Question about 1999 Toyota 4Runner

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99 4runner 3.4

Today i changed back to original plug wires and switched coil pack 1 to 3....i cleared all codes drove to the store with scan tool hooked up...ran fine to store no codes... when i came out and started it, i noticed it was stumbling again, it tru only one code this time po302....i believe the wires i put in were bad or i mixed up cylinders..i think this because i have the original code i started with before changing wires....could it still be the coil pack as to it is showing a code for only one cylinder and the coil connects 2-5 cylinder? im at a lose at the moment and back at ground zero....any advice would be great...thanks

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  • kosmindtrip Dec 28, 2008

    i have very low funds, an am quite good with a wrench...i just need more advice on possible going to try to get an ohms meter to test the coils and injectors..maybe a noid light...if it comes down to changing the injectors i will probably take it in southern california and the techs around here are a total rip off...

    im in the military, pretty much all my tools and resourses are back home...

    i do have an innova 1303 scan tool at my side to help...

  • kosmindtrip Dec 28, 2008

    i have caused no additionsl problems i still have the exact same code..why are you giving me trouble when you should be trying to help? isnt that what this site is for?

  • Marvin
    Marvin May 11, 2010

    U have caused allot of additional problems from lack of skill in this area of auto repair, why do u think dealers charge $120 hour?

  • Marvin
    Marvin May 11, 2010

    why don't u have a qualified professional fix this.



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Ok this is sort of where I started with same problem, which at moment is not solved. You are on the right track as I also just changed my wires, although the readings from wires were ok, We also tried the coil & igniter which is simple to put in as connected by plug ins, I will warn you as I went to a Toyota parts yard $50. and they made the mistake of cutting one of the wires, to which my mechanic had to weld it together. It is held on by two bolts and plug ins so there is no need to cut! I was not getting power to cylinder 2. Thats when I can tell you that my back yard mechanic put in the injector, just to give you an indication in Vancouver, Canada it was $75. then 1hr to put in. It is a little tricky to install, and watch out for the vacuum hose for the fuel regulater as my mechanic didn't tighten it and it came loose! I have gone through a succession of things, latest being A new Coolant Temp Sensor which sends signals to fuel compression etc. It's tempermental in missing and running ruff. I am on here to try and get solutions before I take it to Toyota....arg

Posted on Jan 17, 2009


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1 Answer

06 town and country no spark on 3 and 6

the PCM grounds the coil to produce spark. You can use a scan tool (not a code reader) to energize the individual coils while monitoring the circuit with a volt meter or a test light. If the PCM is supplying ground to the 2/5 and 1/4 coil but not the 3/6 coil than you know you either have a wiring issue between the pcm and the coiul pack or the pcm is bad.

I’m happy to assist further over the phone at

Oct 09, 2016 | Cars & Trucks

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I have a 2003 jeep grand cherokee, It started

wow, no engine option stated, and no DTCs.

4.0L I-6 or 4.7Liters?

WHY DO THAT FIRST. $$$$ parts first.

why not do a tune up first.

you swap in the most expensive parts first? ouch,

The PCM tells you when ckp or cmp fail, with DTC codes

so its not that. but you never posted ALL DTC errors. why not do that.?

do a real tuneup? heat (spark plugs, filters.)

if you have P030x errors,

eg: p0301 is cylinder #1 is misfiring (3 ways to do that not JUST spark)

eg: P0300, random on all cylinders. (fuel mix wrong) or never tuned up.

Misfire 101; (example P0301 DTC)

P030x codes, are all just about spark, misfire is caused by 3 things, (at least)

1: sure spark. weak. (tuneups work as does hV wires sets if no COPS) if 1 cop is bad move it to other location, does failure follow the move>???????? buy new cop boots if engine has cops.

COPS means coil over plug, so v6 has 6, v8 has 8.

coil packs have 3 coils inside for v6 and 4 for V8. called wasted spark to any tech.

2: low compression, think of your v6 (is it) as 6 engines, not 1.

