Rough Idle

[90gmcmoneypit]

Hey guys, thanks in advance for any help...

Just purchased a 99 2.4 Automatic GA with about 190k on the ticker. Got a great deal on it and despite the flaw I'm about to touch on, it was a great buy.

So I'm getting a rough idle when in gear and foot on the brake. Idle speed is around 550-600 and doesn't fluctuate at all. NO codes.

I've replaced the IAC and cleaned out the port fairly thoroughly and it didn't fix the idle trouble. Checked for vacuum lines and at first glance they all seem to be both in great shape and all connected. A friend of mine who has a 97 said that this is indicative of a bad or cracked coil housing. I've read about a couple of culprits that cause rough idle and going down the list I'm trying to get it right before I go replacing sixteen things.

So my question is; Is there an order I should follow in terms of replacing parts to fix this rough idle? Like maybe start with the coil housing/plugs or start with the TPS? I'm not working with much in terms of funds, so I'd like (obviously) for the first fix to be the one that works.

Any help is appreciated!

[thephantom1492]

550-600rpm is normal.

Have you checked the spark plugs? You need quality one there, I don't know for that year but the 2002 ask for iridium plugs.

You said it have 190k on it, if it is still on the originals one they are long time worn out, if they are on the second set they are about gone. Mine only had 82k and the plug had to be replaced... misfire on cylinder 4... They are suposelly rated 120k...

Also, is it old fuel? it might sound stupid, but old fuel tend to have problem burning and can cause rought idle.

[90gmcmoneypit]

I haven't checked the plugs yet but I will replace them when I do the coil pack housing.

Ran through an entire tank of gas. When I purchased the car the fuel light was on and it was damn near empty.

Additionally, I've got some pretty loud lifter noise after the car is warm. Doesn't the 2.4 have self-adjusting lifters? If I'm getting a misfire due to ignition issues, would this also cause the lifters to tick?

Haven't had a chance to look at anything because I'm sans garage and it's been monsoon season here in St. Louis the past few days.

[thephantom1492]

it should have hydraulic lifters, but the knocking could be a misfire too... Really, start by checking the sparkplugs, first step into fire issues.

[90gmcmoneypit]

The ticking is only once the engine is warm. I added some synthetic oil treatment yesterday and that didn't solve the problem. I think I'm actually looking at a combo of issues. I think the car needs to be tuned up. There's an obvious miss/idle issue and I'm almost certain it's in the ignition end. All of my vacuum lines are healthy and connected. Beyond that, I'm fairly confident there are one or more bad mounts because when I throw it in neutral at a red light, the vibrations lessen dramatically.

[thephantom1492]

oil treatment = wasted money in almost all cases.

Why don't you check the sparkplugs instead of wasting time and money on other things?

Neutral does reduce the load on the engine, so make it run better. Not a mount issue.

[90gmcmoneypit]

I have a set of plugs and the treatment was four bucks. I really just wanted to increase the weight of the oil temporarily until this monsoon rain that's been around for the last week disappears and can change the oil. The same applies to the plugs. Have Bosch platinums in the glove box, just waiting on the rain to let up. Ideally, I think I'm going to have to start with the coil, coil housing, plugs, plug boots, TPS and then hope those things clear it up. I've heard from other sources that ticking valve actuators are something that GA owners just "learn to live with" on high mileage GA's.

[90gmcmoneypit]

Additionally, my gas mileage is horrible.

[skeeter123]

Get or borrow a good code reader/scanner. There may be history or pending codes that would point you in the right direction. A scanner could show you "live data" such as short-term&long term fuel trim; these would tell you if it's running leaning or rich. Lean points to possible vacuum leaks, rich could be leaky fuel injector. Hate to chime in on the plugs, but when it stops raining and you pull them out, taking a good look at all of them may tell you if one or more cylinder is missing/oily/too rich/too lean/etc....
another low-buck test is to run it in the dark, after your eyes have adjusted, watch for sparks shorting out to ground from the plugs/wires/coils/etc....
Hope this helps.

[inafogg]

honestly i would leave the bosch plugs in the glove box & use the
original a/c delco thats in there now