: Idle seems rough.



onecad
02-03-04, 09:06 AM
I have just put in a starter and now that everything is together my idle has changed. On a scale of 1 through 10, 1 being stall and 10 being a smooth idle, the idle on my car would be about a 5.

I cannot hear any air leaks and everything seems to be attatched and plugged in. I checked the lines that run under the intake manifold cover, they all seem to be attatched, pcv valve etc.

The car runs fine while driving, and the idle seems not too bad while in park, but when the car is in drive and my foot is on the brake is when it is very noticeable.

Anyone have any ideas?

BeelzeBob
02-03-04, 01:10 PM
I have just put in a starter and now that everything is together my idle has changed. On a scale of 1 through 10, 1 being stall and 10 being a smooth idle, the idle on my car would be about a 5.

I cannot hear any air leaks and everything seems to be attatched and plugged in. I checked the lines that run under the intake manifold cover, they all seem to be attatched, pcv valve etc.

The car runs fine while driving, and the idle seems not too bad while in park, but when the car is in drive and my foot is on the brake is when it is very noticeable.

Anyone have any ideas?

You just put in a starter on a Northstar and now it idles rough??? The intake is not sealed correctly to the cylinder heads and there is a vaccum leak at one or more cylinders. You had the intake off to do the starter and something did not line up correctly when it went back together.

zonie77
02-03-04, 01:12 PM
Have you checked for any codes?

The two things I can think of are:
1) The gaskets may be old enough that they didn't seal and need to be replaced. Even though you can reuse them they don't last indefinitely. Try spraying starting spray around the intake and see if the idle speeds up. That finds a small vauum leak.
2) Taking the intake off may have loosened some carbon and allowed it to get into the EGR and it may be open slightly. You may have to take it off and clean it.

BeelzeBob
02-03-04, 01:20 PM
I have just put in a starter and now that everything is together my idle has changed. On a scale of 1 through 10, 1 being stall and 10 being a smooth idle, the idle on my car would be about a 5.

I cannot hear any air leaks and everything seems to be attatched and plugged in. I checked the lines that run under the intake manifold cover, they all seem to be attatched, pcv valve etc.

The car runs fine while driving, and the idle seems not too bad while in park, but when the car is in drive and my foot is on the brake is when it is very noticeable.

Anyone have any ideas?

It helps if you include the year and engine and type of car....they all run together after awhile if you mentioned it before...

But, wasn't it a 94..???

If it was a 93/94 Northstar then there are the phenolic spacer plates that isolate the intake from the cylinder heads. Those plates have the passages for the PCV and EGR distribution to each port/cylinder. As an aside, it would have been a great opportunity to clean the EGR passages out when the intake was off...it is a necessary service item on a 93/94 after 100K usually. In any case, the phenolic plates have formed in place dowel pins that line up with holes in the head and the intake assembly. If those are out of place the surfaces will not line up and there will be a vacuum leak. I think you need to loosen the four hold down bolts and pop the intake up again to check. While at it, take the phenolic plates out (one per side) and clean the passages and check the gaskets/seals. They are reusuable but could be cut or damaged from handling during the repair. You can repair any uncertainties or cuts or damage to the seals with orange (high temp) RTV. Just use a dab locally on the problem area at reassembly. Don't forget to clean the small machined notch at each port (the mouse hole) that is machined into the parent metal of the cylinder head itself at each port.

onecad
02-03-04, 04:54 PM
Thanks for the replies,
Yes the car is a 94 eldorado with the 4.6 northstar.
When I lifted the intake manifold, I was careful enough that I never disturbed the gaskets. At any rate I still ensured when I put the manifold back down that they were in place according to the positioning notches.

As I mentioned it only seems really noticeable while it is in drive with my foot on the brake, so would it be worth while to spray anything in around the seal to detect a rise in idle????

The gaskets seemed to be in good condition as I looked over them, but without removing them, maybe I will buy a couple new ones and put them on for the hell of it. Do the phenolic spacers lift right off, or are there additional bolts to remove???? (before I go at it again.)

