The engine turns right over and runs after 18 months of inactivity due to cradle, suspension, brake and fuel line replacement, etc.
However, it goes right to about 2200 RPM and there is a very loud hissing noise sounding coming from underneath the air cleaner.
I have everything hooked back up as far as I can see. (The engine did have to come out of the car during restoration.) There are 2 metal air tubes that run together but are unconnected but I believe these go nowhere by design after a recall, correct? The smaller tube terminates underneath the air cleaner on one end (its blocked or clogged at that end- deliberately?) and runs across the front of the engine bay is open at the right end. The larger tube about the width of a finger is about 2 feet long and is open at either end.
Not sure why the hissing noise but it is loud, This photo was taken underneath the car looking up at the two tubes I'm talking about.
------------------ 87 GT Stock 2.8L
[This message has been edited by gregr75 (edited 03-08-2024).]
This 'metal pipe' was connected to the Engine Crankcase Vent as shown in the photo after the recall procedure.
On the other end of this pipe is an Either/Or: 1st Design was connected with an elbow in the bottom of the original rubber Air Intake Duct near to the Air Cleaner Housing. 2nd Design was connected with a prebend rubber hose to the side of the Air Cleaner Housing.
The recall 'Air Intake Duct Kits' removed the original air intake duct (between air cleaner housing/throttle body) and the crankcase vent tube from the pipe on the right. Then installed a New Air Intake Duct which has a port for the New Engine Crankcase Vent Tube on the throttle body end.
Confirm the type of Air Cleaner Housing that the vehicle has; the recall illustrations in the link below shows both designs as well as the original parts were removed/discarded.
If a 1st Design vehicle has the new recall New Air Intake Duct/Vent Tube; the metal pipe was disconnected from the intake/vacuum system directly below the air intake duct.
If a 2nd Design vehicle has the new recall New Air Intake Duct/Vent Tube; CHECK this 'metal pipe' to verify:
*IF the Air Cleaner Housing Side Port has been Sealed (capped off) OR *IF the prebend rubber hose is connected between the metal pipe AND to the Air Cleaner Housing Port.
IF the Air Cleaner Housing Side Port is connected to the pipe; a rubber cap is needed to seal the end (not 'open' as the photo above) as this tube is still 'LIVE' and can draw unfiltered air to the intake/vacuum system which is a dire condition! ------------------ Original Owner of a Silver '88 GT Under 'Production Refurbishment' @ 136k Miles
[This message has been edited by Vintage-Nut (edited 03-09-2024).]
The smaller tube terminates underneath the air cleaner on one end (its blocked or clogged at that end- deliberately?) and runs across the front of the engine bay is open at the right end.
The left side of the smaller tube should be attached to the air filter assembly, and the right side to the EGR solenoid.
quote
Originally posted by gregr75:
The larger tube about the width of a finger is about 2 feet long and is open at either end.
That's fine... although you better check to make sure that the air filter assembly has been plugged where that tube used to attach to before the recall.
quote
Originally posted by gregr75:
Not sure why the hissing noise but it is loud...
Keep looking for the source of the noise. With the idle speed you've reported, you've no doubt got a vacuum connection detached somewhere. Could be under the upper intake plenum or behind the TB etc.
Patrick is correct on the vacuum leak. You will need to check all vacuum lines. Check also for cracked plastic vacuum lines, or simply disconnected lines. If a loud or noticeable hissing sound and high idle, is signs of a vacuum leak. Also check the EGR tube. There is 2 vacuum lines under the TB. Check there too. The other spot that I have already seen a huge hissing noise, I forgot to connect the tube from the valve cover on the bulkhead / firewall side to the TB air filter to TB rubber tube. Behind like this picture, the tube could be just disconnected. Have a look. Check to while your at it, the 2 TB to air filter tube clamps. But this won’t affect the idle speed. It’s just check for proper seal on the intake tube. Just a flat screwdriver is required to check tightening.
Have you driven it on the highway yet? If it has been out of commission for a while, the ECM could have been reset, making it forget it's idle position, which would give it a high idle, also I have heard my IAC valve make a loud hissing sound under certain circumstances, specifically when my PCV valve was clogged, and the IAC valve was a bit gummed up with oil, it can be quite loud, and the sound can seem to come from the plastic water box below the air cleaner assembly, as the air cleaner, rubber tube, and other parts before muffle the sound.