3: wrong FUELING rates. including air leaks to 1 cylinder.

if engine has EGR that too, will cause gross misfiring.

so can an air leak near one intake runner, causing 1 cylinder to misfire.

why not scan it with a real scan tool that can see ALL jeep codes

then post all DTCs found. both idling and driving for 45mph or 1/2hr.

with these facts and what engine is there we can do the remaining tests.

free book

The tune up is this and filters.

do the tune up, new wires, and plugs using correct spark plugs not some bs, magic ones, use spec, plugs first. its in the manual.

then HV wire set on 4.0L,

if cops V8 , 4.7L try new boots on them. or swap them to find bad one.

the USA car V8 has coil on plugs

misfire means ONLY that this cylinder has weak COMBUSTION

its not weak spark only, that is only 1 cause of poor combustion.

post DTC\'s driving and we can fix it

the best tool is the

Innova 3160 scan tool, that is what I use on home cars.

it does all jeep codes, ALL.

i can drive , and scan and log DTCs.

and gather lots of facts on errors.

that is always the best way,

you can not fix cars today with out owning a scan tool.

unless , luckiest man on earth. (guessing)

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Jeep grand cherokee crankshaft position sensor replaced but still given a weak spark

the coil. ? older post.
the PCM reports even one drop out of 10 , on the CKP or CMP sensors. 99.9% of these changed are good.
why not tell me what you have,? full symptoms and evidence.
got P030x misfiring? are you even using a scan tool,? or working blind.
may be its the coil.?
can can you feel the misfiring.c
can you see the engine shake? all of this is evidence.
do not miss out on that.
does the scan too shop pending misfire codes?
stored codes, or codes while driving, learn to use the scan tool.
do a 60k mile tune up yet?
your engine is not COP coils like the V8
its COIL rail that is a COIL pack with 3 coils inside
that runs 2 sparks each called WASTED park.
so did you try new sparkplugs(dah)first then new coil pack wires HV
next , then a new coil pack last.
start with the cheap spark plug and wires, (called a tuneup)
then pop for coil pack./
misfire can be clogged or leaking injectors too, and that ill skip
with out you using the scan tool fully.

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Error Code: P0303
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Ignition system. (Spark plugs gaps)
Fuel injector No. 3.
Fuel pressure.
Running out of fuel.
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Evaporative emission system.
Low compression, cylinder No.3. (check valve clearance and throttle plate for excessive wear)
Engine control module (ECM).

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do you want me to guess?
or do you want DIY testing advice.
mean, it means bad spark, from Ign.coil 1, (2 cyl wasted spark)

DIY , actual tests... per FSM. get one.
only 1 code. and comes back after clearing it?
full scan done?
how many miles on it, when was the last full tune up
page 412 opr, guide in glove box , did you do the 102k mile service?
new spark plugs and 6v wire sets? , now be the the time
not a new coil pack that be last choice.

p2 means factory code, and seems your scan tool works right.
many dont. or are blind to them or get them all wrong.

same car as my main car... JK,
i have the full JK, FSM. factory service manual, go it day 2.
the first thing to do, when doing DIY , is to open the hood
and see what engine you have, as diff, engines have diffr, EFI systems.
mine has the Trenton 3.8L V6. with MAP and TBW system.
TBW is throttle by wire. (map sensor is for speed density system)

P= powertrain
2= jeep private code, not USA fed, spec EPA codes.
3= Fuel and Air Metering (Injector Circuit)
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02= Ignition Coil 1 Secondary Circuit- Insufficient Ionization

this car has a coil pack and is WASTED SPARK
3 coils 6 spark plugs. wasted. (google what that means)
but is important to know because either spark plug can disturb
the current path here.

if my 6v did this, id do the 102k mile service. with NGK parts,.
or Bosch.

we , usually you get P03xx codes with it. misfire.

i open my fsm ,there are 6 tests. for this 1 failure
it says the spark duration is too short or nothing at all.
ill not type out all 6 tests nor the logic, ( has it)
step 1 is to :
clear all DTC
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Car runs rough when warm an accelerator is applied normal

P0306 is a misfire on cylinder number 6. The fact that you have oil on those plugs may or may not be causing it. The oil on the plugs is because of a leaking "internal" valve cover gasket. First thing I'd do is change the valve cover gaskets. Audi will murder you if you want them to do it (I've heard of people quoted $700 or more for this job). It's VERY easy to do. You can order the gaskets from or for about $25 per side. I'd change them for sure, as they're a known issue on these cars.

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99 4runner po302 code

Yes. No clicking indicates a bad injector; you mentioned you had a Noid light; does it pulse?

If you remove the plenum to replace the injector, buy new plenum gaskets. You should not reuse them.

The graciousness of a FixYa rating for my assistance would be appreciated.

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