amused

i've been having this problem lately where if i dont start the car in gear when it's cold (to prevent the coldstart system), it just revs to 3k rpm then stalls out. the other day i got a massive backfire restarting the car after this happened.

has this happened to anyone else before?

NZConvertible

Unplug the AWS solenoid on top of the manifold and it won't happen.

jgrts20

this is going on with me(mine doesnt backfire though, after the second or third time its fine) but i start the car in neutral and it does it!! other post says it might be a leak in the vac hoses or the AFM!! the nights r damp here but nice during the day once my car is warmed up it doesnt do it anymore!! i might try the AWS solenoid(what is the AWS solenoid anyway(duh)!! i will try to start it in gear tomorrow!!

NZConvertible

It's not a fault, it's supposed to do that. It's the accelerated warm-up system (AWS), which is there to bring the cat temp up quicker. It was obviously required to pass emission regs, but I don't think it would be very good for the engine.
Unplugging the AWS solenoid will stop this happening, but even better would be to remove it and cap its connections.

ForsakenRX7

Yea I removed mine ,actually I broke it by accident, but I was going to anyway cause I didnt like the idea of my car reving to 3k first thing and staying there.

wai

I fixed my cold start by accident , but why it only rev to 2300rpm ,not 3000rpm??

Barwick

anyone have a writeup on this? I'd like to remove it and possibly the whole bypass air valve system.. just worthless stuff IMHO

jgrts20

i too would also like to remove the AWS, is there a link on this!! i dont even know what the AWS looks like and where its located!! please help!! PEACE!!

i dont drive my car in the winter time anyway so its worthless for me!!

dr0x

Its not that hard. Unclip the hoses going from the intercooler to the AWS then to the UIM. Unplug the AWS, undo the connector, put a vacuum cap on the nipple on the UIM and IC. Take a zip tie and secure the vac caps.

NZConvertible

No link required, just follow the instructions above. Once you see it, it'll be pretty obvious what needs to be done. Download the EFI chapter of the factory service manual from www.fc3s.org or www.iluvmyrx7.com and look at the schematics. You'll learn a hell of a lot about your car by reading the FSM, info that will help you service, repair and modify your car. This isn't actually a winter thing, it happens when the engines cold. Besides, that's half a year of 7 driving wasted...

HAILERS

jgrts20.....sorry, but its not the AWS on a 86-88. There are TWO valves that make a 86-88 do the 17 second, 3000rpm fast idle. One is the BAC and it's ASSISTED by the Air Bypass Solenoid. If the Air Bypass Solenoid is disconnected......you WILL NOt lose the high rpm on startup. It will diminish down to approx 2400 rpm. Its the BAC that is carrying the load so to speak.

On later cars they decided to chang the name of the solenoid to AWS from Air Bypass Solenoid. You can swap one for the other...same valve/solenoid.

Anyway, why remove it? Just disconnect the two wire connector from it. That'll get you down to 2400 rpm on startup.

wai
See the words directly above for an explanation of why you only see 2300-2400 rpm now.

NZConvertible

Hailers, if you unplug the temp switch in the radiator's bottom tank doesn't that disable the AWS system too?

dr0x

If you are going to unplug it why not just remove it and throw it into your fc parts bin

Henrik

Just bear in mind that this valve is also used for power steering. You may have stalling issues at idle without it. How much it affects it I don't know as I had a manual rack - just test it with the connector disconnected before removing it.

Henrik
87TII

HAILERS

****Hailers, if you unplug the temp switch in the radiator's bottom tank doesn't that disable the AWS system too?*****

Yes/no...I sure don't know all there is to no/know. Think about it. The water temp switch at the bottom of the radiator, has an open circuit when the water is cold. Now tell me.....how disabling a open circuit will do anything at all???????

That said, I KNOW, just like everyone else, that if you disconnect that switch, the 3000rpm start up when the engine is cold.....will happen no more

You tell me how that can happen. I sure don't know. I suspect there is another player, like the water thermo switch that's dealt in during the cold start.

I'm 99.9% sure, positive, correct that the water temp switch at the bottom of the radiator is an open circuit when the water is cold. Go out to your car in the morning and put a ohm meter on the two pins on the sensor. If you don't read an open circuit....you live in Saudia Arabia and it's noon time.

Henrik......Isn't it the Air Supply Valve on the backside of the intake the one that does the power steering trick? The one I took off my engine so I'd have room for a long twisty hose to connect b/t the throttle body and the rear housing (able to lift the throttle body up high enough to disconnect the hose when removing the body for whatever reason). You know, that water hose for the cold start system.

And while I still have time.......if you disconnect the water temp switch at the bottom of the radiator...it will have BAD effects on the RELIEF SOLENOID. What happens is the Relief solenoid will be de-energized when driving around under 3800 rpm. That's only bad if you have to pass emissions etc. With the Relief solenoid de-energized, the acv will dump most all the time. Was not meant to act like that. For disbelievers, just put a LED on the Relief solenoid and observe it while driving with and without the water temp switch connected/disconnected. I'm about 95 percent sure that's the way things are.

Oh yes, I don't suggest removing the air supply valve because it takes too much WORK. Just disconnecting the thing will do. If you remove it then you have to contend with the air hose b/t the intercooler/bac. Yeah, I know, cut hose and stuff a bolt in it. Just contrary here.

The above is just series four. Not applicable to series five...so if you have a series five ....don't go crazy looking for a water temp switch at the bottom of your radiator. Please.

dr0x

Yeah that is it. I dont see why thats hard to remove either, 2 10mm bolts

NZConvertible

You're getting confused with the air supply valve, which raises idle speed when you use your PS. The AWS valve is a different solenoid valve.

HAILERS

Well, I screwed up again. In the second to last paragraph that I wrote above, I MEANT to say *I don't suggest removing the air bypass solenoid*, NOT * I don't suggest removing the air supply valve*. Two different animals, just flubbed up.

And your right dr0x, neither is hard to remove. Just plug the open orifices and be done with it.

Now, does anybody know why removing the plug/plugs off the water temp switch on the bottom of the radiator would stop the 17 second duration, 3000 rpm startup??? Knowing that the water temp switch at the bottom of the radiator is an open circuit when the water is cold??????? Just a series four question. Not for series five owners.