One more question....I don't remember but are those seals between the intake and phenolic spacer a quantity of 2 per side or 1 per side?

thanks
joe

BeelzeBob
02-03-04, 11:52 PM
Thanks for the replies,
Yes the car is a 94 eldorado with the 4.6 northstar.
When I lifted the intake manifold, I was careful enough that I never disturbed the gaskets. At any rate I still ensured when I put the manifold back down that they were in place according to the positioning notches.

As I mentioned it only seems really noticeable while it is in drive with my foot on the brake, so would it be worth while to spray anything in around the seal to detect a rise in idle????

The gaskets seemed to be in good condition as I looked over them, but without removing them, maybe I will buy a couple new ones and put them on for the hell of it. Do the phenolic spacers lift right off, or are there additional bolts to remove???? (before I go at it again.)

One more question....I don't remember but are those seals between the intake and phenolic spacer a quantity of 2 per side or 1 per side?

thanks
joe

The phenolic spacer plates just sit on the heads when the manifold is loose so they could have EASILY been dislodged while working on the starter. You shouldn't need need gaskets or seals. Just spot repair with the RTV as mentioned. There is a seal on the top and bottom of the phenolic spacer plate. One between the plate and the head and one between the plate and the manifold. The gaskets are different top and bottom of the plates but are common side to side. There is one phenolic spacer plate per side and they are identical...they are interchangable side to side. No more bolts in the plates....just remove the 4 bolts that hold the manifold down and lift the manifold up....the plates just life off.

zonie77
02-04-04, 11:25 AM
The starting spray lets you know you have a leak and where and it's easy to do so I would try it. If you know where the leak is (assuming you have a leak) you can either use some RTV as bbobynski suggested or replace them if they seem hard or distorted. They are 10 yrs old so even though they should be reusable but they can get distorted or nicked.
If you pull it off you should take off the spacers and clean the passages. Bbobynski is right that you probably hit them without realizing it. Pretty hard to work in there and never touch them Even lifting and replacing the intake would have moved them slightly.

BeelzeBob
02-04-04, 11:41 AM
If you spray anything around to search for leaks use water....water is not flammable and will plug the leak momentarily and give an indication that there is a leak just like any other liquid...much safer and less chance of damaging plastics and insulation, etc. with strong solvents meant to be used only on metal.

zonie77
02-04-04, 11:48 AM
I never tried using water to find a leak. Try it and let us know how it works.
If you use starting spray you do not need a lot.

onecad
02-04-04, 02:39 PM
So given that the unstable idle is only really noticeable while the car is in drive with my foot on the brake and slightly noticeable while in park idling, this is definetly a vaccuum leak???

Wouldn't the unstable idling and driving condition both be unstable with a leak??? Or wouldn't one atleast assume the idle condition be the same while its in drive idling as it is in park iding??

I just don't want to have to remove the intake again without going over any other possibilites first since the intake removal is a lot more work. I'll check the egr first. But there is nothing else that could possibly cause this condition during the removal of the intake?

thanks
Joe

BeelzeBob
02-04-04, 03:47 PM
So given that the unstable idle is only really noticeable while the car is in drive with my foot on the brake and slightly noticeable while in park idling, this is definetly a vaccuum leak???

Wouldn't the unstable idling and driving condition both be unstable with a leak??? Or wouldn't one atleast assume the idle condition be the same while its in drive idling as it is in park iding??

I just don't want to have to remove the intake again without going over any other possibilites first since the intake removal is a lot more work. I'll check the egr first. But there is nothing else that could possibly cause this condition during the removal of the intake?

thanks
Joe

A vacuum leak is going to cause more problems at the highest vacuum levels and when the engine is most unstable in terms of combustion...i.e....at idle

There are a LOT of things that can cause a rough idle....since you just started getting the rough idle after you had the intake off and on it is logical to start there.

You didn't work on the EGR valve in the process so if it is the problem it is a highly unlikely coincidence that it suddenly failed or started to cause problems now....

The part of the EGR system that you disturbed is downstream of the EGR valve so debris wouldn't go to the valve to stick it open from where you worked. A piece of carbon would have to go thru the combustion chamber and then up the EGR delivery tube to the valve to stick it...not likely.

Check the intake, I'll bet that one of the phenolic spacers or gaskets is out of position and that there is a vacuum leak.

