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Discussion Starter #1 (Edited by Moderator)
The 96 starts up just fine, but as soon as it starts it will not hold an idle. It goes to its higher idle and then drops way down and stalls out.
If I hold my pedal on the throttle a little it will not die and run fine. If I let go of the pedal after a couple of seconds it will not die and drive fine.
If I try to start after driving it acts like a crank no start but when forced to idle it starts and dies unless forced to idle further.

This issue started after I changed out my radiator. Everything I find relating to this points to a Vacuum leak, Faulty IAC Valve, Faulty MAF, Clogged Cats, PCM, or ICM. I have no CEL codes.

I recently went through the whole engine for vacuum leaks 2-16-14 also re-checked everything for leaks just in case, and did not disconnect anything vacuum related, except for the BOV, which I reconnected. I had a new IAC already swapped it in does exactly the same thing.

I have a 90mm Lightning MAF and cleaned it with MAF cleaner, still no help. Tried unplugging it and the car revs then dies, rev then dies, repeatedly, continuously.

I am wondering if coolant got on/into the filter and made it to the MAF and ruined it, but doubt that. I don't believe I have clogged cats, the car drives fine, no white chunks.

I have full 2.5" true duels with High Flow Cats put in sometime in 2013. I have never driven it with engine issues.

I have 2 PCM's I can try to but don't believe this is the issue.. The ICM I believe is fine as I had no issues with it before I changed the radiator, checked it previously for no fan symptoms but it works. Also the fuel pressure gauge that's permanently installed reads around 40 psi which is over 35 psi. Also the Tachometer does move, and I checked to see if all the plug wires were plugged in at the plug and the coil and that the coils were also plugged in, they are.

My car has a custom tune, centrifugal supercharger and the Trick Flow intake manifold. I don't recall if it's the track heat or the street burner version.

Any suggestions on further diagnosis?

Mods please move to Engine 4.6
 

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May be the Idol Air Control (IAC) sensor. Mine did funny things like that when it went out.

Also, pull and check the plugs. It wouldn't hurt to replace them.
 

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Propane test the intake manifold gaskets, and sniff around the throttle body, and anything else that has vacuum behind it for leaks.

Brake booster hose is sometimes overlooked when tracking down a vacuum leak. Although, you'd probably hear that one.

Got an EGR valve? Valves gotta' be closed to idle.

Btw, what does your engine idle at?
 

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If you can make it idle with your foot on the pedal, it's the IAC.

It's hanging closed; you might spray it with carb cleaner and bring it back, but I doubt it.

You might have actually fixed all the vacuum leaks; that makes it ride in a different spot than it was at. :)

I'd still check it; it's cheaper to fix a leak.
 

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Discussion Starter #5 (Edited)
Hey I see it seems it is a consensus that the IAC is my issue but the thing is I've already replaced it with a new one, brand new, and it still does the same thing. Also I have the EGR, how do I check it unplug the vacuum line and see if does the same thing, I do have a block off plate to do some testing with that? I also have a spare EGR as well if that s the issue. I do not think it's the Brake Booster that is a big solid vacuum line it has not collapsed or anything like that, not falling apart either. Then as for the plugs and wires http://forums.tccoa.com/showpost.php?p=1502627&postcount=3 changed them in February 2013, again? I use NGK TR6 and AutoZone wires, can swap out whenever and the plugs are $20 but I literally just did that.

It could be the wiring for the IAC, I'll check that tomorrow, I did have to extend it for the trickflow, soldered, but that was while ago like last summer when I bought it for $500, Ian was with me when I met the guy I bought it like a week later and installed immediately. No issues until I changed the radiator, the only wiring I touched was for the Alternator, since it's backwards for the trickflow and in the way. I also had to extend the wiring for the alternator and use a MKVIII alternator because it has the bolts on the top for mounting. Anyone think this could be apart of the cause?

Also it seems to idle at 1000 in P or N and 900 in D or R that doesn't seem normal does it?

http://youtu.be/50mrmgUaUvA

http://youtu.be/XtQlkrSOHSU

So if not the IAC is there anything else that could cause this?

I'm very interested in the propane test and smoke test but really have no idea on how to go about performing it properly with this car. Any links anyone has on a great how to would be greatly appreciated.

Also this is just some extra info just in case but I did have to remove the battery hold down tray it doesn't fit I need to cut it, and I had to cut the metal around the rubber bushings that hold the stock radiator wider and did not put the rubber back in.
 

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Yes, do double check those wires to the IAC.

In the videos you provided, for the engine to die that quickly would have to be a big vacuum leak. Such would be rather easy to find.

It seems like the IAC valve is not opening at all allowing any bypass air. Which would indicate a possible open circuit in the wires causing a dead IAC.

To test the EGR valve get the engine to idle, and apply vacuum to the EGR valve. If the engine dies you know the valve is working properly. The EGR valve should be serviced at least every 60,000 miles.

Yes, 1000 rpm idle speed does sound a little high. Not sure if this might have something to do with the cams you're running, and the tune. May settle down once you get it to idle, and give the pcm time to adapt.

Here is what you need for a propane vacuum tester.



Simply turn the gas on, and bring the hose down to the suspected area. If there is a leak the gas will get sucked into the combustion chamber, and cause an increase in rpm's.

 

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That engine looks familiar; is that an old y-block?
 

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I do not miss carburation... :D

I have 8 carbs to go thru before I have a bike on the road this year. :bawling:
 

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That engine looks familiar; is that an old y-block?
Lets see...The "Y" block got its name because the block extends down below the center line of the crank, and are Ford engines. These engines also have valve cover bolts that go through the top of the cover.

I got that pic from Google Images, and I can barely make out that the distributor is in the back. So I'm going to say that's a 318 Mopar. Maybe even a poly.
 
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