Missing vacuum line.

[captcorvette]

Have been chasing vacuum leaks, inept (me) mechanic, bad advice from local agencies, missing issues, VATs issues and much, more but slowly making progress thanks to the help, explanations and experiences of many of you. Seems like this is an adventure in "what comes next?".

Chasing down possible leaks one by one when at least one item came to the forefront. Have had the ECM off and on adding piggy back chips, checking pens, looking for any possible damage etc.. Then like the old "forest for the trees" I notice the vacuum line on the bottom of the ECM is gone. Yep completely gone. The "L" fitting is there on the bottom of the ECM housing but no hose in site----any place. Will now have to wait until I get home this evening to break out the FSM to try and backtrack from the ECM to where the hose pipe should be but there are no obvious hoses or pipes that are not connected to any area I can find.

Good thing I like puzzles. But perhaps this is a further sign of progress. One of the reasons I don't like to let anyone else ever work on my toys but sometimes we are forced to let other get their hands in the mess.

Any ideas out there as to where the pipe/hose has gone? How it could be gone without even a remnant remaining?:icon_scra

[sammy]

there is a plastic line that will come from under the plenum to the rubber fitting . jjust take a carefull look ,bet its there somewhere .

[captcorvette]

Thought there should have been one from under the plenum but there is only one on the driver's side and it goes to the one that I had just used to check the vacuum pump which is new and is working correctly. Put my finger over the pipe and the pump shuts off holding vacuum. Finger off and reconnected and the pump runs all the time.

[tomtom72]

:o Just for reference. That vacuum line that appears to be among the missing is from the left side actuator for the port throttles ( secondary blades in the head ports ). It tells the ECM via the MAP sensor under the ECM bracket that the secondary actuation system has enough vacuum to function properly and if needs be the vacuum pump to activate, thus augmenting vacuum to keep the secondaries "ON".

I am fairly sure that any parts store sells that hard plastic line in small spools.

:o just another point of reference. It seems with our cars one has to be wary of just using the soft rubber vacuum hose as a quick fix. Our motors develop a good deal of vacuum and tend to suck shut standard vacuum hose. I think that is one of the reasons why our motors have that hard plastic line everywhere.

:cheers:
Tom

[tomtom72]

This link will give you some background on the secondary vacuum system.

http://www.corvetteactioncenter.com/forums/c4-corvette-zr-1/14272-1990-1995-zr-1-secondary-port-vacuum-diagnosis.html

In one of the picts it shows the hose assembly from under the plenum. In that pict, in the upper portion you can see the hose extension from the left side actuator to the MAP under the ECM, which is the hose you are seeking.

:cheers:
Tom

[QB93Z]

The vacuum line you are looking for is tucked into a wire bundle under the plenum and crosses the back of the engine to get to the vacuum sensor under the ECM.

Note: on later cars the vacuum sensor is under the plenum.

Search all of the wire bundles near the brake fluid resevoirs and around the brake booster, That is the direction that the tubing comes from.

If you still can't find it, I will go out to the garage and get an exact location.

Good luck,

Jim

[captcorvette]

Thank you everyone. Still can't find the bloody tube/pipe. Did stop by a few parts houses this evening on the way home and so far no one has the hard plastic piping. Will try the agencies tomorrow but first need to find the missing pipe source. I have a suspicion that one of the other set of hands that have been in this engine might have just pulled it out not knowing were it was supposed to go so the easy fix was bin it. But finding this problem is progress. Fingers crossed that I don't have to take the plenum off-----again.

[BlackbirdZ07]

I just got through replacing the secondary vacuum harness in my '90, which included this hose. A couple of the posts above are correct; this hose comes from a T connection at the driver side secondary actuator.

If you can't find anything that will work, this hose was just fine in my car and I could send it to you. I would probably check to make sure nothing else is missing first. If anything else is missing I'll send it if I have it, or it may be best just to order the secondary vacuum harness if enough is missing or damaged. Unfortunately, yes, you'll have to take the plenum back off.

[captcorvette]

Jim, Tomtom, blackbird, sammy and all the others we have success! Spent about an hour this morning tracking the plastic pipes down and had managed to find a roll of the hard plastic pipe but it is yellow. No worries yellow would do if it had to!

Opened the bundles and checked every wire/pipe. All went where they were supposed to go at least from what the FSM, sage advise givers and logic would dictate. Checked the rear of the plenum time and time again. No pipe.

Just before biting the bullet and pulling the plenum I decided to use my mini flex camera and look under the plenum. AH HA! There the little digger was and it was doing exactly what everyone said----going to the rear of the plenum. Looked again from the back of the engine and couldn't see the pipe. Flex mini cam to the rear and trace the pipe.

Found it!!! It was neatly cello taped to the bottom side of the big wire bundle at the back of the engine so it could not be seen from above. Would have NEVER seen it without the camera or pulling the plenum.

It is reconnected now and will give it a test this evening when finished with this afternoon duty/work.

But again this is progress and I am pleased about that part. Will have to determine how many issues this does or doesn't solve. Then if enough issues sorted out will install Marc's chip tomorrow on my day off. If The Boss doesn't have too many "honey do's" scheduled.

Much obliged to all.

[tomtom72]

Alright! Don't ya just love it when a plan comes together! Nice find.

:thumbsup:

[scottfab]

Just before biting the bullet and pulling the plenum I decided to use my mini flex camera and look under the plenum. AH HA! There the little digger was and it was doing exactly what everyone said----going to the rear of the plenum. Looked again from the back of the engine and couldn't see the pipe. Flex mini cam to the rear and trace the pipe.

