GavinJuice

So i was on my way to school today and everything was running fine until about running for 5 minutes. I first noticed that it seemed like i was letting off the throttle and getting back on, it hasn't been like my problem in this post, it felt different. Anyways, i came around a corner doing about 20 and i let off the gas and it accelerated, i put the clutch in and the RPM's reved up to around 2300. Thats when i knew something was up. I pulled up to the stoplight and with the clutch in, my car was surging back and forth between 1000 & 2000 RPM. Now this didn't sound like the normal rotary sound, it sounded like it was sputtering. It wasn't like a putt putt, but more of a pfff pff but fast. It's hard to describe, i wish i had a camera or something for someone to hear/see this. The next thing that i notice it i pull through the stoplight and my car starts to lunge forwards hardcore, like the first time driving a car with a hydraulic clutch, back and forth. I come to a stop, the same surging between 1000 & 2000 RPM and the sound. I pull in the parking lot and i put it in neutral with the same reving, but the sound changes to a normal rotary sound.

I have no idea what is going on, this was the most f'ed up experience that has occured with this car so far. I NEED SOME HELP WITH THIS. I am still at school and assuming it's going to do the same thing. Hopefully LONGDUCK can help.

anthrax

Is the car Carbed or EFI?

I had a '96 Grand AM automatic that behaved similarily when part of the the computer went bad.

Could be something like this...

Northern 7

iTrader: (3)

Sounds like a vac leak to me (and a fairly major one) - It may be that your BAC is compensating for the leak and you are cycling. I'm no longduck but check for leaks while you wait for his reply and make sure your TPS is set right.
also, I think this question has been answered before and most likely by Longduck - did you try a serch on SE surging?

web777

GavinJuice

God Damnit, my car is a GSL-SE. I have that in my sig. but it doesn't show up for some reason. Anyways, now that you see it's fuel injected, my TPS should be right on. I had this problem before in the winter and i adjusted it and it took care of my surging and my little idle stumble at about 1500RPM. I've taken off my BAC before and cleaned it out, it wasn't even really dirty. I'm wondering if this has to do with the fuel pump problem that i was having yesterday. It only started when it started to whine, other then that i have had no problems whatsoever related to this.

Also what could be the cause of my car making the different exhaust tone when i put the clutch in, and when i put it in neutral?

This is all is just way to weird and over my head as far as my understanding of how the EFI works. Hopefully longduck can come and save the day.

LongDuck

Boy, you guys have built a lot of faith in me, huh?!

First off, I'd relax a bit - there's nothing wrong with your car. In fact, I would hasten to guess that if you turned it off, let it sit for 10 seconds, and then restarted it, it would have been back to 100% normal. A vehicular 'reboot', if you will.

Some explanations for what you've described, which are simply a shot in the dark, since I'm not there;

Surging is a well-known issue with SE's, and has to do with a lot of different factors. The change in exhaust tone that you've described can be due to a lot of different things, too. Here in AZ, we have a lot of mountains up from deserts, and I've noticed that the exhaust sounds *completely* different at 6000 ft, than at 1450 where I live - this is due to the ECU readjusting the A/F mixture for higher altitude; one of the benefits of an EFI system over a carb. This changes the exhaust tone, and also results in some lost power which all cars would experience at high altitude.

What I'm getting at is that something changed your A/F mixture while you were driving - could be the AFM got stuck in the open position (most likely), or the ECU got a bad signal from it that made it believe that it should have been running at a higher rpm. The fact that this didn't change when you stopped at a light has happened to me before, too. Shutting it down, and restarting it fixed the problem, since this 1) resets the ECU electronics, and 2) shuts the AFM door and everything so that the next start goes smoothly.

You described that it changed when you put the clutch in - also normal. Your clutch pedal has a switch on it that tells the ECU when you have the clutch in, and also on the tranny when you have it in neutral or in a gear (the Neutral Switch - go figure). When cruising the ECU then knows that the clutch is OUT, and if engine RPM is high enough, it alters the 'cold-start' cycle. When you come to a stoplight or stopsign, put the clutch in, the engine rpm increases to keep it running in the electronic 'choke' mode. This is assuming cold coolant and cold oil temperature - as described by your '5-minutes' statement; you were still in cold-start mode.

Some things to check;
1) Does it do it consistently? If not, don't worry about it.
2) Check your Air Cleaner - do you have any holes or gaps that could cause a leaf or something to get by and block the AFM door open?
3) Is the engine running well, or smoking (black is rich, blue is oil, white is coolant)?
4) Does this all go away once it warms up?

Answers to the above will help to find a 'root-cause', but it could just be a fluke. The ECU (N304 unit) is not known for having bad solder joints like a 2nd Gen ECU, and I've never heard of one going out. I keep a spare around, however, just in case. Very unlikely to be anything 'solid-state'. HTH,

Northern 7

iTrader: (3)

Gavinjuice - I didn't say your BAC was bad - I said it may be trying to compensate for a vac leak. Have you checked for leaks?
My experience with SE's is that vac leaks are the 1st thing that usually causes most of the problems. What we then do is try to fix the leak by adjusting idle or throttle settings - and then once everthing is way out of wack, we then find ourselves trying to fix a number of different problems - some of which we have caused our selves by looking in the wrong place to begin with.

BTW, I have no ida why your exhaust note is changing when you depress the clutch - but I doubt it has anything to do with you surging / cycling.

bizarro

iTrader: (1)

POW!!!!!!
Longduck strikes again!

I also agree with Northern 7...

When I was having a problem with my idle, I figured it would be best to change out all the vacuum hoses and intake gaskets to make sure that a vacuum leak was NOT the case...I then adjusted everything that needed adjustment.

rarely but every once in a while i'll notice my car going up and down from 1000 to 1500...but that is after a really long drive and it goes away after like 1 minute...

Lotus00

Cant sticking butterfly valve shafts in the throttle body make it surge too? My car was surging and all I did was spray some WD40 on the butterfly valve shafts (not the right way to lube them, I hear) and the problem went away. Hasnt been back and its been almost 2 weeks.

Its at least worth a try, it only takes 2 min.

GavinJuice

Well here's how my day ended, school is done so i go to start my car and the engine blows up.












Just kidding. HHAAHhahahahha
ACTUALLY, i start my car and it revs up to about 4000 and simply stays there, now im thinking now this isn't the best for it, although it is over 70 degrees. Anyways i pop the hood while it's reving away and start dinking with the TPS and the throttle cable to see if anything is binding. TPS makes it rev even higher when i push it it, not much when i pull it out (turning screw). Anyways i end up just pulling on the throttle cable and reving it a couple times and it simply just drops down, idles like it always had before this whole little problem.
So i brought it home, lubed up any linkage, shaft that correlates to the throttle and the throttle plates.

Running like a champ now, thanks for the advice all, specially LongDuck. Quack.

LongDuck

Fast idle cam got stuck, sounds like. Could also have been the Cruise Control system pulling on the throttle cable when it shouldn't have been - disconnect the CC cable next time and see if that fixes the 4k rpm idle on startup.

Standard 'cold-start' mode should only bump the throttle up to about 2.5k-3k at most. Anything higher than that, and something else is going on.

Glad it didn't blow up - you had me going there for a second.