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Discussion Starter · #1 · (Edited)
Hi all, I have a 2000 LC that has a few symptoms-
intermittent misfire/running rough at these times it has:
dark smoke
uses 3 times the fuel
loss of power (to normal)
will pick up revs slow without running rough and runs normal at high revs.
dies misses and then picks up revs slowly when accelerator is pushed fast to the floor from idle.

Hyundai mechanics checked computer and it coded change spark plug leads this did not fix the problem, and have no idea.

about 6 months ago the car was doing the intermittent thing when it died and liquid was heard splashing on the ground. I found the main petrol line connecting to the pump had come completely off. After replacing all problems ceased and the car ran perfect with full power etc.

about a week ago the problem is back, ive checked the fuel lines none appear to be leaking etc. does anyone have any ideas of what it could be now?
thankyou.
 

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im pretty sure everyone is going to say check the codes to start off with even if u do not have an engine light, and i would check the fuel filter also to see if its clogged or dirty.
 

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Discussion Starter · #3 ·
the mechanic at Hyundai checked the code and replaced the spark plug leads. the car started original symptoms again about 300kms later, road side assist looked at it on 4 occasions and could never find the problem. another mechanic said it was a sensor and "it was fueling up well". I have taken the spark plug leads off one at a time and all make the idle/miss worse, I do think it is in the fuel system and I have replace the fuel filter already.

no one has a computer that will interface with this older technology (we live in a isolated part of Australia)

what are the most likely causes of this symptoms?
and thankyou for your time, the fuel filter is smart advice.
 

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high fuel use and the dark smoke indicates that you're running severely rich. playing with the fuel filter is a complete waste of time. you're getting too much fuel, clogged filter would be not enough.

i'd like to know if you're getting misfires on one cylinder or all. that would change the diagnosis.

you can rule out the plugs since that has been done, but coilpacks have not been ruled out. that would be one or two cylinders missing as these coils are two per unit. testing is easy, use a spark indicator light (mine was $3 at walmart) or a timing light on each wire one at a time if you have one available.

another thought is the injectors themselves if one is not closing as it should. confirm by listening to them with a mechanic's stethoscope one by one and compare how they sound. should be a strong snap. if not, you've found the dud. again, cheap and very useful tool.

finally check your intake for severe clogging in the filter or intake piping. a dirty air filter won't cause this, but one completely blocked might.

there are other possibilities, but i'd like to know what the codes are its throwing before going there. i'd get yourself a code reader. if not available at a store, get one online. probably the most useful tool you will ever buy.

other options would include: oxygen sensor, TPS, coolant temp sensor (mainly if this gets worse as it warms up), crank or cam sensor *might* do the trick.

i do not recommend replacing ANYTHING until you find the problem. that is a waste of time and money.
 

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Discussion Starter · #5 ·
taking the spark plug leads off one at a time- all make the engine run rougher- all leads are throwing big juicy sparks in a regular timing.
the fuel filter has never been replaced- so it was about time.
the air filter was replaced about a month ago as the old one was dirty and worn.
the car heating up does not make any difference to the problem.

a code reader was bought online and will be here in about 6 weeks if it doesn't get lost...
I will check the injectors tonight and go from there checking Oxy sensor etc.
thanks for the starting points.
 

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Discussion Starter · #6 ·
the injectors are all clicking away nicely, one thing I did notice sudden opening of accelerator to half way causes the engine to almost stall, then a POP -like a backfire through the air filter is heard and the engine then picks up in revs.
can the crank or cam sensor come loose and change the timing of the engine causing this problems?
 

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yes, either crank or cam position sensor can cause this and so can the throttle position sensor and the MAP sensor.

there's one trashy test i know of...disconnect the TPS and try to run the car. it will run like ass, but it shouldn't misfire. it will run 'smooth' just poorly. if that happens, it's likely the TPS.

would like to know if you have the 1.5L or the 1.6L engine.

i'd also take the MAP sensor out and check for any blockages/buildup that might cause this. its an easy one, two screws :)

i'd love to pass along the proper testing info for these parts (with a multimeter to check outputs are correct) but the site we got those off is a pay only now....curse their greedy souls.

considering that all of these parts are pretty easy to get your hands on....i might suggest a junkyard. if its a lot you can roll your car into, swap some parts while you're in there one by one to troubleshoot. just don't let them see you, might accuse you of stealing.
 

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Discussion Starter · #8 ·
1.6 ltr engine

greedy souls: there's 2 mechanics within 500kms of here both alcohol fuelled and heartless as well, neither one can fix this car and both have charged my wife a fortune for trying.
 

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Discussion Starter · #9 ·
there's one trashy test i know of...disconnect the TPS and try to run the car. it will run like ass, but it shouldn't misfire. it will run 'smooth' just poorly. if that happens, it's likely the TPS.
Thankyou zero_gravity
I disconnected the cable on the sensor (far right hand side opposite throttle) and the car ran smooth and there was only small lag in picking up revs when the throttle is instantly opened half way- a big improvement.

I will swap out the TPS, it may however be a few weeks to get the part in, but I'll let you know.
cheers.
 

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Discussion Starter · #11 ·
a mate did a parts run on way out here, swapped TPS-
car ran well till it started to heat up, problem is back...

does the coolant temp sensor work on a thermocouple effect (as it heats up the resistance changes), & how do these operate
low ohms when cold increasing or high ohms decreasing under heat?

one way I can just unplug it, the other I have to ground the wire.
just to quickly check that it is the fault and as a guess is messing with the computer?
 

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good thought. the temp sensor works as you describe, but don't call it a thermocouple :p thermocouples generate voltage when heat is applied. this is a thermistor.

with heat, the resistance goes down as with all thermistors.

only information i have is the sensor at 20ºC should be 2.31-2.59k ohm. heat it up to 110ºC and the result should be 146.9 - 147.3 ohm.

i'd suggest using a pot of water near as 20ºC as you can get and then boil it to get near to 100ºC. use a bit of a fudge factor here.
 
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