[ogcaddiedaddy]

I have a 79 Eldog with the 350 Olds fuel injection motor. When I start the car, and its in park, the motor runs super, super fast!

I removed the breather and figured I would just turn the idle screw to slow the motor down a tad, then I discovered the idle screw cant be adjusted as it does not have a visible head on the screw.

Is they're anyone out there that can help?

Sincerely,

 

[cadillac_al]

There is a fast idle thingy on the throttle body. I think it's a kinda round black plastic thing and it should be plugged in. I think it just twists out but this is all off of memory 20 years ago. When they used to fail you didn't have a fast idle, just a slow idle. Hopefully yours may just be a vacuum leak somewhere.

 

[ogcaddiedaddy]

So if I can located the thing that unplugs that you mentioned, and just unplug it, will that help fix the fast idle problem im having?

 

[gmaior]

If you remove the air cleaner and towards the back of the throttle body there is a fast idle valve. It is spring loaded. when it fails it will cause a high idle. Either the micro switch on the side failed or the valve itself failed. You can push straight down on the valve while the engine is running and see if the RPMs drop. There have been post about people shimming the valve to make it work. Also could be the coolant temp sensor at the front right of the intake.

 

[ogcaddiedaddy]

Are you talking about the throttle linkage itself?

Or does the fast idle have anything to do with the long spring thats hooked into the throttle linkage?

----------

Okay I kinda get what you're saying now. I will look for a secondary spring hooked to a valve behind the air breather on it tomorrow.

Thanks for your expertise!

 

[gmaior]

No its not on the linkage. It's actually in the throttle body. its toward the rear and has a flat two wire connector that plugs in. It is spring loaded and you can push down on it.

 

[ogcaddiedaddy]

Hello gmaior!!! That name fits you perfect!!! Thanks for the picture also. I did everything you said to the T.

You are right on the money, that piece does control the idle. I unplugged and unscrewed it, however mine is missing the actual spring itself.

I do have another 79 Eldorado which I bought for the motor, but now its shaping up as a parts car.

I am going to remove the part from the parts car and see if the spring is still attached to the part.

So the spring must be a very important component right?

 

[ogcaddiedaddy]

Would you happen to have a picture of the coolant temp sensor?

 

[1979 Eldorado]

I understand this is a very old post but I thought I would answer a couple of the questions which seemed open:

• The large spring is what keeps the FIV (fast idle valve) open when the "Heater" is cold/ not applying pressure to close the valve. So yes the large spring is important. Gravity and vacuum would tend to close the valve and you would have no fast idle without the large return spring.
• I am adding a photo of the original coolant/air temp sensor. There are two and they are the same PN which is 1609968.

I'm also posting a diagram showing the FIV parts in the TB. The gap between the plunger and the "derby" is what allows more airflow and a fast idle. Once the actuator is heated the pin extends and it closes the gap between the plunger and the "derby" (valve guide). I didn't show the large spring but the post above shows it. I worked for around 2 years to finally come-up with a plug and play replacement. The other temp sensor in the photo is also my creation.

There was also a clip at the bottom of the plunger. That part is not important and some are discovered to be missing. That means either someone already removed it or it was ingested by the engine...

I plan to post a technical thread on this topic but the 70's EFI technology crosses engine types and Cadillac models so I found this thread while trying to determine where I should post the tech thread. In both of the parts I created I tried to really understand and correct common failure modes.

Scott

 

[CarScope]

......
There was also a clip at the bottom of the plunger. That part is not important and some are discovered to be missing. That means either someone already removed it or it was ingested by the engine...
......
Scott

Thanks for mentioning that silly clip. I'm not an enthusiast, just working on a customer's nice 79 Seville. It looks like the clip was possibly installed wrong and kept the seat's "upside-down top hat" part from going into the seat of the throttle body (assuming it was supposed to). The clip was sticking out and keeping the whole thing sitting on top, above the seat. I could not find a picture that showed the assembly with the clip anywhere. I just took it off and it all worked better. He wants it right so I'll be ordering your improved unit. The plunger has one of the vanes broken. Do you sell the plunger parts/assembly too? (assuming you have time to respond to the forum quickly- if not I'll buy one somewhere.)

