Help w/ rough iddle (part 2)

Pepito opined in news:2004112209424216807%josephamadeusNSPAM@mindspringcom:

Do oyu still have the gas smell from the exhaust?

When you say "rough" do you mean like a "miss", meaning does the engine shake? or is the idle speed varying?

Watch the tach while this happens, does it "blip" or does it seem to reflect engine speed variations?

Does the car "ping" on tip-in (slight accel from speed) or at wide open throttle.

ARe your plugs gapped properly

Have you looked at your PCV valve? Replaced it?

I think I still have the gas smell in the exhaust, I will have to check again later on if it went away or not. No check engine light or computer codes. I mean by rough that the engine shakes, sometimes real bad, the tach doesn't reflect speed variations. I made sure all plugs were gapped propertly to factory specs. I have checked the PCV valve and it rattles so I haven't felt the need to replace it. any ideas?

Pepito

I mean by rough that the engine shakes, sometimes real

So the tach is nice and steady during this shaking?

What RPM?

I just took the car for a drive, I will tell you with details what happened so maybe you can figure this out.

I started the car cold, the tach was between 1500 and 2000 rpms for a couple of minutes, then it started to go down but kind of hesitant, you know the niddle was jumpy till it reached around 750 rpms (waited almost 2 more minutes, 4 minutes total for warm up).

I cheched the exaust and there was a strong gas smell. I started driving the car (engine pretty smooth) for 10 minutes and when I parked it, the engine was already shaking but not as bad as some other times. I came back to the car 5 minutes later and started driving back home, the engine was shaky but not like it was when I parked. Seems like the problem settles when the engine is off.

I drove another 10 minutes and when I came back the engine was shaking again kind of hard. I checked the exaust and there was almost no gas smell but the pipe was shaking with the engine. The tach was steady at around 750 rpms like it always is when the shaking happens. I hope this helps you figure out the problem.

I missed the previous thread and work on VW (dropping by the newsgroup for a friend) but is the O2 sensor any good? If you have one, do Mustangs run in safety mode when the sensor disconnected? If so, disconnect it, and see if that smoothes out the performance. Although I'd guess you'd get some sort of error code. Otherwise, I'd consider temperature sensors and vacuum leaks (spray a fine mist of water or my favorite, ether CAUTION!, across fuel rail and vac. lines) I'll go back to the VW group now :-).

Darryl.

Darryl opined in news: snipped-for-privacy@4ax.com:

Well that cant hurt and would explain why you only see it warmed up.

Try it... will be the first example of a BAD (or REALLY SLOW) vs slow O2 sensor I've read on here or the Ford group

So whats next, disconnect the O2 sensor besides check for vaccum leaks?

Pepito opined

Check ALL the tubing/vacuum plumbing first and think again about anything else that isnt working just right.. there is almost always another weird problem that goes along with this kind of fault.

Then use ether or unlit propane torch along all joint and gaskets.

THEN

Like Darryl said... disconnect it drive it and see if the warm idle smooths out. It will set another code and the CEL but if it idles ok warm you know to replace it.

That's what I'd try in my VW experience. ;-)

So what ever happened???

No improvement so far, I tried disconnecting the O2 sensor and didn't make any difference. I will try locating any possible vacuum leak during this week. Brian told me he had the same symptoms in his stang and it was an intake manifold leak. I'll keep you posted.

News update: I tried carb cleaner in all possible leaking parts and didn't do a thing. I am about to give up. Replaced the air filter since the old one was really dirty. I am not sure yet but looks like the poor gas mileage still there and the iddle roughen from time to time. No specific time of the day, can be warm or cold, sometimes it feels like a cycle for example it gets worst for a second or two then slows down, then starts again. Any ideas?

I dunno what car you're talking about... but rough idle for me always meant a worn plug or plug wire. Also, if air filter was dirty... check MAF sensor, IAT sensor, and TPS sensor.

-Mike

-- A happy kid behind the wheel of a 98 Mustang GT Cold air intake FRPP 3.73 gears Steeda Tri-Ax Shifter Flowmaster 40 Series mufflers (self-installed woohoo) Hi-speed fan switch

Won't they give me error codes? I have no error codes in the computer Plugs, cables and air filter are brand new.

Ah... 88 LX. Do you have a mass air system? Or is yours the earlier version (I forget the name)? Also, mine never threw a code. Check the spark plug gap also!

-Mike

-- A happy kid behind the wheel of a 98 Mustang GT Cold air intake FRPP 3.73 gears Steeda Tri-Ax Shifter Flowmaster 40 Series mufflers (self-installed woohoo) Hi-speed fan switch

On Sun, 05 Dec 2004 02:54:41 +0000, memse rearranged some electrons to form:

Speed Density

Yes, thank you.

-Mike

-- A happy kid behind the wheel of a 98 Mustang GT Cold air intake FRPP 3.73 gears Steeda Tri-Ax Shifter Flowmaster 40 Series mufflers (self-installed woohoo) Hi-speed fan switch

Can you guys explain more?

On Sun, 05 Dec 2004 07:54:39 -0500, Pepito rearranged some electrons to form:

Mass Air system actually measures the quantity of air flowing into the engine using a hot-wire sensor in front of the throttle body, and adjusts the air-fuel ratio.

Speed density calculates the quantity of air flowing into the engine based on air temperature, manifold vacuum/pressure, engine RPM, and other factors.