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Hi ! I have a 2002 Chevy Express 1500 conversion van. It has 64,578 miles on it.
The problem I am having is that the service Engine is on and will not come off. The message that its giving is "Misfire p0304" . Because of this misfire the van will not pass inspection. First I was told that the sparkplugs and wireset needed to be changed. We bought all 8 sparkplugs and the wireset and the light never came off. We took it to a mechanic , and he told us that we needed to change the fuel injectors, and the rotor cap , and distributor, All were changed , still the service engine light is on. About 2 weeks after the fuel injectors were changed, the van would not turn on. we took it to a mechanic , and he said we needed a new Fuel pump, we changed it. But the darn Service Engine light is still on. What else can it be?????
The mechanic said that he checked out the pistons in the engine and one of the pistons is damaged . I am confused would a piston cause a misfire like that ? also what are the signs of a damaged piston. He told me there is no way to just change one piston and i would have to replace the whole engine. A whole engine??? they cost almost $3000 between the cost of the engine and the labor. I could prob a get a newer car for that amount! What are the possibilities that he can be wrong about the piston? has anyone experienced this with this type of car before?
You are throwing parts of a specific cylinder. P0304 is a general misfire on cylinder 4. If it is a v8 engine they run with a coil pack to spark plug. There is no distributor on these engines.
It could be an injector, it could be a plug and coil pack. It could be a vacuum leak or a valve dropped.
If you have the time and some basic tools. An OBDII reader, a 12 volt test light and a multimeter are a good starting point.
Or, find a different shop. It sounds like the current shop is milking you for all it's worth. It all starts with basic diagnostics. First, check for vacuum leaks, including the intake gaskets. It is testing the coil pack, testing power to the fuel injector, then starting the engine and listening to the injector with a stethoscope. If it isn't any of those, then, look at the exhaust manifold. The gasket May of blown down. If it isn't any of those then it comes time to open the engine and look inside. That is a last resort.
I just had the intake manifold off on my pickup, a 2000 silverado 2500 with the 6.0 gas. New intake gasket. Cleaned up the throttle body. Vacuum leaks are the biggest PITA of the whole ordeal.
Based on the diagnosis of a damaged piston, I'd run a compression check on the engine cylinders. A low compression reading on a cylinder will definitely cause a misfire.
Perhaps a modern ASE Certified Technician can't replace one piston, but a good old fashioned mechanic sure can.
A real compression check is the only way to verify or disprove the bad piston theory. If the piston is bad, the compression will be low or non-existent.
I once replaced a broken piston in a V8 with a junk yard piston, and the car ran fine for a long time afterward.
I have a similar problem with my Dodge 360 V8. the CEL comes on every now and then, and the read out is always the same: P-0301; #1 cylinder misfire. I ignore it, and the light goes out after 2 or 3 starts.
BUT, I'm lucky; I don't have to worry about inspections.
Find a real mechanic who knows how to trouble shoot an engine without a computer, and have him (or her) check your engine. Yes, doing an individual cylinder compression check on a van can be a total PITA, but it will give you a better indication of what is really going on. Once the bad cylinder is found, a differential compression test will show whether the compression loss is due to a bad piston, bad intake valve, or bad exhaust valve. The piston is placed at top dead center compression stroke, the crankshaft locked in place (THAT can be a problem), and air pressure is injected into the combustion chamber. Bad piston or broken rings, the air will leak into the crankcase. Bad intake valve, the air will leak into the intake manifold. Bad exhaust valve, the air will leak out the exhaust.
Good luck.
Vacuum leaks are the biggest PITA of the whole ordeal.
Agreed.
I have one in my 98 Explorer and nobody can figure it out. P0171. I have a good mechanic and he basically gave up. Changed the upper manifold gasket, wires, plugs, O2 sensors etc. The only thing left is the lower manifold but that is a $1200 job although he is not sure that is the problem.
Solid advice from the posts above. I'll add my worse experience with a P0304 code was on a 2002 jeep with a 4.0. We serviced the engine and when we statrted it, we immediately got the code. After a week of troubleshooting and by process of elimination we determined that the issue had to be in the ECM. I got a ECM out of a wrecked Jeep, had it flashed installed it and the vehicle ran perfect. For the record i posted the issue we were having in a Jeep forum. In my opinion there are quite a few knowledgeable people on that forum including 1 poster that's been a Jeep mechanic for 20+ years and not one suggested it could be a ECM issue. Good luck with solving your problem.
I am sorry perhaps i was not using the correct terms as to certain parts because i see a couple of people telling me there is no rotor or distributor.
To Clarify:
When we first got the van we took it to get an oil change at Zap lube, we asked the attendant there to use the ODBII reader to diagnose the "Service Engine Light". That is where we learned about the the P0304 code, since they only do an oil change at Zap lube the guy told us to take the van to Auto zone and they will tell us what we needed to change. We did just that, at Auto zone the gentleman advised us to change the Spark plugs and wire set. My husband with the help of his mechanic f friend changed all 8 spark plugs and wire set. At that point the light did come off, so we took to a place to do an inspection. In the middle of the inspection the light came back on and it failed. Since we had just changed the spark plugs and wire set we asked them to do a thorough Diagnosis on the van. We left the van with them for a day , and as per their diagnosis report the fuel injectors , the distributor cap /rotor needed to be replaced. They wanted to charge us about $650, so my husband decided to do the repairs himself.
But the service engine light was still on , so we decided to go to a different mechanic, my husband says that the mechanic did do a compression test , but he did not mention to my husband whether it had low or high compression, what he mentioned was that there was some type of leak , and oil was getting into the piston and not allowing it to work properly( please bare with me , this is what i understood) Because of the cost we halted on this repair.
We spoke to a family member who is a mechanic ( unfortunately in another state) , he asked us some questions and said that it did not sound like the van was showing symptoms of a damaged piston. Since the van sometimes would have trouble starting up right away , and the gas meter would read wrong he suggested that something is wrong with the fuel lines and that is when we decided to change the fuel injectors. Then 2 weeks after the fuel injectors change, the van did not want to turn on despite having a full tank , and it turned out to be the fuel pump and that was the last repair we made to the van ( in december)
We are definetely going to check all of the suggestions given here. I just wanted to clarify because a couple of people were saying that there is no rotor or distributor.
Also I forgot to mention this in my initial post, but the van also has a tendency of shutting down if i turn the wheel all the way. Like for example if I am parking and i turn the steering wheel all way to a side if i dont accelerate it will turn off on me, not sure if that also has something to do with the misfire.
I appreciate everyone's help here !!
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. I am confused would a piston cause a misfire like that ? also what are the signs of a damaged piston. He told me there is no way to just change one piston and i would have to replace the whole engine. A whole engine??? they cost almost $3000 between the cost of the engine and the labor. I could prob a get a newer car for that amount! What are the possibilities that he can be wrong about the piston? has anyone experienced this with this type of car before?
