Testing cat for clogging

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Aug 11, 2005 | 11:21 AM

#16

pfogle

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From: Oak Harbor, OH

You said the intake leaks.. Is this a vacuum leak or coolant leak? If it's a vacuum leak it can do all sorts of nasty things.. Burning pistons comes to mind. When you did the timing chain, did you go ahead and replace the plugs/cap/rotor? Have you replaces the fuel and air filters? These may sound like little things, but if they're all old and breaking down they can cause a nasty mess. Don't be afraid to spend money on igntion parts, the ignition system is a vital part of your engine. A typical plug/wire/cap/rotor usually costs us around $125 in parts (motorcraft plugs, napa premium wires [59.99], and napa's high end cap/rotor). You've already done the O2 sensor so that's not a problem... We have an '88 Club Wagon with a 302/AOD (4 speed auto) that is a pig, but she's also got 300,000+ miles on her. It still gets 16mpg tho.

Aug 11, 2005 | 11:40 AM

#17

Dannym

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Air filter and fuel filters have of course been changed over the years.

How could an intake leak be a problem in a MAP system? The computer calculates fuel based on pressure and temp and a vague notion of the throttle position. In an MAF system, you'd have air coming in that was not counted by the MAF sensor but in a MAP system the only thing is it wasn't totally predicted by the throttle position sensor- which was never very accurate in the first place.

It's not that I wouldn't like to do it, but getting that intake manifold off looks difficult on this engine and WAY more difficult with the engine being in this E150 van. There's little room to work around it. I don't know if I would only need to change the upper-to-lower intake gasket or the lower-to-engine gasket. I don't even want to think about what it would take to access the lower one.

The only reason I know it leaks was there was a mechanic who squirted some carb cleaner or something around the intake gasket- upper-to-lower I believe- and the idle changed speed.

Aug 11, 2005 | 12:56 PM

#18

pfogle

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From: Oak Harbor, OH

The MAP sensor in the Ford SD EFI system does a lot more than you think. I don't think it's an issue with the computer not controlling the mixture, I think it's more likely that the vacuum leak is causing a miss at idle, and leaning the mixture way out at higher rpms. Prolonged driving with a leak like that can burn pistons (due to the higher heat in the buring of the leaned out fuel/air mixture). I'd get that fixed before I went messing with the cats. It's really not that bad at all. The upper intake (runners/TB) comes off with 6 bolts, there is one that's torx right in the middle.. That's one can be a pain. We've done a few of 'em..

Aug 11, 2005 | 01:31 PM

#19

Dannym

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It is a vac leak. There is no coolant leak. Would all lower intake problems appear as a coolant leak?

Should I even consider messing with the lower then? Is there an easy way to test it?
How high does the manifold need to be lifted to get it off the bolts? There is not a lot of space here. While I don't have the picture in front of me, does any of the other stuff- throttle, EGR- have to be removed to get at the gasket?

Last edited by Dannym; Aug 11, 2005 at 02:03 PM.

Aug 11, 2005 | 09:50 PM

#20

pfogle

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From: Oak Harbor, OH

The throttlebody can just be unhooked (it has coolant lines hooked to it and a connector on the TPS), and the EGR has to be unhooked. It's not difficult at all to do. it looks like one big monster intake, but it's actually two pieces. Upper and Lower, the upper bolts to the lower, and is only held on by 6 or 8 bolts. The center one can be tricky as you need 12~16 inches of extension and a ratchet to get at it. If you pull the engine cover (or doghouse, or whatever you call it) off you will see that it's all pretty accessable.

Aug 12, 2005 | 11:50 AM

#21

Dannym

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This finally looks like the opportunity to fix my valve cover gaskets too that I was waiting for. They've been leaking ever since I got it but the work needed to fix that right one is just silly. Taking off the intake is all the work.

What do I do about the EFI rails? Where would I unhook it if I have to pull the lower intake?