Okay so I just got an 85’ Fiero with the iron duke and 5 speed manual transmission. I decided to just do a bunch of maintenance at once so I replaced the spark plugs, wires, distributor cap and rotor, pcv valve, EGR, vacuum lines, and then I made my own open air cleaner by putting a breather filter on the valve cover and you get the idea lol
Anyways now I start it up and get a very high idle (it will go up and down from 2000-3500). What did I mess up! It ran fine before!
That’s exactly what I was thinking but I don’t know what I should do. I removed the thermac system thing and blocked off the vacuum port on the throttle body and put a breather filter on the valve cover. Could the thermac system be the issue?
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Originally posted by Patrick:
You probably have a massive vacuum leak. May or may not be related to whatever you did below...
[QUOTE]Originally posted by Scuba_steve45:
...and then I made my own open air cleaner by putting a breather filter on the valve cover and you get the idea lol
Unwanted air is getting into the intake somewhere. Check for obvious things like making sure there's nothing preventing the throttle body butterfly valve from closing. Is the brake booster hose connected?
Hi, my daughter has the exact same car. There are at least a half-dozen vacuum lines on the intake and TBI unit that may have either been compromised or disconnected. Can you take a few pictures of the engine with the air cleaner off, and show us what's going on? Some close-ups of the throttle body and intake would be helpful.
Generally, an open-element air cleaner in a Fiero isn't going to provide more power because you're just drawing heat from the engine compartment. In the factory configuration, you're pulling cool air from the side-scoop, which does actually give you cold air from the outside.
The THERMAC wouldn't cause a massive vacuum leak, but it could / would cause a higher idle since there is in fact a vacuum line that connects to it. With this open, you'd probably get another couple hundred rpms at idle.
Since we have the same car, and my daughter just restored her engine... I can take some pictures to help give an idea of what it SHOULD look like. She's not completely finished with the vacuum lines to the firewall connections yet... but all the ones from the TBI are done.
One thought... the only vacuum line big enough to cause a massive vacuum leak like that, is probably the brake booster. It's the larger of all the vacuum lines. It connects to the drivers side of the TBI unit. If this is disconnected, you're going to be getting some pretty high idle. It's like having the throttle plate cracked 1/4 of the way at all times.
I have not done anything with the brakes or brake booster vacuum line but I’m sure it’s possible it popped off or is just leaking due to age. I did cap off the vacuum port for the thermal valve and replace all of the vacuum lines on the right side of the throttle body because I was thinking it could be a vacuum leak but I will post a picture of all of it when I’m off work.
I also heard that maybe the throttle cable could be bonded up somewhere but it revs out fine and doesn’t get stuck anywhere, it just idles high. Could this be part of the problem?
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Originally posted by 82-T/A [At Work]: Hi, my daughter has the exact same car. There are at least a half-dozen vacuum lines on the intake and TBI unit that may have either been compromised or disconnected. Can you take a few pictures of the engine with the air cleaner off, and show us what's going on? Some close-ups of the throttle body and intake would be helpful.
Generally, an open-element air cleaner in a Fiero isn't going to provide more power because you're just drawing heat from the engine compartment. In the factory configuration, you're pulling cool air from the side-scoop, which does actually give you cold air from the outside.
The THERMAC wouldn't cause a massive vacuum leak, but it could / would cause a higher idle since there is in fact a vacuum line that connects to it. With this open, you'd probably get another couple hundred rpms at idle.
Since we have the same car, and my daughter just restored her engine... I can take some pictures to help give an idea of what it SHOULD look like. She's not completely finished with the vacuum lines to the firewall connections yet... but all the ones from the TBI are done.
One thought... the only vacuum line big enough to cause a massive vacuum leak like that, is probably the brake booster. It's the larger of all the vacuum lines. It connects to the drivers side of the TBI unit. If this is disconnected, you're going to be getting some pretty high idle. It's like having the throttle plate cracked 1/4 of the way at all times.
If your IAC system is OK , most likely you have a vacuum leak. I use a "hiss tube", that's a small diameter steel tube connected to a plastic tube you stick in your ear. With it, even a tiny leak sounds big. I've never seen one for sale, you do have to make it. It's not the same as a stethoscope.
How about the throttle. Is something not letting it close all the way?
Originally posted by Scuba_steve45: I have not done anything with the brakes or brake booster vacuum line but I’m sure it’s possible it popped off or is just leaking due to age. I did cap off the vacuum port for the thermal valve and replace all of the vacuum lines on the right side of the throttle body because I was thinking it could be a vacuum leak but I will post a picture of all of it when I’m off work.
