you might have a weak ignition or lean cylinder at idle. One or two injectors that don't flow quite properly can cause this. You may also have weak spark at a couple of holes. A slight vacuum leak can also cause lean miss at low RPMs.

Idle under no load would be fairly stable, but loading at low RPM would cause a noticable "miss".

Unfortunately, there is no "jumper wire" method to retrieve DTCs from an OBDII PCM. You need to connect a serial reader to the ALDL to read stored codes and operating parameters.

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Later,
Vader
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"Make Me Bad"
Adobe Acrobat Reader 4.0

 

I was afraid if that....

 

Next time you are at 1/4, put some GM port fuel cleaner in your tank, and run it down to "E" and see if that does't help. These engines are known for there Poppet nozzle deposits that build up and effect drivability. Also, make sure things like your plugs and wires are OK. You will notice your distributer cap looks a little funky. It is the HVS distributer, but are subject to the same quirks as any other ignition system.

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few things you can check, but i'd start with the coil wire. there is a campaign on it for rubbing through and causing missfire at high loads. gets worse as it wears more. just one place i'd say to start.