Rough Idle, Backfiring, Lean code, and Multiple/Random Misfire code.
Thread Starter
Instructor
Joined: Dec 2006
Posts: 155
Likes: 0
From: SJ CA
Rough Idle, Backfiring, Lean code, and Multiple/Random Misfire code.
Car is running like crap!
Symptoms:
-Idles rough
-Backfires
-Slow acceleration
-Lean code
-Multiple/Random Misfire code
Mods I've recently done:
-New NGK TR55 plugs gapped at .055
-New plug wires
-New O2 Sensors
Symptoms:
-Idles rough
-Backfires
-Slow acceleration
-Lean code
-Multiple/Random Misfire code
Mods I've recently done:
-New NGK TR55 plugs gapped at .055
-New plug wires
-New O2 Sensors
Last edited by VinnyVette; Sep 20, 2015 at 06:25 AM.
Le Mans Master
Joined: Mar 2004
Posts: 5,562
Likes: 5
From: South East coast Florida
Could be injectors, I would watch out for the Lean Code as that is saying the trims are greater than 25% out.
I would also look into the Header install and possible wiring associated with the O2 sensors, injectors or even plug wires. They may have taken a while to burn through and are now suspect. Also, make sure you don't have any issues with the air intake path and MAF as far as leaks or connector/wiring (loose, burned etc).
If you can find a buddy who has HP Tuner, EFI Live or even a Tech II, you can scan the Injector duty cycle to see if that is your issue.
Good luck and let us know how it comes out
Ed
I would also look into the Header install and possible wiring associated with the O2 sensors, injectors or even plug wires. They may have taken a while to burn through and are now suspect. Also, make sure you don't have any issues with the air intake path and MAF as far as leaks or connector/wiring (loose, burned etc).
If you can find a buddy who has HP Tuner, EFI Live or even a Tech II, you can scan the Injector duty cycle to see if that is your issue.
Good luck and let us know how it comes out
Ed
Safety Car
Joined: Dec 2004
Posts: 3,526
Likes: 18
From: Santa Fe TX
And don't assume the two codes are related.
You could be getting the misfire code due to plug wires not fully seated(common), or worse crossthreaded plug (uncommon).
The lean code is more than likely o2 sensor, and could be
a) o2 harness wiring melting(common problem with header install)
b) exhaust leak sucking in fresh air(common with header installs and clamp style joints loosen over time)
c) vacuum/intake leak
d) faulty o2 sensors (especially if they were ebay replacements, less likely from local store or OEM)
And as for your symptoms, it definitely a fueling issue and more than likely you are pig rich (does it smell like raw gas?) With the misfire code it could be a firing issue on top of the fueling issue. Front o2 sensors will cause all sorts of problems.
The computer reads lean, thinks lean, dumps gas, still lean, dumps more gas, throws code because still shows lean.
Last edited by jedblanks; Aug 31, 2008 at 11:43 AM.
Thread Starter
Instructor
Joined: Dec 2006
Posts: 155
Likes: 0
From: SJ CA
I figured it out. Turns out the spark plugs were bad. Out of curiosity, is there a way to test spark plugs to determine if they are bad? I replaced the plugs with AC Delco Iridium gapped at .040 as recommended on their website. Car runs like a frickin champ.
That would explain the Random/Multiple misfire code. As for the Lean code, I had a Granatelli MAF Sensor with cold air tune. Put stock one back on. Problem solved. Guess I need a special tune for that.
That would explain the Random/Multiple misfire code. As for the Lean code, I had a Granatelli MAF Sensor with cold air tune. Put stock one back on. Problem solved. Guess I need a special tune for that.
Last edited by VinnyVette; Sep 5, 2008 at 05:44 AM.
Le Mans Master
Joined: Mar 2004
Posts: 5,562
Likes: 5
From: South East coast Florida
I figured it out. Turns out the spark plugs were bad. Out of curiosity, is there a way to test spark plugs to determine if they are bad? I replaced the plugs with AC Delco Iridium gapped at .040 as recommended on their website. Car runs like a frickin champ. That would explain the Random/Multiple misfire code. As for the Lean code, I had a Granatelli MAF Sensor with cold air tune. Put stock one back on. Problem solved. Guess I need a special tune for that.
That would explain the Random/Multiple misfire code. As for the Lean code, I had a Granatelli MAF Sensor with cold air tune. Put stock one back on. Problem solved. Guess I need a special tune for that. Congrats 
