nrd186

ok guys, here it is. i am a new fc owner(88 non turbo) and i am having some cold start problems and wonder if it is has to do with the bac valve. the car runs almost perfect when it is warmed up but when it is cold it shuts off. when i start the car i have to hold my foot on the gas around 2000 rpm for about 20 seconds. then when i let go it will rev itself up from 1000 rpm to 1500 rpm. as the car warms up it will gradually go down only reving up to 1400 rpm then 1300 rpm, etc. until it finally idles at 1000 rpm. also i was told these cars are supposed to idle at 1000 rpm. is that correct? and the last thing is i have an electric fan and when it comes on the car will drop 100 rpm down to 900 rpm and wont go back up until it shuts off. is that normal? any help would be awesome. i love this car!

RotaryVsPiston

im having the same problem

mike@awdmotorsports

Good luck resolving the issue.. I hear its very common..

Aaron Cake

iTrader: (1)

750 RPM +- 50 RPM is the factory spec.

There area number of problems at work here.

The TPS is out of adjustment.

There is a vacuum leak (or several).

The cold start cam assembly at the back of the throttle body is missing/stuck/rusted.

And the BAC valve may be clogged/sticking/unplugged.

Also, when is the last time the car had a simple tuneup?

nrd186

well i did adjust the tps and i also cleaned out the bac valve with some brake cleaner. the vacuum line with the coolant going into it was clogged but i did notice that when i have the key turned in the "on" position the BAC just makes a humming sound like it is stuck. is there a way to fix it or do i just have to buy a new one? so expensive. and also where and what is the cold start cam you mentioned behind the throttle body?


....oh and one more thing. i did the sea foam intake cleaning when my car is cold and it went through the cold start perfect but after leaving it alone for about an hour it goes right back to shutting off on me.

RotaryRocket88

iTrader: (7)

The accelerated warmup system (BAC & AWS solenoid valve) should boost idle up to ~3k right at startup. If you remove either of these devices, the other will still allow enough air into the intake to bring idle up to around the same mark. But if both are removed/broken/disabled, idle will only go to 1500 rpm initially.

As the engine temp rises, the idle speed will drop from 1500 to 750 rpm. This is due to a second cold start assist device: the thermowax. There is a piston on the end of the thermowax housing that moves a cam, which rotates the throttle plates slightly. When cold, the plates are opened more than when the wax is warm.

You will be able to spot the thermowax on the back side of the throttlebody. It has 2 coolant lines (in & out). If the piston does not extend/retract properly, or the fast idle cam is siezed, as aaroncake suggested, the idle speed will not be adjusted properly.

Another option for a high idle could simply be that someone opened the bypass air screw too far, which will boost overall idle speed. This screw is on top of the throttlebody, and usually has a rubber blind cap over it. Turning it clockwise will close-off the air passageway a bit, which will decrease air flow and reduce idle speed.

nrd186

thanks for the info, i had no idea about the thermowax and i did adjust that idle screw on top and actually ad to let more air in so the car would stay on during cold start. unfortunately the result is high idle when it is warmed up. i just want to get this thing so i don't have to hold the gas pedal down til it warms up. oh and does the humming sound coming from the BAC mean it is broken or is that normal. it has been like that since i bought it.

ROTARY MANIAC

Some Of These Problems That U R Facing Hav A Lot 2 Do With The Tps But Wat I Found Out Is That The Iac Valve On The Intake Manifold Is Shot Try 2 Clean It Out

Oni19

I was also having this issue, your plug might be going bad i had checked all the stuff described but i was still having truble in the cold weather, a friend of mine told me get new better plugs, and it starts like a charm even in 2C.

RotaryRocket88

iTrader: (7)

How loud is the humming noise from the BAC? I've never had any of mine make a noise that I could hear over the engine at least.

Check that you have the AWS solenoid valve (by the oil filter w/ a hose routed into the manifold), and clean out the BAC. See if that has any effect.

If you want to buy a new BAC, get one off of ebay or the classified section here. It should only cost you $5-10.