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TBI running rich

stockk5

stockk5

1/2 ton status
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Hey guys i have a 87 K5 with a tbi 350. It is running very rich right now. I can smell gas when driving, it barely idols and studders bad when first starting to drive but once im at like 40mph on the gas it runs ok. I need to fix this fast. I replaced the plugs, didnt help, i think the 02 sensor is next option to figure this stupid thing out. What do you guys think could cause this a TBI to run rich? thanks guys!
 
you should be able to flash the prom for error codes, and that should point you in the right direction.

but, i would say the O2 sensor is the next logical step. aside from that, check your air filter, the IAC valve could be bad, or it could be the ECM.

also, just because i know ive done this more than once, make sure your plug wires are routed correctly... i know, i know, but go ahead and make SURE. normally the ones that get me are the numbers 6 and 8. crossed plug wires will cause all kinds of issues but the engine will still run often without a perceptable misfire. although you might get some rpm jump.
 
Yea definately check the Coolant sensor for the ECM and the connector. An O2 sensor does not have enough control to make your truck run that rich but if your cts is bad it can tell your truck that it's -40 degrees and add all kinds of fuel.
 
Before you go throwing a bunch of parts at it without knowing what is going on.
Check the trouble codes. The ECM may tell you exactly what is wrong.
Most autoparts stores will check the codes for free.
or you can do it yourself
Here:http://www.troublecodes.net/GM/
 
alright well i know it is giving me a code 42.. i put another ignition module in it, i know what that the map sensor and tps is.. but i have no clue what the other things are you guys are talking bot :o lil help on where and what it is? i cant get it to run right, new 02 sensor and plugs so far, a different ing. module tried it out no difference. So anymore help?
 
well a code 42 is the EST fault code.

basically if you have a code 42, your timing is all fouled up because the circuitry that controls your advance is somehow malfunctioning.

check to make sure the single connector on the harness is still connected, its often referred to as the "timing connector". Im not really sure where it is on trucks, on my camaro is was by the HVAC stuff on the passenger side firewall, a tan wire.
 
if your talking about the single wire on the back of the ignition module i knwo thats clipped in tight.. other than that im not to sure.. ill check the timing tommrow.
 
EST (Electronic Spark Timing) wire is located near the brake booster and is a single usually black wire with tan stripe IIRC.
 
ok good to know. what exactly does this wire go to? what does it physically look like? (sorry for all the newbie questions this tbi stuffs confusing and frustrating)
 
Here is some good info i just found with a quick search.

That Annoying GM Code 42

[SIZE=-2]Posted 5/17/1997[/SIZE]
[SIZE=-1]By Ken Hughes


This is a common code that is often difficult to diagnose and scan tools can't help. The following understanding of how the electronic spark timing (EST) system works - what is taking place and why - is a big step toward a quicker and easier diagnosis of this circuit. When the engine is turning over, but below the run threshold of 400 RPM, the ECM holds the module's bypass voltage too low (0 volts) to energize its solid-state switch (ignition module). Another way of looking at the solid-state switch is to think of it as a relay. When voltage is applied, the relay is energized. With no voltage applied, the relay is de-energized. The pick-up coil/crank sensor pulses are amplified and shaped by the ignition module. These pulses are used to complete the circuit creating a magnetic field in the ignition coils primary winding that, when collapsing, will induce a high voltage in the secondary winding. Therefore, for every crank sensor/pick-up pulse, the coil is triggered. This is known as the bypass mode or module mode of operation. In this mode, the engine is running on the timing advance that is built into the ignition module.
With the voltage low on the bypass wire, the EST is pulled to ground through a resistor in the ignition module. This keeps the voltage on the EST wire at around 300 mV. When the ECM sees the RPM over the run threshold, it will then apply 5 volts to the bypass wire that will activate the solid-state switch (relay). This in turn will switch the EST from ground to the base of the transistor that controls the primary coil. In this mode, the primary coil winding is being triggered by the altered signal sent out from the ECM. The ECM will alter the signal to the ignition module and control the timing based on the inputs from various sensors. This is referred to as the EST mode.
This is how the system is designed to work! Now let's look at some of the things that can cause problems and set a Code 42. Under 400 RPM, no voltage on the bypass wire, the ECM expects to see low voltage (300 mV) on the EST line during this condition. If it sees 0 volts, indicating an open in the EST circuit - or higher than 500 mV - it sets a Code 42 and stays in the bypass mode.
If the bypass line is open, or grounded, the ignition module will not switch to the EST mode. The ignition module needs the bypass voltage to activate the solid-state switch so the EST voltage will be low over 400 RPM and a Code 42 will set. If the EST line is grounded, the ignition module will switch to the EST - but because the line is grounded, there will be no EST signal. A Code 42 will set.
To check the ignition module to see if the solid-state switch is capable of switching when the 5 volts are applied, the engine should not be running and the ECM connectors should be disconnected. An ohm meter and test light can be used. With the ohm meter on the EST circuit, it should read less that 500 ohms (in some cases, a lot less). Using a test light to battery voltage, probe the bypass wire. With this voltage applied to the bypass wire, the solid-state switch inside the ignition module should switch and the ohm meter on the EST circuit should go over 5,000 ohms. There is also another way to check this with the engine running: by removing the bypass and the EST wire from the module or ECM, run a jumper from the reference wire to the EST circuit. The reference signal is the signal that is used in the bypass mode to trigger the primary coil voltage. Apply 5 volts from one of the 5-volt reference circuits or a test light to battery voltage. This voltage on the bypass wire will activate the solid-state switch, in turn switching the module. On some models, the 5 volts or test light will have to be applied before starting or the motor will stall when the voltage is applied to the bypass. If the module is switching OK, the car will continue to run on the reference signal. If it stalls, the ignition module is not switching properly.
There are some other checks that can be made when working with an intermittent Code 42. When using a digital volt ohm meter (DVOM), there should be 5 volts on the bypass wire. On the EST wire, with the engine running, there will be close to 2.3 volts. The EST is a 5 volt on/off digital signal, so with a volt meter you will see the average of the high and the low. With the EST signal being a digital on/off signal, if you have a meter that will read in Hz, you can also pick up a Hz reading on the EST wire. Normally, you will see about 28 Hz with the engine idling and will increase with RPM. If the EST circuit would become momentarily grounded, or open, the engine will cut out. The voltage reading will jump down to as low as 1.3 volts and the Hz reading will jump from as low as 17 to 128 Hz. If there is a problem in the EST circuit, the voltage on the bypass wire will not change. If the bypass wire is momentarily grounded or open, the reading on the EST wire will be the same as if it was grounding or going open, but unlike a problem on the EST circuit, the bypass voltage will be pulled low if it becomes grounded or goes open. If this happens fast enough, the engine will cut out. The voltages will vary, but the SES light will not come on and no codes will be set.
With the EST circuit open, engine running, the voltage will stay low on the bypass wire and the ECM will not put out the 5 volts. With the EST shorted to ground, the voltage on the bypass wire will be high (5 volts) for a very short time (three seconds or less) then the ECM will remove the 5 volts. Using a min/max on the DVOM is the best way to see this voltage. With the bypass open, the EST circuit OK, the ECM will put out the 5 volts. By using a DVOM on both the EST and bypass wire, you can tap on the ECM, wiggle and tug on the wiring to see if the voltage or Hz reading will change. If it does, this is an indication that you have located the problem area.
spacerline.jpg
[FONT=_verdana_][SIZE=-1]Ken Hughes is ASE master and L1 certified. He is an Autoline GM specialist with 29 years experience. [/SIZE][/SIZE][/FONT]
 
