Riddle me this... IAC question...

[jmpSHO]

Just figured I would add my 2 cents. I have an Explorer that had the same exact sympoms when I bought it and the previous owner told me that the IAC was bad. I finally got fed up with the idle issue that I went and bought a new IAC from AZ, which was a mistake. I put the new one in and after about a week I had the same syptoms. I returned it and it happened again. I could never find a vac leak so I once againI returned it and now everything is fine.

 

[raff18]

one way i know to find a vac leak is to take intake clearer can and spray around and if the idle jumps u found a spot if it has a straw that attach's to the spray head use it as it will help pin point the leak

 

[Eric VerValin]

one way i know to find a vac leak is to take intake clearer can and spray around and if the idle jumps u found a spot if it has a straw that attach's to the spray head use it as it will help pin point the leak

He's been informed of that, but at the time it wouldn't stay running long enough to even try.

 

[boat]

rgr, Just got done putting it back together, the car now, starts and the idle is still alittle high.... but it now idles at about 500... doesn't die just idles rough... engine shaking....

I don't know what magic Bubba worked, but he said when he left the car, it would run on its own WITH the IAC plugged in. First thing I did when I got to the shop, went to the car with keys, put in the ignition and BLAMO! nothing different than before, runs up to 2500 rpm then stalls. The idling he is talking about, is what it is doing with the IAC unplugged, but I saw it at around 1300.

I had a car guy stop over last night, He has me start it up, he plays with the throttle keeps it running around 2k, he listens, we shut the car off, and he said, "I can tell you that it is where your intake is meeting the heads. Take your 10mm and pop that intake off, put some RTV on those metal gaskets, and that should fix your problem." I pointed to the couplers, and other vac lines and asked if those could be the problem, he said with no hesitation "No."

This guy has worked around cars his whole life 44, last 25+ years of his life, old school and currently restoring a 67 camaro and 67 mustang fastback. What really really blew my mind, he has never worked on a SHO and knew those were 10mm bolts on the intake.

Something else I thought of, is that maybe the metal gaskets have that raised portion in the middle of all the openings to the heads and intake, my thought is maybe they are upside down and backwards, not sure how, but something to check.

NOW don't tongue lash me here, I had places to go last night and couldn't get to any of this to check it out.

I am going to check those gaskets tonight and see how they are oriented and using the best pair I have, then try the RTV (black), and THEN get the vac tester Bob recommended. I really don't have anything to lose trying those 2 things first.

Having used stock metal gaskets many times over and over, with paint chips, without paint chips, and sometimes cleaned up, repainted and used over again, I can safely say that the gaskets probably aren't the issue. At least not a big enough issue to cause the problems he's having.

This is kind of what I thought, too. That shouldn't be enough of an air gap with missing paint to cause it not to stay running. The gaskets I HAD on there, the ones Bubba took out, are the newest that I have, and they are not in as bad of condition as portrayed.

 

[Bob Gervais]

I would definitely not use RTV on them, unless you're just going to brush on a very thin coating with an acid brush or something.

They can be cleaned up with carb cleaner, brakleen, or something like that, and then resprayed.

Because of the dowel pins that locate the intake, and the gaskets, there is only one way to put them on there so that shouldn't be the issue.

Personally, I'd grab a vac gauge from Autozone or something and check that first, before tearing into things.

 

[boat]

Ok. I was thinking after I posted all of that I probably should just get the vac gauge first, like you said.

I would definitely not use RTV on them, unless you're just going to brush on a very thin coating with an acid brush or something.

They can be cleaned up with carb cleaner, brakleen, or something like that, and then resprayed.

Because of the dowel pins that locate the intake, and the gaskets, there is only one way to put them on there so that shouldn't be the issue.

Personally, I'd grab a vac gauge from Autozone or something and check that first, before tearing into things.

EDIT: The car guy did say a thin coat of RTV, not gloping thick. Will do the vac test first, tho

 

[Bob Gervais]

Ok. I was thinking after I posted all of that I probably should just get the vac gauge first, like you said.



EDIT: The car guy did say a thin coat of RTV, not gloping thick. Will do the vac test first, tho

Thin coat is good, paint is faster. I'd use whatever you have on hand, to save time.

