Knocking / Surging / Missing / Erratic Idle?

[mholhut]

Issue #1: Like everyone else it seems, my '94 atx (160K) suddenly developed a poor driveablility issue pertaining to the idle. It started a few days ago when the temps dropped. I started the car at work and it rumbled like crap. Felt like it was going to stall. Driving it home, the car was bucking like a mule when under slight load at highway speeds. Felt like I roasted an ignition coil on my old V8 SHO. Gas mileage has been getting worse... from ~300 miles a tank to ~240. The exhaust has a noticeable stench to it and doesn't sound smooth at all. The motor shakes and vibrates the whole car. So, I searched here and SHOTimes and cleaned the IAB, the MAF and disconnected the battery. Did nothing to dispose of the symptoms. I'll probably run the codes later this weekend to see what turns up. Any ideas?

Issue #2: On a seperate but possibly related note, the car has what I can only descripe as a knocking sound, from either the top or front of the motor. It's consistent at idle, but goes away as RPMs increase. It's been this way since I bought the car a few weeks ago. It hasn't changed or gotten better / worse since. The car was supposedly 60k'd a few weeks before I bought it. Looking for input so any ideas would be appreciated.

 

[wood_e]

What sort of maintenance has been done and not done? Any codes?

 

[shonole]

Have you checked your spark plugs? I found that my car tends to do this exact thing after a hard rain. Water gets in the with the oil that is already on my spark plugs and keeps them from firing properly. (Yes, I know I am in DESPERATE need of a 60k)

Hope this helps! Good luck!

 

[Ishodu]

Check codes and let us know what you find. Click link in my sig if you need help on how to.

 

[mholhut]

What sort of maintenance has been done and not done? Any codes?

It was allegedly just 60K'd, but I'm having some doubts now. I'll probably run the codes tomarrow... if/when it stops snowing

 

[mholhut]

Have you checked your spark plugs? I found that my car tends to do this exact thing after a hard rain. Water gets in the with the oil that is already on my spark plugs and keeps them from firing properly. (Yes, I know I am in DESPERATE need of a 60k)

Hope this helps! Good luck!

I checked the plugs and they're not bad. No seepage in the wells but there is alot of crap in there... like someone used some sort of compound on the plug boots a long time ago, and the compound dried up. I'll have to blow them out with compressed air before I change them.

 

[mholhut]

Check codes and let us know what you find. Click link in my sig if you need help on how to.

Will do. I was trying to avoid this because the process is a little confusing. But it looks like I'll have to. I'll post more info when I have it.

 

[luigisho]

Just take it to autozone and let them run the codes for you. Did you check the tps voltage? If the boots look bad maybe a bad wire? If it was 60k'd recently do the plugs and wires look new? That's one of the main parts of the maintenance schedule. Maybe some of your local SHO folk will let you swap a set out to see if that fixes anything before you drop any coin on new stuff. You could swap the tps, wires etc..

Knocking is bad. Slight ticking is normal. I wonder if you have spun a bearing?

 

[mholhut]

I'll be checking the codes tonight. I just wanted to add another tidbit of information.

As well as the crappy gas mileage, the rpm's have been way off when at highway speeds. Sometimes the cars at 3000 rpms while only doing 70mph... other times, it seems normal; more like 2600 rpms while doing 75-80mph. Think theres some detonation or some cylinders miss-firing here?

 

[luigisho]

Alot of things are possible at this point. Could be as simple as plugs and wires or a failing sensor or it could be the timing is off if the belt jumped a little or a problem with internals. Any chance of getting it to Fred or Kirk for a once over?

 

[mholhut]

Any chance of getting it to Fred or Kirk for a once over?

That's where it came from :wave:

Just brought the car in the garage now and I'm getting the directions to run the codes. Hoping for a simple TPS code.

 

[stevemainian]

Symptoms of failing o2's.

 

[mholhut]

OK, test results:

KOEO: 111
KOER: 116 Engine Coolant (ECT) sensor out of range - ECT

Cylinder Balance Test:
Flashed 4
Flashed 6
Paused
Flashed 4
Flashed 6

Problems with cylinders #4 and #6?

Thinking plugs and wires or maybe the coil.

 

[mholhut]

Well, one small victory

Replaced the plugs in cylinders 4 and 6. Wells were dry, but had a ton of crap in them. Had to chip away at the crud around the #6 plug in order to get the socket to fit on. Blew all the debris out of the wells before I removed them. Now the motor runs nice and smooth again... at least it's not bucking like a whore.

The knocking is still there which means other issues, and there's still a little popping from the exhaust note at idle. So, I'll change all the plugs next weekend and that should solve/prevent those symptoms from happening again.

Thanks for the help folks and if anyone can reccommend anything to look for with the rapping / knocking sound, I'd appreciate it.