Hey guys,

I have a 1989 rx-7, its an automatic (ya i know, its a handmedown from my sister) but I'm having a real strange problem, when I'm stopped anywhere idling, my engine rpm's sputter and fluctuate between 250-1000, and all the engines warning lights all light up in sync with the rpms.

I have the same problem with the warning lights when I'm actually driving, but my rpm's don't sputter.

I have asked around, and searched this forum for the problem, cant seem to find it, hoping maybe someone knows what this could be?

I'm not very mechanical, so any insight at all would really help.

thanks everyone in advance

 

Well due to the warning lights flashing I would think that your charging system isn't functioning properly. I'd pull off the alternator and take it to an Auto Parts store to be tested. Either that or replace it.

 

Well, on an S4 at least, warning lights coming on is a sign that the alternator is failing. I'm not sure it's the same on an S5, but it's easy to check the voltage at the negative battery terminal and positive lead on the alternator.

Other than that, I'd check error codes, TPS, vac leaks, mixture settings.

 

thanks, I'm going to my uncles to get it checked out now.

 

Does the engine always get like that at idle though? The warning lights come on when the alternator isn't putting out juice on any car, usually at a super low RPM, like 250. I don't think the alternator is causing your idle to drop to 250RPM and fluctuate up to 1000. I'd say you need a good tune up.

 

well whatever the case, my uncle advised i take it to get diagnosed, so its gone till tomorrow, wish me luck (or rather a not very expensive problem)
by the way, nice avatar beef

 

At 250 rpms the alternator isn't putting out, so it puts a gnd on the white/black wire which in turn pulls a relay in that in turn puts a gnd on the idiot light cluster which in turn makes the idiot lights come on.

Rpms rise from the two fifty and the alternator puts out, the gnd is removed from the relay mentioned and in turn the idiot lights go out.

Low rpms are making the idiot lights come on, not the alternator per se.

 

Did anyone ever answer this problem anywhere? I'm having this same problem with my s5 its real random, it doesn't do it all the time only sometimes has it done a weird idle that goes really low and sometimes will turn off the car.

 

all the warning lights come on? if the idle drops to far they all do that. the system thinks the engine isnt running and the alt isnt putting out power. I would make sure your tps is adjusted if its doing the surging thing. They love to do that

 

Yeah all the lights come on since it turns off completely. I've readjusted the TPS before; the idle is good, but only sometimes does it do the weird idle thing, say when I'm waiting and the light is red I hear my idle start surging up and down and when I start to go the car starts to do this weird cut off or jerk and hesitates its pretty violent as it pushes me forward and feels like the car wants to stop but then goes again.

 

Are you sure the TPS is set right? Are you sure the timing is correct? Does it do this when the engine is cold, warm (improves after warming up) or both? Does it do it immediately after a stop or after the car has been standing still for a while?

 

Since its an automatic its probably more of a problem then in a manual. Ive had similar issues but its hard to say how I fixed mine or what the problem actually was. Do a search up on the BAC and I would recommend testing and cleaning it. If that fixes the surge great, if not you'll have to look at some other things on the tb. Theres also plenty of threads on this as well. In my particular case I ended up cleaning the BAC, I also took of the tb to inspect it. For some reason my thermowax was not working right so when my car warmed up or was warming up it had some issues. And after it was warm the surging was present and my idle was a little off. So I screwed a screw in all the way on the TB, might have been the fast idle cam screw. Doing this is just a temporary fix since now I have to hold my foot on the gas till shes warm. After I did this I cleaned and painted the tb and put it back on. Then I readjusted my tps again and set my idle a little high at 900 rpms. The main reason I set it higher was with my heat on high and my hid lights on it seemed to be too much and my idle would drop just a hair to much and I knew it would be just a tad low to keep a charge on the battery. So now everything has been working great except I have to hold my foot on the gas to warm it up. One other thing I just thought of is the dashpot, look into this as this could be a reason for the idiot lights coming on. Im pretty sure mine was dirty and when coming to a stop it would dip the rpms to low and the idiot lights would come on since the car was about to stall. I may have some of this stuff wrong as I'm no mechanic but it should get you looking in the right direction.

 

The tps is set right thats for sure as for the timing that I am not sure of at all I will have to look into that. And I'd say it only does it after the car is very warmed up, nothing bad happens when the car is cold. And its after it has been standing for awhile and then the rpms surge up and down and then I go and bam some damn violent jerks so what I do is just rev it high and then usually it'll go away after a bit.

 

To 86rxna the car is manual it is actually an auto to manual conversion car s5. But I will look into Cleaning the BAC and checking the dashpot as well since it can be this I got the car half a year ago and it was sitting in a lot for maybe 3 years or so, so I'm sure something are dirty as well.

 

So you set the TPS ( Green/Red wire measures 1 volt w/key to on) "after" the car is as warm as possible, which usually requires a 20 minute drive. Before the idle fluctuates are you aware of the voltage gauge and what it is reading? And what does your car normally idle at w/respect to rpm? And your problem "might" be related to the Water Thermosensor.

 

Okay so to start off I am not sure if the TPS is at 1 volt, but the voltage gauge is reading I'd say off of the top of my head about 14 or somewhere around there once its warmed up fully. And my idle is normally at 850 or 9 a bit higher than normal but thats because we had to set it again the other day, but the idle is good not bad. And can the thermosensor seriously cause this? I hadn't mentioned that I actually got a code that the thermosensor is bad so you might be right. But just makes me wonder that a themrosensor can really make it work so violently. But yes, the problems usually start once the car is driven a good amount an hour or so then it starts acting up a bit.

 

The TPS needs to be set to 1 volt under the conditions specified. Secondly, if you know you have an error code and you know the engine is not operating up to speed then you should share this info, no? Thirdly, the sensor in question helps the ECU decide how much fuel is used according to the engine temp (coolant actually) so this is an important aspect of the engine's operation.