Oil Cap Removed No Engine RPM Drop Anymore??

GrowIt · 06-21-2005, 01:13 PM

1988 3.2 75K all maintanence up to date, wires, plugs, cap & rotor etc.: I noticed this weekend when I checked the oil, engine RPM did not drop and run rough (lean). In the past it would run rough (lean out) when the oil cap was removed. I am not sure how long it has not leaned out when cap is removed but noticed it this time (car does not leave the garage enough). Any guesses on what this is telling me? Car seemed to idle and run fine. Any thoughts? Thanks ahead for any starting places to check.

einreb · 06-21-2005, 01:21 PM

Quote:

Originally posted by GrowIt
Any guesses on what this is telling me? Car seemed to idle and run fine. Any thoughts? Thanks ahead for any starting places to check.

Just so I understand this correctly... when you remove the cap, the car idles and runs fine? I'd take it to a dealer ASAP for a fluid flush and fresh muffler bearings. It sounds like your engine could go any minute.

I don't think you have anything to worry about

GrowIt · 06-21-2005, 01:28 PM

Thanks for the fast answer. With the cap on and out on the road, the car idles and seems to run fine. With the cap removed no change in idle or smoothness. It used to idle rough and rpm would drop when the cap was removed.
Not ready for that engine rebuild yet.

Bill Verburg · Bill Verburg's Garage

Sounds like you may have a leak of unmetered air else where in the system, which has beeen compaensted for by some other means.

The oil vent system should be a closed system that affects idle when opened.

GrowIt · 06-21-2005, 01:35 PM

Bill, Thanks. Any guesses where to start or should I just open the manuels up and start searching. I felt this might be the case, but did not want to create a problem when there was not one.

Bill Verburg · Bill Verburg's Garage

It's got to be down stream of the throttle body

GrowIt · 06-21-2005, 01:41 PM

Great, will start there. Thanks again

einreb · 02:07 PM

Quote:

Originally posted by Bill Verburg
The oil vent system should be a closed system that affects idle when opened.

True, but shouldn't the idle then pick back up and remain steady? Thats what mine does.

the only time I had trouble was when I mistakenly threw away my air restrictor valve when i replaced my breather hoses. If he wants a rough idle... that will do it for him

.

Bill Verburg · Bill Verburg's Garage

Quote:

shouldn't the idle then pick back up and remain steady? Thats what mine does

Mine too but it would depend on the DME parameters being used, my chip is set up rich so extra air leans the idle out a little at slightly higher rpm.

GrowIt · 06-21-2005, 02:40 PM

I know mine used to lean out when the cap was removed creating the open oil vent system = lean mix, rough idle. Saturday when the cap was removed no rough idle, no lean mix. Which means my oil vent system is always open even with the cap on or not opening with the cap removed. I do have a Steve W. chip in there. RPM stays at 900 with cap on or off.
A few months ago I was in there replacing fuel injectors, rear fuel line, fuel regulators etc.. Maybe I knocked something lose. Thanks again for all input.

No - I prefer my smooth running engine.

jbrinkley · 06-21-2005, 02:59 PM

not the greatest but in case you need it

GrowIt · 06-21-2005, 03:26 PM

Thanks, Jerry. I printed it to have on hand. Thanks.

pa911 · 06-21-2005, 05:12 PM

I just noticed the same thing with my 3.0 cis last week,I took the oil cap off and idle remained constant.

rbcsaver · 05:32 PM

Quote:

Originally posted by einreb
Just so I understand this correctly... when you remove the cap, the car idles and runs fine? I'd take it to a dealer ASAP for a fluid flush and fresh muffler bearings. It sounds like your engine could go any minute.

I don't think you have anything to worry about

The person that asked for HELP, had a legitimate question and request. I too have been there on line all the way back to "Porchephiles." This person, known via the einreb acronym responds with a non-helpful BS remark about non-exsting "muffler bearings" The post by "einreb" about "muffler bearings" and other nonsense has been posted by einreb and others on Pelican and Rennlist. It is not helpful, contributes nothing and only sucks bandwidth resources.

First of all. if someone needs help there is no need for Ahole. BS remarks. Everyone needs help from time to time. As my mother used to say when I was young... If you have nothing good to say, then say nothing of STFUp!
And if you celieve in your post then have the B's to sign your name after your post.Otherwise, it is just like unsigned newspaper editorials!

To the question posted,
It sounds like a vac leak via the oil fill cap or an ancillary line. The caps and their rubber seals do wear out.

regards
Steve

regarding

einreb · 06:49 PM

I actually had something good to say to him... I didn't think anything was broken.

GrowIt -my appologies if I sounded like I was belittling your problem.

-Bernie (my username backwards)

87coupe · 87coupe's Garage

I have a small leak at the oil level sender on the oil tank, and have noticed the same (no idle change) behavior. Does anyone think that is the source, or should I keep hunting? TIA

autobonrun · autobonrun's Garage

My idle use to change when I took the cap off also. The only difference I know of is that I know for certain my AAR is now stuck open. Maybe one of the CIS gurus will know if this would be a reason for no change in idle. If so, you may have the same issue.

I'm running so rich with my SSI's that it only showed up as being stuck open in the analyzer printout when I did a dyno test.

jbrinkley · 06-21-2005, 07:18 PM

check this also

Beethoven · 06-21-2005, 07:34 PM

Wow, is Pelican now a joke-free zone? I'm mean it wasn't like GrowIT was stranded somewhere in the middle of the night.
I have the same symptons, btw, but don't think it is a problem.

ChrisBennet · ChrisBennet's Garage

On a 3.2 the computer controlled idle stabilizer valve (ISV) should correct the idle whenever the cap is removal. (A CIS car won't do this.) The ISV just routes a computer controlled amount of air around the closed throttle plate.

The idle is controlled by the computer and as long as the engine "wants" to idle around the programmed idle point things are fine. If the natural/non-compensated idle is too far off from the where the computer wants it to idle, the idle will "hunt" as the computer (using the ISV) tries to "pull" the idle back into range.

When some part of the engine management system is either broken or misadjusted the computer may still be able to compensate for it. It's not uncommon for an "out of tune" 3.2's to idle fine until the weather turns cold for example. The change in the weather is just enough to push the engine's natural idle out of the range that the computer can compensate for.

Air leaks, bad or failing sensors and worn out ISV's can cause idle problems.

-Chris