Too fast idle

See if the canister purge solenoid is stuck open?

does it have any codes???

the idle air control may be the issue or the passages may be loaded with carbon and need to be cleaned

Roy

Just put the iac valve in start the car and let the idle set itself.Let me know what you find.

One other has me wonder bout the solenoid, fuel gage doing weird stuff and heavy fuel fumes. Can you tell me exactly how many hoses are connected to the solenoid?

There should be the vaccum source from the engine and another hose that goes back to the canister.

I will look again at the purge solenoid. I remember the connection but not sure how many hoses I saw. More to come

Alright keep me posted.

After looking at a photo of the EVAP purge valve/control solenoid, I'm seriously considering this specific area to be my problem and here's why. When I first replaced the hose from the PCV to the solenoid, the idle issue surged then immediately went to normal. This was fine for about half a day, then surged back high. I think I also told you I had replaced the PCV on this same day. I do hear hissing like from a vacuum leak but the place where this valve/solenoid is located means I need to use a mirror to see and repair/replace. According to the manual, and internet searches, there are two hose connectors...which one goes where? I'm not sure if I have seen the hose for the other connector, and I will verify that today. All I know is this car eats gas now as if I have a bank account just to feed it (lol). Anyway I will let you know what I find out.

Update...
Here's what I did this morning.
1. checked coolant and topped off
2. checked the ecu fuse was good.
3. started engine, idle still high so
I disconnected PVC line checked for vacuum, was good
Disconnected fuel pressure regulator line, vac good there
Checked booster vacuum, good
visually checked the vacuum lines on Purge valve solenoid, all connections good, and disconnected power to the valve.
4. Shut engine off. At this time the only connector not connected in the engine compartment was the purge valve solenoid.
5. Started engine, still high, connected solenoid valve plug, let run for about 1 minute, then shut off engine.
6. Restarted engine and idle returned to normal. Run A/C, Shifted transmission from park through selection ranges, still normal idle, back shift back to park, and idle still normal.
My synopsis is that when I had the bad PCV line to the solenoid, after a bit of time the solenoid stuck in the open position because of vacuum failure (would that be a correct guess?) By resetting the solenoid, the operation of the part went back to normal operations. What I thought was a vacuum leak was not, I wanted to find out if there was an issue of vacuum and the Evap service line did not give me any indication of a leak there either even with the engine running. I will let you know if anything else happens, but for now all seems well.

If the canister purge solenoind is stuck open it can cause high idles dieing etc.The vacuum leak is just happening in the gas tank.When you have the idle see if the valve is stuck open.

That also would explain why my gas level fluctuated as much as it did. The idle did sneak back up. I purchased a new purge solenoid. Will change it next.

I did get the purge solenoid changed. Idle is good. I did hear hissing near the tank, not noticing this before because I've gotten like really picky about the noises my car makes lol. Is the hissing sound normal?

When do you hear the noise after tuning the engine off?where is the noise coming from?

When the car is running.

So is this after the car has warmed up and this was after you changed the solenoid?

Here's an interesting design issue. The replacement PVC line is not sufficiently sealed where a secure plug was installed and the hose diameter is different on both sides of the secure plug. The hose has come loose at both sections of the plug. I think the fix for this is either a tubing splice or a single piece hose. It seems the leak is here. When the engine is running, and the hose pieces are held in position the idle returns to normal. So my temp solution is possibly using high temp sealant over the entire hose joint. More to follow.
And the issue of the hissing is when the engine is running and the sound is at or near the evap canister. I've not heard this sound in the four years I've had this car even prior to all this recent engine evap work.

Some hose clamps maybe?

I can try some clamps. It seems that whenever I either move the line the idle goes to normal then after a while the engine surges and goes back high. If I'm at a stop and restart the engine the idle is fine. The hose ends where they go into this secure plug t has some sealant that looks to have gone bad so any serious vibration cause it to lose seal. There seems to be no other leaks at the engine and electrically everything else is ok. When the engine transitions from normal to high idle the engine violently shudders as if to shut off.

Gentlemen, thank you for unintentionally saving me some time. My mom has an 01 century as a secondary car. A few months ago I did a full engine rebuild due to some blown gaskets, even polished the heads. It ran like champ and was getting 32mpg highway up until last week. I have the same problems, taking the throttle assembly right now. Hers is throwing a code for the iac but I replaced that when I did the rebuild, with mass airflow sensor and tps. Mileage has been slipping, idle getting rougher, and I too have noticed what sounds like a vacuum leak but, again, I replaced most of the lines. Very frustrating. Keep me posted if you find a solution, I will check back and let you know if I find a fix on this one. Best of luck!

Use some clamps or get a smaller hose and some lube to get them on.