Bridge the aldl connector like you would to read codes, turn on key, wait for 30+seconds, and with key still on and ALDL connector still bridged, unplug the IAC valve, that will disconnect it in the closed position, so there is no idle air flowing, then turn key off/unbridge the aldl connector, start the car, if it starts and runs just fine (maybe with a slightly lower high idle), and you still hear the hissing, you definitely have a vacuum leak or a very very plugged up IAC valve. If it is slightly hard to start, and has a very low idle (600rpm) or you need to give it a bit of gas to keep it running, but the hissing is gone, the ECM just didn't have a chance to bring the idle down, and/or your IAC valve is somewhat gunked up, which caused the air going through it to "hiss".
Most Vac leaks often make No noise yet can still have high idle. Many time if have big vac leaks that maybe make noise then engine hard or won't start because way too much air.
High Idle can be vac leaks or completely normal.
Examples: If ECM loses standby power for any reason, yes IAC needs to "reset" & requires Fiero V6 & older L4 to drive over 35mph. Engine Cold, low battery, etc, then ECM can/will force high idle too.
⚠️ Very Low to dead battery can kill the alternator because pulls too many amps. You need to charge or replace a "Dead" battery before starting. "Dumb" SI can simply fry for low battery. "Smarter" CS turn Off for low battery but "jump starting" fake out the alt & turn On when should not.
------------------ Dr. Ian Malcolm: Yeah, but your scientists were so preoccupied with whether or not they could, they didn't stop to think if they should. (Jurassic Park)
gregr75: There are 2 metal air tubes that run together but are unconnected but I believe these go nowhere by design after a recall, correct?
Incorrect *The larger metal pipe was ‘removed’ from the engine {See Recall Thread Above} CHECK if you have the 1st Design or the 2nd Design in the link *The smaller tube STILL must be connected on both ends {Outside Air to EGR Solenoid Vacuum}
quote
The smaller tube terminates underneath the air cleaner on one end (its blocked or clogged at that end- deliberately?) and runs across the front of the engine bay is open at the right end.
Incorrect {Outside Air to EGR Solenoid Vacuum} The smaller tube is connected to Outside Air (before the air filter housing input) and the “open end” goes to the EGR Solenoid Vacuum which feeds two ports: the EGR Valve and to the Throttle Body.
NOTICE on the Larger Metal Pipe w/ 'Open' Ends: 1st Design: the metal pipe was disconnected from the intake/vacuum system and replaced with a different (recall) Air Intake Duct 2nd Design: If both ends of this pipe is 'open' - CHECK the Air Cleaner Housing Side Port has been Sealed (capped off)
quote
However, it goes right to about 2200 RPM and there is a very loud hissing noise sounding coming from underneath the air cleaner.
If you hear a vacuum leak underneath the air cleaner; check the air intake/vacuum system for 'open' ports (like the Air Cleaner Housing Side Port) which will draw unfiltered air to the system.
[This message has been edited by Vintage-Nut (edited 03-09-2024).]
OK thank you everyone for your replies, wow this was a wealth of information, And I appreciate the effort that went into marking up some of these pics.
It looks like I have a second gen regarding the pcv redesign. However, the smaller metal tube thats supposed to connect to egr solenoid on the right side isnt connected, theres just a foot long length of hose dangling from solenoid. I could easily connect the tube and hose there but I have heard of other people just letting that solenoid hose dangle there because it's just ambient air right? This shouldn't affect EGR operation?
On the left side, where the small metal tube goes into air cleaner (see pic) The tube is blocked with something hard. Previous owner did a crude EGR delete, and I'm wondering if he deliberately blocked this tube.
I also performed the IAC reset procedure via ALDL for 20 seconds. heard some strange buzzing noises which didn't sound normal. I then cleaned the throttlebody and IAC porthole before the butterfly valve. Lastly, I install the air filter and cap and snorkel put everything together, fired up the engine and I now have 1000 RPM but very lumpy and almost stalling. Absolutely no idea why the loud hissing is gone, but I am very pleased with this and no more high idle.
