Cold car runs very rich
 

My car runs very rich in 30-40 degree weather and takes forever to warm up. After going into town I use a noticible amount of gas like 10mpg.

I normally take off after 2 minute warm up and use fully synthetic motor oil, diff fluid but not trans fluid.

Once its warmed up everything is normal.


How can I improve gas mileage in cold weather on on my 89 tbi 4 speed?

Re: Cold car runs very rich
 

Replace thermostat - it might be stuck open.

//RF

Re: Cold car runs very rich
 

Its new and there easy to install.

Re: Cold car runs very rich
 

Could have a coolant temp sensor that just doesnt work as good in the cold. When the car is cold it is in open loop meanign the computer doesnt really control it. It's more in a full fuel dump mode. The coolant temp. sensor is what tells the computer where the engine temp is and the computer adjusts as such. but only when warm enough and in closed loop. It's not too expensive. It's easy to change and it may take care of your problem.

Re: Cold car runs very rich
 

Well I know that coolent sensors are not all that accurate but sometimes mine goes up to 180 then drops to 160 and then fully warm it stablizises around 210-220. At 40F and below all I hear are the tbi injecors hissing from dumping lots of fuel into the engine for about 2 minutes. Also many people claim there tbi sprays sequentially or batch fires but mine spray constantly but with a nice even mist pattern.

Re: Cold car runs very rich
 

Jay

It may appear as a constant spay but TBI injectors (at idle) are alternating firing - with about 1.7 mSec (CTS = 90C) per injector fuel pulses, 2x each for one engine revolution. When engine is cold injector pulse width is increased for richer fuel mixture. At idle (600RPM) it takes about 100 mSec for engine to make a full revolution during which each injector fires twice. To a human eye it appears as a continuous stream. The best way to look at a spay pattern is with timing light - just point at injectors and you may catch stop - start of the spay.

Actually Delco CTS is reasonably accurate, the same can not be said about aftermarket CTS sensors. CTS is very easy to check with a DVM. Delco CTS part number 12146312 at 5C should measure 7,354 Ohm, and at normal operating temperature - 90C should measure 244.8 Ohm. At room temperature - 25C 2,830Ohm should be the expected normal value.

//RF