Idle issues - duratac

[Clskmstg]

Well - I've been getting a slight rough idle in and out lately. I took a 250 mile trip over the weekend - this morning, after I came back - as it was idling, the check engine light was going on and off. When I put it in drive - it went off.

I now work at a local auto parts house - I used our scanner and it showed a p0171 code (system adaptive fuel too lean bank 1) and a p0303 code - cylinder misfire #3 -

The one thing that was common between both of them is plenum gaskets. I've known I've been needing to replace them. Now, the light is on all the time.

Would that cause my issues? Also - I tested the fuel pressure. roughly 30 at idle - on the rev, about 35 - that seems low to me. The filter *may* have been changed once in 223,000+ miles. I had the fuel pump changed 90,000 miles or so ago - it wouldn't surprise me to find out if the mechanic didn't replace the filter.

My thinking is - do the plenum gaskets (hopefully, that's not hard) and change the filter - then, re-test the fuel pressure.

Thoughts?

[Breeves002]

That is low enough for it to be running lean. Should be around 40psi at idle. I'd change the filter. Easy change. Just see what quality of fuel comes out of the old filter and that will tell you if it's ever been changed...

Seems like if the misfire is related to the fuel system changing the gaskets won't do anything helpful. Check out your fuel trims at idle and under load. When does the miss happen? Is it noticeable?

If it isn't related to the low fuel pressure, then could be a vacuum leak, like the gaskets, or plug, coil, etc... Check compression on the #3 and compare it to the others. Don't go changing the gaskets till you change the fuel filter though.

[behlinla]

Misfires can cause lean codes, so don't rule out a bad spark plug, coil, or injector on #3.

Having said that, fuel pressure should be 35-55 psi, so you can try changing out the fuel filter first to see if it helps.

[Clskmstg]

It's a low in miss at idle - but, not all the time. Otherwise, it runs and sounds great for 223,000 miles. Surely this isn't too serious??

[behlinla]

If it's a slight miss it's not too bad, but if the misfire gets bad it can wreck your catalytic convertors. Either way a misfire code is not something I would ignore for long on my car.

[Breeves002]

^
+1

Usually a miss only gets worse, not better. It's just a matter of time until you start noticing it more (probably). New fuel filter first, then go ahead and move on to the next thing if it still exists.

[sheila]

How's the pcv hose assy.?

[Clskmstg]

I did the PCV last year (what a pain) - I've not checked it, but it's all new. I don't plan to ignore it - but, the miss (only at idle) has been so slight - it's hard to even notice. None of this tripped the light until yesterday.

[sheila]

Probably plug or coil.

[Clskmstg]

Well, just changed the filter. It's been changed once. It was rusted, and the fuel coming out was pretty grungy. Interesting - the fuel pressure only improved a pound or two.... it isn't going down as far. However, when I put the fitting on the line, (adapter) fuel sprayed out maybe 7 inches in the air - yesterday, it wouldn't do that. So - some sort of improvement.

It tripped the check engine light again coming home. It's running fine. I'm going to check the codes again at work. My thinking is to now do the plenum gaskets - see if this stops this check engine light situation. If it happens again - would you look to the coil, or replace the fuel pump? (I'd rather not do that)

AC