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1988 Ford F250 possible vacuum leak?


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Rob Strunk
Novice

Feb 19, 2013, 7:28 AM

Post #1 of 19 (2314 views)
1988 Ford F250 possible vacuum leak? Sign In

I just bought a 1988 F250 2 wheel drive a couple days ago with a 5.8L. 136,000 miles on it.

The guy I got it from said he thinks it has a vacuum leak. He replaced all the vacuum lines he could reach on top of the engine. He tried a couple other things but I can't remember the names of the parts i believe a computer unit and another small part he showed me.

The one part looks similar to a car radio amp (sorry don't know how else to put it) and on the back it says E8TF-AU1B in small numbers then 8TN in larger numbers. It's a box about 8 inches by about 5.5 inches. And has a place in front where something plugged into it.

The other part is about 4.5 inchs long and a couple inches wide has a plug in in front and 3 prongs on one side. It says Motorcraft E3EF-12A297-A1A.

So he said not to replace those as he already did. but he couldn't still find the problem.

What the truck is doing is at low RPMs it wants to stall and sometime quit while idling.Once driving down the road it has its power but every so often at highway speeds as i let off the accelerator a bit you can feel it kind of stall a little until you get back into the gas. Once you give it gas it seems alright for the most part but still acts up a little. He put new plug wires on it. i don't know why he didn't replace the plugs and distributor cap and rotor but i will be putting those on soon.

Would bad plugs, cap, rotor maybe cause this? No clue how old they are or does this sound like a vacuum leak or maybe something else?

Any advice or direction on what to check for is greatly appreciated.

I forgot to add, when the truck is just idling, the rpms will dive down like it;s going to quit then go back up to normal. It will do this the entire time it's running then sometimes as the rpms dip it just dies. But starts right back up only to keep doing the same.


(This post was edited by Rob Strunk on Feb 19, 2013, 7:31 AM)


Hammer Time
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Feb 19, 2013, 7:35 AM

Post #2 of 19 (2302 views)
Re: 1988 Ford F250 possible vacuum leak? Sign In

The first thing you need to stop doing is throwing parts at it because you will go broke without solving the problem.

Is this basically just an unstable idle problem and runs good at all other RPMs?

Have the computer scanned for stored trouble codes and post the numbers here.



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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



Rob Strunk
Novice

Feb 19, 2013, 7:40 AM

Post #3 of 19 (2296 views)
Re: 1988 Ford F250 possible vacuum leak? Sign In

I just bought the truck so I haven't bought anything for it other than the aformentioned tune up stuff I mentioned and i was going to do that anyway. But that's why I came here. I don't want to throw any parts at it until I can maybe figure it out. When the engine is cold it does cut out at other rpms as well but once it warms up it runs pretty decent but still does cut out similar to the engine "missing" but not real bad. Can you advise me where to get the codes and how much that would cost? thanks.


Hammer Time
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Feb 19, 2013, 7:49 AM

Post #4 of 19 (2289 views)
Re: 1988 Ford F250 possible vacuum leak? Sign In

Do you have access to an analog (needle) type voltmeter or a digital lab scope?



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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



Rob Strunk
Novice

Feb 19, 2013, 7:53 AM

Post #5 of 19 (2285 views)
Re: 1988 Ford F250 possible vacuum leak? Sign In

I do have a volt meter. I don't know what a lab scope is though.


(This post was edited by Rob Strunk on Feb 19, 2013, 7:54 AM)


Hammer Time
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Feb 19, 2013, 8:31 AM

Post #6 of 19 (2265 views)
Re: 1988 Ford F250 possible vacuum leak? Sign In

I asked about a specific type of meter, one with a needle, not digital.



~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



Tom Greenleaf
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Feb 19, 2013, 8:51 AM

Post #7 of 19 (2255 views)
Re: 1988 Ford F250 possible vacuum leak? Sign In

You can probably still get a code reader (have one for these) but it's mostly getting the book with what the #s mean. It's a cheap thing that just plugs in underhood to connector and blinks there and you count them for the #. Frankly I never found them very helpful unfortunately and now at the age you should be looking for a breach in vacuum no matter what has already been done. Lots of plastic vacuum line that breaks like raw speghetti if touched by now that goes into rubber plug connectors here and there.

It's no fun nor practical to toss parts - fortunately most are not expensive anymore is about the only good thing. The IAC motor (thingy) hanging on back of throttle body will cause erratic idle up to stalling or that wondering to find an idle. It also hold idle high when cold till it's happy (have to make things happy) and should calm down within a minute. You could clean it and the ports where it mounts. Just slightly fussy two 5/16 or 8mm bolts hold the thing on throttle intake. High chance you can re-use the gasket with a smear of Permatex gasket maker to hold it together and seal. Grease surfaces so you can do it again if it is getting replaced. Looks like this.......


Been a while and I own two now! This stuff lasts near forever if oil is always changed and some good fuel solvent specifically Chevron's Techron used in fuel with some regularity - suks to add to cost of fuel but you don't need to use it all the time just some now and then. No joke - forget most other brands.

