Misfire at idle: is it the ECU running running really rich?
 

I have a Petitt unlimited ECU and I've noticed that the car misfires at idle. Could it be that the car is running really rich? I noticed it backfired a couple of times while just shifting gears at low rpms. Any ideas on what could be the cause? In addition to the ECU I have a dp and mp, hard pipe intake kit and a catback exhaust. The plugs are new NGKs and I have fairly new spark plug wires. Also, the engine has just been rebuilt but it was not ported. I'd appreciate any troubleshooting help.

If you removed the airpump, you'll need to set the idle for around 1000-1100 rpms for it to be smoothed out.

It's idling at 1000-1100 rpms; I can hear misfiring at idle.

Does this happen when your water temp is above 180F and idling, or when it's just been started?

It is misfiring all the time at idle. I am also getting really bad gas mileage. The gauge moved from about 3/4th tank to a little over half-tank for a short ~40 mile drive. I did a search and it seems like plugs and plug wires are the main culripts. These are in good order so I'm thinking it is the ecu causing the misfire.

As of right now I think it's the ECU running super-rich that is causing this, but I was wondering if anyone with similar mods may have encountered this problem in the past.

I can the Pettit ECU with DP, Hi-flo cat, catback and intake for a long time with no problem.

I doubt it's the ECU, but you can always borrow a local's stock ECU to plug in and verify that.

Are your emissions components (solenoids) removed?

Hmmm, I have to check. Could that be the problem if they are removed?

I'm going to try and post a video of the idle.

What about the rest of the emissions components? Are they disconnected with resistors in their place?

Have you also verify the TPS has been adjusted?

Found out what the problem was...I had a bad ECU ground.

How did you find out it was bad? Where does the wire ground to? (BTW, I see you on the Anteater forums a lot)

wait, if we disconnect the soldenoids, we have to put resistors in its place?? what about if were using a PFC???

thx!

WaLieN said, which grounds are you talking about.

The PFC doesn't care if the stock solenoids are there or not.

Are we talking about the ground wires that are connected to the moutning nuts on the stock ecu brackets? I don't know what a pettit unlimited ecu looks like. Does it look like a PFC? The PFC show no areas where a ground can really be attached. Is there a ground wire in the harness?

Jeremy

The Petit ECU looks just like the stock one.

Mahjik can you please explain that a little more. My 7 only does it, when its just been started. Also sometimes when i press the throttle very LIGHTLY (around 1500rpms) , when i need to move forward in traffic.

Idling problem....
 

Hi Mahjik,

How do you set the rpms to 1000 - 1100 without correctly set values of the TPS?
I get the oil pressure jumping up and down....

And when i change gear, the idling drops to 500 - 400 range....... not sure if this is the same problem tho. What do you think can be the cause? Thanks for you advise in advance!

Idling problem....
 

Hey JJ.... sori Im using yr thread to post my questions.. :D