I removed the top manifold, and screwed up somewhere - Muscular Mustangs
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post #1 of 19 Old 11-16-2007, 04:53 PM Thread Starter
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I removed the top manifold, and screwed up somewhere

On my 1990 Mustang 5.0 I removed the top manifold, to replace the Valve covers, after it was all back together, the idle is all screwed up, any Idea's?

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post #2 of 19 Old 11-16-2007, 07:05 PM
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It may be as simple as this:
https://www.muscularmustangs.com/idlereset.php


If not try this:
https://www.muscularmustangs.com/iac.php

'87 GT with a battery
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post #3 of 19 Old 11-16-2007, 08:55 PM
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It's likely that you left the IAC unplugged, forgot to hook a vacuum line back up, or the upper to lower gasket may not be sealing correctly. Try looking around and see if you can hear any vacuum leaks.



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post #4 of 19 Old 11-17-2007, 02:56 PM Thread Starter
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I don't hear any leaks. can't see any Vac lines not hooked up. A strange thing though, someone told me to disconnect the battery, then hook it up again, I did and is doing different things, like when starting it cold, couldn't idle, had to keep it reved up for a while till it got warm, then idled very low, like 6-7 rpm. still running rough at low rpm, smoths out at higher. Why would removing the oil filler cap reduce the rpm's, isn't the enging breathing properly?

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Originally Posted by quick5pnt0
It's likely that you left the IAC unplugged, forgot to hook a vacuum line back up, or the upper to lower gasket may not be sealing correctly. Try looking around and see if you can hear any vacuum leaks.

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post #5 of 19 Old 11-17-2007, 03:06 PM
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Quote:
Originally Posted by pfhannan
I don't hear any leaks. can't see any Vac lines not hooked up. A strange thing though, someone told me to disconnect the battery, then hook it up again, I did and is doing different things, like when starting it cold, couldn't idle, had to keep it reved up for a while till it got warm, then idled very low, like 6-7 rpm. still running rough at low rpm, smoths out at higher. Why would removing the oil filler cap reduce the rpm's, isn't the enging breathing properly?
Well you are going to get weird things happening when you disconnect the battery because the computer then needs to relearn certain things such as where to place the idle.

As for the oil cap thats pretty weird. Have you ever changed the PCV valve and the mesh screen underneath it? It could be that they're really clogged (very common) which is causing that but I don't think that would be your overall idle problem.

I never asked, what exactly is the idle doing? Is it too high? Or too low? Or surging?



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post #6 of 19 Old 11-17-2007, 03:28 PM Thread Starter
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The reason I changed the Valve covers in the first place was because the previous owner put some aftermarket covers, and he gave me the stock ones, so I put them back, want this car as original as possible. Now he had a PCV valve going into the valve cover, but that now is gone, so I don't know where another is??

Quote:
Originally Posted by quick5pnt0
Quote:
Originally Posted by pfhannan
I don't hear any leaks. can't see any Vac lines not hooked up. A strange thing though, someone told me to disconnect the battery, then hook it up again, I did and is doing different things, like when starting it cold, couldn't idle, had to keep it reved up for a while till it got warm, then idled very low, like 6-7 rpm. still running rough at low rpm, smoths out at higher. Why would removing the oil filler cap reduce the rpm's, isn't the enging breathing properly?
Well you are going to get weird things happening when you disconnect the battery because the computer then needs to relearn certain things such as where to place the idle.

As for the oil cap thats pretty weird. Have you ever changed the PCV valve and the mesh screen underneath it? It could be that they're really clogged (very common) which is causing that but I don't think that would be your overall idle problem.

I never asked, what exactly is the idle doing? Is it too high? Or too low? Or surging?

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post #7 of 19 Old 11-17-2007, 04:11 PM
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That's likely the problem. On a stock Mustang the PCV valve is on the back of the engine in the lower intake manifold. It's possible that he got rid of that one altogether and plugged up the hole.

Usually if you look at the back of the lower intake manifold you'll see a rubber hose going to the pcv valve and underneath that is a mesh screen. It's usually pretty hard to see because of the upper intake but you can get to it with the upper intake in place.

I've got a diagram attached below, but I'm not sure how useful it'll be because it doesn't show where the pcv hose goes. BTW that diagram is showing the rear end of the engine.



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post #8 of 19 Old 11-18-2007, 09:34 AM Thread Starter
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I can not see the PCV valve on the back of the engine in the lower intake manifold. your diagram is so small I really can't see it. I can send you a pic of what I can see it this would help.
paul
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Quote:
Originally Posted by quick5pnt0
That's likely the problem. On a stock Mustang the PCV valve is on the back of the engine in the lower intake manifold. It's possible that he got rid of that one altogether and plugged up the hole.

Usually if you look at the back of the lower intake manifold you'll see a rubber hose going to the pcv valve and underneath that is a mesh screen. It's usually pretty hard to see because of the upper intake but you can get to it with the upper intake in place.

I've got a diagram attached below, but I'm not sure how useful it'll be because it doesn't show where the pcv hose goes. BTW that diagram is showing the rear end of the engine.

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post #9 of 19 Old 11-18-2007, 09:36 AM Thread Starter
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More symptoms

When driving, the idle is so low when not accellerating the car is bucking.
paul



Quote:
Originally Posted by quick5pnt0
That's likely the problem. On a stock Mustang the PCV valve is on the back of the engine in the lower intake manifold. It's possible that he got rid of that one altogether and plugged up the hole.

Usually if you look at the back of the lower intake manifold you'll see a rubber hose going to the pcv valve and underneath that is a mesh screen. It's usually pretty hard to see because of the upper intake but you can get to it with the upper intake in place.

I've got a diagram attached below, but I'm not sure how useful it'll be because it doesn't show where the pcv hose goes. BTW that diagram is showing the rear end of the engine.

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post #10 of 19 Old 11-18-2007, 07:24 PM
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Click on the pic to enlarge.. And this no PCV thing will cause idle issues, as well poor mileage, sludge build up, poor vaccume.....

'87 GT with a battery
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