Very rough engine from cold
 

When my car has been sitting in the driveway for maybe a day or so, maybe over the weekend. I start it up to drive after that time period and idle is extremely choppy, the revs are at the normal level but the engine sounds almost like a lawnmower "chuff chuff chuff chuff" I starting driving and the "chuffing" doesn't go away it just gets faster. It has actually made me stall at an intersection at some point. After about 5-10mins of anxious driving it finally returns to normal. It has happened consistently the last 3 start ups. Any ideas?

Re: Very rough engine from cold
 

Sounds like one or more cylinders aren't firing. That could be caused by a bad coil pack, or a bad injector that is leaking when the engine is shut off, and is fouling the spark plug in that cylinder.

The first thing that I would do is to pull each of the injector connectors off each cylinder to determine which cylinders are causing the problem. Once you have determined that, you may want to pull the spark plug and coil from that cylinder and have a look at them.

The ignition coils used on the SVX coil-on-plug ignition system can and do go bad. Usually, the spark burns through the plastic on the coil, and shorts directly to ground through the cylinder head instead of through the plug.

Alternatively, you may just need to replace your spark plugs.......

Jason.

Re: Very rough engine from cold
 

Good to know will look into it

Re: Very rough engine from cold
 

Was this resolved? My dad runs a shop and we did some injectors after unplugging 2 with no effect on the idle however it didn't resolve the issue. He doesnt have time to look at it because he is quite busy but I have all the tools to diagnose. I'm thinking coil packs but I don't see why this would be limited to a cold engine.

Edit: we have checked the spark plugs and they do not appear fouled. Curious as to what I can look for on the coil to verify.

Re: Very rough engine from cold
 

The coils can fail from the internal contacts corroding or developing cracks from thermal stress. Metal contracts when cold, opening the circuit and killing the coil. As the coil gets hot from the engine block, the metal expands and can restore contact between sides of the fissured connection, making it work again.

Re: Very rough engine from cold
 

Makes sense... I had a similar situation with my starter once actually when I think about it. Except it was opposite. Once it had warmed up it could no longer make the connection so you had 1 good start to get where your going then you have to wait a couple hours XD. Anyways I'm gunna pull it in to an open bay tomorrow and pull some coils and check em out.

Re: Very rough engine from cold
 

Is there an aftermarket set available at a reasonable price?

Right now the price we get through Worldpac is $99.99 for OEM. We are quite sure that the problem does lie in the coilpacks and we ordered one already but if I can find a higher performance set for a decent price than I'll just have my dad return this one.

Re: Very rough engine from cold
 

There is no aftermarket. Only OEM coils:)

Re: Very rough engine from cold
 

All right, so if either one of you two want to look through the threads that I've created on the topic, you may. Basically, I had the same problem. Cold starts made for on and off misfire (sometimes constant) and it wouldn't go away until the car was warm.

I replaced two sets of spark plugs, replaced two coil packs @ $80 each (I also examined every other coil for leakage, cracks, etc.), and replaced almost every sensor available. I then, last shot, hoped it wasn't electrical at all. So, I had the air/fuel induction service done at the dealer (basically, they run a potent chemical straight through the fuel rails through the injectors - MOTORVAC is the same idea). Fixed my car right up. Seriously. Not a plug for the dealer, but definitely getting injector service.

Re: Very rough engine from cold
 

I actually did read your thread and since I've already done a fuel induction service I ruled that out. Not that it was a waste because in a 15 year old car a fuel induction service is in order anyways. I've narrowed it down to which cylinders are misfiring when cold and I've done injectors so it pretty much has to be coilpacks.

I agree with you though... If your car is misfiring and you have yet to have a fuel induction service performed I highly recommend it.