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Engine misfire on no 1 plug code 0300/0301 open loop cat getting red hot

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A P0301 code means that the the car's computer has detected that one of the engine's cylinders is not firing properly. In this case it's cylinder #1.

FB.init("dd7d9e9681341cde77587bc6a2029f6f"); on Facebook Symptoms may include:

  • the engine may be harder to start
  • the engine may stumble / stumble, and/or hesitate
  • other symptoms may also be present

Causes:A code P0301 may mean that one or more of the following has happened:
  • Faulty spark plug or wire
  • Faulty coil (pack)
  • Faulty oxygen sensor(s)
  • Faulty fuel injector
  • Burned exhaust valve
  • Faulty catalytic converter(s)
  • Running out of fuel
  • Poor compression
  • Defective computer

Possible Solutions:If there are no symptoms, the simplest thing to do is to reset the code and see if it comes back.

If there are symptoms such as the engine is stumbling or hesitating, check all wiring and connectors that lead to the cylinders (i.e. spark plugs). Depending on how long the ignition components have been in the car, it may be a good idea to replace them as part of your regular maintenance schedule. I would suggest spark plugs, spark plug wires, distributor cap, and rotor (if applicable). Otherwise, check the coils (a.k.a. coil packs). In some cases, the catalytic converter has gone bad. If you smell rotten eggs in the exhaust, your cat converter needs to be replaced. I've also heard in other cases the problems were faulty fuel injectors.

Hope helps; tell us news and keep in touch (remember rated this help).

Posted on Jul 10, 2010


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98 jeep wrangler tj 4.0 code 320 crank sensor exhaust glowing red acceleration not going over 2000 showing signal on scan tool that crank sensor is working.

Good morning
Questions (sorry)
so it runs perfect and only red glow? no, it has lost engine power.
GIVE It A FULL 60K MILE TUNE UP YET, BUY The book the decades?
the 98 is obd2, technology USA< and allscantools work this year
and will all report 1 miss in 10 on all sensor like that, CMP or CKP

that red glow means tons of fuel and air are landing outide engine
this is caused by gross misfire. ever misfire dumps load of fuel and 20% oxygen there, like the afterburner on a jet, but this case is wasted so, MISFIRE is the prime symptom.
if running a turbo ,it be normal. (red glow only)

so what cause misfire,
there is a huge list if reason , can i assume you have no DTC errors thrown?
are the spark wire routed, in the correct firing order.
is the engine timed to spec>?
got 150 or more PSI compression on all 6 cylinders?
The PCM;/ECU can also go to limphome mode, and do that. easy.
bad sensor inputs, do that, and DTCs are stored.
is that a real scanner or just cheap code reader, if real there are lots of checks. can i list them? all EFI fuses good.
  1. ECT shows ambient temp , cold started, the goes to 180F and holds hot? if not the thermostat is no good, bingo. stuck in cold start mode for ever.
  2. I keyon and see the TPS work, not started, called throttle angle.
  3. i start and TPS ANGLES show, low then high as i gun the throttle
  4. The engine worms up and gets to closed loop status. CL.
  5. if not I fix that first, after all fixing idle hard fails is 10x easier than flying down the road at 2000 rpm.
  6. Ok got closed loop at idle (i bet not) then while parked can i get CL status, at 2000 rpm, in neutral or park.?
  7. id bed not. id bet 6 fails all fail able, or?
  8. so why is it not. well that can be easy or hard, what can you do ,well lots really , bad 02 sensor (front) or exhaust leaks near it?
  9. its and old 4L so do the compression test as we do on all old motors, its after all, old. can run a dead engine with EFI.
  10. IS fuel pressure too high (gauged)
  11. Is the Fpreg working, (gauged)
  12. is the MAP WORKING (voltmeter) ask for scale i have it.
  13. leaking injectors. (for 3 reasons/cause) "gauged leak down tests"
  14. more sure but above may land on the

some 4L liter in CAL have 2 front 02 sensors, due to split exhuast header man. so that takes a quick look there.

Dec 27, 2014 | Jeep Cars & Trucks

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Why am i getting engine code p0421 on this 2002 mitsubishi lancer?

this code is lazy cat (or weak or dead)420's are very hard to diagnose
here is the order.
1: NO EXHAUST leaks near any oxy sensor. zero, (cracks, or gaskets) any where near or upstream of any oxy sensor.!!!
2: Engine runs perfectly CEL out running and no stored or live DTCS (besides 421) and engine holds closed loop at hot idle and light flat cruise, steady right foot, if not , the CAT gets punished.
3: good front oxz sensors, a mUST.
4: AND 2nd last , new rear cat sensors (421s come from this sensor)
5: a NEW cat.

that is the crash course, can do 100s pages.
but no. just 1.

