My friend has a DX (94 or 93, don't remember which), it's a hatchback (not that that makes any difference)

He has this weird problem with eradic idle...

It goes like this:
He starts it up on a cold day, it runs high (like it's supposed to), then sometimes it drops down to it's normal 800 rpm idle ro sometimes it only goes to 1200 RPM's, and it'll hover there... If you let it warm up for 10 minutes or so (which should be more than enough for it to be through the warmup state and into the regular running stage) and hit teh gas, it'll JUMP up to like 3.5k and hover there, then maybe drop back down slowly, back down to 800 over the course of like 10 seconds... Then if you drive the thing, it idles so high sometimes you don't even have to give it gas to launch, you just lpull out the clutch and the damn RPM's are so high it takes the hell off (at like 3k)...

If it's running at it's normal 800 after 10 minutes of warming up, then I drive it to the end of the road (or he does..or anybody does), when you push in the clutch when slowing to a stop sign approx. <400 meters from his house, the RPM's shoot up to like 2.9, 3.3k... then if you let it sit there for a second they'll ever so slowly (like steps, come down to it's normal idle back at 800, or sometimes they'll only go to 1.1k.)

Then when it's idling for logn periods of time AFTER being warmed up (long time for this car is like <5 minuts), it starts going up and down on idle, sometimes when the fan comes on, sometimes not, (that's another thing I noticed, when the fan kicks on it like, surges the idle, it jumps like 500 RPM's then goes back to where it was)..anyways, it fluxuates, and jumps, up, down, up, down, up, down, sometimes stallls, sometimes doesn't. I feel the reason for this part is that the idle is too high or something (which doesn't make sense because it idles at 800 when it's being good) and it's going up to like 1k and I think the ECU is killing the fuel injectors which is knocking it down to like 300, and then it tries to give it mroe gas to keep it running so it pops it back up, and it creates a paradox ending in either somebody giving it gas or it stalling (usually doesn't stop or even out on its own)..

The thing that really got me was his cat was clogged...so some dude he knows took a long bar screwdriver and emptied out the cat, completely emptied it, as in it's nothing but a tank now.. Then he broke a gasket taking it off so when he put it back on it leaks like a mother ****** and if you roll down the windows while driving you'll die... So I'm feeling that maybe the secondary O2 sensor is getting a bad reading because the cat (or lack there of) and is ******* with the idle, I don't know, or maybe the O2 sensor is bad (front or back), I don't know, this problem is relatively annoying, especially when I drive his car.

I'm not sure what engine it has or anything, but I know it's COMPLETELY stock, stock, original, engine -- as in nothing at all short of a full size tire/rim in the trunk (because doughnuts suck), and I highly, highly, highly doubt that's it. Also it only has 85k on it so it's not like it's a really high mileage engine..

So if somebody could plz help me help him so we can get that piece working right, I think I'd be eternally in debt to you as I drive this car often (don't ask why, I just end up driving it a lot because of situations like "hey greg, can I borrow ur GTI" - so I'm car-less and I take his..) -- Anyways, help plz -- Any help is thx

 

Not sure but it sounds like a vacuum leak

 

I was afraid of that since I don't know how to test for that..

 

yeah lol wtf, vaccum leak hahah

 

umm, is that a question? or a comment on his post? what exactly are u saying?

 

IT COULD BE A VACCUM PROBLEM THAN AGAIN IT COULD BE THE FAST IDLE VALVE OR ALOT OF THINGS. TO CHECK IF ITS A VACCUM PROBLEM TAKE SOME WATER OR SOME LIQUID AND SPRAY IT ON THE TB AND ON ALL THE HOSES IF IT BLOWS THE WATER OFF OR THE PROBLEM STOPS THAN WHERE YOU SPRAYED THE WATER THERES THE LEAK. BUT IF THERES A C.E.L ON THAN YOU COULD HAVE A REAL PROBLEM. BUT TRY THE WATER AND LET US KNOW

 

check for vaccum leaks. get a can of brake cleaner and slowly spray aroud all the vaccum hoses, gaskets (intake mani, throttle body) that you see (one at a time) cause if you have a leak the car will surge, then you found your leaks. clean the iac, fitc will help too.

worst come to worst you can bypass it there is a how to on here you have to search for it, but you live up north then it would not help.

 

Okay, thanks, I'll try looking for leaks tomorrow, I'm still open to other ideas

I mean this has to be a problem that somebody's had before, it's weird the way the CEL just comes on when there's excessive stress on the engine but then just shuts off like 20 seconds later...

But how do you know for sure it isn't a sensor? Is there any way to actually test sensors? Like can you hook them up to an ohm meter like you can a light bulb to see if they're good?

Okay, thanks, I'll look for leaks tomorrow, but still, any ideas are open, this problem is really starting to eat at me..

 

I had a similar problem (I think everyone has had an idle problem) but mine was a loose throttle cable. Might wanna check that.

 

did, throttle cable's nice and tight, and yeah, I hate these problems, idle problems especially... like my friend's maxima wouldn't idle when it was cold out for more than 5 min at like 10 degrees, it was rediculous, and my friend who owns this civic, he's worse than me when it comes to engines, he doesn't know a manifold from a muffler (one of those pple who don't care what's under the hood as long as it goes from point A to point B) -- and of course everything you try is all maybes until it's actually fixed

So when I get home from practice today I'ma go to my friend's house and try that water thing to see if there's a vaccum leak, thanks in advance, I hope this works O.o