BeelzeBob
02-04-04, 03:52 PM
BTW.....idle park is more susceptable to a vacuum leak than idle drive due to the fact that there is less load on the engine in idle park/neutral. The less load on the engine and the higher the vacuum the more susceptable the engine is to a vacuum leak causing roughness. compare to a very low vacuum point (high thru put) the amount coming thru the vacuum leak is so small compared to the overall flow that it basically doesn't matter. At high vacuum (low thru put or low flow thru the engine) the amount thru the vacuum leak is a high percentage of what is going into the engine.

onecad
02-04-04, 06:06 PM
Another question.....when i try to start the car, from the time I turn the key to the time the starter cranks is about 3 to 4 second. Is there any reason for this, or is it because the solenoid in this used starter that I put in going bad?
I know my old starter always use to crank over almost immediatley from what I remember.
In case you guys think this is the starter I'd like to know now while I have the intake off again.

thanks for all the help,
joe

onecad
02-05-04, 11:07 AM
Something else I should mention, because I changed my starter, hence my other ongoing post....lol, I had to disconnect my battery. Which means the pcm would have reset right?? Does this not mean I would "possibly" have to do the TP Sensor/Idle Learn procedure????? (which I cannot do because its like -17 outside)

Or is this irrelevant?

zonie77
02-05-04, 02:24 PM
I would suspect the used starter. If it works ,even with the delay, I'd cross my fingers and wait for it to warm up a little (like May!). Where are you?

BeelzeBob
02-05-04, 02:43 PM
Something else I should mention, because I changed my starter, hence my other ongoing post....lol, I had to disconnect my battery. Which means the pcm would have reset right?? Does this not mean I would "possibly" have to do the TP Sensor/Idle Learn procedure????? (which I cannot do because its like -17 outside)

Or is this irrelevant?

You don't have to do any sort of learn procedure.

The idle speed control "learns" the offset required due to the gradual buildup of deposits around the perimeter of the throttle blade sealing off the air flow at idle. So, over time the throttle has to be opened a little more...or a little more bypass air is necessary on the 96 and later engines... and the PCM remembers this. This value is reset when the battery is disonnected. If the throttle body is clean this is a non-issue. If it was dirty, then you might notice some lower idle speeds at first until the system adapts. But it doesn't affect idle quality...the shaking and roughness you report. In any case, after the engine has idled 5 to 10 seconds the PCM will correct the idle speed so this should not be an issue in your case.

onecad
02-05-04, 03:30 PM
I am in Ontario, Canada.

I guess my only option is to take the intake off. I will do so and report my findings and results.

Is it ok to drive the car this way for a few days????? I may not be able to get to removing the intake for a couple of days.
thanks Guys,
Joe

onecad
02-07-04, 12:25 PM
Not to be repetative.....but I would really like to know if it is ok to drive my car for a few days with a small vaccuum leak in the intake manifold seal??

thanks

zonie77
02-07-04, 09:13 PM
I would drive it reasonable distances with a small vacuum leak. Commuting 10-20 miles shouldn't be a problem. I would avoid a cross country trip.

onecad
02-09-04, 10:23 PM
problem solved.....

I removed the intake, and the phenolic spacers, cleaned up all the carbon and the mouse holes in the cylinder head. There was a wack of carbon build up.
There were certain parts on one gasket that needed some rtv which I fixed and evrything seems fine. There is no unstable or fluctuating idle now.
The mouse holes were jammed full of carbon, and I am surprised that the problem wasn't worse because of that, since until I removed the intake manifold the first time to replace the starter it seemed to run fine.

Thanks for all the help....by the way, I have taken pictures with my digital camera to aid those who may, or will be in the same predicament I was. So if there is a place for me to upload these pictures I would be more than happy to.

We need a place to do this, it would be convenient if there was a break down of individual repairs to which pictures can be uploaded specifically to that "section", which people could access when needed. I think it would strongly help those who are new to any specific repair, and cut down on the searching aspect of this forum, since any diagrams or pictures seem scattered, which can be tedious and time consuming to search for.
Just my opinion....this is a great place to receive help, and save money.

Thanks again, Joe