Jun 28, 2014 | 2002 Mitsubishi Lancer

1 Answer

P0420 p1399

99 civic? ever tune it up, or run the cam belt fore ever?
you do now, ignoring the bent, ends in bent valves, right?

which engine option, cylinder count and displacment. USA 1.6L? I-4?

misfiring. ever tune it up this decade? or 60k miles? with cam belt.
1399 is misfire (let me guess, the CEL flashes )
do not skip the belt if due, or you will lunch the engine.

420 is: (ID IGNORE THIS, till the MISFIRE ENDS !!!)
Possible causes
- Three way catalyst converter Bank 1
- Exhaust tube
- Intake air leaks
- Fuel injectors may be faulty
- Fuel injector leaks
- Spark plugs may be faulty
- Improper ignition timing
- Engine Control Module (ECM)

(the bar room answer for 420 is, the CAT is weak, )
the autoshop class>? ASE.. if the cat is or was tortured (misfire)
then fix that first and pray the cat bakes dry and passes 42x codes
if bake many dry, and 420s cleared.
what happens is you overload the CAT with raw fuel, ignore it.
the CEL flashing (USA) means you are KILLING THE CAT.

now we cover, misfire
there are huge possibles.
in a big shop we connect 5 gas to tail and start there .
in a lesser shop, plenty. we check closed loop at idle
if not in closed loop at idle, we fix that first. (easy ,car is parked)
(later closed loop at 40mph light flat cruise, steady right foot) no hills.
Misfire, :
Bad engine, bent a valve> do to ignoring the belt. got vacuum bounce?
bad spark
bad injection rates, or injectors clogged ,dead or weak or leaking.

me, i watch pendings to see of P0301 , to P030x (x is cylinder num)
if the scan tools shows any misfire codes, i do a leak down
on the cylinder that misfires, 300s is random.

lots of ways, EGR stuck open
AFR runing lean, scan too sees that...
AFR stuck rich, same.
the best order is this. (no clues with extra DTCS
compression test. and leak down. if smart.
spark tests.
last fueling, rates, (fails closed loop at idle spark good , engine good.
i do the the injector leak down tests. and balance,

i also do the cAT melted test. cat back pressure test
less that 2psi at 2500rpm.

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1 Answer

Random multiple misfire code. Cat gets glowing red hot. Sluggish lack of power/acceleration

Combining the hot cat converter and the missfire code, I would lean toward a fuel problem. Too lean or pressure too low.
If it was an ignition problem the cat would usually not be hot.
If the exhaust was stopped up, you would not usually get the multiple missfire issue. Just lack of power.
It could be a leaking EGR or other vac problem, and a dirty fuel filter too.

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2003 ford ranger catylitic converter glowing red

if cat is glowing red it is most likely plugged. will need to replace cat.

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My 2002 mustang gt misfires on cylinder 1 ( cylinder 1 misfire/circuit malfunction) While misfire i get lots of fuel dumping. Loss of power.

I assume your CEL light is flashing. You will ruin your $1000 catalytic converts if you drive it this way. Your cats will turn red hot and self destruct.

You have a bad COP, Coil on Plug (if your vehcile has that system, and it could have damaged your PCM engine computer. Remote chance it's just a plug.

Your injectoris still pumping fuel into that cylinder and teh cat has to over work to treat the unburned fuel.

You did not say if you have a V8 or V6 engine which is important.

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My chec engine light comes on after driving for a while, typically 20 miles or so on the freeway, a guy at checker said possibly something in the cat, and recommended sea foam, I know the alternator or the...

Check engine like is it red or yellow? if it's yellow it could be a misfiring spark plug, or a lazy 02 sensor, that means you drive the truck till it gets in closed loop then the 02 sensor is connected to fuel trim and is not changing fast enough causing the light to come on. Since the 02 sensor is bypassed until engine is warm this could be your issue, it could also be a spark plug wire or even the heater on the 02 sensor, since it's a 89 it has a sensor on each side of the engine and one after the cat, if there is a spark plug problem if the check engine light starts flashing it means a catastrophic misfire that will destroy the cat so it is a fuel or spark problem.

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3 Answers

I need help

this is caused because a misfire, misfire will be caused by defective or misrouted spark plug wires, make sure to check the firing order, on the plug wires, and if you just replace the spark plugs, then most likelly the wires are misrouted, and the cat gets hot because unburnt fuel like runing too rich, and will be related with misfire.

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