RPM goes up every 8 sec.

[seb001]

I have a 2000 Jimmy with only 80000km on it.

Either in park or in drive while pressing the brake, the RPM goes up every 8 seconds for about 3 seconds and goes back down to normal. It goes up by 100-300RPM.

It does it more when the car is cold. I can't tell if it also does it while driving.

Once the truck is warm, it seems to still do it every 8 sec, but the RPM does not go up by as much.

Not sure if these are related: I need a new thermostat, the existing one failed open.
Might be an EGR problem, since the NOx test was a bit high.

Thanks for the help.

Seb

[MT-2500]

Originally Posted by seb001

I have a 2000 Jimmy with only 80000km on it.

Either in park or in drive while pressing the brake, the RPM goes up every 8 seconds for about 3 seconds and goes back down to normal. It goes up by 100-300RPM.

It does it more when the car is cold. I can't tell if it also does it while driving.

Once the truck is warm, it seems to still do it every 8 sec, but the RPM does not go up by as much.

Not sure if these are related: I need a new thermostat, the existing one failed open.
Might be an EGR problem, since the NOx test was a bit high.

Thanks for the help.

Seb

What engine?
Any codes or check engine lights on or blinking driving?

For starters replace the stat with 195 stat.
Confirm a good AC delco parts tune up.
Clean TBI buttery fly and MAF sensor and checkm vacumn and PCV valve.
Make sure fuel pressure is up to par.

[seb001]

The engine is a 4.3L Vortec.
There are no emission codes.

When you write: "Confirm a good AC delco parts tune up", are you talking about generic stuff like air filter, spark plug, wires.

I have code reader/scanner that can read the engine signals while it's running. Is there anything I can look for specifically?

Thanks

[MT-2500]

Originally Posted by seb001

The engine is a 4.3L Vortec.
There are no emission codes.

When you write: "Confirm a good AC delco parts tune up", are you talking about generic stuff like air filter, spark plug, wires.

I have code reader/scanner that can read the engine signals while it's running. Is there anything I can look for specifically?

Thanks

Ac delco tune starts with AC delco plugs and all other AC delco parts used in tune up.
When was you last tune up?
Are you getting any check engine lights on runnning or blinking driving?
Have you replaced the stat yet?

On the scanner check for codes past present or history?
OBD11 does not giveall good sensor data only basic reading.
Here is a good start.
Missfire data.
Fuel trim data.
Engine running temt correct.
Camshaft retard settings.
Confirm all 02 sensors are in range.
Egr reading actual and desired.
TPS sensor readings
Also fuel pressure needs checked with a fuel pressure gauge for up to specs pressure.
Cold start engine running and the rechecked on the road after 3 minutes or more driving.
60/66 lbs pressure

[GMCustomerService]

I would also recommend contacting GM of Canada for more assistance. You can contact them at 800-263-3777. The hours of operation are M-F 7:30am - 11:30pm, Sat 7:30am - 6:00 EST. I hope this helps. Thank you.

Tricia, GM Customer Service.