1986 240 DL fluctuating idle

[93Regina]

What about IAC?

IAC is possible...but, throttle plate and throttle switch must be to OEM specs, plus, your brake-vacuum booster must not be leaking air into intake, plus, no vacuum leaks into intake.

One needs to fix the cause, not the effect...any vacuum leak can screw the IAC pooch.

[mhgreen]

Just found a crack on the intake manifold.

check valve hose - - -> nipple on bolt that screws into the manifold - - -> crack around the area where the bolt goes into manifold.

I am assuming this is the hissing noise I can hear when I lean down over the manifold while the car idles.

Thoughts?

[93Regina]

..this is the hissing noise...

Semantics...it don't hiss.

Starting fluid (ether) will find any intake vacuum leaks in that area. I use John Deere's starting fluid...they say some of that consumer starting fluid is diluted. WD-40, years ago, had more volatile mixture, but they removed it.

If intake manifold is cracked, get a salvage yard one...might be cheaper than welding it.

[mhgreen]

I already have a "new" manifold. Bought one today after I saw that crack for $10. I figure I should do the manifold gasket and I am going to do fuel injector o rings as well. Any other jobs I should do while I have the manifold off?

[93Regina]

Any other jobs I should do while I have the manifold off?

Clean flametrap....and... Flame Trap Relocation 1983/242...see last post also.

One might use a dab of grease when re-connecting brake vacuum hose...in case you want to do a test to see if brake-booster is sucking extra vacuum.

[mhgreen]

I am going to buy 6 inches of 5/8" pcv hose. Can I just throw the flame trap away? And I don't understand the brake booster test. Can you explain? I recently replaced the booster hose to intake.

[93Regina]

I think most stores sell it in foot size, so buy a foot of 5/8" pcv hose.

I would keep flame trap intact; it also sucks blow-by out of crankcase.

After its put back together, see how it runs. I plug off brake booster, where its inlet is on intake manifold, when tested.

[mhgreen]

UPDATE:

- intake manifold replaced + new gasket

- fuel injector seals replaced (they weren't awful, but while you're in there, what the hell)

- flame trap relocated using 5/8" hose. This was a bit challenging as the hose diameter was a difficult fit on the flame trap side. Ideally, the hose would be ballooned out on one side, but I made it work. Flame trap was clean

- replaced a heater hose while we were in there

- - - - -- - - - - - - - - - - -- - - - - - - - -- - - - - - - - -- - - - - - - - - - -

The car is driving much, much better (and idling better) now that the cracked manifold is replaced. I would say thank you to 'everyone', but really I just need to thank 93Regina. I appreciate the guidance.


Matt

[lummert]

Glad to hear that you got it fixed.