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Discussion Starter · #1 ·
Need help from someone and running out of things to replace....

3 months ago car went into LHM w/ CEL on. Ran computer for codes and had several for TPS/Accelerator position sensor/ motor. Replaced both plenum and throttle body from a 2004 XG350, new peddle position sensor from dealer. Still in LHM so towed it to dealer and payed them $100 to hook it up to their computer to diagnose the problem which they said was the O2 fuse was blown and replaced it and it came out of LHM. Car ran fine for 1 week then went into LHM again and found the o2 fuse was blown again, replaced it and it came out of LHM. Then a code came on for misfire in Cylinder #2, replaced ignition coil and cleared code, ran for 30 miles then CEL for misfire on Cylinder #6, replaced another ignition coil and replaced all autolite plugs and wires with NGK Iridium plugs and NGK wires. Reset computer drove another 25 miles and CEL came back on for misfire in Cylinder #6 again plus heard a vacuum leak coming from intake manifold. Took top end of motor apart to replace intake manifold gasket along with plenum gasket and somehow or someone dropped a washer into the intake port ( didn't know till engine was back together that it was thrashing around in Cylinder #5). Took engine apart, front cylinder head off found washer crushed and embedded into the piston ( no scratches in cylinder wall, minor "dent" (washer impaled into the piston) on top of cylinder #5 and small "dents" next to the intake/exhaust valve, filed down the high dent parts). Replaced head gasket, valve cover gasket and center Valve cover O ring Gaskets, new o2 sensor, then installed rest of the motor with all new gaskets. Made sure all ignition wires were correctly installed and none crossed each other ( Per 2002 Hyundai repair manual from Dealer). Engine ran but timing off one tooth. Replaced Timing belt, Idler pulley and tension pulley. Now engine runs, timing is correct, Idle is at 1000 motor cold, lowers to 400 in N at Normal operating Temp w/ AC off, 500 rpm with AC on, in D or R its at 400 rpm w/wo AC on or off. When adjusting idle with TPS car goes into LHM, turn engine off put TPS back to stock and it takes itself out of LHM but idle is still rough. test drove it 25 miles and it went into LHM again and the o2 fuse was popped again, replaced fuse at it came out of LHM, then today it misfired on #6 again.

I'm running out of ideas and patience, I've even lost my job because of this car (drove 3 hours to get to work and home twice a week).

Anyone have an idea of what is going on, I'm looking at replacing EGR valve (back of motor, attached to intake plenum w/ pipe running to back exhaust manifold), knock sensor, ignition condenser, and ignition timing sensor.

Any help is greatly appreciated as I am coming to a brick wall and fast....
 

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WOW! I think you have redefined the word "frustrating".

I don't think its the EGR, I don't see how that could blow an O2 sensor fuse. I think the key might be in why the O2 fuse is blowing. Which fuse is it? With the fuse number, size, and location I should be able to find it in the service manual and see what else is on that circuit. There are multiple O2 sensors on the XG, which one(s) did you replace? If the car runs for 1/2 hour or more once the O2 fuse is replaced before blowing the fuse again, I'd be tempted to try a slightly bigger fuse to see if that changes anything (being careful of coarse). I'd also try and measure the current through the O2 fuse if possible. You could have an intermittent (insulation just starting to wear away) short in the wiring harness that blows the O2 sensor fuse when conditions are right (you hit a bump or something). Once the O2 sensor loses power, I can imagine limp home, cylinder misfire codes on any/all cylinders associated to that O2 sensor, bad idle, etc.

If it is an intermittent short, the slightly larger fuse shouldn't change anything other than let you know when it blows that you do have a major current overload.

Dan
 

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What spark plugs did you use to replace the old ones with? Have you done a compression check since all this trouble?
 

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Discussion Starter · #4 ·
No compression check, dont have the right tool for the job since the spark plugs sit to low in the engine. As for o2 sensors the only one I replaced was the front one on the exhaust manifold above the cat because the wires were cut open and didnt know if it was arcing. As for the plugs and wires i used NGK iridium plugs gaped at .039, and bought NGK wires. From what Ive read in the service manual from Hyundai several things use the same fuse as the o2 (I believe fuse #9 15 amp), MAF sensor, o2 sensors, cam shaft and crank shaft sensors and the EGR solenoid vacuum sensor. But the book also is wrong on so many levels when it comes to other things in the book.

Now the engine is idling where its suppose to but yet again after running it for 10 minutes (this morning) CEL for misfire cylinder #6 and EVAP small leak.
 

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Discussion Starter · #5 ·
Later this afternoon CEL came on yet again for misfire cylinder #6 and P1191/1193 for Limp Home Valve Low RPM. Putting car in the air tonight maybe tomorrow and looking at the timing marks, see if they are off, if not then im going to look at the crankshaft and cam shaft sensors....
 

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Seems to me the first thing you do if you find crushed washer in the chamber is do a compression check to make sure you don't have engine damage.
 