Many times when you have a code 42 it is the magnetic pick up coil in the distributor.
When they go bad they cause issues similar to what you have going on.
You need an OHM meeter to test it. Pop the DISt cap. INSIDE you will see a 2 wire lead plugged into the module. Unplug the lead and test the 2 wires going to the pick up coil. It should read between 500-1500 Ohms. If out of specs replace.
You have to pull the dist and take the gear of the shaft to replace it.
 
Before you go through all that unhook the batt. and see if the code comes right back. that code can be stored in the system from un hooking the timing connector while setting the timing. If it doesn't some back don't worry bout it till it does IMO. Anyhow, to answer your other question when you unhook the timing conector you just diable the computers ability to advance or retard the timing so you can set the base timing acurately. to figure out what's actaully wrong with your truck you will more than likely need to see engine data. more times than not with what your describing look at the CTS (coolant temp sensor). It's at the front of the intake right next to the thermostat housing, a two wire connectorplugs onto it with a yellow and a black wire I think. If you don't have acess to a scan tool with data I personally would take a leap and spend the $8 or so and replace it....
 
thanks for all the help guys. today i was playing around with it some more and i realized when i had the air filter off and im looking at the fuel going into the ports from the passanger side injector and its spraying a TON more than the driver side, and when i actually unplug the injector when the engines running it continues to spray the same amount and nothing changes, however when i unplug the driver side injector the engine starts to die off a lil. So i am thinking something in the injector is stuck open, not pulsing at all. Does this seem possible?
 
Sounds like a dirty injector that isn't closing even when you disconnect the wiring. I found a place in Wa. that cleans, and flows test these injectors for 18.00 ea. http://witchhunter.com/

I had them clean and flow test 4 of my 454 injectors. Very quick turn around also.
 
Alrighty.. so far i have swaped out the coil/ignition module/injector and the main computer in the dash for alternative ones from my bros truck, still gives me code 42. The injector still sprays all funny and looks like way to much. I am hearing a ticking noise from the IAC solinoid if i turn the key on to ignition but dont fire the engine over. This IAC just controls the idle air mix correct? I havent swapped this out yet tho... this is my DD so its kinda sucking getting to work right now thanks for the help tho guys.
 
You explained the injector is an issue...fix it, forget about throwing other parts at the problem. Once that problem is fixed move on to the next one, IF there is one.
 
The injector has an oring seal around it that can go bad. Buy the TBI rebuild kit for $5 from Auto Zone. Take the top plate off replace the orings and go from there. While it is apart clean it all with carb cleaner and put in all the new gaskets. If you dont stop it quickly it can cause more serious damage. The extra fuel will wash down the cylinder walls and cause the rings to die quickly.
 
Check the injector pods for leaks both when cold and after the engine is warmed up. There should be no fuel dripping from the injectors when the engine is off ( cold or hot ).
 
still happening...gotta replace the distributor i've replaced ignition module, coil, tps, coolant temp sensor, iac, one injector, new tbi mounting gasket, main computer in dash, plugs/wires, the map i believe.. so only few things left... still runs like death right at idol or right off idol until like 20mph or so. oh ps im on my bro's name thanks guys
 
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