Fuelie Loads up when cold--HELP

[truckfan]

So with my '88 w/ a Throttle body FI bone-stock 454, it seems to run incredibly rich when cold and first starting. smells like gas and rolls smoke like unburned fuel (not oil) out the tailpipe. changed all the plugs (used E3 plugs) and cap and rotor--all of which seemed to need it. a couple of the plugs were black and carbon-looking, even up on the white insulators. it certainly runs better, but still does this when cold. it seems to straighten out and runs pretty good once it warms up. with an old school Q jet, i'd say its got a float sticking or an auto choke problem. with the FI, i have no idea. maybe a TPS or something like that? check engine light is NOT on. any suggestions appreciated.

[munice]

IAC valve?

[Hulk Will Smash]

Mine is pretty rich on cold start too. I don't think it's the O2 sensor since we have single wire sensors that don't start to work until we get some temp into them (as I understand it). I'm due for smog in April so I'm going to replace the O2 sensor at least, in the near future. I'm curious to see what other people have to say too.
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[Hulk Will Smash]

I've checked my IAC and it appears to be working properly. I wait until I hear it click into place before I start my truck.
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[LOW1TON]

I have the same year truck and engine, I also have the exact same problem, I installed new water temp sending unit, also e3 plugs, cap wires, iac ect. Made it better but still idols very rich. I am eager to see others responses.
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[meter swinger]

same here, 88 ccdrw. runs really rich until hot. haven't done the plugs and rotor like you guys yet, would probably help some.

[snm95ls]

Honestly, that is pretty typical operation for these TBI systems. Seeing as they are a wet flow style system, fuel and air travel though the intake manifold, they are prone to the same issues that plague carb setups when the engine is cold.

How cold has it been in your area?

What is the cold idle speed like? Is it running rich enough that cold isdle speed is too low?

Is your base ignition timing set correctly?

Any other driveability issues?

It will not be an oxygen sensor. The ECM only uses the voltage output from the oxygen sensor for closed loop feedback. The ECM does not enter closed loop operation until the coolant temperature is above about 168 degrees F.

The two main sensors that usually greatly affect the air fuel mixture when not in closed loop (open loop) are the IAT (intake air temperature) sensor and the ECT (engine coolant temperature) sensor. If either of those are out of range, then they will cause an incorrect fuel mixture. For what it is worth, the ECT is the two prong sensor that is usually screwed into a water port on the front part of the intake manifold. The gauge cluster uses a separate single wire sending unit.

The MAP (manifold absolute pressure) sensor is also highly responsible for giving the ECM proper information for calculating how much fuel to inject. I would not suspect the MAP unless you are having other driveability issues even when the engine is up to full operating temperature.

HTH.

[truckfan]

Ttt

[truckfan]

Originally Posted by snm95ls

Honestly, that is pretty typical operation for these TBI systems. Seeing as they are a wet flow style system, fuel and air travel though the intake manifold, they are prone to the same issues that plague carb setups when the engine is cold.

How cold has it been in your area?

What is the cold idle speed like? Is it running rich enough that cold isdle speed is too low?

Is your base ignition timing set correctly?

Any other driveability issues?

It will not be an oxygen sensor. The ECM only uses the voltage output from the oxygen sensor for closed loop feedback. The ECM does not enter closed loop operation until the coolant temperature is above about 168 degrees F.

The two main sensors that usually greatly affect the air fuel mixture when not in closed loop (open loop) are the IAT (intake air temperature) sensor and the ECT (engine coolant temperature) sensor. If either of those are out of range, then they will cause an incorrect fuel mixture. For what it is worth, the ECT is the two prong sensor that is usually screwed into a water port on the front part of the intake manifold. The gauge cluster uses a separate single wire sending unit.

The MAP (manifold absolute pressure) sensor is also highly responsible for giving the ECM proper information for calculating how much fuel to inject. I would not suspect the MAP unless you are having other driveability issues even when the engine is up to full operating temperature.

HTH.

It has been cold, but today it did it at 40 degrees or so. it does not seem to cold idle unreasonably high. once it warms up, it runs great

[Hulk Will Smash]

Originally Posted by snm95ls

Honestly, that is pretty typical operation for these TBI systems. Seeing as they are a wet flow style system, fuel and air travel though the intake manifold, they are prone to the same issues that plague carb setups when the engine is cold.

How cold has it been in your area?

What is the cold idle speed like? Is it running rich enough that cold isdle speed is too low?

Is your base ignition timing set correctly?

Any other driveability issues?

It will not be an oxygen sensor. The ECM only uses the voltage output from the oxygen sensor for closed loop feedback. The ECM does not enter closed loop operation until the coolant temperature is above about 168 degrees F.

The two main sensors that usually greatly affect the air fuel mixture when not in closed loop (open loop) are the IAT (intake air temperature) sensor and the ECT (engine coolant temperature) sensor. If either of those are out of range, then they will cause an incorrect fuel mixture. For what it is worth, the ECT is the two prong sensor that is usually screwed into a water port on the front part of the intake manifold. The gauge cluster uses a separate single wire sending unit.

The MAP (manifold absolute pressure) sensor is also highly responsible for giving the ECM proper information for calculating how much fuel to inject. I would not suspect the MAP unless you are having other driveability issues even when the engine is up to full operating temperature.

HTH.

Thanks. Mine idles at around 1100-1200 cold and it has been in the mid 40 degree range here. Runs good warm. I've replaced the ect but it's been about a year.
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[wyattglock]

Thanks. Mine idles at around 1100-1200 cold and it has been in the mid 40 degree range here. Runs good warm. I've replaced the ect but it's been about a year.


That is where mine idles cold also. Right around 1100-1200rpm. When it warms up the idle slows to between 600-700rpm.

[406 Q-ship]

Bad coolant temp sensors can make the system run rich cold or lean cold. If you can get your hands on a scan tool, check to see if the coolant temp and the outside temp are close to one another before cold start. If the oudside temp is 40° and the coolant temp reads -10° then you need to replace the coolant temp sensor. On start up the O2 does not control the fuel mixture until the system goes into closed loop, IAC just regulates the idle speed and has no effect on amount of fuel going into the engine.

Another area to look at is the vacuum hose too the MAP sensor and if the MAP sensor can fail causing a rich condition, but it usually will happen all the time not only when the engine is cold.