 

[bubba]

Bob there's paint at the shop... just not black... should I strip them and paint them? or should you just paint them? I agree that he should just put the vac gauge on it.... I'm pretty sure it's where we pointed it to in the first place!

Thin coat is good, paint is faster. I'd use whatever you have on hand, to save time.

 

[SuperHO]

so it's not crank cancer...maybe it's lupus?

 

[Eric VerValin]

If your gaskets are fine like you say,then why are you considering RTV'ing them? And the only reason I pick about the gaskets are because Bubba told me they weren't all that straight, not to mention the paint. Then your friend says its where the intake meets the heads.... where else could it be? I guess the gauge will tell the tale...


Otherwise, I'm starting to think it's crank cancer too... lol

 

[Bob Gervais]

Bob there's paint at the shop... just not black... should I strip them and paint them? or should you just paint them? I agree that he should just put the vac gauge on it.... I'm pretty sure it's where we pointed it to in the first place!

Nope, no need to strip them. Spray them with the cleaner, let them dry, and shoot them with the paint. Heck, it's almost the holiday season, candycane 'em if you have red and white.

 

[boat]

I think it is my SHO's brother, Murphy, stepping in to give his .02...

so it's not crank cancer...maybe it's lupus?

 

[bubba]

Got both of them.... thanks man!

Nope, no need to strip them. Spray them with the cleaner, let them dry, and shoot them with the paint. Heck, it's almost the holiday season, candycane 'em if you have red and white.

 

[Bob Gervais]

You know, of course, we'll need pics of the candycane intake gaskets!

 

[boat]

I took a bunch of pics last night and was going to upload them to SHO Speed, but for whatever the reason, I couldn't log in due to an Internal Server Error and Photobucket is not accessable to me at work either. No internet at home either.

I got the vacuum pressure tester, but at first wasn't sure how to use it.

So I proceeded with taking the intake off. I cleaned all of the surfaces. The heads, the best set of gaskets I had, and the intake itself. The gaskets had no paint missing that I could tell. There was some sticky stuff on them, but I emptied out about half a can of Brakleen on them, they came out pretty clean. And they lay nice and flat, with just very little raising up on the ends. By the time the intake is put on, these end get flattened out. Even made sure we had the right torque values on the intake to the heads.

I put it all back together, and got the same results. I did finally read the directions for the vac tester (helps if you read instructions sometimes ). I plugged it into the port on the intake right by the IAB, unplugged the PCV hose from the intake, plugged it like the instructions said. The instructions called out to have the IAC unplugged, did that. Then, I started the car, even idling at 1250, I got a reading on the gauge of: (well I tried to put a pic up here as an attachment, but by the time I resized it, one cannot even read the gauge in the picture).

I got a reading of 17 In Hg, I really don't know what this means. Could someone explain this to me? What should I get as a reading?

I have not done anything with RTV at this point.

So, what's next? Running out of things to check.

 

[Bob Gervais]

In-Hg is simply a pressure/vacuum value, much like PSI is to pressure.

Normal readings for a normal operating temp, good condition engine with no vacuum leaks should be about 18-21 Hg-In. Yours is a little low, but could be just inaccuracy in the gauge.

At this point I'd check the obvious stuff: All 4 screws in the DIS, all ground points of the intake attached, all hoses attached and not cracked or leaking, spray brakleen around vac lines and manifold and watch for idle speed changes.

I forget at this point, but have you ran the codes yet? Maybe a KOER will reveal something.

 

[Eric VerValin]

Damn I was close.. lol I was thinking 17-21 was about "normal". Hey Boat.. did you try to snap the throttle at all when you had that tester hooked up? It should "snap" nice and quick.. It'll get up to 25 or so, snap to 5ish then pop right back to your 17. I would almost imagine you could google this for a video of it... someone probally posted one up somewhere. Probally not a SHO but the guage works the same way in other cars too.


Time to pick your brain a little Bob... would his reading maybe a little low be partially from the valve seats, and or guides being "normally worn" a little ? Is there a way to plug the intake and do a leak down type of test on the intake? How long do you have that guage for Boat? Maybe try testing it out on my car to see how close to "normal" your at.


