Missing vacuum line

Topic: Missing vacuum line (Read 2721 times) previous topic - next topic

Missing vacuum line

November 09, 2014, 07:44:36 PM

Hey folks! Hope you all had a good Halloween! Spent mine learning more about these engines. Never owned a car with a 'puter (save the Neon, whcih I really didn't care to work on, and the Cordoba whose computer was so primitive it didn't require any tune up procedures beyond the regular 'old engine' stuff), so my diagnostic skills are still pretty poor here.

We did a top end rebuilt on our '88 thunderbird 3.8 after HG demise. Had some issues and codes after rebuild, got it all cleared up with some assistance from the EVTM (thanks Trinom!), but there's an unused barb on the PCV valve that was previously wrapped with duct tape. Nothing's been deleted as far as I can tell. All the smog and A/C equipment is present and working, but can't seem to figure out what's supposed to plug in there.
Now, if I plug the port, the car runs like . If I let it leak, the car runs like . If I restrict it, the car runs great - no idle issues, no stumble, nothing untowards. Still throwing no codes KOEO or KEOR. No vacuum leak with the port plugged.

Unfortunately, the fan shroud is no help...

Can't even find a picture of the emissions decal for the 88 3.8 online - but lots of pictures of 88 5.0 decals and even decals themselves on ebay.

Neither was this Chiltons diagram for the '87 3.8 (they had diagrams for 83-87 and 89-90. WTH? :flip:)

PCV runs to purge valve and intake (assuming that the electronic fuel control assembly is the throttle/plenum/intake), but still has an open port.

Here's what I'm looking at:

(New TPS connector is on the way. Roadside crack lighter solder job isn't going to hold to much longer...)

:punchballs: Been pulling my hair out over this for days. Sure, I could just stick an inline filter and a vrest on it and call it a day, but I kinda like this car - don't wanna ghetto rig it. Anybody know what's supposed to go there, or have a 88 3.8 efi specific emissions decal/vacuum diagram that may shed some light?

Missing vacuum line

Reply #1 – November 09, 2014, 08:10:04 PM

Most of the auto parts store replacements have two ports. They typically come with a plug to block off the extra port if you do not need it. I always buy the one that only has one port as that is all that is needed with the 5.0 cars. The only other thing I can think of is when my car was CFI I want to say there was a vacuum line that went to the air cleaner but I cannot remember much about it. In your case just go to a parts store and get a cap of the correct diameter and plug it off. They should have a tray with all kinds of them behind the counter or in the Help section.

Darren

Missing vacuum line

Reply #2 – November 09, 2014, 09:01:48 PM

Thanks for the quick reply!
Have it plugged with the backyard bolt-in-vacuum line method. Perhaps I need to be a little more liberal in setting the base idle. Went to set it to spec and found my old tach/dwell has decided to retire itself. My definition of "barely running" may be more conservative than the author of the forum post I read describing the procedure. Idles fine in park, but the block starts doing the twist in gear.
I found find a pic in the forums of a member's Cougar with a similar setup that had the same lonely barb. A plug would explain my confusion on that.

Missing vacuum line

Reply #3 – November 09, 2014, 10:57:32 PM

I set mine low enough the engine has a miss and bucks a bit at idle in park, then plug the iac in and all should be good as long as tps is set right and you have no other vacuum lines leaking.

Missing vacuum line

Reply #4 – November 10, 2014, 02:44:34 AM

Yeah, definitely had it set lower than missing and bucking just a bit. Spec is 550 RPM with the IAC unplugged which, when I think about it now, is basically just a low idle - not a struggling engine. Will try setting to a higher base tomorrow and check the TPS range if no joy. Thanks!

Missing vacuum line

Reply #5 – November 10, 2014, 06:26:23 PM

Well, no luck. Drove the idle up a little and tested until the EEC threw a 13 on KOER, but still idling like in gear. Also a whistle when I plug it properly, so there must be a leak somewhere.
It also threw a 24, which is interesting because the ECT sensor is brand new. Replaced it because my temp gauge reads way, way low (the needle never moves more than a mm or two beyond 'C'). The new sensor didn't remedy the problem, so I figured the cluster VR was going out. Wondering if I have a wiring issue.
Also wondering how much hysteresis the MCU gives the sensors before throwing a fault code. Perhaps that py solder joint is providing enough resistance to cause drivability issues, but not enough to throw a code? Didn't screw with the TPS connector or try to find the whistle today - got our first freeze/snow, body's not quite used to it yet. It was 70 yesterday.

Missing vacuum line

Reply #6 – November 10, 2014, 06:54:46 PM

I believe the stock temperature gauge is driven off of its own sensor in the intake manifold? Not sure about that if the car has a digital cluster so do some searching. Have you or are you attempting to do a base idle reset? Another thing you need to verify is if the fuel pressure is correct.

