Hey guys!
I've been dealing with a rough idle on my 2002 Neon ES since I bought it from a friend a few months ago. I've found partial solutions to the problem. I did a tune-up, got new wires and plugs. Seafoamed the crap out of it. Run several tanks with different additives. Replaced upper and lower torque struts measured correctly. New PCV valve. Replaced the throttle body and ECM(flashed). Purged the power steering system and Even did an engine flush with ATF with no leaks.

I have to say, those things have made a substantial difference, and the car runs great now, and seems to have good compression and power. The problem is that the vibrations are still present. I don't feel them like before, but definitely can feel it on my steering wheel, and have a rattling sound coming from the dashboard as well as a humming sound from the engine bay. All this at idle only; being worst when in gear or reverse and my foot on the brake pedal. It gets a little stronger if I turn on the antifogger, headlamps or defroster, meaning under electrical load. The battery is fine end the alternator has good output.

One thing that actually helped the car run better and have more power on take off is the addition of an oil catch can... You guys have to see how much oil goes past the PCV valve ready to clog that precious MAP sensor and make a mess beyond there. I'm glad I got the catch can.


Well. Today I tried something new. I unplugged the vacuum line that comes from the charcoal canister in the EVAP system to the throttle body. It raised the idle by about 50-80 RPM, and the vibration went away almost completely. Drove the car for a few blocks and WOW! what a difference. I mean, the whole powerband improved!... I can't say it will be the same at highway speeds and higher RPMs, but it was good for the few blocks of the test. Now my question: Is there going to be a drop in my already mediocre gas mileage with this mod?. Will it throw an EVAP code since is not sucking the fumes out of the tank anymore?...

To be safe I routed the hose to my cold air intake so it will be "clean" air what will go to the manifold.... To me the logic of this is that it works like the 1/8" hole in the throttle valve that some people have tried for their low RPM issue. It's an induced vacuum leak, so I don't know how mileage/top end are going to be affected and how the ECM will see the extra unmetered air going in. I wonder if I can get away with this until Spring when I will take things apart to replace the timing belt, water pump and center motor mount...

Any input will be greatly appreciated... I will try and post a picture tomorrow during the day!

 

If the torque struts were bad, it's possible the motor mount went bad. That will cause horrible vibrations. How close are you to needing to change the timing belt?

 

I'm at 87881 at the moment. So I still have a couple moths to go.

 

Might just hold out until your timing belt change, get a new OEM motor mount and see what happens after you replace it. I'll say ahead of time, even if the old mount isn't broken, it's a good idea to replace it anyways as it is the last thing that gets removed before the timing belt cover. That'd suck to have to redo all of that work a short time later if it broke shortly after. As someone who elected not to replace the $2 cam and crank seals during the timing belt job because "they were fine and not leaking oil" and started leaking oil just a couple thousand miles after...do it.

 

Ahhh the little details!!!!... Yes, I will see if I can find an OEM for cheap. I have a brand new Anchor, but I'm affraid it won't last as long.
I've been testing the disconnected EVAP hose and so far so good. The mileage is crappy, but this has been tested in stop and go traffic, so it would suck anyway. So far no check engine light, and the car runs better than before.

 

 

That's a mess. What's the fuel filter for?

 

Brake booster. To make sure no impurities are going to the intake. I'll leave it there for a week to see if it stays clean.