Idle and cruise control probs

[gadget73]

Mine lay on the fenderwell near the brake booster.

I forget about the wire/CE trick because my car doesn't have a CE light. There is supposed to be a way to wire a light onto the plug and read them that way, but I've never bothered.

[Paul_]

http://www.grandmarq.net/forum/viewtopic.php?t=85

heres the thread wit the codes. my bad, it was in 5.0/5.8 lol

[Paul_]

usually on the drivers side on the fenderwell.

my jeep was even easier. turn the key to igntion 3 times and the cel starts flashing at you. nothing to fuck with under the hood

[qazvick]

That sounds like the same exact way I pulled codes on my RX-7. I guess I'll look for those codes and see what happens? Where under the hood are these plugs?

[Paul_]

you really don't even have to get a code scanner. theres two plugs under the hood. one is a single plug and the other has 5 contacts in it. looks like a house roof. iirc, you take a paper clip and put one end in the top right of the house plug and the other end into the single plug. you turn the key to ignition, and the check engine light will flash at you in sequience . you do this also with the motor running. in the cfi/electrical forum theres a sticky with the codes.

figure i'd save you a trip to vato zone

[gadget73]

You can buy one online or at most automotive stores. Not sure if places like Autozone can do old style OBD1 diagnostics, but a scanner should only run about $30 or so.

IAC has nothing to do with cruise. You'll need to replace the VSS probably. Check the wiring first though, it might have just gotten damaged somehow and the computer isn't getting a signal from it.

[qazvick]

I tried a different IAC which I was told was a known good one. Made no difference in idle or the way the engine ran at cruise speed. I'll check into the EGR valve idea.

Do you know where I can get a code scanner? Or could I just take it to the auto store where they pull codes for you?

[gadget73]

Could also be a stuck open EGR valve causing the idle problem. Wouldn't hurt to pull it off and make sure the "button" will push in and the passage isn't totally clogged with carbon buildup.

If you have access to one, I'd really think about using a code scanner to see what it has to say.

[qazvick]

Ok I unplugged the iac and it stalled even quicker than before. I also adjusted the tps and got the voltage to read .97V and nothing changed. So I guess first I'm going to go swap out the iac with a known good one and see what happens.

[Paul_]

unplug the iac with the motor running. if the engine stalls the iac is good. if the motor does not stall, the iac is shot

[qazvick]

Alright I'll do the tps adjustment tomorrow and get back to ya. Thanks for the help tonight guys

[TommyN]

A junkyard throttle body would likely come with a TPS and IAC and might cost the same as an IAC.

Why not get the TPS adjusted first, then see how it idles. Not sure your IAC needs replacement.

Tom

[qazvick]

"A junkyard throttle body might be something to try if you can get it cheap enough. "

Are you saying I need a whole new TB?

"If you want to get that TPS under 1.0 volts, you can unbolt it, drill the holes in it oversized, then reinstall. Now you will be able to loosen the screws, and twist the TPS to get it to idle .90 - .95 volts. "

You mean so I can "pivot" the tps and adjust it like that? I'll try that out tomorrow and see what happens. SOUNDS BETTER than spending $30 on a new one haha.

But it still sounds like I need a new IAC too right?

[TommyN]

Your TPS might be bad if you had the idle screw backed all the way off and it was still 1.07V.

A junkyard throttle body might be something to try if you can get it cheap enough.

If you want to get that TPS under 1.0 volts, you can unbolt it, drill the holes in it oversized, then reinstall. Now you will be able to loosen the screws, and twist the TPS to get it to idle .90 - .95 volts.

You can tell when the screw is backed off far enough because it won't be touching the lever at the bottom of the throttle body. Maybe back it off so it is not touching, get it to barely touch it, then give it 1/2 turn more.

Tom

[qazvick]

Ok well before I even got the car the idle screw was all the way in. I did unscrew it as far as it would go with the spring on the screw still having some pressure on it, but the lowest I could get the voltage to go was 1.07. It still ran the same way. Crappy cruise, hardly any idle, nothing changed. I did remove the IAC and cleaned it with carb cleaner, also cleaned along where the air enters the TB.

I'm still wondering if it's worth a shot at the junkyard for another IAC (cause there are 2390482908342 of these things out there)