top end oil leak, somehow related to rough idle?

[GPXSS]

Ive had this horrible problem with the GP since I put the 3.4 in it over a year ago. In a nutshell, on cold starts it has zero low rpm idle resolution. When it idles or warms up, it will either be below 700rpm, or above 2500. It constantly revs way up, sometimes to 4000rpm, then drops down and almost cuts off. It does finally settle down after awhile, and with me nursing the gas a bit.. it will come down to 2000rpm or so. It still idles very rough when it does, like a huge lopy cam.

Anyway, after replacing everything known to man on this thing, it still does it. Yesterday I changed the oil after about 6 or 7 months. I only drive it to the bus stop up the road, and then back to home.. so maybe 2 miles per day. I noticed that the bottom of the engine was oily, something I vowed to not happen after I pulled out the 3.1. I couldnt figure out where it was coming from because I didnt see any area's of leak, the bottom half of the engine/trans was just washed with oil/dirt.

I traced it back up to the oil distribution area in the middle of the V, under the intake manifold. There are puddles of oil behind the distribution block, and it is not from the distributor shaft cap. Whats odd and probably related, when I pulled the plenum a few months ago to replace the injectors, oil literally poured out of the EGR base plate in the plenum. I have also caught a bit of blue smoke on startup which only lasts for a few seconds.

Heres the point of the thread: After changing the oil yesterday and letting it all drain out beforehand, it ran fine this morning.. like it should. It Idled perfectly, and there was no gap in lowrpm throttle at all.. very smooth. In the past it has also done this after letting the car sit for 4 or 5 days without driving it.

[Mach10]

If you've got oil leaking down into your cylinders, it'll make it idle like hammered shit. Do you have any greasy deposits on the plugs?

I'd make sure your PCV isn't pumping oil into your intake (and hence the oil in the plenum).

It's possible you have an oil leak in that crossover. If it's a goodly sized leak, not only will is spit oil, but it'll act like it has a huge vacuum leak too, as the motor pulls fresh air in right by the PCV vacuum port in the "lifter galley"

In fact, make sure that vacuum line is intact. The two problems might not be related.

[HayesPerformance]

Hey GPXSS

Hey GPXSS,

There are many things it could be to be honest. To bad you weren't close by I'd find the problem for you. So there is no check engine light now? Make sure that you have NO EGR at an Idle. That is ONE thing that will also cause it to do what your describing.

Keep us up to date as you check Each of these things and we'll try and help you.

Best Regards,
David

[GPXSS]

list of things replaced:

MAF
TPS
IAT
Injectors
O2 sensor
ECM
Purge solonoid

Fuel pump provides adequate pressure
This is 95 ECM, so trouble codes are only read by a scantool. Yes the SES light is on, No I do not have a reliable way to get the codes. EFI Live says its code P1640: QDM A. I replaced the Purge Solonoid because of that, no change. I have not replaced the TCC solonoid which I beleive Is acting up. I have also noticed that the SES light coming on, and a weird drop in idle while decel are related somehow. Its possible I have 2 problems that are compounding each other.

The car has a problem also with Decel.. as in, it doesnt. While in OD, the car will maintain speed when you let off the gas since the car wants to always idle around 2000rpm (it didnt do this today.. so this is not a throttle plate setting problem). If I am crusing at say 70mph and want to decel.. if I drop it into D, every 5 or 6 seconds its like the trans will catch and for 1 second it will decel.. then it will release and coast again. It will continue to do this down to a certain speed. Also, at certain cruising speeds/conditions, it will shift fine from 1-2-3 up to OD. In 3 or OD, when the TC lockup happens, there is this funny rise and fall in rpms.. like it first disengages a clutch, rpms rise, then locks up and rpm's drop considerably.

Its an odd beast, sometimes makes me want to sell it and get something else.. im just tired of messing with it.

[bszopi]

Should have just kept that 3200 in there...

Glad to see you back, but for some odd reason I doubt you'll be around much.

[Mach10]

Dunno mang, sure stinks like "vacuum leak" to me.

[HayesPerformance]

If the light is on......


If that SES light is coming on, you better find a way to get those codes pulled. know anyone that may have a scanner? It may surprise you as to what is wrong. Any time the SES light is thrown on means that faulty sensor, etc. has finally opperated out of its specified range for a long enough period of time to through a code.

Dave

[GPXSS]

Dunno mang, sure stinks like "vacuum leak" to me.

This was the first thing I checked. I pulled hoses to see what a vacuum leak would do, it actually dropped the idle.. it didnt raise it. While the car is acting up the way it does, it wants to idle very very high. If it finally settles down, its after a few minutes and it still is higher than normal.

This is definitely a sensor/ecm problem though, somewhere somehow, the ecm is telling the engine to idle the way it does. I just havent found out why, or even what is making it do it. (suprise suprise, its not the IAC valve)

[HayesPerformance]

remember

Hey GPXSS,

I can be a problem with the Pig tail that plugs in IAC or he connectors, even the wires to the ECM.

Do you Have a Muli-meter?????

I'll tell you what wires to test and so on.

REMEMBER:
The ONLY air the engine gets to stay running at an idle Comes past the IAC ONLY at an idle!
The IAC CONTROLS THE AMOUNT OF AIR COMING INTO THE ENIGINE AT AN IDLE.
If you were to block the IAC air bypass you would kill the engine.
At an Idle if the IAC opens up a long way it will rev to high heaven.


One thing to note though rough idle does result if there is not only a vacuum leak but also if there is a intake leak some where.

If you want to know if there is ANY SORT of a vacuum leak get a Vacuum Gauge and a "T" conector and hook it into one of the vacuum line going to the intake.
IF IT DOES NOT STAY AT A STEADY GOOD VACUUM WITHOUT MOVING, then YOU HAVE A VACUUM LEAK, SOMEWHERE.

I will help you through all the steps to find the problem IF YOU HAVE THE TOOLS.

Best Regards,
David

[CBR Rider]

GPXSS-

Dido. I tried replacing everything like you to resolve horrible idle. My 3.4L would race to 3-4k after cold start and idle very low when warm. This was very aggravating - it used to run silky smooth.

replaced: EGR, MAF, plug wires, vacuum harness, plenum gaskets, injector orings, etc. Most of these items were in disrepair, but did not fix the core issue.

The key that solved mine was this: teardown the intake [again] and replace the two intake gaskets. Mine aged allowed vacuum leaks right at the intake. My engine started, idled and ran like new immediately after replacment. Hope this helps.