Rough idle problem - Hyundai Performance Forums

Black03Accent · 05-06-2006, 02:51 AM

2003 Accent. 1.6 DOHC. Mostly stock, only mod is a turbo muffler.

Fine cold starts, fine warm starts, no problems driving around or anything. Idle when it's all the way warmed up is rough... like it's only running on about 3 cylinders. I've tried pulling the plug wires, and all 4 cylinders are definitely getting spark. I've wiggled the injector connectors and they all seem fine. The tach makes it look like it's idling at about 750? It doesn't seem unusually low, just rough. Any ideas? About 55,000 miles. Wires all seem solid, but I do have a volt tester if someone has specs for them.

boob · 05-06-2006, 05:11 AM

my car is pretty much the same. it isn't like "shake the car to bits" rough, but it isn't super smooth either. i can feel the good vibrations in my drivers seat!:duh:

GregsterGSi · 05-06-2006, 06:13 AM

Id change the plugs and wires regarless of when hyundai says they need to be changed, the fuel filter and id clean out the combustion chambers

Black03Accent · 05-06-2006, 03:09 PM

Plugs are new within the last 2000 miles. I forgot to add, I bypassed the throttle body coolant thingie after this started and it made no noticeable difference.

Is the fuel filter that thing behind the manifold with the weird built in sensor? I've been meaning to run a can of seafoam through it, just haven't gotten around to it yet. I know the last owner never shifted past 3 grand, so it's probably all carboned to hell

uzzled:

Danath256 · 05-06-2006, 05:57 PM

The fuel filter is under the rear seat, right on top of the fuel tank. Its really simple to change, just make sure you depressureize the line first and have a bowl or something you can put the filter in and catch some of the gas that drains out, so it doesn't get in your car.

Black03Accent · 05-07-2006, 06:51 PM

I'll replace the fuel filter later this week.

One other thing:

I stuck a timing light on it, and the timing is really erratic, jumping all over the place (at idle), but mostly staying around 10° BTDC. Is there some test connector I need to jumper first before checking the timing? Not like I can set it, I suppose... no distributor and all.

f0rbidden · 05-07-2006, 08:04 PM

Won't be your plugs and wires.
( because it ran fine cold idle )

Is any of your vacuum hose lose?
Did you compression test your car when you change your plugs? (did you unplug the coil connector?)
Do you have enough coolant/water in your Radiator? ( affects sensor reading )

f0rbidden · 05-07-2006, 08:07 PM

Check throttle plate see if it's dirty.

You don't have to take the sensor out to test it.
If any of the sensor is not good at the throttle body, you'll get a CEL.

[Edited by f0rbidden on May 7, 2006 4:08 PM]

Black03Accent · 05-09-2006, 04:17 PM

Allright. Cleaned the TB. Replaced the fuel filter. Ran some Seafoam through it. Enough coolant. No check engine light.

WTF.

Guess I'll just have to live with it.

f0rbidden · 05-12-2006, 07:38 PM

Did you gap your spark plugs to the OEM spec?
try making it 0.045"

with engine on, idling, spray carb clean or throttlebody clean around all the vacuum hose, and all gasket area for the intake manifold & TB
see if you get some idling change than you know if you get a vacuum leak.
(avoid getting them to the exhaust side.)

And don't use synthetic oil.