Tib Is Dead...please Help! P0304 Misfire
02-15-2009, 10:14 AM
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Looking to the RDT community for any possible answers and solutions to this problem as it has been VERY aggravating and expensive!!! Ok, here it goes…
I recently bought the car a few months ago (non-running) and began working on it. There were a few wires cut on the engine harness by the air box in the engine bay (don’t ask me how it happened). Probably 5 or so. I looked up the wiring diagram and went over it, but to avoid confusion with possibly connecting the wrong wires and save time I put a new engine harness in with all the connectors. After starting it for the first time it began to run fine (since the engine was cold) but, immediately began to sputter and idle rough when it warmed up.
My second thought was that the computer was possibly fried so I got another one from an identical car and put it in. Still the same problem. Took it to Autozone to have the code read and the guy said the TPS was most likely bad. I replaced it with a Keifco. Still the same problem.
After looking at the car myself I determined it had to be a fuel or ignition problem since I already replaced most of the electrical. I pulled the fuel pump, fuel pressure regulator, fuel rail and injectors and cleaned/checked everything. Checked the fuel line pressure and installed a new fuel filter. Everything was within specifications but still same problem.
After getting the code read a second time the scanner said it had a multiple misfire. In my opinion this was probably from bad coil packs on the ignition coil or weak spark from bad plugs or wires. Frustrated as hell I replaced everything I could on the ignition system. I put in a NEW ignition coil from Autozone along with NEW wires and NGK plugs. STILL THE SAME DAMN PROBLEM.
After doing some research and looking around I found a post which was talking about a broken MAF sensor and that when it's not functioning properly it will give the car a rich fuel mixture. (which in fact was running rich at the time) even when the gas pedal isn't depressed. So I checked it and sure enough it was broken. I essentially thought I found the real problem but everyone knows nothing ever goes the way you want it to. After I threw a new one in, still no luck. The MAF sensor took care of the idle problem (at least for a while) and ran a lot smoother but you could still hear the misfire in the motor.
Took it down to Autozone (3rd time) and it shot out the code P0304 (Cylinder 4 Misfire). This made no sense to me because I replaced everything that could have possibly caused a misfire. On the way home the check engine light went out and the car ran extremely perfect! I couldn't understand it!
I parked it that night, took it for a drive up the road the next day and it ran perfectly again. Went to take it later that day for a car wash and it was back to the same problem as before. Check engine light was flashing indicating a misfire and it had the rough idle.
After this I replaced both oxygen sensors and checked all the sensors such as the crank, cam, MAF, acceleration, tps, knock, temperature and idle speed sensor for the proper resistance and everything checked out ok.
With my mechanical knowledge and all the years I've spent working on cars I have to say this one has me stumped! I’ve never seen a problem like this before. This past Thursday as a last ditch effort I took it to the Hyundai dealership to have them put it on the diagnostic computer. Their results were a P0304 misfire and a bad intake air temperature sensor. I talked to the mechanic and he said it was reading -45 degrees (which explains why it had the rich mixture). We replaced it with a new one and it did idle better but still had a misfire. He said plugs and possibly wires would fix it for sure. I told him I was on my 3rd set of plugs and the ones that were in it only had 2 miles on them before I brought it to the dealership!
Anyway, I put NEW NGK wires and NGK plugs in the damn thing yesterday and sure enough it didn’t fix it. Now I’m just going to take it back tomorrow and make him look like an asshole…
As of now, it still has a misfire and plugs are fouling in all cylinders. If anyone has any helpful information or possible solutions I would greatly appreciate it! If you have any questions feel free to ask and I will respond as best as I can. Sorry for the long post but I wanted to clarify everything in order to avoid confusion.
Thanks,
Mike
I recently bought the car a few months ago (non-running) and began working on it. There were a few wires cut on the engine harness by the air box in the engine bay (don’t ask me how it happened). Probably 5 or so. I looked up the wiring diagram and went over it, but to avoid confusion with possibly connecting the wrong wires and save time I put a new engine harness in with all the connectors. After starting it for the first time it began to run fine (since the engine was cold) but, immediately began to sputter and idle rough when it warmed up.
My second thought was that the computer was possibly fried so I got another one from an identical car and put it in. Still the same problem. Took it to Autozone to have the code read and the guy said the TPS was most likely bad. I replaced it with a Keifco. Still the same problem.
