Right everyone, here goes:

Last year my Accent MVi (1.5 16v) started having some weird power lag. For example if I floored it, it held back between 20-40mph then suddenly returned to normal.

Can describe it as like a big rubber band working against car when I try to accelerate.

Changed the spark plugs, idle sensor, HT leads, coil pack and battery. After research I replaced the fuel filter two weeks ago. It seemed fine up until yesterday morning :-(. For the past two weeks the car was more responsive, the throttle was smoother and not as jerky as it had been.

Has anyone had the same problem? I really love this car and want to nail the problem. I've had it hooked up to a diag and it came up with MAF, idle and TP sensor (only cause I disconnected them to see how/if engine reacted).

When the problem occurs the engine sounds really muffly, like it's being starved of something. Anyone with an Accent MVi/GT knows that they sound very rorty but it sounds very suppressed when the hesitation happens. Another problem I found is that I had to thrash it on the motorway to get any speed, and every now and then, white smoke would shoot of the the exhaust for a few seconds.

Is this a fuel problem? It seems weird that replacing the fuel filter (the one in the engine bay before the fuel rail) cured the problem for two weeks then the problem came back. Is there another filter in the fuel line? TBH the Hyundai dealer I took it to for the diag has been useless, they said they'd call me back everytime I phoned up asking for advice on the problem (still waiting). and every time I've asked questions they've been reluctant to respond. I'd like to solve this problem cause I'm sick of my friends using 'because it's a Hyundai' as a reason for this problem. I love this car, and want to keep it on form.

Here are the key facts:

- Hesitates on acceleration, fuel filter cured problem for a bit, now it's back, but not as severe as before.
- Sounds muffled or stifled when problem occurs, not rorty
- Have replaced sparks, coil pack, idle sensor, HT leads, battery - finally fuel filter
- Timing belt due in 1000 miles time (80000)
- Problem happens irregularly, but happens mostly when engine warmed up or has been run earlier in the day (like when I go out for lunch or head off home)
- After fuel filter replacement, car ran smoother and throttle was less jerky so clutch return was smoother and so was acceleration
- Has K&N filter element

HELP ME PLEASE!!!

Mad love and respect to anyone willing to advise.

 

Sounds like a fuel problem. Had you run out of fuel, or let the tank get very low before this happened in the first place? You can sometimes drag some dirt through the fuel line which will block the filter. If this has happened, it is possible that the new filter has become blocked as well. If it has, the best thing to do is flush the fuel line through by disconnecting it at the filter and turning the engine over several times, before replacing the filter again and this should hopefully cure the problem. Chris.

 

Aw dude, sounds like a great idea. You're right, I have been running on empty for while now :-( - what can I say, car goes quicker like that lol

few things, how do I depressurise the fuel system? I tried unbolting the filter before without depressurising and nearly caused some major damage by bending the end of the fuel pipe! I understand that there's a way to do it and it must be done otherwise I could repeat the same mistake.

Once filter is removed, do I just keep turning key, stop, then repeat a few times yeah?

Finally, is there any way to clean the new filter if it has become contaminated? Or should I just buy a new filter?

Major thanks for your advice by the way Chris, much appreciated.

 

The easiest way to release pressure from the fuel system is to take the gas cap off.

 

Right everyone, I've tried everything you guys suggested. No difference tho :-(

I've had a look at the manifold, taken off the MAF sensor and found traces of oil in the manifold - is this normal? If not, what could be causing it. My frind suggests it's gonna be either timing belt of blocked PCV valve. Could it be the timing belt? Could traces of oil in the manifold be a blocked breather? I've seen two pipes that run to the cam cover. One's on the manifold and one's on the throttle flap.

1:Could I relocate the MAF sensor to the airpipe?

or

How would I go about unblocking the breathers?

Any help much appreciated.

 

have you even tried to look at engine vacuum?.................to see if maybe you have a plugged Catalytic converter, or looked at real fuel pressure under acceleration to see if the pump is fading(fuel).......or how bout this, look at Scanner Data and watch fuel trim and see if it's negative......look for separated pins at the MAF sensor

 

SUCCESS!!!!!!!!

OK guys n gals - it's fixed! I have some very strong advice:

1: DO NOT INSTALL A K&N REPLACEMENT FILTER - It was starving the engine of air flow hence the hesitation
2: DO NOT INSTALL BOSCH SUPER 4 SPARKS - They suck! Go for NGK all the way. Any Jap engine forum I've read slates Bosch and it's so true. Car is so much quicker and smoother now!!!

Thanks for your input guys. Trust the mechanic. He took off my cat and inspected it, said it was fine then told me he made an 'adjustment' and told me to run it for a couple of days without telling me what he'd done. As it transpires he took out the K&N and ran it free breathing.

Then bought a stock filter from Hyundai and instantly cured problem. The sparks were causing an issue too cause the Bosch are designed primarily for German cars which peak at low revs. They can't handle highly strung engines like Hyundai/Honda/Mitsu etc. NGK all the way!!

So lesson learned. Dealer couldn't fix it, but the mechanic with the knowledge and experience took me seriously and spent time with it. Hail to the mechanic! He had the car for a whole day and only charged me £25. Bargain!