musclecar70sfan

iTrader: (1)

Hey guys, I was looking under the hood of my car and I noticed this:










From what I understand (correct me if I'm wrong) those are the vacuum lines. And they look pretty old and cracked. Do you think that they may be (at least partly) responsible for my rough idle and difficult warm restarts? And is this DIY job? I personally don't see why not.


Oh and the car is a 91 T/A with the 305 TPI engine with 98,000 miles.

musclecar70sfan

iTrader: (1)

And one more...

musclecar70sfan

iTrader: (1)

bump.... nothing yet?

///DAN///

iTrader: (1)

you can buy vacuum tube from any parts store and replace them and they could very well cause a rough idle I'm not sure about the warm up , little tip do them one at a time pull one off and put the new one right on so they all get back together right it's not hard at all good luck hope that fixes you problems.

KnottyBuoyz

iTrader: (2)

One of the old tricks I've used on cracked & suspect vacuum lines (on boats) is "Liquid Electrical Tape". Just paste some on the crack. Run the engine for a half minute. Shut it down for 10 mins (allowing the L.E.T to dry) and away you go. It's not a permanent fix though..... There's also a "self healing" rescue tape I've seen used but never had any myself.

SavageLaw

I need to know what the black thing that is in-line with the vacuum hose is. It has a cone at the end of it. Mine broke and I don't have a clue as to what I should be searching for. I could post a picture of mine if you guys can't see the picture. I can only see one and it is from google image search. My car has a slightly rough idle and it acts like it is being starved of fuel when I lightly touch the pedal. it will drop down 500 or so rpms put not die.

SavageLaw

That is what it looks like. I need a new one since that one broke in half. I superglued it back together but that is only temporary until I figure out what it is called. I used the search function and found this post but I am unsure what it is even called. One end connects to a T connector. After that, one end goes into the firewall to on the passanger side of the engine bay and disappears. The other side of the T goes into what, me and my roommate, think is the wiper motor. The side opposite of the T connector goes into the driver side firewall and disappears. Does anyone know what it is? Please help. My car Idles a bit high on start up (2000-2500RPM) for a little bit and then goes down to around 850rpm. Sometimes it goes back up to around 1500RPM until I rev the engine, then it goes back down. My vents only blow hot air, but I can change where it comes out (defroster, vents, floor) sometimes. Checked the fuses under the dash, driverside, and everything is good. Am I looking at a few different problems or just one that manifests in different places? I looked for vacuum diagrams but only found the ones that pertain to the engine itself, not the AC/Cruise control/HVAC. Thank you.

SavageLaw

If anyone has some kind of idea or even needs more pics/videos. I will take'em/record them to get this fixed. Just let me know what is needed and I will do my best.

Exxon Limited

There is nothing wrong with your car. Mine does the same thing its called fast idle and prevents the engine from quitting. Basically used to warm the engine up in other words. However Im not sure on where the vacuum lines lead.

SavageLaw

Thanks for the reply. What does your car idle at? Mine is a 1985 iroc with a TPI 305 stock everything. Mine idles just above 1k. That is a bit high isn't it? I replaced the IAC valve and it stopped it from hesitating and stuff on a cold start. I also sprayed a lot of carb cleaner into the intake, so that also could have cleaned everything up. The IAC has threads on it but I am unsure if it is supposed to catch something or be, like, stripped out. It didn't hold very much when I first got it and thought it might be bad. but I installed it just to see and it seems fine. How do I adjust the idle? is it a computer thing I can't do or do I unplug the IAC valve, turn on secondary power, turn it back off and then plug everything back in. then run it? I didn't do that yet. Not sure if I need to or if it will even help.

Exxon Limited

If its a cold start about 2500 then it drops to around 2000 and after about 20 seconds I give it some gas and it drops to normal which is 850. Mines an 84 tbi so I'm not familiar with the tpi stuff. But I think your idle is computer controlled considering you have fuel injection. Id try unplugging it and so on.

ASE doc

Exxon, you realize you replied to a 3 month old post? Since there are no updates to the post, I imagine the poster gave up or figured it out and never updated the thread. It wasn't his thread to begin with, he was posting on another member's 3 year old thread. Not the best way to get advice. Hard to say what was going on with his car since he didn't tell us what engine it has. You are right about the fast idle on start up. Normal operation. The cone shaped item in the photo is a check valve. I believe that line feeds the HVAC vacuum controls.

SavageLaw

Thank you exxon

ASE doc

Sorry Savage Law. I was just calling Exxon on a mistake I made a few times when I was new here. Running across an old thread and replying, not realizing no one was even watching it anymore.

