frozenwings

Hi, I just got an 85 RX-7 that won't idle below 1200 RPMs (give or take 50). Tried to back out the idle speed screw and it won't drop any further. Should I try messing around with the mixture screw or is the problem elsewhere?

Also when I stay at a constant speed my car chugs slightly like it might not be getting the proper amount of gas. If I give it any more gas it accelerates, so I find myself constantly accelerating very slowly to stop the horrid chugging. I notice that the lower my speed is, the worse it chugs. In second gear staying at a constant speed (20-25mph) the chugging is just horrible.

I'm not sure if these problems are connected at all, and any help would be appreciated. Thanks.

cdrad51

Assiming your car is stock, unusually high idle is caused by

- Improperly adjusted dash pot

- Malfunction of hot idle compensator valve

- malfunction of throtle opener system

blwfly

iTrader: (4)

dont forget vaccum leaks
while cars runin get some carb cleaner try not to spray everywhere but spray on those little yellow plastic tubes just the ones on the carb and if you hear a sudden increse on revs could be a vaccum leak

if you have the ratsnest and dont have smog where you live i would research and remove this as its common for vacc leaks and also make problem solving easeyer
i wasnt lucky that myn was already gone cause i wanted to have the fun of doin it lol but thats just me
good luck

cdrad51

Vacuum leaks my account for a rough idle, but not a high idle.

frozenwings

Well the dash pot is almost impossible to get to, so that sucks. Also my knowledge in cars is almost none when it comes to the inner workings under the hood. Im not stupid enough to not know how to turn a screw and twist things around, but I'm afraid of messing something up. How much do you think it would cost to take the car to someone that knows whats up to get the settings all straight?

Rob Stolz

what is it supposed to idle at?

Rob Stolz

I had a rough idle after i put my header on, i turned the mixture screw on the carb a bit and then it idled perfect, i also raised my idle from 200 to around 700-800 by adjusting the nuts on the piece of linkage behind the carb

cdrad51

Idle is supposed to be 750.

frozenwings

Yeah, I was hoping to get around 800-900 but I cant get below 1100 ever, and most of the time its around 1200. I dont think the mixture screw has anything to do with my case, I think it could be the dash pot though. I downloaded a schematic for the carb and after looking at all the different settings and tuning options, it looked like the dash pot was not performing well or not adjusted properly. But the stupid nut is in a retarded spot under some hoses and some other doohickey on the carb.

cdrad51

It shouldn't cost more than an hour's worth of service, since that is the time it would take to somebody who knows what's up to straigthen the issue out. Problem is, finding such mechanic...

frozenwings

Yeah

cdrad51

Well at least is not a critical problem. Your mileage won't be the same but otherwise it's no big deal. If you check forum data and the service manual, you should be able to learn how to deal with the idle issue yourself. If you don't have emissions in your area, removing the rats' nest will give you a much cleaner engine bay to work in.

You can also check the regional forum and see if there is another rotorhead nearby who can give you a hand.

frozenwings

Well the little rod that comes out of the dash pot, should it be protruding and touching the throttle lever?

The carb guide thingy I'm looking at says "Before starting the engine, check to make sure that the dash pot does not keep the throttle lever from returning to the idle stop." What exactly does that mean? I notice that even before I start the engine the rod is touching the throttle lever and pushing it down a ways. Could this be a problem or does it sound normal?

cdrad51

The dash pot rod is supposed to be touching the throttle lever when the lever is at the idle position. Is supposed to stop touching the lever when you accelerate and reach 3800-4200 rpm. The idea of the dash pot is to help the throttle close gradually. So say you accelerate in idle to 5k rpm. When you release the throttle, the lever will touch the dash pot rod on its way to idle position, and the spring-like action of the rod will slow it down so it doesn't return to idle position suddenly. But if the dash pot is adjusted incorrectly, it will prevent the throttle lever from reaching its idle stop, determined by the idle screw. The position of the idle screw determines when the throttle lever stops. Or at least it should. If it doesn't, something else is preventing it from reaching its rest position, and if it is the dash pot, it needs to be adjusted. If you don't have a tach you can connect to the engine, have a friend rev up the car to 4500 rpm or so and then gradually release the accel pedal. See at what point the dash pot rod touches the lever and have your friend tell you the tach reading. Adjust as needed.

brandon davis

iTrader: (3)

Sounds silly but have you lifted up on the gas pedal? If so then go with what cdrad51 said.

frozenwings

Yeah I'm hoping its just the dash pot, as the idle screw isnt setting the RPMs any lower than 1200. I tried getting to it today, but its hard to get to the nut through whatever the hell is the little thing right above it on the carb and theres a few hoses in the way too. There is almost no leverage to try and loosen it. I will be more aggressive about it tomorrow.

cdrad51

an alternative quick method of checking if the dash pot is the culprit: with engine on, push the rod in to the point where is not touching the throttle lever. If the rpms go down, bingo!

frozenwings

Well it wasnt the dash pot, at least I dont think it was. However I did lift up on my gas pedal and the car immediately stalled out. I messed with the idle screw a bit and now when iI push up on the gas it drops to around 900 RPMs but sounds like its about to die. It definately can't go any lower like this. Is my gas pedal getting stuck or something? When can I do to make it so it doesnt sound like its about to give out?

mazdaverx713b

iTrader: (91)

i would check you idle compensator. its function is to raise the idle when it senses a load on the engine such as when the a/c is on(to prevent stalling) it's much like a BAVC. they like to stick or the spring likes to break and or stretch. it's solenoid operated, so you may want to check operation of the solenoid as well.

frozenwings

Well after mucking around with it for a bit, my friend and I loosened the nuts on the accelerator cable and now its not sticking anymore. When I let off the gas it goes down to whatever teh idle screw is set to, so that is cool. However, I still cant get around 750 RPMs, when it drops down it sounds like its about to stall and the compensator kicks in and takes me up to around 900-1000. Should I mess around with the mixture screw at all? If not, I still have to set it up to around 1100-1200 RPMs to get it so it doesnt idle rough. I think the person who owned it before me might have set the accelerator cable how it was on purpose because of this.

EDIT: Maybe I should have mentioned this before, but the anti-tampering cap is still on. I have been trying to get it off all day but cant through all the hoses and whatnot. So my main problem I should say is getting the bastard off, because if it was I would be "tampering" with it as we speak/type/read.

frozenwings

Sorry for the double post guys. But after scouring the forums here I saw a couple threads saying that if the cap is still on, not to mess with it because it probably hasnt been messed with before. If this is the case, what are some of the reasons I can't get my car to idle well around 800 RPMs?

cdrad51

you'll have to do a search on that one. It's been covered a gazillion times before.

chedda_j

Ok do me a favor and tell me where you downloaded the schematic of the carb is, im having this exact same problem.