I need to make sure his misfire is something small first, and if so- will be ordering soon.

Thanks again... wasted a bunch of time figuring it out. Appreciate your post. Maybe others will find it first.

 

[1979 Eldorado]

Hi CarScope,
There is a failure mode referred to in the "blue" EFI manual as a "latched" condition. It's that clip which can become latched but to be fair it needs to be inserted a long way and probably during assembly. A latched condition would hold the plunger into the derby so far there is no bypass and thus no FIV function even though everything might be ok. If the hat/derby is upside down (should have the taller end down and plunger should enter from the short side) it would cause the derby sleeve to ride higher up on the plunger and would likely eliminate the function as well (or even crack the derby).

On the misfire I don't know if you are aware of it but there is a Seville based website where all of the diagnostic trees are listed (I think the entire "blue book" is there). They're pretty clear and they direct you to the appropriate tree based on your main symptom. I think for misfire they suggest checking everything spark/ignition related first but if you are at a shop and you can check the fuel pressure easily you may want to check that. Here's the link to the Seville site:

'76 to '79 Cadillac Seville home page

1976 1977 1978 1979 Cadillac Seville information

www.cadillacseville.org

Almost everything can be fixed and because a couple of us are trying to keep these things running they aren't crazy expensive because we've covered most of the bases. There's another member named Bruce Roe (a little more active on the CLC forum) who is a retired electrical engineer and he's a magician when it comes to the ECU's. He also suggests an external fuel pump relay. The pumps can take a lot of power and they route it inside the ECU (some are claiming the ethanol containing fuel is causing pumps to get hotter). As the pumps require more draw a common problem is burning one of the ECU pins and so the external relay prevents that. I did a write-up on my 79 Eldorado. I was able to unpin the factory connectors and make all of the connections within the existing plug with the exception of a ground. Here's the link for that thread including photos:

70’s ECU Wiring: Bruce Roe kit install on a 79 Eldorado

70’s ECU Wiring: Bruce Roe kit install on a 79 Eldorado

forums.cadillaclasalleclub.org

I do have some used springs, plungers and "derbies" so once you know what you wish to do just send me a "DM" (Direct message).

Scott
PS: The middle manual is the "blue" book.

 

[CarScope]

Wow. Thanks.
The misfire won't likely be a problem diagnosing, unless it gets weird with injector issues, then I might need the manual and diagrams. I will definitely save the manual from the site, if I can find it. I didn't see it at a glance.

Originally, I just couldn't tell it was misfiring with the cold idle so low and stalling. I started with that issue first. It was very likely latched (though I did not see a picture, the very term describes it perfectly).

Fuel pressure was decent: 30-34 running, 40 with the hose off. But it acted like it may have been a pump at first, in the lot trying to drive into the shop... though it was not getting air either, probably just flooded it.

Actually, he came in for a door lock clicking/battery draw issue (repaired the popped-apart switch for that). He did not mention any driveability issues, which is kind of funny as horrible as it was running.

I'll PM Monday after I check the misfire. Thanks again.

btw, Nice diagnostic tree on the site. Unusually useful, especially for that era.

 

[CarScope]

Oh, I found the manual- on the home page . I was checking menus.

This guy may do the upgrades EFI, he said he wants it right. Some of them will be a little pricier to have a shop them. (I am his mechanic doing it for him at our repair shop). But he has spent some money making it pretty, it'd be worth the investment, I'd think. It may have 50k original miles, btw! Looks new, original stickers under the hood etc.

 

[1979 Eldorado]

One other simple thing to check is the coolant and air temp sensors. Sometimes they're a bit difficult to unplug but they are easy to test. You just need to know the temp and check the resistance. If the FIV was latched or otherwise not allowing bypass and especially the coolant sensor failed with too low resistance the car could be running pretty rich. I'll attach the resistance curve from the factory manual.

