Rough Idle
 

Hello. Well since it's gettin a little colder out my car is suddenly started idling rough on me. First of all I've been searching around thread and really haven't found anything that sounded like my predicament and nothing really adds up.

But the first couple of days after 80 to 70 degree weather turned into 50-40 degrees my car really didn't show any signs of anything abnormal. but just a week ago my idle began to surge and was at about 250-500 RPM and sounds to be miss firing a little because the car seemed to vibrate a little more than usual.

The car is NOT throwing any CEL codes. So the first thing i did was to check my TPS adjustment and that was a little low sitting at .380, so i readjusted to .5 volts while the engine was at operating temp (unsure if needed to do it when engine cold or warm). Also take into consideration that i have been checking the voltage for a while seeing that i had done an engine reseal about 2000 miles ago. Unless i didn't tighten the screws very tight or i have suspicion that the TPS could be going.

I have doubts that i have vacuum leaks seeing as i replace what could have been 20 year old lines. In addition i also replace PCV and i do get a sound when i rev the engine to what sound like the valve sputtering as i let of the throttle.

Earlier today I had unplugged the coils one by one on the passenger side to see if coils were bad and i got a reaction each time, although i had not check the driver side. And i plan on pulling out the spark pugs to see if there is anything abnormal there.

But besides all of this, I dont know what to next. I feel like an idiot because i can rebuild a tranny and reseal the engine but cant diagnose this problem.

So any help is greatly appreciated in advance and id like to here what you guys have to say with any greater knowledge that you may have to help me figure this out.

Re: Rough Idle
 

Today was 70 degrees and the idle was sitting at 500 rpm and didnt sound abnormal today

Re: Rough Idle
 

When is surges is it in park? does it go away with a little load on the motor as in turning the heat on?

Re: Rough Idle
 

Well it surging while in park and gear but in park its trying to find the idle the it just keeps raising. But i did give the coil packs another look. The first time i could tell the difference in firing when unplugging the coils and then i checked them out again tonight and the idle doesnt change when unplugging the cylinder to closest to the firewall on the passenger side. So I think I may have found the problem.

Re: Rough Idle
 

No not at all no difference... But i swapped the coils out and it didnt make a difference and now the car seems to be driving worse. I also did a cylinder compression check as well and each cylider was good. But the car seems to have extreme power loss and when i get on it (even when i put it in power mode) to speed up with traffic on the highway, the RPM's only go up to 4,000 and it stays there and doesnt accelerate at all. There is now a loud noise coming from the air box thats sounds almost like it could be exhaust. When inspecting it and revving the engine, i found this quite odd....


I'm really getting frustrated at this point and nothing seem to be adding up to what the problem is....
I might even take a video and post it.

Re: Rough Idle
 

Check your exhaust line. Maybe a blockage or a hole somewhere.

Re: Rough Idle
 

Mine had the same effects (minus the loss of power and noise) without throwing a CEL and it was just my O2 sensors. Maybe you have multiple problems at once, I mean, you do own an SVX. ;)

Re: Rough Idle
 

When you say there's an exhaust sound coming from the airbox, are you referring to a sound like an air leak? You can try posting a video if you want, it might help.

Re: Rough Idle
 

no the airbox just growls A LOT more than before i changed the coils. I did just change the MAF sensor ad took it for a drive. It seemed to help a little when accelerating, but the idle and throttle is still very jerky when i come to a stop and go again. And when im driving and mash on the acceleration pedal I only get to about 4,000 RPM before I lose power.