And.... what do those clamps look like on all your hoses... I forget... you may be losing some vac where those old factory crapo clamps are.. for a couple of bucks you can put some real ones on there and maybe tighten those up a bit. Could also cut some of those hoses back an inch or so, so they fit tight again...


Also... maybe try talking some smack to your car... tell it your thinking about selling it and see if it dosen't act right... lol I swear I gotta start talking about my 3lb hammer before my car cooperates sometimes..

 

[Bob Gervais]

Time to pick your brain a little Bob... would his reading maybe a little low be partially from the valve seats, and or guides being "normally worn" a little ? Is there a way to plug the intake and do a leak down type of test on the intake? How long do you have that guage for Boat? Maybe try testing it out on my car to see how close to "normal" your at.

Eric, it's very possible that a worn engine would be a little askew from what is considered a "normal" reading. Also, as I mentioned above, there's always inaccuracy in any gauge. The cheaper the gauge, the higher the percentage of inaccuracy. He's not that far off from a normal reading, so I'm really thinking at this point that his problem lies elsewhere, but it never hurts to do the spray check for minor leaks. Also, the snap test like you mentioned is helpful, as well as watching the needle to see if it's jumping around or not. Usually a weak cylinder will make the needle jump around, indicating valve or piston ring damage.

Your idea about the hoses is a good one, they harden up and take a set over time, and can often be a source of minor leaks.

Leakdown testers are great, if you have the time and effort to put into using them. Especially if, for example, you're swapping in a used motor and want to check the condition.

http://www.carcraft.com/techarticles/116_0406_cylinder_leakdown_tester/index.html

This is a pretty good article on leakdown testers, fyi.

 

[rubydist]

I would not expect idle vacuum readings to be a little low due to 'normally worn' valve guides and/or lands because at idle I would expect the valve springs to fully close the valves even if the guide was a little sloppy.

It is more likely that there is a small but significant leak in one of those vacuum lines that was mentioned, especially since it showed up after the intake was off and on.

Since the iac was unplugged, and you have said that the engine will sort of idle with it unplugged, I would have expected a vacuum reading similar to what you got. I'd like to see what the vacuum gauge says when you plug the iac in and start the car. My guess is that the vacuum will not get to 17 until after the engine has rev'd to 2500 or whatever it goes to, because the apparent leak plug the iac opening will allow too much air for that.

I think its time to let it idle and carefully spray around all the vacuum hoses with starting fluid, to try to find a leak.

 

[boat]

All 4 screws are there for the DIS, all grounds (one at the back, 2 at the cross over tube, one by the IAC, and the one that holds up the heater core line), the hoses need to be checked. I did try to spray the brakleen around the manifold, but I was not entirely sure where to spray, as nothing changed much.

Where should I spray around the intake? Where are the vacuum hoses? Like the ones for the butterfly's, the big one on the back of the intake, the PCV hose to the bottom of the TB? Are there any others I should spray around?

I ran the codes on Sunday. I got 111 and 542. I know that both of those, the one is everything is good, the other is secondary fuel pump failure, Eric and I reduced that one to that it threw that code because it died while running.

Now, I when I replaced the coolant distrubuition housing on the back of the engine, I unplugged a bunch of electrical stuff, but I checked and rechecked all of that, too, it is all plugged back in, no lose connectors or anything. Did this to move the fuel rail enough if the cross over tube came out when I pulled that old housing out and it did come out of the water pump. Put the new o-rings on the ends of that tube, and put it back together also.

Could any of that be causing the issues I am having now?

In-Hg is simply a pressure/vacuum value, much like PSI is to pressure.

Normal readings for a normal operating temp, good condition engine with no vacuum leaks should be about 18-21 Hg-In. Yours is a little low, but could be just inaccuracy in the gauge.

At this point I'd check the obvious stuff: All 4 screws in the DIS, all ground points of the intake attached, all hoses attached and not cracked or leaking, spray brakleen around vac lines and manifold and watch for idle speed changes.

I forget at this point, but have you ran the codes yet? Maybe a KOER will reveal something.