99 regal rough idle

[teddo15]

hi there, i need some help, i have a 99 buick regal with about 60k miles on it and I am having a problem with rough idle and the check engine light coming on. when I read the fault it told me I was having a misfire in cylinder #2. have been to dealer and local shops and alhtough they like to take my money, no one has been able to solve the problem. it is especally noticable if you lift up lightly on the brake. really feels rough. if you give it any gas it runs smooth. also heres what I have done so far. fuel injector cleaner through the rails twice. new plugs, new wires , coil pack and ignition module, hi test gas and about 5 bottles of injection cleaner through the fuel tank.after the last time I got the car back, the check engine light stayed off for about 100 mile and now its back on again. any help anyone can give me will be greatly appreciated.
thanks Teddo

[Mr_D]

I have the same problem on a 1998 Regal 3.8L K series engine (not supercharged). It started missing while cold, and 2 days later it does it all the time, only 33K miles on it. I haven't found the problem yet. This info applies to the 1998 3.8L. 1999 should be the same.

Some of this will require special tools and a ScanTool to diagnose.

Are there other DTC's beside "misfire" recorded? DTC is Computer (Diagnostic trouble code).

Inspect vacuum hoses for splits, kinks, or improper routing or connections.

Inspect PCV valve and PCV O-rings.

Inspect throttle body inlet screen or damage or the presence of foreign objects that may alter the air flow through the MAF sensor.

Check Fuel pressure (48-55 psi) if above idle.

Check for excessive water, alcohol, or other fuel contaminents.

Inspect the PCM injector grounds, power grounds, and sensor grounds ensuring they are clean and tight.

Inspect for vacuum leaks in the:
Intake manifold
EGR adapter
EGR Valve
EGR feed pipes
Injector O-rings

Remove and inpect the EGR valve to ensure that the pintle is not sticking partially open. also check for carbon deposits that may interfere with pintle closing.

Check fuel injector operation. Injector leakdown test pulses each injector, one at a time, and measures the change in fuel pressure with engine off. The fuel rail can be charged by turning on the ignition a couple times. Each time ignition is turned on (not started) the fuel pump runs for 2 seconds to prime the system. The fuel pump remains on only if the engine is running and during starter cranking. The fuel rail remains charged for days unless there is a leak.

A 2nd fuel injector test measures injector current draw. Mine were all 12 ohms while off. That is not a complete test but just a baseline and doesn't indicate if they function, just that the coil is intact.

Check Ignition Wires, coils and spark plugs. Check wires for carbon tracking, damaged insulation, or improper routing that could conduct the spark to ground or other wires.

Measure ignition wire resistance, should be below 7K ohm. Mine was 1K ohm. Longer wires will read slightly higher.

Measure ignition coil secondary resistance, spec is 5-8K ohm.
Check for carbon tracking here also.

Check for a damaged accessory drive belt, pulley, or accessory.

Check for lose or broken motor mounts.

Check tranny TCC (torque converter clutch operation). Should appear like a 5th gear above 50mph and generally stay engaged at speed.

Replace ignition control module.

That's it. There are much more details but almost too much to write here. Of course, a worn cam lobe, valve or bent valvetrain component could also cause a problem, but it wouldn't come and go, That would be all the time.
Mr_D.

[jeepguy1]

i'm wondering if the intake gasket is leaking , also check the #2 plug gap and porcliline for cracks etc .also possibly the #2 injector could be bad ,another thing which i dont think is related but good to do is remove the idle air control valve and see if there is alot of build up on the pintle if so good to clean it up as well as the throttle body housing and butterfly .