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Items noted

1:Using Dave Darling's diagram the line coming off the throttle body to the cap side port of the vacuum advance unit is plugged with a screw and not connected to the vacuum advance unit shown in top of picture. Does this line need to be connected to the cap side port of the vacuum advance unit?

2: The line from the back of the vacuum advance line is omited because the car is a 74 and does not have a port on the throttle body.

the cap-side port off the ditributor is vac retard. It needs to see full time vacuum (from plenum), otherwise timing will be advanced and cause high idle. Could you post darlings diagram?

kevin here. so the vacum can port pictured should have a line connected to the tb port shown in the second picture, yes? there are a number of odities on this system as it's currently configured. i'm at jack's house.

k

the port pointing to the right off the distributor in the top pic needs to be connected to the port pointing to the left off the tb on the bottom pic. (which already a tube connected to it).

brief history...jack's car produced an extremely high idle. prior to today. we connected the line from the tb to the vac port. the car wanted to start, but was ragged so he shut it down. others items don't seem right too. heres dave's diagram. i wish i could find the "Dr's".

in d's diagram the aar line should run to the port with the black elbow on the fitler housing. currently the oil fill tower vent is on the fitting. this line should relocate to the a fitting on the plenum?

k

the upstream aar port (pointing to the right) needs filtered air (no vacuum), however you want to do it. Those 2 filter housing positions are equivalent. The downstream side of the aar goes to the left rear vac port on the plenum along with the cold start valve. darlings pic confuses me because it looks like the case vent goes to what on my '76 would be a plenum vac port. your case vent looks ok though. I took off my decel valve and therefore plugged the 2 plenum vac ports on the front right. But, I can't see how everything else is hooked up on your engine. good luck.

the vaccum hoses were a mess, hookup wise. we replaced them and put them on in the fashioned as outlined in george's diagram. found it in a search. problem persists. jack and i were brainstorming. a few more details came to light, and we may have solved the problem.

the car is hard to start. when it does it's straight to 3k+ with the throttle plate in the fully closed position. the fuel pump runs continously when the key is turned to the first position. not 5 seconds and off. jack told me the car backfired just before the idle issue. "stack (thru the tb) or out the muffler?". back up thru the tb possibly resulting in damage to the TPS or it was jammed out of it's proper setting. our guess is the ecu is seeing a signal for near or wide open throttle. he came by my place after i had left and picked up a TPS and a harness plug end that had been modified with 2 test leads. he'll test the TPS settings and recal it, replacing if ness. it was a good learning experience for the both of us. time well spent. brad ander's site was extremely informative.

k

Kevin thanks again for all your help. I agree it was a great learning experience. I am beat for today, but I will be checking resistance on the TPS switch tommorrow. Hopefully the switch will be bad and then the problem will be fixed.

Kevin you were a big help and I owe you big.

The PCV connects to the plenum port
AAR valve connects to the air filter port
Whats connected to the plenum port?

3k idle is usually too much air coming into! misconnected hoses is my guess...

I think if the TPS is stuck to WOT it would flood the engine (too rich) as you need the extra air to get that idle rpm

Kevin and I followed the "DR'S" diagram exactly. When we were done we still had the high idle as before. We have checked all the hoses, and they are now correct, the ECU tested good and the MPS also tested good.


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3K RPM cannot be caused by just a sensor reading incorrectly. You do have air going in there somewhere; probably a large vacuum leak.

--DD

note the fuel pump running all the time issue. brad's writtings on the tps, and one of it's functions leads me to suspect the tps. we shall see.

one of the plenum ports had nothing connected to it. as pictured, the vac adv port had no hose, #3 in the diagram. #17 on the aar valve was unconnected (pictured). #8 was connected to the filter housing port for #17. the decel hose #6 was connected to the F shaped fitting for #8. the various vapor hoses were either non-existant and the ones that were there were hookedup incorrectly. the F fitting i had on hand is marginal, jack will need to source one. a finger wipe in the tailpipe came out heavily sooted. pig rich. like a set of webers that are set up wrong or having excessive fuel pressure. we'll see what jack discovers today. something else...note the big herky helper throttle return spring on the tb plate shaft. the tbs i have at home don't have them. it that a late, late tb version?

interesting. the previous owner had the engine rebuilt at well known shop on the eastside. the way the fi and various hoses were configured was the way they sent the car out the door.

there are some pretty disinct difs in george's and dave's diagrams. note #7 and #8 in g's vs d's.

yup, time to look for a vacuum leak

thats a late 73-74 style TB with the dual springs.

Kevin/Jack...

I think its great you guys are putting your heads together to slay this dragon. After reading through this post here is what I can offer at the moment:

I can only assume that you have checked every component, every vacuum line and everything check out. Valves adjusted, dwell and timing correct etc.

The high idle is almost surely (99.999%) a vacuum leak or leaks, downstream of the throttle valve, supporting what others have suggested. All you can do is check source for an intake manifold leak. Is the AAR stuck open? TB gasket airtight? Injector seals airtight? Runner-air plenum gaskets tight?

I have attached the vacuum hose diagrams I use for my 74 cars, also found on my website, if I recall they are subtly different than either Dave or Georges. I have another version not yet online, but it only swaps two of the decel valve hoses.