I removed the IAC valve, and did a reset procedure again, really out of curiousity to see how it works and the spring and pintle went flying out but I was able to locate both parts.
Sorry for the long post but my questions are
1) Do I need to unclog the metal tube where it enters the air cleaner on the left side (see pic)and hook the EGR solenoid hose on the right side? Will this really affect solenoid operation versus just having a foot long hose hang off the solenoid like it is right now? It seems it wouldn't really matter because it's ambient air.
2) I screwed in the pintle of the IAC valve as far as I could go, now the slots in the pintle are lining up with the plastic guides in the valve body. is this how i should reinstall it? fully screwed in?
Do I need to unclog the metal tube where it enters the air cleaner on the left side (see pic)and hook the EGR solenoid hose on the right side? Will this really affect solenoid operation versus just having a foot long hose hang off the solenoid like it is right now? It seems it wouldn't really matter because it's ambient air.
It probably makes little difference, do whatever you feel comfortable with. Do it like Pontiac intended, or have the hose just hanging off the end of the EGR solenoid. Your choice.
quote
Originally posted by gregr75:
On the left side, where the small metal tube goes into air cleaner (see pic) The tube is blocked with something hard. Previous owner did a crude EGR delete, and I'm wondering if he deliberately blocked this tube.
As I stated in the 2nd response in this thread, if the larger tube is open at both ends, make sure the hole in the air filter canister is plugged. The larger tube originally connected to the filtered side, whereas the smaller tube connects to the unfiltered side. The smaller tube being plugged at the air filter assembly makes no sense whatsoever.
[This message has been edited by Patrick (edited 03-09-2024).]
OK thank you everyone for your replies, wow this was a wealth of information, And I appreciate the effort that went into marking up some of these pics.
It looks like I have a second gen regarding the pcv redesign. However, the smaller metal tube thats supposed to connect to egr solenoid on the right side isnt connected, theres just a foot long length of hose dangling from solenoid. I could easily connect the tube and hose there but I have heard of other people just letting that solenoid hose dangle there because it's just ambient air right? This shouldn't affect EGR operation?
On the left side, where the small metal tube goes into air cleaner (see pic) The tube is blocked with something hard. Previous owner did a crude EGR delete, and I'm wondering if he deliberately blocked this tube.
I also performed the IAC reset procedure via ALDL for 20 seconds. heard some strange buzzing noises which didn't sound normal. I then cleaned the throttlebody and IAC porthole before the butterfly valve. Lastly, I install the air filter and cap and snorkel put everything together, fired up the engine and I now have 1000 RPM but very lumpy and almost stalling. Absolutely no idea why the loud hissing is gone, but I am very pleased with this and no more high idle.
I removed the IAC valve, and did a reset procedure again, really out of curiousity to see how it works and the spring and pintle went flying out but I was able to locate both parts.
Sorry for the long post but my questions are
1) Do I need to unclog the metal tube where it enters the air cleaner on the left side (see pic)and hook the EGR solenoid hose on the right side? Will this really affect solenoid operation versus just having a foot long hose hang off the solenoid like it is right now? It seems it wouldn't really matter because it's ambient air.
2) I screwed in the pintle of the IAC valve as far as I could go, now the slots in the pintle are lining up with the plastic guides in the valve body. is this how i should reinstall it? fully screwed in?
Ok, I'm not sure on the EGR connection, someone more knowledgeable will tell you what to do with that, as for the IAC test you did, sounds like exactly what I thought, at certain positions the air rushing past the IAC will make that hissing sound and since the ECM had been reset, it forced a high idle, which happened to be a position that made the IAC hiss. When reconnecting everything and driving above 35mph, the ECM will learn the idle again, and it should idle at 1000, no hissing, should be good. The reason the idle went to 1000 and was lumpy, with no hissing when the IAC was disconnected, is the ECM then can't control the idle, and it is somewhat lumpy because of that, the hissing was gone because no air was going through the IAC valve to make it hiss, the sound the IAC valve made was normal, if the IAC valve was reassembled and still works, you should be good, no problems other then the EGR ambient air tube, just drive it, and the idle should go down and since you cleaned the throttle body, the hissing should be reduced or gone.
make sure the hole in the air filter canister is plugged.
