Idle/misfire/fueling issues
Thread Starter
Staging Lane
Joined: Feb 2012
Posts: 87
Likes: 0
From: Colorado Springs
Idle/misfire/fueling issues I need your help. For a while now, my car in the signature has been acting up.
Symptoms:
-I did have 60lbs injectors installed and tuned down to 40% duty cycle. I changed the injectors out to 36lbs ones, re-tuned the ECM from a local Tuner. Now running 80% duty cycle.
-The plugs were gapped to .059 and I pulled all 8 out and they looked like this:
One of the plugs was wiped off (third one from the right). Looks a little too much fuel. So I put all new plugs in and gapped at .050. Car ran great....for a afternoon. The car started stumbling at low rpm and/or take off like I am running on 5 cylinders...then takes off like a bolt of lightning.
-I have also had an annoying high idle issue. This comes and goes. Sometimes I will be driving along and coming to a stop and my idle is around 2-2400 rpm and will not drop until I come to a complete stop and wait a few seconds (around 5-10) to idle down. This comes and goes as well. Flippen sucks. I was coming down a long mountain pass not long ago and shifted the trans in neutral and let out the clutch. Idle stayed at 2200 rpm for over 5 miles and only came down to idle rpm after I came to a complete stop.
The tuner said my IAC was working just fine, so I haven't swapped it out. There is no carbon buildup on the actuator.
I did have the car re-tuned again and the tuner adjusted the IAC.
So what do you think? Two separate issues or one that I am overlooking?
When the car is running like normal, it is great. I have a hard time believing that my cam would cause some many idle and driveability issues as this.
Symptoms:
-I did have 60lbs injectors installed and tuned down to 40% duty cycle. I changed the injectors out to 36lbs ones, re-tuned the ECM from a local Tuner. Now running 80% duty cycle.
-The plugs were gapped to .059 and I pulled all 8 out and they looked like this:
One of the plugs was wiped off (third one from the right). Looks a little too much fuel. So I put all new plugs in and gapped at .050. Car ran great....for a afternoon. The car started stumbling at low rpm and/or take off like I am running on 5 cylinders...then takes off like a bolt of lightning.
-I have also had an annoying high idle issue. This comes and goes. Sometimes I will be driving along and coming to a stop and my idle is around 2-2400 rpm and will not drop until I come to a complete stop and wait a few seconds (around 5-10) to idle down. This comes and goes as well. Flippen sucks. I was coming down a long mountain pass not long ago and shifted the trans in neutral and let out the clutch. Idle stayed at 2200 rpm for over 5 miles and only came down to idle rpm after I came to a complete stop.
The tuner said my IAC was working just fine, so I haven't swapped it out. There is no carbon buildup on the actuator.
I did have the car re-tuned again and the tuner adjusted the IAC.
So what do you think? Two separate issues or one that I am overlooking?
When the car is running like normal, it is great. I have a hard time believing that my cam would cause some many idle and driveability issues as this.
TECH Addict
Joined: Sep 2009
Posts: 2,481
Likes: 5
From: PA/MD
60lb injectors seam pretty big for your setup.....you shouldn't be anywhere meet 80% duty cycle on them...I'm running 60lb injectors in my 8,000 rpm 408 and only touch 70% just before fuel cut, so the 36 lb ones should be about right for yours.
It looks like it is running WAY too rich still, might want to take your injector minimum pulse width and shorten it. It's been a few months since I've been in Hptuners, but if I remember right when you do drop minimum pulse you have to change it in a couple of spots.
Bigger cams need more fuel up in the mid to higher rpms, but take less than stock at idle/ low rpms, and no matter how rich the o2 sensors see the computer can only drop back to a certain set value.
I think you have to change and match "minimum pulse", and "default pulse"
It looks like it is running WAY too rich still, might want to take your injector minimum pulse width and shorten it. It's been a few months since I've been in Hptuners, but if I remember right when you do drop minimum pulse you have to change it in a couple of spots.
Bigger cams need more fuel up in the mid to higher rpms, but take less than stock at idle/ low rpms, and no matter how rich the o2 sensors see the computer can only drop back to a certain set value.
I think you have to change and match "minimum pulse", and "default pulse"
Thread Starter
Staging Lane
Joined: Feb 2012
Posts: 87
Likes: 0
From: Colorado Springs
Me too. I am dropping the car off this weekend so he can test it out for a while. I don't think a compression test is needed, but hopefully the it is a quick fix and back on the road.