After looking at the car myself I determined it had to be a fuel or ignition problem since I already replaced most of the electrical. I pulled the fuel pump, fuel pressure regulator, fuel rail and injectors and cleaned/checked everything. Checked the fuel line pressure and installed a new fuel filter. Everything was within specifications but still same problem.
After getting the code read a second time the scanner said it had a multiple misfire. In my opinion this was probably from bad coil packs on the ignition coil or weak spark from bad plugs or wires. Frustrated as hell I replaced everything I could on the ignition system. I put in a NEW ignition coil from Autozone along with NEW wires and NGK plugs. STILL THE SAME DAMN PROBLEM.
After doing some research and looking around I found a post which was talking about a broken MAF sensor and that when it's not functioning properly it will give the car a rich fuel mixture. (which in fact was running rich at the time) even when the gas pedal isn't depressed. So I checked it and sure enough it was broken. I essentially thought I found the real problem but everyone knows nothing ever goes the way you want it to. After I threw a new one in, still no luck. The MAF sensor took care of the idle problem (at least for a while) and ran a lot smoother but you could still hear the misfire in the motor.
Took it down to Autozone (3rd time) and it shot out the code P0304 (Cylinder 4 Misfire). This made no sense to me because I replaced everything that could have possibly caused a misfire. On the way home the check engine light went out and the car ran extremely perfect! I couldn't understand it!
I parked it that night, took it for a drive up the road the next day and it ran perfectly again. Went to take it later that day for a car wash and it was back to the same problem as before. Check engine light was flashing indicating a misfire and it had the rough idle.
After this I replaced both oxygen sensors and checked all the sensors such as the crank, cam, MAF, acceleration, tps, knock, temperature and idle speed sensor for the proper resistance and everything checked out ok.
With my mechanical knowledge and all the years I've spent working on cars I have to say this one has me stumped! I’ve never seen a problem like this before. This past Thursday as a last ditch effort I took it to the Hyundai dealership to have them put it on the diagnostic computer. Their results were a P0304 misfire and a bad intake air temperature sensor. I talked to the mechanic and he said it was reading -45 degrees (which explains why it had the rich mixture). We replaced it with a new one and it did idle better but still had a misfire. He said plugs and possibly wires would fix it for sure. I told him I was on my 3rd set of plugs and the ones that were in it only had 2 miles on them before I brought it to the dealership!
Anyway, I put NEW NGK wires and NGK plugs in the damn thing yesterday and sure enough it didn’t fix it. Now I’m just going to take it back tomorrow and make him look like an asshole…
As of now, it still has a misfire and plugs are fouling in all cylinders. If anyone has any helpful information or possible solutions I would greatly appreciate it! If you have any questions feel free to ask and I will respond as best as I can. Sorry for the long post but I wanted to clarify everything in order to avoid confusion.
Thanks,
Mike
02-15-2009, 10:17 AM
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Vehicle: 2001 Hyundai Tiburon
Maybe try a compression test? Also, did you take the crank sensor out or just check resistance? Weve been seeing them get some rust in there and push them out slightly causing a miss at times.
02-15-2009, 10:24 AM
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Sorry, forgot to add about the compression test. Yeah, compression checked out ok across all four cylinders. As far as the crank sensor, checked the resistance but didn't take it out.
02-15-2009, 11:41 AM
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Vehicle: 2001 Hyundai Tiburon, 2004 Kia Sorento, 2010 Kia Soul
Well, you've done a lot of work, but the wires that were cut on the original harness, which were they?
If you can figuree that out, you might be able to figure out WHY they were cut. Probably something to do with a intake chip or something.
Next, since youv'e already done so much, do these 2 things.
1. Go over the entire harness you replaced, confirm that all connections are tight, that there are no worn cables, and that all connectors are clean and actually CONNECTING.
2. Go over the troubleshootiong manual for the electronics and see what the procedures are for troubleshooting that CEL.
Also, did you replace it with a brand new or used harness?
If you can figuree that out, you might be able to figure out WHY they were cut. Probably something to do with a intake chip or something.
Next, since youv'e already done so much, do these 2 things.
1. Go over the entire harness you replaced, confirm that all connections are tight, that there are no worn cables, and that all connectors are clean and actually CONNECTING.
