Jaime-TA-84

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Seems to be doing this a lot lately. Started happening occasionally a few weeks ago and it seems more common now. When I accelerate to 25-30 or more and let go of the gas pedal, the car will maintain velocity and RPM. It's pretty weird, its as if I had cruise control enabled, but its not. Normally when I let go of the gas pedal, the RPM's will go down to under 1000rpm (at street speeds) and the velocity will decrease steadily. Last time it happened, it went on at the same speed for a few hundred feet until I had to brake for a stop light.

What could the problem be? Failing transmission? Failing carb?
I have not noticed any shifting problems with the transmission when accelerating, but maybe this problem is a failure of the transmission to downshift? The A/C is not on so it cant be the idle stop solenoid (and it would stay at high RPM when I brake).

stroker_SS

maybe the lock up convertor is staying locked?

fbodyorbust

check for a vacuum leak......
i just replaced my carb and had the same problem untill i got my vacuum all figured out

Jaime-TA-84

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I don't even think the torque convert locks up. I have tried testing it by slightly pressing the brake pedal while going about 70mph and I dont see the RPMs go up (as it should if the torque converter released). Should the torque converter even lock while at a slow speed like 30mph?

I'm thinking fbodyorbust may be right. I uncapped one of the connectors on the "F" vacuum port on top of the manifold the other day to add a vacuum line to the hood intake solenoid vacuum switch. Could this be the cause? I'll verify the connections to make sure there are no leaks. I know I have a leak at the plastic Y splitter (its cracked) that is a couple of inches away from the PCV valve.

Could there be any other causes for this problem i'm having other than vacuum leaks?

fbodyorbust

i think the vacuum leaks will take care of it......either that or the throttle position sensor could be bad....thats the fatter of the two connectors on the top of the carb........

when your talking about the F im asuming your talking about the vacuum switch that is right in front of your carb kind of to the left there with two fat hoses coming out of it.....one goes to the canister by the head light and the other goes to the emissions cluster**** right there in front of the carb...........that vacuum switch is ported.....it will open and close on the top and bottom due to engine temperature....if you were to unscrew it you would have antifreeze spew all over the place...theres a little temperature plunger that sits there and regulates when the two valves open......vacuum will take the least path of resistance so when that switch is activated your vacuum is not going where it should its going to your hood intake soleniod or whatever you hooked up......shutting off the vacuum to the canister down there which in turn is fooling it witch fools something else and its trying to think it has cruise controll activated.....get rid of that tap in there and do it somewhere else it will go away.........

Jaime-TA-84

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No, the stuff in front of the carb is hooked up correctly (I think ) The "F" looking connector im talking about is behind the carb on the intake manifold. It has two ports for vacuum. One used to be plugged, but I opened it and connected a hose to the hood solenoid vacuum switch.

fbodyorbust

well i would try the throttle position sensor......hopefully that will take care of the problem........if your sensor is bad it thinks you have the gas pressed and will deliver fuel.........have you checked the linkage to make sure its not sticking?.....other than that im pretty much out of ideas brother

Jaime-TA-84

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Thanks. I'll test the TPS over the weekend and try to diagnose it more, then post back my findings.

Jaime-TA-84

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Today I found out that the idle would go back up to the normal 500rpm (from the ~300rpm that it is now when cold, in open loop) if I unplugged either the TPS, MCS, or both. The MCS would also stop clicking when the TPS was disconnected. Does this mean one of the two is bad?

hotrodZ28

the mcs or the tps could possible be bad but should test the sensor itself first

fbodyorbust

You might try replacing the cruise switch.....its an odd ball idea but if its freaking out it could be telling the car to cruise when it shouldnt.......i doubt thats it but it might give you some more things to trouble shoot.

dimented24x7

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Have you checked to make sure teh throttle isnt sticking open? As the throttle shafts wear into the casting, the butterflies get off center in the bore and get hung up.

Jaime-TA-84

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If the throttle stuck open, would it "unstick" itself when I came to a stop? Because its not idling high when i come to a complete stop. It just seems like it will maintain velocity and RPMs but will stop as soon as I press the brake. I am able to stop and it will go back down to normal RPMs.

I dont think it's the cruise control. If it were, I would be able to hear the throttle surge every time the actuator tries to compensate for a loss of velocity.

The best way I can describe it is as if I held down the gas pedal, but I'm not. It the throttle were sticking, wouldnt it idle high when i stop?

dimented24x7

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Does the car push when you come to a stop? IOW, does it surge forward as soon as the brake is released? The TC will stall and keep the car idling around 1200 RPM or so even if the throttle is partially open. Does the idle come back down when you lightly press the brake? What happens if you place it in neutral while this is happening?

Jaime-TA-84

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It goes forward slowly when I release the brake pedal since its at 500rpm. I placed it in neutral while it was happening and there was no change.

I got my electronic tach/dwell meter today in the mail. I hooked it up in the V6 setting while idling after a 50 minute drive on the freeway (so it was completely warm) and it said at 31.5 degrees. It did not change at all, but I didnt check at different RPMs (only at 500rpm). When I disconnected the mixture control solenoid, it went to 60 degrees. Plugged it back in and it went back to 31.5 degrees. Unplugged the Throttle position sensor and it went to 0 degrees. Plugged it back in and it went back to 31.5 degrees. Does that mean the mixture control solenoid is working properly?

Gramps

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id start looking at your throddle cable first, its by far the cheapest thing to look at or fix. does it happen from just cruising or when your pedal is to the metal?

Jaime-TA-84

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It happens when cruising.

I'm going to do the "System Performance Check" in the service manual on Wednesday and see if that helps anything (dont have time before then, since its final exam week )

Brianbajnuth

I know that this is a very old post but did you ever find the problem? I have a similar problem

Jessica Howland

Did anyone ever figure out this problem? I am having the same issue with my 2013 Hyundai Accent. I get it up to about 40mph or higher and let go off the gas and it will stay at that speed. It sounds like it is still revving up and then just very slowly decelerate. Also it is very loud and almost sound like an airplane engine.

Jaime-TA-84

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Unless your 2013 Hyundai has a V8 Chevy engine with a Carburetor, you are not having the same issue. This is a 1982-1992 Camaro and Firebird forum. Not a Hyundai forum. Recommend you search for a Hyundai forum and ask there.
For anyone wondering, I never did figure out the cause. I think it randomly stopped doing this at some point.

Jessica Howland

Ok. Thank you. I didn't think it matters if it was a V8 with a carburator or not. It is still having the same issue of keeping an RPM at a certain speed when my foot is no longer on the gas. When I search Google, this was the only forum that I could find that had a car doing the same thing. Sorry that I don't have a Camaro or Firebird. I figured someone out there could still help me. Sorry for bothering this forum.

JWCC

Hi Jaime and others ,
Have anybody fixed this problem ? Appreciate your advise . Thanks

Jorge Neri

Did you ever figured out a fix to the problem. Because I have the same issue (even though I don't have a 2013 Hyundai Accent).

sofakingdom

iTrader: (1)

What kind of car DO you have?