1990 5.7L TBI flooding???

[sackett2622]

Sitting here awaiting thursday, (payday) so I can buy an IAC sensor for my truck. Hope someone out there has an idea or suggestion to this problem.
Truck ran great, took it 6 miles up the road, shut it off. Got back in it, it started ok, idled a little high and could not "kick it down" using the gas peadal so I headed for home. Drove 2 blocks to a red light, where it died rolling to stop at the light. Only way it would restart is by holding the gas to the floor, I made it hiome but it missed/sputtered all the way there. Now, it starts great when cold, runs about 10 minutes til it warms up, then fuel is visibly FLOODING into both chambers below the fuel injectors, it puffs out white smoke at the TBI, black smoke at the tailpipes, and misses. If you even act like you're going to touch the gas pedal it dies. Even if you don't touch it, it eventually sputters to a halt. Since this all started, on the advice of friends I have put on new;
TBI gasket
Spark Plugs
Fuel Pressure Regulator
Throttle Position Sensor
Oxygen Sensor
Ran Lucas injector cleaner thru the tank
Took ignition coil to auto zone it tested "good"
new fuel filter

I also took both injectors out and inspected the large and small o rings, and the filters at the base of the nozzle on each injector, they are good and clean as a pin. ANY ideas will be appreciated.

[2000CAYukon]

Sounds like a classic case of a bad Engine Coolant Temp sensor (located in the intake manifold near the tstat). It tells the ECM the temp of the engine and the ECM uses this information to control the amount of fuel delivered to the engine. Cold needs more fuel than warm. Use an OHM meter and measure the resistance across the two pins of the sensor when the engine is cold and when the engine is warm. Report back what you find.

The high idle indicates a possible vacuum leak so check all the vacuum hoses carefully. On my 90 K1500, the PCV gromet was a source of my vacuum leak.

Also check the MAP hose. A leak here will cause it to run rich as well as a MAP that does not hold a vacuum.

//2000CAYukon

[webbch]

Is the coolant temperature sensor only used in closed-loop operation? Reading the initial problem, I was going to question the O2 sensor, since I know that gets brought in once the engine temperature comes up and the computer swtiches to closed loop operation. If the CTS gets brought in to the fuel calculation at that point as well, it could have the same effects I would think.

[2000CAYukon]

Originally Posted by webbch

Is the coolant temperature sensor only used in closed-loop operation? Reading the initial problem, I was going to question the O2 sensor, since I know that gets brought in once the engine temperature comes up and the computer swtiches to closed loop operation. If the CTS gets brought in to the fuel calculation at that point as well, it could have the same effects I would think.

In closed loop, Throttle Position, MAP Sensor reading, CTS reading and O2 are used for fuel calculation.

In open loop, the CTS is also used for fuel calculation but I believe the 02 is not used in open loop (I have the factory manuals at home and I can't remember if O2 is used only in closed loop).

A high idle (especially when warm) can be a bad CTS sensor as long as there are no vacuum leaks. If I let my 90 warm up and put the CTS harness off the sensor, the idle will jump since it thinks the engine is now running very cold.

//2000CAYukon

[sackett2622]

Hi there! Well, I went to NAPA and got a new cts, installed it as you suggested and voila!!!!! Truck runs like a dream once again! Thanks very much for the excellent advice. I am taking it to get it timed today, as it is a little off from where I pulled the distributor shaft to put in a new pick up coil. I would like you'r opinion on something, if you don't mind. My brother in law has a 1981 Ford F 150 351 V8 4x4 for sale. I am thinking about selling mine and buying it, it is a flat bed, more like a work truck/hauler, it has a hitch also. It has high miles but runs good, some rust, the dual exhaust is shot and it has a weak leaf spring on it, (1/2 ton. Do you know anything about this year, or problems with it? I hear Fords are hard to work on, and harder to get parts for than a chevy. Plus, it only gets about 10 MPG. What do you think?
Thanks again for all your help!!

[webbch]

In open loop, the CTS is also used for fuel calculation but I believe the 02 is not used in open loop (I have the factory manuals at home and I can't remember if O2 is used only in closed loop).

Late reply I know, but thanks for the info. I'm pretty certain the O2 is not used in open loop mode, was just wondering about the CTS.

Glad the CTS replacement fixed the problem.

[RWitcraft]

I just wanted to thank you guys for this thread. My 1989 G30 based motorhome (350 TBI motor) was having the same problem that it'd flood and die when it got warm.

I switched out the fuel filter, cap, rotor, plugs, idle control valve, and O2 sensor. Every little thing seemed to help it run smoother when cold (the O2 sensor had broken in half), but it'd still die out just as the original poster's truck did when it got warm.

Almost ready to give it, I jumped on the trusty internet and read this thread. I went back to the auto parts store for the 4th time that day and bought a new coolant temperature sender and put it in. And now it runs better then it has in years.

[2000CAYukon]

Originally Posted by webbch

Late reply I know, but thanks for the info. I'm pretty certain the O2 is not used in open loop mode, was just wondering about the CTS.

Glad the CTS replacement fixed the problem.

See http://www.customefis.com/GMEFI.html

02 is ignored in Open Loop but CTS is not.

//2000CAYukon