Yes, i double checked and it was properly capped the whole time.
quote
Originally posted by 1985 Fiero GT:
The reason the idle went to 1000 and was lumpy, with no hissing when the IAC was disconnected
Actually, I got the lumpy idle around 1000 after cleaning the throttlebody and IAC port hole and installing the air filter and everything but still had the IAC valve connected. I removed it afterwards to investigate it.
Actually, I got the lumpy idle around 1000 after cleaning the throttlebody and IAC port hole and installing the air filter and everything but still had the IAC valve connected. I removed it afterwards to investigate it.
Ok, have you driven it yet, above 35mph, and let it warm up, both of those conditions need to have been met before the idle will be where it is supposed to be, if it remains lumpy after that, there are a lot of potential things that can cause that, usually more on the sensors and vacuum systems, ex. TPS sensor could be just out of range enough to need the ECM up, but not so much that it generated a code, or the big one I found were vacuum leaks, if there's a vacuum leak, that means no matter what the ECM does, it can't fully control how much air enters the engine, which confuses it and ends up modulating back and forth.
The reason it needs to warm up is 2 fold, the ECM likes the engine to be warm before getting the idle perfect, and the oil can be a thicker consistency when cold, and it may not all thin out at once, on the odd occasion my Fieros idle gets lumpy, the oil pressure gauge will closely follow the rpm, pressure increases for some reason, making more load on the engine, rpm decreases, ECM sees that and adds air as oil pressure decreases, leaving less load on the engine, and more air/fuel then rpm increases, ECM cuts air at the same time that oil pressure raises again from increased rpm, etc.
I haven't gotten the car back on the road yet, I need to fill it up with more coolant, and button up some other things to get it roadworthy. Probably in a couple weeks. Also I have to figure out how to reinstall this IAC valve and retract the pintle if possible. i do see some threads about partially putting a finger over the iac port hole while running to trick the iac pintle into retracting.
My car also has a parasitic electrical draw, so I was disconnecting the battery everytime i walked away from the car but now have it on a battery tender so the ecm can keep any codes that come up.
[This message has been edited by gregr75 (edited 03-09-2024).]
gregr75:: Previous owner did a crude EGR delete {and} I have heard of other people just letting that solenoid hose dangle there because it's just ambient air right?
With a stock system, 'Outside Air' is not 'Ambient Air ' when the engine is running. This air input before the air filter housing input is lower than atmospheric pressure or a.k.a. 'vacuum'.
quote
My car also has a parasitic electrical draw, so I was disconnecting the battery everytime i walked away from the car...
BTW My experience with a 'weird' parasitic draw issue: I got a parasitic electrical draw when (a) the engine/trunk deck was open and (b) the parking brake was 'Off' as I was working on the engine and the brake system. With the trunk light bulb out, current will still flow even though the ignition is 'Off" which will drain the battery.
Because the deck was open for months for engine service and a complete brake system service - my temporary 'fix' was to disconnect the trunk solenoid connector in the engine bay which stopped the battery drain.
I didn't dive into the circuit and added 'Check Factory Inline Diode' on my list to see if the diode is shorted or not.......
[This message has been edited by Vintage-Nut (edited 03-10-2024).]
The small rubber hose going into the air box that runs along the firewall to the passenger is for the hose we were talking about earlier, the EGR solenoid.
Both of my 88GTs, have them removed. I never had an issue for performance, and even the SES light coming in.
I did replace the EGR solenoid with a PFF member that had them refurbished, and my SES light never came on for an EGR related issue. I have Rodney’s SS vacuum line kit, new EGR valve and tube.
My other 88GT is an original car, and that hose to the EGR solenoid was already off and not even on the car when I bought it. The recall was done with the proper caps and hardware that GM supplied.
Jelly2m8 is the one who first told me about the hose for the EGR solenoid, so I give him the credit for educating me on this. He mentioned that he removed / removes them also.
The thing about that small hose (or even just the fitting on the end on the EGR solenoid) is that it sucks in air. When the EGR/solenoid is not active, it switches the ported engine vacuum to "atmosphere" (aka "that hose"). It isn't "vacuum" all the time, but when it is, it can suck in unfiltered air. (If you block that port off, it effectively just connects ported vacuum straight to the EGR valve.)