Just to iterate, the brake booster vacuum line is the LARGE vacuum line that connects to the drivers side of the TBI unit. If it's popped off anywhere, whether at the firewall, at the TBI unit, or at the intermediary tube, you're going to get at least 600+ more rpms.
I'll also take several pictures of the engine either today or tomorrow. The engine is friggin' immaculate, and all the original hoses were used, so it can provide a good indication of where most things should go... as I said, she still hasn't connected the firewall vacuum lines back up (to include cruise control, and all that). But at least on the TBI... everything is connected. So I'll try to get that tonight.
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Originally posted by Scuba_steve45: I also heard that maybe the throttle cable could be bonded up somewhere but it revs out fine and doesn’t get stuck anywhere, it just idles high. Could this be part of the problem?
If it is... you'd see it immediately... as in, with the air cleaner off, the throttle plate would be pitched open somewhat. When the car is idling, the throttle plate should be completely closed... that's because the IAC (as Yellow-88 mentions) gets its air through a separate passage in the base of the TBI unit, which bypasses the throttle plate. So just to reiterate, when the car is just idling, the throttle plate should be completely closed.
... but yeah, post some good quality pictures tonight, and we'll take a look.
I’m not by the car now but I’m 95% sure the throttle plate was kinda open at idle. I’ll double check today and keep you posted. About the brake booster line too.
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Originally posted by 82-T/A [At Work]:
If it is... you'd see it immediately... as in, with the air cleaner off, the throttle plate would be pitched open somewhat. When the car is idling, the throttle plate should be completely closed... that's because the IAC (as Yellow-88 mentions) gets its air through a separate passage in the base of the TBI unit, which bypasses the throttle plate. So just to reiterate, when the car is just idling, the throttle plate should be completely closed.
... but yeah, post some good quality pictures tonight, and we'll take a look.
I’m not by the car now but I’m 95% sure the throttle plate was kinda open at idle. I’ll double check today and keep you posted. About the brake booster line too.
Take a picture of the throttle linkage then too... there are a few things you'll want to check: - Whether the cable is properly seated on the bracket. - The intermediary bracket with extension tube (I'll take pictures so you can see) - The return spring (usually yellow, unless it's rusted... I'll take pictures of this as well)
It could just be that the throttle is getting stuck in the TBI.
But, it may even be as simple as the gas pedal getting stuck on the floor mat. This is literally a thing that happens (and has happened to me) when you replace the carpets with aftermarket ones, sometimes... so check that too.
I’m not sure if this is what you want to see but here is the throttle. The throttle cable seems fine although I don’t know what to look for lol.
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Originally posted by 82-T/A [At Work]: Take a picture of the throttle linkage then too... there are a few things you'll want to check: - Whether the cable is properly seated on the bracket. - The intermediary bracket with extension tube (I'll take pictures so you can see) - The return spring (usually yellow, unless it's rusted... I'll take pictures of this as well)
It could just be that the throttle is getting stuck in the TBI.
But, it may even be as simple as the gas pedal getting stuck on the floor mat. This is literally a thing that happens (and has happened to me) when you replace the carpets with aftermarket ones, sometimes... so check that too.
[This message has been edited by Scuba_steve45 (edited 09-18-2024).]
X 2 a vacuum leak. Buy borrow, rent or build yourself a smoke machine. Feed the smoke into the intake manifold (engine off) Get an LED flashlight and watch all around where the smoke is seen coming out. There is your leak. If you lived closer we could do this for you as it only takes a few minutes.
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I take what I said back… the throttle play is closed on idle.
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Originally posted by 82-T/A [At Work]:
If it is... you'd see it immediately... as in, with the air cleaner off, the throttle plate would be pitched open somewhat. When the car is idling, the throttle plate should be completely closed... that's because the IAC (as Yellow-88 mentions) gets its air through a separate passage in the base of the TBI unit, which bypasses the throttle plate. So just to reiterate, when the car is just idling, the throttle plate should be completely closed.
... but yeah, post some good quality pictures tonight, and we'll take a look.
I take what I said back… the throttle play is closed on idle.
bro I can litterally see a vaccum line leak in the photo. use zip ties instead of hose clamps for vaccum line or ya know buy the right size and I can see the remnants of crumbling line so check your booster line into the manifold that's on the drivers side
I was using the size that another person used and they said worked fine. I have always used the metal hose clamps on the ends of vacuum lines as well and it worked just fine so I assumed it would be fine on this engine as well.
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Originally posted by cartercarbaficionado:
bro I can litterally see a vaccum line leak in the photo. use zip ties instead of hose clamps for vaccum line or ya know buy the right size and I can see the remnants of crumbling line so check your booster line into the manifold that's on the drivers side
I don't know if you still need pictures, but I'll take several tonight... just been working late. But I'm off work now, and heading into the garage. I'll post them tonight.