Darren

Missing vacuum line

Reply #7 – November 12, 2014, 07:59:53 AM

Ah, it does appear to have a dedicated sending unit. The car has a semi-digi cluster. Maybe a blast or two of contact cleaner will clear that up. Need to get a suitable fuel pressure gauge, so no, haven't done fuel pressure check. Going to have to make a trip to harbor freight...
Suspecting I may have a ECT (parts store brand), gonna have to test it. Pretty sure I replaced it the same day I replaced the PCV duct tape with the plug. Was running reasonably well for about a hundred miles prior. Sounded a bit more 'poppy' than it should and was running a little bit rich, but could definitely feel the restored power from repairing the HG (which also solved the mystery of the disappearing coolant we had since we got the car). Making a list of tests to perform from the literature I've been reading - starting to piece together a clear picture of how these EEC systems work. Pretty darn impressive stuff for its day. Feeling a bit more confident in diagnosing this thing, looking forward to the temps rising back above the teens. Sucks not having a shop, or a garage - or even offstreet parking. Had the pleasure a couple years ago of changing the bird's broken flywheel out in the snowy street. I've never been more bitter about how recklessly many people tear down city sidestreets.
:2gunsfiri :burnout:
[video=youtube;oT-uhxkNLhM]https://www.youtube.com/watch?v=oT-uhxkNLhM&t=31[/video]

Missing vacuum line

Reply #8 – November 13, 2014, 07:01:15 PM

Eureka!

Got a little warmer today, so I finally got a chance to have a look without risking hypothermia. That ECT was garbage; wouldn't go any lower than 18Ω.
Did another vacuum test, this time using butane instead of the pump. Turns out my main issue was the fuel reg line.

It's back in full action. Thanks again for all the help! These forums have been invaluable since we acquired the bird. The community here is impressive - very knowlegable techs around here willing to help the clueless like myself. Gonna let it warm a bit more before I tackle the gauge issue.

Thanks again!

Missing vacuum line

Reply #9 – November 13, 2014, 08:47:04 PM

Ewww. What's all that nasty shiznit in the last picture?

Oh, why I do believe it is called snow.

And you can have all of what we're going to get this weekend. Seriously, come and haul it all off, and bring me a truck load of warmer temps...from somewhere down around Mexico City would do fine. :hick:

Good score on the fuel regulator line. If you have an engine miss, stumble or a rich problem, and the first, easy, and apparent fixes don't cure it...always look at the fuel pressure regulator. Between it, the IAC, and TPS, that covers about half the common symptoms on the EFI 5.0, and of course the '88 3.8 also applies to this, as it's pretty much the same setup, except for a couple less cylinders, and a balance shaft under the intake (but only for '88 Tbirds/Cats).

One other unrelated word of advice. There's a little rod on your transmission linkage. It basically connects the TV cable to the transmission, anyway, if your engine mounts are broken, the engine can lurch around on real hard throttle, or bad bumps and cause one end of that little rod to pop off. If it it does, the transmission will act like it doesn't want to shift. Driving with it off for very long...like a few miles...10-15 or so will burn up and ruin the AOD. If this happens, stop immediately and check to see if it popped off. I had two different '88 3.8 Birds...the second of which had this issue a lot. I dealt with it until the engine decided to kill itself, and when I was pulling it, I found that both mounts were broken, and this contributed to several issues besides the linkage problem. It caused the passenger exhaust mani to rub a hole in the brake line down by the kmember and she got crispy one afternoon in 2006, and that was the end of that car.

Missing vacuum line

Reply #10 – November 13, 2014, 10:57:55 PM

^^She got really crispy?! uh oh, like caught fire? :(

Missing vacuum line

Reply #11 – November 14, 2014, 03:57:11 AM

That's why Denver sucks. No snow here and we haven't even hit 29 yet.

All joking aside, if you ever end up out west a bit more, let me know. I spent the night in Denver a month ago.

Missing vacuum line

Reply #12 – November 14, 2014, 04:36:21 AM

That sounds like a bad afternoon indeed! Never seen brake fluid ignite, but I'd imagine it's pretty wicked once you get it going. Talk about poor man's napalm. Glad you survived!
Saw an Explorer burst into flames on a more seedy stretch of Colfax Ave once. Crackheads are like rhinoceroses - they came out of the woodwork by the dozens, full trigger on their motel room extinguishers before they're even in range of the vehicle.

Thanks for the heads up on the rod. I know the one - had to get it jiggly to get at the driver's side exhaust . I'll be sure to pass that wisdom on to m'lady as well - it's actually her ride. (Gifted to her on condition that its name remained "Roadrage." It's not too bad, but you can see along the roof, trunk lid, and pillars why we appended the 'Rusty' bit. It's our red-headed step child.) The mounts appear to be in pretty good shape, were probably replaced when the motor was rebuilt. We were having a good laugh about that regulator. Checked the regulator itself, but not the vacuum line. It was the plenum side that cracked. The obvious will always bite you in the ass.
Noticed a kink in the nylon return line at the fuel rail spring-lock connects. Should probably fix that sooner than later.

P.S. I'll take as much snow as you wanna give, but you can keep the negative temps. On the other hand, I finally had a couple days peace and quiet from the construction. They've been at it 7 days a week since they ditched the 'Coming Summer 2014' sign...

Missing vacuum line

Reply #13 – November 14, 2014, 04:43:50 AM

Yeah, it's those ed mountains. The weather always seems to follow along the East side.
Definitely, we're wanting to get this bird fit for flight. Last time we were out that way was in an E-250 with a 460. Didn't gouge our wallet as bad as we expected, but it still wasn't easy on it.
Some rat stole it couple years ago.

Likewise, drop me a line when you find yourself on the other side of the rock again!