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Discussion Starter · #7 ·
only damage done was a small dent on the piston, but not enough to mess with compression, and that damage was on cylinder #5, all the problems i been having is on #6. My dad has ordering the OBD2 laptop program and scan tool from scantool.net. It will allow me to see Freeze Frame data and I hope allow me to see when it is misfiring and why.

While I have the car on jack stands I'm going to look at the other o2 sensors to see if any of them might have damages, otherwise i'll buy one more and start doing a hit n miss, see which one is causing it to go into LHM.
 

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Discussion Starter · #8 ·
Jacked the car up 2 days ago and the car is still timed, so not sure why it idles rough. Still waiting for the computer program to come in the mail. Now to see why it misfires in Cylinder #6 per CEL....
 

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Discussion Starter · #9 ·
So some new News, Fixed the misfire by replacing the ignition misfire sensor. Now the CEL is on for a P0446 Evap Small Leak... At 38k dealer replaced the canister and CCV (Canister Close Valve) and that was under P0442. Both are for the Emission Control System. I took the Canister down and checked it for any cracks or holes but its solid. Could it be the Valve that sits next to the Canister attached to the small air filter?
 

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2002 XG350 replacing to many parts
I have read the entire thread. I own an XG350L. purchased it new in 2002.
I have had all or most of these codes and operational issues. Except the blown fuse problem. I can tell you that I have found several of the o2 sensors loose. Whether that would blow the fuse or not I don't know. My guess is that it was not the o2 sensors that was blowing the fuse. I think there are (6) sensors total.
Your problem is like mine. When Hyundai says 10 yrs/100,000 miles they are not kidding. Save yourself a lot of time and trouble and get rid of the car. If you choose to fight the good fight Hear is what I found to be the primary cause of all the system problems. First and at the top of the list is replace the ECM computer. The computer is junk after 10 yrs. and throws all kinds of codes and check engine lights that are false.
Secondly, you got real close to the primary engine operation problem.
Here it is.... The intake manifold on these XG/S have (6) air intake flapper valve's to control air flow to each cylinder after the throttle body valve. They are controlled by the ECM by a unit mounted at the opposite end of the intake manifold from the throttle body. Inside this module you will find a small gray gear (size about 1-1/2" dia.) mounted on a shaft that has all six plate valves. That gear is driven by a small worm gear. If you look this gear contact area over you will find as I did that when the intake manifold gets carboned up as the throttle body does the worm gear is powerful enough to strip out the teeth on the gear. Of course at this point the individual throttle valves can rotate where ever they want i.e. all the way closed to all the way open. You can imagine the poor combustion that can be happening in your engine. Mine seemed to stay about 50% open when no engine load/vac. was placed on the system but this condition drove the 02 sensors and fuel to air ratios and timing adjustments crazy.
At my dealership parts dept. the guys found out that the gear is not replaceable as a replacement part. You have to purchase a new intake manifold at 450.00 to fix it. I would find the gear part in an auto wreaking yard at much less cost.
P.S. The mechanics at my dealership said they had not ever repaired this problem. That means they had been repairing the symptoms and not the cause.
 

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Discussion Starter · #11 ·
Well a lot has changed in these last several months. Car is still in garage...lol, not a change there. But... We ended up doing a compression test after having to buy a new compression gauge and found that 2 and 4 had around 175 psi and number 6 TA DA had.... around 90 psi. So.. We ended up ripping apart the block and after much frustration replaced the number 6 piston with new rings crankshaft seals and (brainfart... the piston arm (technical term?)... Bought a rebuilt cylinder head, and new head gasket, reinstalled all items, now the car runs, idle acts off (like a misfire yet again) we did a compression check on all three front cylinders and all came back at 145 psi... After further investigation we found that the fuel filter has never been changed and the car has a whole lotta miles on it, in retrospect its still the original filter since the car was purchased new in 02... So tonight i had to cut the fuel filter out ( lots of rust) and when you turn the furl filter downward and watch the fuel come out its brown, like really really brown, lol, that would cause it to run like junk... So tomorrow my dad will be going to the store to get a new filter, new fuel lines and new fittings... Hopefully this fixes the problem and the car can finally come out of the garage... Ill try to keep everyone updated more now that I am home from work...
 

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connecting rod
Evap line can be replaced with 0.80 per foot fuel line; the original crumbles with rust and can cause leak codes sometimes.

Sounds like you doing a Hyundai apprenticeship; maybe its not all just wasted time.
 

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Discussion Starter · #14 ·
Well, im actually a truck driver and well need this car to get me to and from work. Plus when this project was started it was only one issue, then after getting into it and fixing the problem we found even more wrong, so being this far into it why not just fix it. Otherwise for some minor body rust once the engine gets fixed and runs really nice it will be a car that will last a bit more longer...

Also thanks for the technical term, i knew what it was just at the time couldn't think of the name... It comes with the old age....
 
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