Never did as I have the reader but can get blinks of CEL doing this AYOR as this just came off the web if this diagram shows.......



You'll make me go read my book on how to count the blinks which should repeat. By rights it should show if an IAC is a problem area - meaning area not absolutely that it is bad!

The plug as shown above as an irregular trapezoid should be just hanging underhood if anything like the cars of that era.

If you unplug that IAC motor if you will it should just about stall or really stall. Part new is now under $70 if you want to waste more $$ and not test things out more. Not that common to need these but all these were newer before they hopelessly rusted out too rendering the vehicles unfix able just for that.

Again - more common to break those plastic vacuum lines even just checking automatic trans fluid level or changing plugs! If you find one broken you can splice in vacuum hose that fits tight over broken area.

Hey - at the age about anything could be wrong and IAC is only going by the info it gets and clearly it's not getting good info or bad now as that is the most likely to cause the wondering idle,

T



Hammer Time
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Feb 19, 2013, 8:57 AM

Post #8 of 19 (2248 views)
Re: 1988 Ford F250 possible vacuum leak? Sign In

OK Tom you can finish this.



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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



Rob Strunk
Novice

Feb 19, 2013, 9:11 AM

Post #9 of 19 (2242 views)
Re: 1988 Ford F250 possible vacuum leak? Sign In

Thanks guys. I'll check those things out and see what happens. Fingers crossed and again, thank you both for your advice.


nickwarner
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Feb 19, 2013, 6:37 PM

Post #10 of 19 (2216 views)
Re: 1988 Ford F250 possible vacuum leak? Sign In

That distributor cap is right in the front of the motor and needs no tools to pop it off. Have you looked inside it to see the condition of the terminals?


Rob Strunk
Novice

Feb 19, 2013, 8:56 PM

Post #11 of 19 (2208 views)
Re: 1988 Ford F250 possible vacuum leak? Sign In

I haven't done anything yet. The truck is too long to fit into my garage so I can't close the garage door. And's it been cold and very windy and snowing so I'm waiting out the weather for a couple more days. haha. Weather should be better in a couple days. When I was younger i didn't let the weather bother me but now days I'm a wuss. Haha.


Sidom
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Feb 19, 2013, 8:57 PM

Post #12 of 19 (2208 views)
Re: 1988 Ford F250 possible vacuum leak? Sign In

Interesting........ I knew you could pull the codes the way Desi posted with an analog volt meter but I hadn't heard of the test light method before..... Looking at that diagram.....makes sense....


Tom Greenleaf
Ultimate Carjunky / Moderator
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Feb 20, 2013, 3:37 AM

Post #13 of 19 (2197 views)
Re: 1988 Ford F250 possible vacuum leak? Sign In

These are not rocket science which is why I still drive them myself! Short bucks to keep and maintain and long life - what happened? Haven't seen one in ages here as they too rusted out........... Tom


Rob Strunk
Novice

Feb 20, 2013, 5:53 PM

Post #14 of 19 (2182 views)
Re: 1988 Ford F250 possible vacuum leak? Sign In

I agree they rust out really bad. I was lucky this is a truck from the south. It is only showing slight hints of rust bubbling though on the rear wheel wells and i'll be taking care of that soon and it's straight not dented. Paint is weathered and faded a bit but thats about it. Interior is nice. I paid $800 for it and I hope the engine stuff will be an inexpensive fix. I think I did ok on it. I'd post a pic of it but I don't know if this site allows that or not.


nickwarner
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Feb 20, 2013, 7:14 PM

Post #15 of 19 (2176 views)
Re: 1988 Ford F250 possible vacuum leak? Sign In

You can post pics but not directly uploading. Go to a video hosting site like photobucket and then paste the link onto your next post.


Rob Strunk
Novice

Feb 22, 2013, 4:55 PM

Post #16 of 19 (2154 views)
Re: 1988 Ford F250 possible vacuum leak? Sign In


In Reply To
You can post pics but not directly uploading. Go to a video hosting site like photobucket and then paste the link onto your next post.

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nickwarner
Veteran / Moderator
nickwarner profile image

Feb 22, 2013, 5:03 PM

Post #17 of 19 (2152 views)
Re: 1988 Ford F250 possible vacuum leak? Sign In

I haven't seen one that clean around here in 15 years.


Discretesignals
Ultimate Carjunky / Moderator
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Feb 22, 2013, 5:19 PM

Post #18 of 19 (2151 views)
Re: 1988 Ford F250 possible vacuum leak? Sign In

Is that what snow looks like?....woahhh





Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.


Rob Strunk
Novice

Feb 22, 2013, 8:57 PM

Post #19 of 19 (2144 views)
Re: 1988 Ford F250 possible vacuum leak? Sign In


In Reply To
Is that what snow looks like?....woahhh
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HaHa. that's a little bit of snow. Haven't had much of a winter as far as snow goes this year.






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