The sensor and FIV are quick changes. The external relay is more involved. I posted all of the info which would make it fast work on the Eldorado but Bruce mentioned something about the purple wire function being specific to the Eldorado. Probably the best would be comparing the original pinouts on the Seville to the diagram I posted.

Sounds like the owner is lucky he has someone willing to take the time to understand the car.

If the sensor(s) need changing, very common, I recommend Teflon tape. The torque is a little inconsistent in the FSM instructions (attached). I would describe it as snug but not overly tight and roughly 12-13ft-lbs; not so easy to measure due to location and wires though.

Scott

 

[CarScope]

I did see the info about their common failure and was planning on checking them. I only saw one sensor with that style connector though. It is on the front left, as the manual says is the coolant. Where is the intake air sensor meant to be? I suspect someone changed the sensor and connector to a single wire (if they even exist). If so, it may now be grounding through the manifold instead of a second wire... I will measure resistance Monday, and if needed pull it/them out and see which is in the air intake.

Thanks again. And for the chart, that saved some time

 

[1979 Eldorado]

See diagram attached...
There are actually 3 coolant temp sensors but only one coolant sensor for the EFI. The EFI sensors are 2 wire. There is also a warning light temp sensor (single wire ~240F), a stop driving now sensor (single ~260F) and even a 4th which looks like a sensor but it's really a normally open switch/delay for the blower circuit. I wish Cadillac had offered a gauge package for my Eldorado.

Edit: To clarify the EFI air and coolant temp sensors are the same PN. I didn't count the air sensor in the total of coolant sensors.

Scott

 

[CarScope]

I saw the gauge sending unit (or one of them) next to the ECT... it had no wire on it, btw. I was going to look into that Monday too. Funny they had two sensors, in a way that would alert people better who don't watch the gauge, or scare them further when the second light comes on. I did not even look at the cluster to see what this has in the way of lights and gauges,

Does the switch/blower delay have the same connector as the sensors? I assume it has two wires?

And I looked around back there for the IAT, but apparently missed it. Thanks. I'll look closer.

I am dumbfounded by the care and attention you guys take... you must love these old caddies. Thanks a lot Scott. If the customer doesn't run out of money I'll get this one running like new, or better (with your upgrade).

 

[1979 Eldorado]

The blower delay on the Cadillac has a single wire and grounds through the sensor body to intake. I also have a 1979 Toronado and it has a 2 blade connection located on the heater valve. So same body style and different idea for a basic function.

I'm not certain if they gave the Seville anything more than the Eldorado but the Eldorado has a speedometer and a fuel gauge (photo attached). It also has 2 lights for indicating good economy (green) and "lesser" economy (amber). Everything else is idiot light. I only discovered the economy lights when I was replacing a broken gear for my trip odometer. I checked all the bulbs while things were apart and the green bulb was blown. The dash was also nicely illuminated once all the bulbs were working again.

There was full gauge package for the Toronado which included coolant temp, oil pressure, and volt meter. Even the Toronado basic gauge package had a temp gauge.

Scott

 

[CarScope]

Very good then, I saw two single wire senders and the ECT up front on the intake. That leaves the IAT in the back and another single wire I probably am forgetting about or did not see. That makes it easier. Shouldn't be too hard to see which single wire sender/switch is doing what, now that I know what to look for. Thanks again.

 

[CarScope]

Looks like 4 cylinders are misfiring (1,5 and 4 and 6)! I'd have never guessed that many. No gross vacuum leaks apparent. slowed with added fuel, like they were dead misses. Good spark at cap dfor all four and least at cylinders on 1 and 5. No fuel on the plugs, good compression

I checked the fuel injectors on the left bank so far. 1 and 5 have no injector pulse. This system appears to have a positive supplied pulse rather than the negative grounding modern method. I have to leave the shop for now, but will ohm check all the injectors when I get back, to see if one or more are shorted. It looks (by color wire) that it is left and right bank fired, and I have misfires on both sides. I suspect one or more bad injectors, one on each bank.

btw, the temp sensors were matching 944 ohms before starting and seem fine, or at least close enough.