2. Go over the troubleshootiong manual for the electronics and see what the procedures are for troubleshooting that CEL.
Also, did you replace it with a brand new or used harness?
02-15-2009, 11:48 AM
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2001 > G 2.0 DOHC > ENGINE > G 2.0 DOHC > DTC - P0301, P0302, P0303, P0304
TROUBLESHOOTING FOR DTC P0301, P0302, P0303, P0304DTCDiagnostic ItemP0301P0302P0303P0304Misfire Detected (Cylinder 1)Misfire Detected (Cylinder 2)Misfire Detected (Cylinder 3)Misfire Detected (Cylinder 4)
DESCRIPTIONTROUBLESHOOTING GUIDEDTC detection conditionProbable causeBackgrounda.If misfiring occurs while the engine is running, the engine speed suddenly changes.b.The engine control module checks for changes in the engine speed.Check Areaa.Five seconds or more have passed after the engine was started.b.Engine speed is between 500 and 6,000 r/min.c.Engine coolant temperature is higher than -10°C (14°F).d.Intake air temperature is higher than -10°C (14°F).e.Running free from sudden accelerations/decelerations such as shift change.Judgment Criteria (change in the angular acceleration of the crankshaft is used for misfire detection.)a.Misfire has occurred more frequently than allowed during the last 200 revolutions. [when the catalyst temperature is higher than 950°C (1,742°F)].b.Misfire has occurred more frequently than the allowed number of time (2%) during 1,000 motor revolutions.a.Ignition system related part(s) failedb.Poor crankshaft position sensor signalc.Incorrect air/fuel ratiod.Low compression pressuree.Engine coolant temperature sensor failedf.Timing belt missing teethg.Injector failedh.Engine control module failed
CIRCUIT DIAGRAM
TEST PROCEDURE
Just for reference, every time I've had a 304 it was because water was in my plugs. I believe this is a ignition timing problem. Plugs set to .42?
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02-15-2009, 02:03 PM
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Redz, as far as the orignal harness goes I don't know which wires were cut becuase after looking at the wiring diagram for my vehicle the wire colors on the diagram were totally different from the ones that were in the car at the time.
1. I did go over the connections once already even while the car was running unplugging, tapping, and wiggling connections to see if any of them were loose. Nothing changed however. I guess it wouldn't hurt to do it again. I didn't see any missing pins or anything though in any of the connections.
I didn't replace it with a NEW wiring harness because I couldn't find one but I did put a good harness in it from one out of salvage yard. I talked to the guy and he said he just brought the car in a week before I called him and it was in fact running. Same year, manual tranny and everything. Just totaled.
DTN, not sure if I understand the procedure you listed. Look like for troubleshooting the IAT sensor? If so, that's what the dealer said it was and they replaced it with a new one. As far as plugs, there's no water in them. This is my 4th set, just carbon fouled all the time. The specifications also say to gap them .039 - .044. I gapped mine to .040.
1. I did go over the connections once already even while the car was running unplugging, tapping, and wiggling connections to see if any of them were loose. Nothing changed however. I guess it wouldn't hurt to do it again. I didn't see any missing pins or anything though in any of the connections.
I didn't replace it with a NEW wiring harness because I couldn't find one but I did put a good harness in it from one out of salvage yard. I talked to the guy and he said he just brought the car in a week before I called him and it was in fact running. Same year, manual tranny and everything. Just totaled.
DTN, not sure if I understand the procedure you listed. Look like for troubleshooting the IAT sensor? If so, that's what the dealer said it was and they replaced it with a new one. As far as plugs, there's no water in them. This is my 4th set, just carbon fouled all the time. The specifications also say to gap them .039 - .044. I gapped mine to .040.
02-15-2009, 03:17 PM
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I pulled the line of the top of the FPR that runs to the intake it that's the one your talking about. I started it and no gas runs out anywhere but there is vacuum on the hose. Does this mean everything is good or bad? I did have the FPR off before to check if it's working. It took around 45-50 psi for it to open so I assumed since the fuel pressure was around there that it wasn't defective.
02-15-2009, 03:21 PM
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Ya as long as the line doesnt smell like gas it should be fine. I had one pouring gas into the IM from the FPR diaphragm going bad causing the same thing you are describing.