[bossvt]

I have a 2002 Sable with the Duratec DOHC and 76000 miles. I've had this on-going intermittent rough idle for quite some time and need new ideas on how to solve it. Took it to a mechanic today and he wasn't any help. Here are the details on the problem and attempted fixes to date:

Rough idle (probable mis-fire) at start up and after the car warms up. Most prevalent when A/C is turned on (whether heat or AC). Worse on humid days. Only check engine light has been 1 occurance of "misfire on cylinder 3 during first 1000 revolutions". No other codes.

Here is what has been done so far: New plugs, wires and ignition coil. Replaced IAC and the PCV elbow hose connecting the UIM (clearly the PCV hose was bad. The ignition wires were also bad and arcing. Had the UIM off and checked UIM and LIM gaskets, no evidence of leakage, gaskets look fine.

Have my doubts about fuel side, because it's only at idle.

Realize one person had a similar problem solved with a new PCM. Not sure I'm willing to go to that expense.

Any ideas are welcome. I've chased most of the similar problems in the forum.

 

[shoz123]

Did you check the plug gap when you installed them? Might want to take that one out too and do a resistance check on it both when hot and cold/ oven or freezer.

 

[wjc]

What brand of plugs & wires, and how did you check the lower intake gasket?

 

[Monsoon]

Based on your mileage this has the look and smell of either:
* leaky intake manifold gaskets
* leaky egr valve

Both of these scenarios will have the engine check light come on.

Verify the egr valve is not leaking by cleaning it up. Replace if necessary.

Use propane and a hose around the intake manifold gaskets. If the engine all of a sudden gets smooth then that's where the leak is.

Leaky intake manifold gaskets are most notable at lower altitudes.

 

[Jeff K]

Check fuel trims, and look for significant bank to bank differences as a start. For example, bank idle 1 LTFT @ 2% and bank 2 LTFT @ 16%. This would indicte a vac leak or injector problem on bank 2. Note CEL will set only if fuel trims go over about +/- 22%.

 

[bossvt]

Ok, after reading everyone's ideas, I decided to go back and replace all the intake manifold gaskets (both UIM and LIM). I was getting some smell of gas in the car when the climate control was turned on. I know that is a symptom of the gaskets. Just finished the job this morning.

So far it runs great and I'm pretty confident this may have fixed the problem.

 

[wjc]

Congrats, although the fuel smell in the cabin would not be a symptom of intake gaskets. That's something else, could be an oil leak too, they sometimes can have a fuel smell.

 

[bossvt]

Right, while the car continues to run great, I noticed the fuel smell is still there. Gonna start another thread on that one.

 

[lapka]

I have similar problem on duratec. Replaced wires,plugs and ignition coil, IAC cleaned. What does mean UIM and LIM ?

 

[sheila]

Upper and lower intake manifolds.