If that matters to you, find a piece of foam, and make a blind hole in it, small/deep enough to allow it to slip on to the fitting on the end of the EGR solenoid. Maybe glue it in place, in a manner that doesn't block the fitting. Or you can take a hose and connect from the fitting to a small (lawnmower type?) fuel filter. Just a thought. I really doubt that it can suck in enough dirt to do any damage, but it's worth consideration.
I don't understand the problem some people have connecting a short rubber hose from the EGR solenoid to the small metal tube on the firewall. Pontiac designed it that way for a reason, overwise they would've saved a nickel and not bothered with it. The recall eliminated the need to use the large metal tube on the firewall, not the small one. It's there, why not use it?
Ok I'll probably hookup the EGR solenoid hose the way Pontiac intended…
I'll chalk up the loud hissing noise to an IAC valve that was stuck open (retracted position) I can't find any other explanation it went away after I sprayed the whole throttle body area with carb cleaner.
However In playing with the valve and experimenting with it, the spring and pintle went flying out and I ruined it trying to put it back together.
I just received a new IAC valve, The pintle sticks out less than 1 1/4" The Pontiac service manual says " No physical adjustment is made to the IAC assembly after installation. IAC resetting occurs after reinstallation on the vehicle, and is controlled by ECM action when the vehicle is operated."
So, why do some people perform a "reset procedure" by jumpering the ALDL after the IAC is installed. I guess I don't understand the purpose of it if the IAC valve is self adjusting.
[This message has been edited by gregr75 (edited 03-14-2024).]
Ok I'll probably hookup the EGR solenoid hose the way Pontiac intended…
I'll chalk up the loud hissing noise to an IAC valve that was stuck open (retracted position) I can't find any other explanation it went away after I sprayed the whole throttle body area with carb cleaner.
However In playing with the valve and experimenting with it, the spring and pintle went flying out and I ruined it trying to put it back together.
I just received a new IAC valve, The pintle sticks out less than 1 1/4" The Pontiac service manual says " No physical adjustment is made to the IAC assembly after installation. IAC resetting occurs after reinstallation on the vehicle, and is controlled by ECM action when the vehicle is operated."
So, why do some people perform a "reset procedure" by jumpering the ALDL. I guess I don't understand the purpose of it if the IAC valve is self adjusting.
The reset procedure is just a trouble shooting step, if you have a vacuum leak, and the ECM is trying to control idle, it is hard to find the leak, it is easy to "turn off" the ECM supplied air by extending/shutting the IAC valve, then disconnecting it. You also do that if the idle air screw was messed up, to reset the base, uncontrolled idle, so the ECM is happy later. The hissing sound was likely just some debris/oil/carbon in there, the PCV system can spit oil into the rubber snorkel if the PCV valve is jammed, causing other stuff in the intake to get clogged.
It can also help if you can't drive the car to let the ECM learn the idle speed, if it is way off, and you need to run the engine, you just close the IAC valve with the procedure, and run the engine, the ECM won't try to control the idle until it is driven, so it will stay wherever it was, if the IAC valve gets closed, the idle will be nice and low.
aaaah ok that makes sense. When I had extended the IAC all the way via ALDL the car was almost stalling and i had to goose the throtte to keep it alive so I probably don't have a vacuum leak.
Will install the new valve and see how it goes. Thanks!
aaaah ok that makes sense. When I had extended the IAC all the way via ALDL the car was almost stalling and i had to goose the throtte to keep it alive so I probably don't have a vacuum leak.
Will install the new valve and see how it goes. Thanks!
Yeah, sounds like it is as it is supposed to be, is supposed to be like 600rpm with the IAC disabled, with the engine fully warmed up, without it warmed up, it will want to stall at those rpms.
When I "tested" the IAC valve while it was removed from my duke years ago... the pintle shot off into the grass. It was difficult to find. However, I at least knew the IAC valve was functioning.
Keep in mind the IAC valve can be working fine, but if there's crud in the passageway blocking smooth movement of the pintle, then it'll never extend/close properly.
It was difficult to find. However, I at least knew the IAC valve was functioning.
