Did compression check it went all to cylinder 3 being the misfire now the shop that has it says there is something wrong with 4. they say it runs good until you put a load on it. you can drive it till you try to stomp the gas then it has a little hesitation.
I had the same problem with my firebird and i'd try changing the plugs and wires first and if that doesn't work try changing the coil pack for that cylinder. Those are the main components that make your cylinders fire.
An expert who has achieved level 3 by getting 1000 points
An expert that got 10 achievements.
An expert that got 5 achievements.
An expert whose answer got voted for 100 times.
Re: 1999 pontiac firebird
I dont understand,
what were the compressions readings for each cylinder?
Please list and when you find a low cylinder put about a spoon full of engine oil in the spark plug hole and re do the compression test and send me that result also please.
- If you need clarification, ask it in the comment box above.
- Better answers use proper spelling and grammar.
- Provide details, support with references or personal experience.
Tell us some more! Your answer needs to include more details to help people.You can't post answers that contain an email address.Please enter a valid email address.The email address entered is already associated to an account.Login to postPlease use English characters only.
Tip: The max point reward for answering a question is 15.
Check these three things in the misfiring cylinder: spark, gas, and compression. One of them is wrong or missing. For spark check the spark plug and wire. Make sure you have spark on the plug wire, a strong blue spark. For gas, the fuel/air mixture may be wrong. Does the fuel injector pulse, putting gas into the cylinder? Possibly you may have a leaking injector or a clogged injector.
If gas and spark seem okay, you need to check compression in the cylinder. Low compression will cause a misfire. If compression is 20 or 25% lower than adjacent cylinders, that could be causing a misfire. For example, say numbers 1 and 3 cylinders had about 150 psi compression. 80% of 150 = 120, so if cylinder 2 is 120psi or less, that could be setting the misfire code. Low compression can be caused by valves not seating well, or bad piston rings, bad head gasket- something in the combustion area of the cylinder is losing compression.
Try a new plug wire on cyl 3 if that doesn't fix it you could have a bad valve or compression problem on cyl 3 Try doing a compression test also If it has injectors for each cylinder you could have a bad injector for cylinder number 3
Misfiring can be cause by ignition coil,spark plugs,wires,engine valve,cylinder compression,
if it's a quad four then crack around the ignition coil. there is 2 coils like 1-4 coil and 2-3 coil
first check spark plug color or foul of gaz
hope it help
P0300 means that a misfire was detected. Unfortunately that doesn't narrow it down much. You'll need to do more diagnostics to find out if it's being caused by ignition or fuel. A good scanner will have a misfire counter that can help tell which cylinder is causing it unless it's intermittent. Good luck.
Had the same problem, car was misfiring on cylinder 3 and 4. replaced wires, plugs, and ignition coil. still misfired on the same cynlinders. turned out the main engine wiring harness plug in was coming loose. spent well over $150 on the unneccesary repairs and ultimately fixed the problem wit a $3 bag of wire ties to hold the plug in...
I hope you used all factory parts, it makes a difference. Compression test? nope valve guides I really doubt it
have someone do a smoke test for vacuum leaks you can have a sucked intake manifold gasket smoke test is really the only way to find a small vacuum leak
contact me at firstname.lastname@example.org with any questions and feedback please
Thank you, Randy
Do we know for sure that the PCM (computer) is actually firing all the injectors? you need a
NOID LIGHT for this test
Check your alternator see if you have a drop in voltage on your tack,then it is the problem.I too was a victim of high price tune up and still had a problem with a misfire.and cover your coil pack with a piece of rubber water run of onto your power pack .Another thing is to use a silicone spray on all wires.