Found it!!! It was neatly cello taped to the bottom side of the big wire bundle at the back of the engine so it could not be seen from above. Would have NEVER seen it without the camera or pulling the plenum.


You didn't by chance get the mini cam at Harbor Freight? If not where and how much?

[captcorvette]

I only wish I could get items shipped to me over here from Harbour freight, Sears and on and on. But usually not possible. Ordered this from a local company that imports items from all over the world. This one is from one of the suppliers for computer devices. If memory serves it was just under $200. Works quiet well but does require a computer so I use my net book or note book depending what other issues I am chasing at the time. Netbook is better as it more easily one hand held while the other hand fiddles with the camera.

For the first time since I have owned this car it appears to be working about 90% of what it should do. The secondaries are coming on and the power is noticeable.

Still has:
high idle,
hesitation on throttle application
missing under load
feels like retarded timing
noise at idle like a preignition and perhaps a bit of a chain rattle?
during day time the information panel is dim turn park lights on it the panel is readable. Have checked two grounds (battery and front of car) both are good
shifting is stiff sort of feels like and old international harvester tractor shifting

BUT I am very happy to have made this much progress. Plan on driving it a bit to give it a bit of use then tomorrow check plugs, wires and check all fluids again after a couple of hundred miles use.

Put the scanner on it on the way home this evening and NO CODES! Hot Dog! But I keep getting an error reading when I try to take data readings hope to sort that out tomorrow as I think it might be a dodgy OBDII receptacle as it is just hanging there and not fitted in the proper manner.

If you notice a particular bright glow from over on this side of the world it might be from this grin.:D

[ghlkal]

Just before biting the bullet and pulling the plenum I decided to use my mini flex camera and look under the plenum.

Ingenious! Cool solution


during day time the information panel is dim turn park lights on it the panel is readable. Have checked two grounds (battery and front of car) both are good


I have this same issue. I haven't pulled the dash yet to check the lights, but in addition to the grounds I'm wondering if the light sensor could be causing this problem.

[SteelBlueZR1]

Likely light sensor is your problem. Try cleaning it with Q tip and Windex. Also, you may have burnt out bulbs in your instrument panel. I have taken mine out twice, and it turns out my problem was the polarized coating on the LCD screen was sunburnt... I bought polarization film and cut it to size and now my LCD speedometer, et al. is showing dark crisp numerals vs. dim greyed out digits.

[BlackbirdZ07]

You didn't by chance get the mini cam at Harbor Freight? If not where and how much?

I got one at Costco last year for $150. I noticed they had them again around Christmas. It's made by Whistler, has about a 3' cable with another 3' extension. It has a little LED light on the end where the camera is so it lights up what you're looking at. It also has a wireless feature and digital recording.

I couldn't account for a screw during my plenum pull, and I used the camera to look down into the ports of the injector housings to make sure it wasn't down there. I later found the screw in my tool box, but the camera worked great! You might ask at Costco if they can get one.

[RHanselman]

I will be out there sometime before the end of the year. I'll check with you before I leave to see if I can bring you anything. I can also take a look at some of those pesky problems...

Cheers,
Ron

[captcorvette]

That is great news Ron. Hopefully I can make some progress on the pesky problems in the continuous learning process of having this toy. Bring your appetite eh?:handshak:

[tomtom72]

Still has:
high idle,
hesitation on throttle application
missing under load
feels like retarded timing
noise at idle like a preignition and perhaps a bit of a chain rattle?
during day time the information panel is dim turn park lights on it the panel is readable. Have checked two grounds (battery and front of car) both are good
shifting is stiff sort of feels like and old international harvester tractor shifting

Put the scanner on it on the way home this evening and NO CODES! Hot Dog! But I keep getting an error reading when I try to take data readings hope to sort that out tomorrow as I think it might be a dodgy OBDII receptacle as it is just hanging there and not fitted in the proper manner.

If you notice a particular bright glow from over on this side of the world it might be from this grin.:D

Okay, so I'm going to take a stab at your shortening list!:o
You first need to square away your data cable and the ALDL plug in the car as you will need to see what the motor is doing at idle at least. That said I'll submit the following:
High Idle: TPS out of adjustment, sticking blades in T/B, vacuum leak.
Hesitation: TPS, vacuum leak, bad ign sys components, bad electrical connections @ sensors and or battery also check engine grounds.
Missing under load: How much load? WOT? or just 1/2 throttle, or just all the time? Anyway: ign. system components, TPS, vac. leak, fuel system, injectors & wiring. It's easy to pinch the injector wires as it's tight in there. Ask Jim about that one.
Retarded Timing: flat or bogs or just not too much response to the go pedal, could be your miss is all the time so go up one and look over that stuff.
Noise like spark knock = Dual Mass flywheel rattling in response to the miss.
I can't help with the LCD as mine does the same thing and I'm no good at this electronic stuff! :o

Transmission: what is the condition of the fluid, what type of fluid; what is the condition of the clutch hydraulic system and it's fluid? I use the Castrol stuff and when it's down around 40*F or less the trans needs some time to come to temp. If the clutch fluid is cloudy then that affects the release of the P/plate and thus the shifting. That's just a fwiw....unless the trans is out of alignment?

Sorry to be so long winded!:o
:cheers:
Tom

[captcorvette]

I like long winded. Have been called verbose myself which is most likely true.

Will address each point you have raised and see the results then post up a reply on what was found, action taken and then results. Thanks.
Wayne:cheers:

[tomtom72]

Well, Mr. Verbosity I presume? I'm Mr. Blowhard, pleased to make your acquaintance! :handshak: :mrgreen:

We will all hang in there till we get your Z back to her old self!:thumbsup:

:cheers:
Tom