[cmd146]

I have a 1995 Thunderbird LX, 3.8 NA. Car has 130,000 miles but runs strong. The engine has a noticiable shake about it only while idleing in park or sittng at a light in drive. Step on the gas - it straightens out, and runs great. I've replaced all the normal tune up parts (plugs, distributor cap, rotor, plug wires). I've checked the EGR valve and all EGR related sensors and actuators - they seem to work fine. No computer codes. No apparent vacuum leaks. Vacuum test gauge shows stedy vacuum. I replaced the head gaskets 30,000 miles ago, but it's been doing this shake for the last 20,000 miles or so. It was very subtle at first, but it been getting worse. I did a compression test 20,000 miles ago - it was fine, I'm going to check it again within a week. Any ideas are appreciated!

Thanks in advance.

 

[krusher]

Had the same problem

Well, actually I have the same problem. I'm still replacing things. Its really funny actually... Each thing I replace makes it idle better but not normal... So far I've replaced in order:
plugs/wires
fuel filter
replaced MAF
intake manifold gasket
cleaned EGR valve
replaced O2 sensors
That's what I've done so far... it still idles a little rough... not stalls though... next thing to replace is the sensor that sends engine temp to the ECC.

 

[Rodeo Joe]

Could be the IAC (idle air control) valve. Real easy to get to on the 3.8, 2 screws on top of the throttle body. People say you can clean them, some say just replace it. Just a thought.

Joe

 

[JSGAuto]

I second what Joe said. My car had bad idle and base timming at idle. It tured out to be the iac.

 

[cmd146]

Thanks for the suggestions. I actually did replace the IAC a few years back tracing down an unrelated stalling problem. But that was about 60,000 miles ago. The idle speed doesn't surge or anything, it stays pretty constant. It feels a lot like a vacuum leak, but I can't find any. Could a bad IAC cause this kind of shake?

Thanks.

 

[JSGAuto]

I would replace the iac. Last week my car developed a shake. It was different feeling from the idle problem, but it is difficult to explain. It turned out to be incorect TV cable setting. So start with the IAC and if that doesnt work, you may want to check the tv settings.
Jim

 

[Alex]

This is gonna sounds stupid but, have you tried just adding more oil? I had this problem and all i needed was a little more oil in the sucker and it fixed it.

 

[cmd146]

Oil level is ok.

Nothing sounds stupid when dealing with a Ford 3.8! It's a very quirky engine, but with proper care it's a good one.

I'll try the IAC. Thanks for the suggestions.

 

[Gary]

Rough running 3.8

I had my 87 Cougar in and spent $2500 trying to find why it runs rough, changed virtually everything. I just discouvered what it is. Go outside where it is pitch black. Wait for 15 to 20 minutes, then (no lights of any sort allowed here so prepare ahead of time to cover or disconnect any that may work) open hood, start engine and peer into engine compartment approximately where you would expect to see the spark plugs, spark plug wires, coil wire, and the coil. Now, take your time and watch for little spikes of electricity jumping to ground. It looks like miniture lightning strikes. If you see any you need to replace the defective part. Mine turned out to be the coil, it must be defective because it is arcing to ground along it's sides, not at where the coil wire is attached at the top. I can see there are one an maybe two of those brand new plug wires arcing too. The engine would run fine for sometimes a week, then go crazy. Not one mechanic could find the friggin problem.

 

[glowing escape]

have you checked your motor mounts? cause both times my idle was rough, it was from one of the motor mounts going bad. if they are bad, itd be a good idea to switch to solid (rubber or poly) because we have liquids in there as stock and they suck. -greg

 

[Tim Groth]

Engine treatments...

You may have done this, but here's a story....

....My car had a similar problem starting to develope and I'm all scared the headgaskets will let go again so I went to advanced and told them the deal said I wanted some engine treatments just to make sure. Guy sold me this stuff called Sea Foam (at first I was like but it's not in a fancy bottle...) I put it in earlier in the day, drove to work kicked the beast in a few times to get the stuff in the engine, no smells or anything. Came to a light, I couldn't even tell the engine was running(normally the antenna would shake). Got off work tonight, the engine once again ran so smooth that I had no clue i had turned it over. For a while she would kinda chug to turn over and then once started she'd run good as you said.

I also replaced my plugs, wires...ect and come to find out it was just some build up. Let me know how it turns out for you.


here's a link to the product I'm refering to.

http://www.seafoamsales.com/motorTuneUp.htm

 

[rzimmerl]

have got the same problems, the rough idle is only when the car is warm and go to restart it, after driving like 50 feet runs fine, have already cleaned the iac and the throttle body, think o2s are going bad, is shooting codes put dont have my reader on me when it does. when the light is off the reader doesnt pick up any codes. just lost on what to do. dont really want to go buy parts that dont need. replace head gasket plugs, wires, cap and rotor, o2s 20000 miles ago. any help would be appreciated.