So you know, the method for setting minimum idle air is, as follows: Put the system in diagnostic mode by connecting terminals A & B of the ALDL. Turn the key on and wait one minute for the IAC to completely close. Disconnect the IAC with the key still on and remove the jumper from the ALDL. Start the engine. Set base idle to 500rpm(450rpm for the 350). Minimum idle air is now set. This assumes of course that IAC is working correctly, the TB throttle shaft bores aren't worn beyond service limit, and the TPS is accurate.

My service information says to adjust minimum idle in drive with automatic
transmission. Doing it that way, if the engine will support idle at 500rpm in gear, will produce a higher base idle. If that doesn't work out, try it in park. I've done it both ways and then you can also play with it a little. At least once minimum air is set, you'll know where you are. Shut off engine and reconnect the IAC.


You've already performed most of the test for the IAC. The fact that your car idles up on start up then comes down to about normal idle says that the IAC is working. I also like to use a scan tool and watch IAC counts when I turn accessories on and off. The TPS should be at .5 volts +/- .05, with the throttle set at minimum idle. Idle strategy is an adaptive of the ECM. This means that the ECM learns idle control strategy as you drive the car. Once minimum idle is set, you may notice the idle is different for a little while, until the strategy is learned by the ECM. The quick way to help it learn is to drive the car at 30-35 miles an hour for a while under varying loads.

As for rough idle, check for vacuum leaks with propane or brake cleaner sprayed around the intake and vacuum lines. make sure the EGR isn't stuck partly open. How is you tune up? Make sure the ignition is all in good shape and that the timing is right. Are you injectors original? If so, they are very old for injectors and likely not performing like they were designed to. Before you spend alot of money on parts, be sure to check compression. One good indicator of engine health too is spark plugs. Are they flagged with oil ash? This is common sign of worn piston rings. Especially on cylinders 5 & 7, since they have the biggest issue with cooling.

If compression is low on any cylinders or you have oil flagging on plugs, you may be due for an overhaul(opportunity to step up to a 350). Replace injectors when you reassemble the engine.

EDIT: BTW, if your HVAC system is slow to change or sometimes doesn't change modes, that indicates a leak in the vacuum supply to the control head, a leaky control head, or a leaky actuator. Listen for leaking air under the dash. The vacuum supply includes a reservoir that is mounted under the purge canister at the left front corner of the car. Look for the line to the reservoir to be cracked or disconnected. If the modes seem to change when you accelerate, this means that the check valve in your photo is not holding and/or that the reservoir isn't connected. You said that you thought that line goes to the wiper motor? The windshield washer pump is in the bottom of the wiper motor with hoses running to it. Be sure you're looking at the right thing. There is also a vacuum line going to a switch on the brake pedal arm that is part of the cruise control.

SavageLaw

I did as you instructed and the idle is down a bit, around 700-ish. I might have not waited long enough. While in drive, the rpm's go down to 500-450 at a stop and it idles fine also.
I might have not done it correctly so I will try again tomorrow after I get done with my workout and let you know what's up.

I am hearing a leak or something coming from my dash. It only seems to do it when I have my defroster on and it goes away when I turn on my heater. Since those are the only two that work unless I try to get my AC going (which doesn't work currently. Something to do with the refrigerant). It sounds like it is coming from the inside of the car so...I might end up tearing apart my dash correct?

My rough idle was solved when I changed out my IAC a few weeks ago with my roommate. We had the intake off and the throttle body was dirty. He said "That is what happens when it runs rich" and started cleaning it off with throttle body/carb cleaner. He sprayed a decent amount into it to get everything all good and then proceeded to change the IAC. On first fire up, it idled rough for a second but then returned to (prior to this it was a rough idle) smooth idle.

ASE doc

Sounds like you're making progress. The vacuum leak at the HVAC is probably right at the control head, in the vacuum switch.

SavageLaw

ok. So I messed with my idle and recalibrated it for 550 rpm minimum air (from what I can tell anyways). I also adjusted my throttle positioning sensor to 0.54v from 0.85v. My minimum air was set to 750 rpms. Now I am getting a weird kind of idle. What it is doing is, it tries to die, then it revs back up. It just keeps doing that and then it will eventually die unless I manually give it gas and hold it steady. I was wondering. What does this sound like? I think it might be a vacuum leak and I planned on replacing all of the old 29 year old rubber hoses with newer silicone hoses. The reason I think this is because I found a video (when I was looking for more how to fix my idle problem videos) and the guy said "if you have a vacuum leak, you might have idle issues where it is trying to hard to stay at a normal idle and it will run rich because the computer is trying to compensate for the lack of air". I will try to find the video, but that is basically what he said. I just want some new input and someone elses idea's of what it could be. I could also take a video of what it is doing if my description isn't enough .