As far as the continuous fuel pump condition, I understand that circuit is controlled by the ECU. If the engine does not start or is stalled the fuel pump should shut down after a couple seconds. So if its running continuously I would suspect the ECU.

PS the TPS wont have much resistance, it only is a continuity switch. Check the idle contacts for on/off and of course the TPS calibration, and then check for what is 21 clicks during acceleration. Since its only continuit, you can verify ever function with an ohmmeter.

Well I tested the TPS today with an ohm meter and I believe it checks out fine. Looked at all the connections again and then pulled out the PCV. The PCV has a small gasket that broke apart in my hands as I took it out. So I guess I will be tracking down a PCV and put it all back together and try it again.

Jeff, thanks for the diagram. Question is why are there so many diffrences in all the different vacuum diagrams for the same year/motor?

The only good thing about this whole mess is I am learning a load about D-Jet.

Ditto on the air leaks. When I was trying to track down a high idle problem on my 76 2.0 D-jet I found my problem to be the seals between the plenum and the runners. 8 hose clamps later and she purred.

Jim

The plenum itself can be cracked and leak .... especially around the two support tubes.

Checked the timing? Hard start & high idle = well advanced timing

Constant running fuel pump = check the fuel pump relay also for stuck closed contacts.

you guys rock. jack, i fell asleep after dinner last night and will call you this evening. i'll go thru my stuff tonight. first thing, swing by and pick up a known to be good relay and you'll eliminate that ? straight away. it'll thake about 30 seconds. then try jeff's diagram. there aren't too many difs to the way things are currently "hosed". haha. don't forget to call george.

k

just found. PVC-opens and closes nicely via oral vacuum. NEW tb gasket. lots-o AARs. lots-o relays, one HAS to function. r&r the one in the engine relay board and see if the pump turns off. lots-o plenums, that one we had at your house had everything on it. came off of a good running 74'. put on your tb. get new inj seals, and intake to head phenolic gaskets. i suppose you could seal the replacement plenum openings, duct tape?, and put a vac on it to double check for leaks prior to install. i'd just start new and go forward at this point.

ps was the broken gasket you told me about last nite the cork one on the base of the oil fill tower? got a new one of those too.

k

You can easily eliminate the AAR and DV as potential air leaks. Just pull the hoses to those things off of the air cleaner and plug them, and they should (assuming the hoses are tight) have no more air going through them.

I would look for a fitting on the manifold that has no hose plugged into it, or any hose that goes straight from the air cleaner to the manifold with no "component" in the way. 3K RPM is high enough that it almost has to be a missing hose.

--DD

dave when you say "plug them", you mean the open ports or the hose ends taken off except for the vac advance? all of the lines were replaced with NEW hoses and they fit tightly save for the used stacked elbow. take it off and plug the port? there's a 'tiny bit more' to the whole story but that's jack's tale to tell. further thought steers me to a plenum issue.

k

There's a hose from the AAR that plugs into the air cleaner. Pull that hose off of the air cleaner, and plug the end of the hose. You can ignore the fitting on the air cleaner, except if it bothers you to let unfiltered air into the engine.

Do the same thing to the hose from the DV to the air cleaner.

The hoses to the distributor are too small to cause the size of leak that we're talking about.

And if there's any hose that goes straight from the air cleaner to the manifold, you need to figure out what should go there and do that.

--DD

I have not got a chance to work on the car in a couple of days, work and snow getting in the way. I do have a couple of questions.

1: The line from the TB that goes to the vacuum retard was not connected and plugged with a screw. The car at one timewas running great with this line like this. Why?

2: Before I take the entire plenum off, what would happen if I removed the air cleaner, started the car, and put my hand over the TB? Could I eliminate the cause of the vacuum leak by doing this, and can I do this?

Kevin, I got your message I just got home really late last night and tonight. I will give you a call tomorrow about all this.

Jack

Kevin,

You are a virtual parts store! I will probably need the gasket on the base of the fill tower. It is not cracked or broken, but I would be leary that it will not seal again correctly. The gasket that I was taking about was a small gasket that goes over the PVC. It cushions the mating area between the fill tower and the PVC.

Unknown. It isn't really needed that much for the car to run, but it would bring the idle down slightly to have the vacuum retard hooked up. (You're talking about the line to the fitting on the distributor dashpot that points back toward the distributor body, right? That's the retard. The advance points away from the distributor body.)



The engine should die; if it does not you absolutely have a vacuum leak.

--DD

Yes the fitting that points back towards the distributor body. I thought that the engine should die by putting my hand over the tb.

Dave, thanks for all your help and info. It is greatly appreciated.

first thing i would do is, take one of the headlight relays out, presuming your headlights worked properly. the relays are located in the front trunk under the black plastic covers next to the headlight motors. swap one out for item #12, fig 9.21 p.128 of your haynes. turn the key to the first position and see if the fuel pump runs briefly and shuts down.

k

Just to throw another curve .... I had a car with a high idle 1500+ rpm .... throttle body bushing on butterfly shaft were worn .... leaking air.

Thanks Ron. I will check that out also.

Damn this is so spot on. I too had the plenum problem. I pulled out the plenum and did a check. The two little support holes /rod that runs through the plenum on each side were pulled up just enough around the supports to create a leak in the body. I welded the suckers and rechecked. Put it back in and no more high idle. Talk about a happy guy!