I think my problem is the EGR valve, it sounds like that's where the hissing is coming from, and it's the only part in that area that I didn't change during the rebuild. Buying it in the morning, will report back tomorrow

Isnt your egr valve a linear one meaning its electronic not a diagram type?

Bad hose is my situation and clamps won't work. More to come

Smaller hoses and lube have you tried that yet?

because of how the hose is constructed a home made remedy will not work. Where the two lines come together in a "t" it actually vacuums from the valve cover through to the purge solenoid valve, the line is obviously bad. However, this morning I had disconnected the booster vac line and started the engine (of course I forgot I had disconnected it) plugged the pcv hose back into the original purge solenoid valve and the evap line to the lower connector, and plug. With the booster vac line disconnected, it repeated the horrible starting and idle runs I had been experiencing. when I reconnected this line back to the booster, the idle immediately went high and stayed there. When I shut off the engine, restarted it, the idle was slightly higher than normal, but quickly settled down. I let the engine run about 10 min, shifted the transmission in all drive positions, A/C on, and no stumbling,nor hickup or rise in idle. So you wonder what was the fix? until a new pcv hose arrives, a little dab of superglue on the "t" fitting lines. Once the lines sealed to the fitting, all, for now is well. I have started and run the engine four times, with great success. Will let you know if anything changes.

Sounds good keep us posted.

Where is purge solenoid located? I'm doing the EGR valve now (it started raining, took a break). Last night while looking at it seemed to be the source of the "whooshing" sound. It's about the only old part left.

The canister evap purge solenoid is just behind the egr valve. Follow the pcv hose behind and under the ignition coils(if u have the 3.1 eng). There are two vac lines one from the pcv the other goes to the evap canister.

Thanks

at a loss...now what is happening is the engine performance is really bad. When starting, the engine runs extremely rough to the point of stalling. when the engine is shut off and restarted repeately, the problem does not go away...although when letting the car sit idle for about 5 minutes the idle is then fine. Do you remember telling me something about the coolant temp sensor? would this be my culprit??

Thanks for this web site!
1999 buick century has high idle. Replaced IAC. Replaced O2 sensor before catalytic. Had it checked for tune up - it was okay.

Don't know what else to do. :cry:

Please help...Thanks again.

it could be a vacuum leak..........does it have any codes set?

:?:

Are all the hoses fixed?Do you have any coded in the computer?

No trouble codes.

you will enjoy this...
I"m not sure what fixed the idle issue but, it is gone...possibly combination of repairs
1. PCV
2. PCV vent tube
3. Evap canister vent solenoid
4. IAC valve
5. Cleaned EGR Valve.

Now I have no codes except for a random engine misfire. My goal at this point is to replace all the wires. The coils all have good fire and I'm not sure what plugs/wires age are at this point. So I will go there. I pray the injectors are good, but that is another issue.
I did have my codes checked at autozone and a P0300 and P0404 hence why I cleaned out the EGR Valve and replaced the seal/gasket. As of Now, I have NO codes...repeat NO codes from the engine. Even the cylinder misfire code 0300 has not resurfaced. More to come...

I would start by checking for vacuum leaks. with the engine idling you can carefully spray around the vacuum hoses...........if the rpm's or the sound of the engine changes, you are getting very close. The vacuum tee near the throttle body close to the throttle linkage is a common place for a leak. :idea:

very important : be careful when doing this test....remember the spray is very flammable. (I'm sure that I stated the obvious here, just doing what I do) 8) :roll:

Wow you went all out on that engine lol keep me posted.

Thanks! I'll give it a try...

I replaced the EGR valve and the Buick ran perfect. The rough idle and poor gas mileage went away; it ran like a dream all week. Today my mom called and told me that the rough idle has returned. Why on earth would it run great for a week and then go right back to having this problem?! As I said before I had rebuilt the engine from the heads up a few months ago, the EGR valve was the only part I had not replaced. It was running better than new up until a few weeks ago, now, like you, I'm stuck with this mysterious problem. It runs fine, plenty of power and smooth, but it's idling rough and losing gas mileage. This is getting frustrating!

here's the situation at this point
I have replaced all 6 plugs
four broke at the ceramics, two had worn tips but suspect bad gap and just old plugs. They had Autolite 606 plugs.
Got the new plugs in, starts and idles fine, BUT, still have surging and misfiring. When the car is running and I'm driving for about 1/4 mile it runs horribly, but after that, the car settles and runs fine. This happens anytime the car is shut down and restarted. Any other suggestions?? I have checked the coils, but they seem to be producing good spark. I will take the coil wire caps off and look at the spark in order and see if they seem to be weak at the cap...then possibly look into either coil, or bad ICM.