Yes please… I’ve been trying to post pictures of my vacuum lines but everytime I add a picture it tries not to let me lol
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Originally posted by 82-T/A [At Work]:
I don't know if you still need pictures, but I'll take several tonight... just been working late. But I'm off work now, and heading into the garage. I'll post them tonight.
Just did a smoke test a few minutes ago and every time the smoke just came out of the top of the throttle body even when I plugged it with a rag.
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Originally posted by Dennis LaGrua:
X 2 a vacuum leak. Buy borrow, rent or build yourself a smoke machine. Feed the smoke into the intake manifold (engine off) Get an LED flashlight and watch all around where the smoke is seen coming out. There is your leak. If you lived closer we could do this for you as it only takes a few minutes.
Yes please… I’ve been trying to post pictures of my vacuum lines but everytime I add a picture it tries not to let me lol
Ok, here is what I have, there are a few missing... I apologize, my daughter is not as far along as I thought she was, but almost everything is connected... I hope this helps somewhat...
1 - When you look at picture #4 and #5. That vacuum port on the TBI unit that doesn't have anything connected to it, THAT connects to the vacuum line on the air cleaner, which connects to the blue or white thermalstatic valve, which then connects to the ThermAC. It's disconnected of course because I had to remove the air cleaner. The others should be pretty obvious, if not, let me know.
2 - When you look at the screw-in "tree" on the intake manifold, which has the THREE ports sticking off of it at 30 degree angles from each other. The larger middle one connects to the rubber tube that connects to the brake booster hard line (which you see going around the eye-loop and the fuel filter, and then past the air cleaner to the firewall).
3 - The other two connectors on that tree thing... she's supposed to be looking it up in the service manual, so I have no idea. But if anyone knows, I'd love to hear it. I know one side connects to the air tube that runs along the rear firewall, which powers the cruise control (if you have cruise, but I think from the previous picture... you do not). The other one... I THINK is supposed to be capped off. But maybe someone else can chime in.
Ok, I fixed a couple of things on my daughter's car. I just connected the firewall vacuum line to one of the two ports on the "tree" of the intake here:
And then the other line, where my daughter had the thermac plugged into, that actually goes to the large firewall line that sticks out directly underneath the dog bone (you can't see it, but you can feel for it back there).
Port "A" on the diagram above is the one that goes to the ThermAC. For the time being, you can plug that one off.
I believe I have all of my vacuum lines in the right location based on the diagram and your pictures. Something I should mention, I’m not sure if this is important and I honestly forgot it even happened, but when this issue first started I was working on my car and I accidentally swapped the map and tps connectors. Could this have messed something up electrically?
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Originally posted by 82-T/A [At Work]:
Ok, I fixed a couple of things on my daughter's car. I just connected the firewall vacuum line to one of the two ports on the "tree" of the intake here:
And then the other line, where my daughter had the thermac plugged into, that actually goes to the large firewall line that sticks out directly underneath the dog bone (you can't see it, but you can feel for it back there).
Port "A" on the diagram above is the one that goes to the ThermAC. For the time being, you can plug that one off.
I believe I have all of my vacuum lines in the right location based on the diagram and your pictures. Something I should mention, I’m not sure if this is important and I honestly forgot it even happened, but when this issue first started I was working on my car and I accidentally swapped the map and tps connectors. Could this have messed something up electrically?
yeah that could be. are they still swapped? also like how they should be physically impossible to swap based on wire length (on a stock harness or a proper connector replacement)
I guess I made it possible lol. They’re not still connected I noticed when I pulled the codes after the first start. Could this have messed up the ecu? I already replaced tps with a tested sensor and new connector.
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Originally posted by cartercarbaficionado:
yeah that could be. are they still swapped? also like how they should be physically impossible to swap based on wire length (on a stock harness or a proper connector replacement)
I guess I made it possible lol. They’re not still connected I noticed when I pulled the codes after the first start. Could this have messed up the ecu? I already replaced tps with a tested sensor and new connector.
Can you try to pull the codes and see what you're getting?
I'm still thinking you have a vacuum leak... but I'd like to see what the codes say.
I did a vacuum leak test and came up with nothing. It just kept coming out the top of the throttle body even when I blocked it off. I did have a code 22 but I replaced the tps sensor and connector and it went away.
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Originally posted by 82-T/A [At Work]: Can you try to pull the codes and see what you're getting?
I'm still thinking you have a vacuum leak... but I'd like to see what the codes say.
