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Means random misfire. (really means weak combustion x4)
ever change that slipped cam timing belt?
if the belt slips, compression likes to drop from 180psi to 80psi
as the retards to H3LL.
missfire can be caused by 50 things. but is just 4 in physices
1: bad 12vdc power to the EFI system (and spark)
2: low engine compression, Tbelt is top fail. on all 4 too.
3: bad spark (150k on spark plugs? and friends) tuneup time?
4: bad fueling (to much or too little fuel mix)
there are tests to do. ask'
a dirty maf can cause lean fuel ratios and 300s. easy
clean it from 12" far, or you will damage it. the part is $1000 as suz.
and rising./. or $300 for rebuilt so treat it like plastic gold.
more common causes, not guesses, based on 5years data.
a: low fuel pressure, 15 not 34 PSI. Gauge test is easy, ask.
b: all spark plugs end of life and the wire sets, or rotor/cap bad.
c: MAF is weak, reads too low air flow for reality, (dirty hot wire)
d: EGR stuck wide open, seems they all do at 50,000 miles.
e: leaking injectors ore clogged. but the misfire would show which cylinder. and 300s. (eg; 300s and say 302)
f: Main air intake leaks, even cracks in that huge tube. (old car)
lots of others, ill skip them.
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I'm assuming you mean codes P0300 and P0301. Black soot on the plugs is usually because the fuel system is running 'rich'. This is when the fuel/air mixture going into the engine has too much fuel in it. Changing the spark plugs was a good step to take but it won't fix the problem.
When was the vehicle last given a full service? Something as simple as an old, dirty air filter can cause problems.
If you are not familiar with working on engines take the vehicle to a good mechanic and get them to look at it for you.
p300, is a generic code for misfires. Could be any of the cylinders or all. When's the last time you had a tune up? Start with the cheap stuff, fuel filter, air filter, and clean the throttle body. If that doesn't clear it up, replace the plugs and wires.
I would get a compression test done. The car should still run at idle with a coil or 2 disconnected, perhaps rough but should still run. I don't want to get ahead of myself but I am thinking head gasket issues.
I believe the p300 and p301 codes are emission control codes. Rough idle? Usually changing some emission parts will help. Especially if you have to pass air quality. So i recommend changing the PCV valve. If your car has a lot of miles,you should change EGR valve O2 sensor. These items can be pricey. Your cars computer will adjust itself for these conditions. Eventually,the car will just run poorly though.After you fix it,the codes can be erased at your dealer.
P300 is random multiple misfire,301 is cylinder 1 misfire. 302 is cylinder 2 misfire & 306 is cylinder 6 misfire. P161 is a bad heater circuit in oxygen sensor bank 2 sensor 2. It is behind catalytic convertor. I would replace downstream oxygen sensor & clear codes. Run vehicle it may be all that is wrong.
Some things to check since it has sat so long.
Bad gas
Fuel filter
dirty injectors
dirty throttle body
The p300 code is a multiple cylinder misfire code. It sounds to me from what you described, that you are having some type of fuel pressure issues.
Only way to know whats going on is to retrieve the trouble code for the check engine light by using a OBD II diagnostic's tool, it's likely the poor hesitation in the vehicle's acceleration is causing the check engine light to appear, the OBD II diagnostic tool plugs into a data link connector under the driver's side dash, you can buy one at most auto parts store's, or if you don't want to buy one some auto parts store's will do a autoscan of your vehicle at no cost.
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