IAC Cleaned, TPS Adjusted, Revs Up & Down Now

**kc-** · 4-5-09, 23:40

As the title states, I cleaned my iac, throttle body, and adjusted my tps using the proper method in diagnoses mode.

Now when I start the car it'll rev right up to 2,200 and then fluctuate between 1,500 and 2,200 over and over again consistently. *It has never done this before* I switched the tps with a known working one and the exact same problem in the same rev areas.

It would be great to find this out as this is the last step to fixing my problem.

Any ideas?

**kc-** · 4-6-09, 12:26

Nobody knows???

**vandejm** · 4-6-09, 13:08

the idle on these things can be finicky.

i had a slightly thicker than stock gasket between the throttlebody and IM and could NOT get it to idle right.

is there anything that isn't stock around there?

**kc-** · 4-6-09, 13:56

Well I gobbed this brown gasket maker around there...the gasket was ripped at the bolt holes but I threw a bunch of gasket maker in there. Do you think a leak in the throttle body gasket would cause up and down revving consistently? It seems like an electronic problem.

Right as I start it, the revs go up to 2,000 then as they start coming back down it'll stop at 1,500 and then after about 5 seconds of idling it'll jump up between 1,500 and 2,200 non stop over and over again.

**xXCloud** · 4-6-09, 14:28

I just messed around with the screw when it was bouncing that seemed to stop it.

How do you set the car to diag mode?

**kc-** · 4-6-09, 14:38

Take a paper clip, bend it into a U shape, then look underneath the cap that says "DIAGNOSES" and just like the fuse box, it'll show you what each little socket is. You want to stick one end in "TEN" and the other in "GND" or "GRND" which essentially just means ground.

I tried turning the screw in and out but once all the way in, it just sticks at 2,200 with a once-in-a-while rev down to 1,500. It basically slows down the timing of the fluctuating rev between 1,500-2,200.

I'll go mess with it now and report back.

**kc-** · 4-6-09, 15:16

Alright I messed around with the idle air screw, didnt help. I'm stuck guys...

**kc-** · 4-6-09, 15:42

I think I might have fried the IAC, I listened to another guy's post in another thread and he said that he hooked up the IAC to the battery to open the valve so he could spray into it. He used speaker wire, as did I, only I got sparking and smoke inside the IAC.

Could it be that since I may have fried the IAC that it would cause my idle to fluctuate when engine is warm?

Only when the engine is warm it fluctuates.

ninog · 4-6-09, 17:00

kc, I'm in the exact same boat as you dude. My car also has trouble idling, it idles rough between 650 and 1,100 rpm and then while I'm driving you can just feel the power loss if the throttle is like a quarter depressed. If you manage to figure out what the problem is I'd be more than appreciative to hear if and how you solved it.

QuickShift · 4-6-09, 17:27

I am in the same boat to

I just droped in a new 93 PGT engine into my 93 LS. My idle is constantly at 2k rpm to.
The idle screw did not help at all. (does it have to be adjusted in diag. mode)?
I think is a vacuum leak, i was looking at my vac lines between the eng. and the firewall.
The vac line that connects to the EGR Solenoid was broken off of it the "male part". I'm not sure if it twas the Vent or vacuum solenoid, and I can not find one at auto zone

Does anybody know if this can cause a bad and high idle?

Also, a off the subject question. I have a MT, and when i press the clutch I cannot get it to go into gear. i thinkg the piece that goes into the clutch isnt connected properly. Is there a way to "re-connect" it w/o taking out the tranny?

Lambera · 4-6-09, 17:37

To test for a vac leak take off the intake disconnect the VAF and IAC then tape off the TB and try to start the car.

**xXCloud** · 4-6-09, 22:30

I still have the problem but I just messed with the screw while it was bouncing hasn't acted up again but I'm sure it will. I hope we can all find out the answer to this a lot of people seem to be having this problem. The problem started for me after I installed an after market intake due to my stock intake having cracks all over it.

**Mazda_Powered** · 4-6-09, 23:29

im having idle issues too, but my IAC and TPS are working great, with no vac leaks

all i did was clean the EGR passage out

any ideas people?

**kc-** · 4-7-09, 0:10

BAAAAA lol, sorry but SOOO many people tell me they have had the same problems. Every time I'm working on my car outside with the engine running and revving by itself, a random guy will Always walk up to me and say "it sounds like a vacuum leak" it's weird, and then I'll say "I've checked all the lines..." and he'll say "oh then adjust your TPS" and I just tell them that i've done all that and then they say how they used to own a probe "back in the day". It's kinda funny though because we all share the same problems.

This is what I'm gonna do, not tomorrow or the next day, but on the weekend I'm buying a new IAC valve and gasket. I'm gonna install it and see where that takes me. As I might have mentioned before...might have....this has Never happened before, this up and down revving continuously, it only happened After I cleaned the IAC and reassembled everything.

I'll do Lambera's vacuum leak test to see what happens, but I have to get some shut eye now, I'm picking up a classic set of TSW stealths from a guy tomorrow so I'll try and find time to test for vacuum leaks.

If we all work together investigating and narrowing in on the problem, then we can get a sticky posted up on how to fix this notorious problem with these cars. I'm surprised after all of these years that there isn't a solution, let's make history boys LOL.

**bmxfuel007** · 4-7-09, 1:08

i'm actually gonna clean one of my iac valves. took it apart today and took a look and things are black. going to use the cleaner that's safe for electrical components and spray it in there and then use compressed air to dry it off. i'm too scared to use straight up carb cleaner. hopefully it works. then i'll reseal with a bead of gasket maker on the old gasket. have fun finding a ZE iac valve gasket. it's not the same size as the de one

Quote:

Originally Posted by kc-

BAAAAA lol, sorry but SOOO many people tell me they have had the same problems. Every time I'm working on my car outside with the engine running and revving by itself, a random guy will Always walk up to me and say "it sounds like a vacuum leak" it's weird, and then I'll say "I've checked all the lines..." and he'll say "oh then adjust your TPS" and I just tell them that i've done all that and then they say how they used to own a probe "back in the day". It's kinda funny though because we all share the same problems.

This is what I'm gonna do, not tomorrow or the next day, but on the weekend I'm buying a new IAC valve and gasket. I'm gonna install it and see where that takes me. As I might have mentioned before...might have....this has Never happened before, this up and down revving continuously, it only happened After I cleaned the IAC and reassembled everything.

I'll do Lambera's vacuum leak test to see what happens, but I have to get some shut eye now, I'm picking up a classic set of TSW stealths from a guy tomorrow so I'll try and find time to test for vacuum leaks.

If we all work together investigating and narrowing in on the problem, then we can get a sticky posted up on how to fix this notorious problem with these cars. I'm surprised after all of these years that there isn't a solution, let's make history boys LOL.