Hello,
Late last year I bought a '96 LX450 with 218k, now at 222k. I'm currently experiencing P0300, P0303 and P0304 with rough idle. Roughness is especially pronounced when in drive/reverse and brake depressed (like at a stop light). CEL on, and blinks for ~20 seconds when first driving after starting the truck, then stays on constantly for the rest of the drive. My thoughts below incorporate, to the best of my searching, previous threads on this topic but this is my first post so please bear with me if I missed one.
Relevant history:
- PO had engine out to replace head gaskets, spark plugs, spark plug wires, distributor, ignition coil and hoses attached to the engine
- PO installed snorkel and new filter box and air intake plumbing thru to engine intake
- There was a hint of a misfire before the roughness began. At idle in Park, every ~15 seconds the engine would stutter very slightly
- Idles fine at 650
- O2 sensors appear original
- At parking lot speed, steering turned hard left/right with brake applied causes engine stutter and stall
Recent diagnosis info:
- Confirmed leaking exhaust connection between Y-pipe and exhaust manifold by spraying soapy water on it while idling
- Replaced spark plugs with iridium units, spark plug wires and ignition coil
- Local shop is fixing the exhaust leak
- Local shop believes the injectors are fine, but that cylinders 3-6 are all misfiring, not just 3 and 4
- Local shop doesn't believe it's the pressure check valve on the brake booster
Thoughts on what to do going forward? I'm thinking, in sequence of cost/complexity:
- Fix exhaust leak (being done now)
- Replace O2 sensors
- Replace EGR
- Replace brake booster check valve
This is my first post so here's a little on my rig. I've benefitted from looking through the various MUD forums to learn how to fix and replace many parts on my truck. I've listed what I've done below. Except for the sound deadening, most of it's pretty plain vanilla and already-discussed so I won't waste people's time.
Replaced:
- Rear door and tailgate lock actuator motors
- 4 window runs replaced
- Rear tailgate gas struts
- Alpine ILX-407 head unit, 5.25" Focal Auditor (front) and 4" rear
- Deleted factory amp and bypassed front tweeter and console woofer
- Fixed shaky driver mirror
- Double cardan front drive shaft greatly reduced vibration noise when releasing accelerator at highway speeds
- LED lighting all around
- Weatherstripping (4 doors, car and door side rubber)
Sound deadening:
Also installed Resonix CLD squares inside 4 doors and all over the trunk floor and rear wheel wells. Bought 1 box of 40 ft2 to try and results were fruitful. A db measurement app on my phone previously measured at the driver's head 76db at 65mph with little/no traffic around me. I'm now at 69/70db before sound deadenning the passenger area floor or firewall. An old Motortrend article from '96 described the cabin noise at 71db at the same speed so I'd say the weatherstripping and Resonix were a win. The Resonix alone dropped the interior noise by 3 db and the weatherstripping took it the rest of the way.
Truck already had:
- 3" Dobinsons lift and steering damper
- ARB front bumper and brush guard
- Dobinsons rear bumper with swing spare tire and jerry can holders
- Triple locked with TJM pneumatic
- 17.5k# Smittybuilt winch up front with Factor 55
- Safari snorkel
- Stock 16" rims with 33" BFG KO2
- Emerald Green
Thanks in advance, folks!
- Jason
Late last year I bought a '96 LX450 with 218k, now at 222k. I'm currently experiencing P0300, P0303 and P0304 with rough idle. Roughness is especially pronounced when in drive/reverse and brake depressed (like at a stop light). CEL on, and blinks for ~20 seconds when first driving after starting the truck, then stays on constantly for the rest of the drive. My thoughts below incorporate, to the best of my searching, previous threads on this topic but this is my first post so please bear with me if I missed one.
Relevant history:
- PO had engine out to replace head gaskets, spark plugs, spark plug wires, distributor, ignition coil and hoses attached to the engine
- PO installed snorkel and new filter box and air intake plumbing thru to engine intake
- There was a hint of a misfire before the roughness began. At idle in Park, every ~15 seconds the engine would stutter very slightly
- Idles fine at 650
- O2 sensors appear original
- At parking lot speed, steering turned hard left/right with brake applied causes engine stutter and stall
Recent diagnosis info:
- Confirmed leaking exhaust connection between Y-pipe and exhaust manifold by spraying soapy water on it while idling
- Replaced spark plugs with iridium units, spark plug wires and ignition coil
- Local shop is fixing the exhaust leak
- Local shop believes the injectors are fine, but that cylinders 3-6 are all misfiring, not just 3 and 4
- Local shop doesn't believe it's the pressure check valve on the brake booster
Thoughts on what to do going forward? I'm thinking, in sequence of cost/complexity:
- Fix exhaust leak (being done now)
- Replace O2 sensors
- Replace EGR
- Replace brake booster check valve
This is my first post so here's a little on my rig. I've benefitted from looking through the various MUD forums to learn how to fix and replace many parts on my truck. I've listed what I've done below. Except for the sound deadening, most of it's pretty plain vanilla and already-discussed so I won't waste people's time.
Replaced:
- Rear door and tailgate lock actuator motors
- 4 window runs replaced
- Rear tailgate gas struts
- Alpine ILX-407 head unit, 5.25" Focal Auditor (front) and 4" rear
- Deleted factory amp and bypassed front tweeter and console woofer
- Fixed shaky driver mirror
- Double cardan front drive shaft greatly reduced vibration noise when releasing accelerator at highway speeds
- LED lighting all around
- Weatherstripping (4 doors, car and door side rubber)
Sound deadening:
Also installed Resonix CLD squares inside 4 doors and all over the trunk floor and rear wheel wells. Bought 1 box of 40 ft2 to try and results were fruitful. A db measurement app on my phone previously measured at the driver's head 76db at 65mph with little/no traffic around me. I'm now at 69/70db before sound deadenning the passenger area floor or firewall. An old Motortrend article from '96 described the cabin noise at 71db at the same speed so I'd say the weatherstripping and Resonix were a win. The Resonix alone dropped the interior noise by 3 db and the weatherstripping took it the rest of the way.
Truck already had:
- 3" Dobinsons lift and steering damper
- ARB front bumper and brush guard
- Dobinsons rear bumper with swing spare tire and jerry can holders
- Triple locked with TJM pneumatic
- 17.5k# Smittybuilt winch up front with Factor 55
- Safari snorkel
- Stock 16" rims with 33" BFG KO2
- Emerald Green
Thanks in advance, folks!
- Jason