I did a vacuum leak test and came up with nothing. It just kept coming out the top of the throttle body even when I blocked it off. I did have a code 22 but I replaced the tps sensor and connector and it went away.
This was a smoke test? And smoke came out of the throttle body only. It should not be able to pass the throttle plate. Some one can add here. Does the IAC close fully when the ignition is off? If it does no smoke should exit any were.
I like the hiss tube in this case, at this point because one can probe the throttle plate to "see" a tiny leak there. A worn throttle shaft can be another source of a leak.
Yes I did a smoke test I apologize for calling it a vacuum test lol. I assumed it was supposed to because fuel sprays onto the “closed” throttle plate on idle so there has to be a way for it to reach the intake and such. I could be completely wrong lol I’ve never done anything with a tbi unit. Please let me know what you think I should do next? Thank everyone for their help so far!!
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Originally posted by Yellow-88:
This was a smoke test? And smoke came out of the throttle body only. It should not be able to pass the throttle plate. Some one can add here. Does the IAC close fully when the ignition is off? If it does no smoke should exit any were.
I like the hiss tube in this case, at this point because one can probe the throttle plate to "see" a tiny leak there. A worn throttle shaft can be another source of a leak.
Yes I did a smoke test I apologize for calling it a vacuum test lol. I assumed it was supposed to because fuel sprays onto the “closed” throttle plate on idle so there has to be a way for it to reach the intake and such. I could be completely wrong lol I’ve never done anything with a tbi unit. Please let me know what you think I should do next? Thank everyone for their help so far!!
I have only 2.8 so I can't go look at a TBI unit. We need a TBI guy to jump in. I'll ask should the IAC valve be completely closed with ignition off?
There is an air way that bypasses the throttle plate. The Idle Air Control, IAC valve is a needle and seat type valve controlled by a "stepper" motor so that the air way can be very accurately controlled. Crap in the valve seat from dirty air or carbon crud can screw it up.
You didn't do anything to affect timing so I'll stick with Vacuum leak at the throttle body, either past the plate or through the IAC valve.
I have only 2.8 so I can't go look at a TBI unit. We need a TBI guy to jump in. I'll ask should the IAC valve be completely closed with ignition off?
There is an air way that bypasses the throttle plate. The Idle Air Control, IAC valve is a needle and seat type valve controlled by a "stepper" motor so that the air way can be very accurately controlled. Crap in the valve seat from dirty air or carbon crud can screw it up.
You didn't do anything to affect timing so I'll stick with Vacuum leak at the throttle body, either past the plate or through the IAC valve.
How should I test this? Is the only method the “hiss tube” that was mentioned earlier? I did not mess with the throttle body or IAC itself besides replacing vacuum lines AFTER the iidling issue began.
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Originally posted by Yellow-88:
I have only 2.8 so I can't go look at a TBI unit. We need a TBI guy to jump in. I'll ask should the IAC valve be completely closed with ignition off?
There is an air way that bypasses the throttle plate. The Idle Air Control, IAC valve is a needle and seat type valve controlled by a "stepper" motor so that the air way can be very accurately controlled. Crap in the valve seat from dirty air or carbon crud can screw it up.
You didn't do anything to affect timing so I'll stick with Vacuum leak at the throttle body, either past the plate or through the IAC valve.
You've pretty much narrowed it down to the throttle body with the smoke test. The only way out is through the IAC valve or past the throttle plate. From the picture, a lot of dirty air got into where it wasn't supposed to. The throttle body is a place that needs to be clean and smooth. I use WD40 and a brush. The IAC does unscrew so you can easily clean it and the seat in the TB. Just don't plug it in when it's out. And don't change the distance the cone is from the body. If you do a search on this forum for IAC I think you'll find a lot written on it.
A hiss tube can check if any air is leaking past the closed plate. With the engine running, the inlet to the IAC will hiss. It will take careful probing to be sure your hearing just the hairline crack at the edge of the plate.
Alright I’ll try that out tomorrow when I’m back home and let you know what happens. I’m hoping I’ll figure out a solution soon!!
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Originally posted by Yellow-88:
You've pretty much narrowed it down to the throttle body with the smoke test. The only way out is through the IAC valve or past the throttle plate. From the picture, a lot of dirty air got into where it wasn't supposed to. The throttle body is a place that needs to be clean and smooth. I use WD40 and a brush. The IAC does unscrew so you can easily clean it and the seat in the TB. Just don't plug it in when it's out. And don't change the distance the cone is from the body. If you do a search on this forum for IAC I think you'll find a lot written on it.
A hiss tube can check if any air is leaking past the closed plate. With the engine running, the inlet to the IAC will hiss. It will take careful probing to be sure your hearing just the hairline crack at the edge of the plate.
