2007 9-3 2.0 rough idle, tapping sound when cold

[loganpopo]

Hi guys,

2007 9-3 2.0T wagon.

Always has a rough idle when cold.Then changed the plugs. Same problem, when the car idles down there is a tapping sound, which is not at the speed of the RPM's, but goes away if you rev it to 1,500 RPM, and the tapping at idle goes away after about 3 minutes of warming up. Car throws a cylinder 2 misfire code, but it seems fine once warmed up and at WOT, so swapped the cylinder 2 and 4 ignition coil to see if it was the coil, and the car still threw the Cylinder 2 misfire code, same rough idle. The car also seems to take 10 minutes to warm up, longer than most of the cars I've owned. Possible the thermostat is stuck open?

Just trying to see if anyone can tell me what to do before I throw 4 new coils in it.

Thanks,
Logan

[Digger]

Would be nice to know how many miles on the motor before making any service suggestions. Tossing out an opinion based on general automotive experience, swapping coils didn't move the misfire and four new coils might smooth out your rough idle, but odds are against this fixing your #2 misfire.

Before tossing a couple hundred bucks at new coils, spend a couple of minutes and check cold compression on the cylinders, you might just need to clean out some carbon.

[loganpopo]

It has 78K miles on it.

[Digger]

At 78K you could be into the tech bulletin noted 07, 08, 09 valve problem and you really should do a compression test before doing anything, but my gut tells me 4 reman injectors and a new fuel filter are money well spent.

A reman injector is nothing more than a cleaned injector with a tested coil and a new O-ring, you could clean these yourself, but for what they cost after core exchange, it's not worth the effort. A leaky injector will wash the oil off the rings when it bleeds down, give you low to no compression on start and rough idle, all that and bad fueling is bad for the valves.

Costs money to have compression checked at a shop and if you're on a budget, there are simple things that should be done, that will tell you a lot about what might be happening without costing you one extra penny.

It's 2017 and if it hasn't been changed, the fuel filter is now ten years old, no money wasted by replacing, as you don't spend money on injectors and not change the filter. You can make this a two part job, or do it all at once. Change the filter tonight when your done driving for the day, clear the codes and if your #2 misfire comes back in the morning, you can be pretty sure it wasn't caused by the injector leaking pressurized fuel into the cylinder overnight, changing the filter will remove the pressure from the line. So you change the injectors at the same time and you only deal with depressurizing the gas line once, or you can wait and see what happens.

Change injectors and filter at the same time and if it fixes the rough idle and misfire great, if not be prepared to deal with cruddy or bad valve seats. Either way the injectors aren't wasted money as you will spend about the same amount to have a shop do a compression check and you would probably replace the injectors if you had to pull the head.

[WMichaeli82]

So this is interesting because I have a similar issue with my '06. I'll have to find out when these two were changed and cleaned but mine has 153k+ miles on it. Someone at a garage also told me to run Seafoam through the vacuum line to the manifold but when I removed the plastic covering it looks like there are 3 lines. One short one and two long ones that lead to the short one. Would the short one be the main line or is there another hose that I should be looking for? I'd like to do this first since I already have the Seafoam on hand.

[Digger]

Seafoam spray goes in through the throttle body, liquid goes into the gas tank and it will eventually clean the injectors after a couple of tank full treatments. Direct feed injector cleaner to the fuel rail is quicker, but not easier. Personally I prefer Lucas for the tank and throttle body cleaner for the throttle body. There is better stuff to use down the manifold vac, but you might already have the Seafoam and to syphon this stuff in, don't run it through any hose you plan to leave on the car, use your own hose and plug direct to the manifold vacuum port. Do let the car warm up first.

Shop for a fuel filter now and be ready to replace it one tank full of gas after you're done running the fuel cleaner through the tank. If it's never been done before you could free up a lot of crud and the whole idea is to clean things up, not plug them up worse.

[WMichaeli82]

Which one is the manifold vacuum port though? It's hard to tell without the repair guide.

[Digger]

Which one is the manifold vacuum port though? It's hard to tell without the repair guide.

Even with the wis it's hard to tell as the wis expects you to know what you're doing. Normally I would say pull the egr valve and suck it in through there, but pulling the egr valve on this motor means removing the intake manifold. Some systems are sealed up so tight that you go to best other vacuum source, so the next best manifold vacuum has a check valve in the way, not a good thing to run this stuff through and another project to remove. The wis doesn't provide pictures of vacuum points that don't need service or testing and you need to pull a hose to identify which side has vacuum and follow the hose back to manifold source and not the vacuum pump.

If you really need seafoam to remove carbon, have someone that knows how to do it. Might I suggest you put the seafoam in the tank and find a u-tube that shows how to use water to do the job. With someone holding the foot feed steady at a couple thousand rpms, it's pretty hard to squeeze a spritz bottle fast enough to hydro lock a motor. Don't mean to be discouraging, but if you don't know how to find manifold vacuum, you really should at least see how this is done, before you try doing it yourself.

[WMichaeli82]

I'm sure the WIS isn't the only repair guide. All the YouTube videos show the after affects of Seafoam or other cars that have a single vacuum line right at the front. Although i wonder if i just answered my own question. I'll post a pic of what I'm talking about later, to dark to get a good one now.

[Digger]

On this engine the egr valve is tucked inside the manifold and gets its vac the throttle body intake opening, the EVAP canister purge valve is directly below the throttle body and it gets its vacuum direct from manifold. Sorry the line art from the manual is pdf and isn't accepted by image upload.


The vac line to the evap purge valve is on the front of the engine, expects to see some moist fuel and is far enough below the intake that if the engine should kill you have a chance to stop the syphon flow before it floods out the egr valve.