Intermittent Throttle and White Gas Smoke

Hi everyone. Let me start off by saying no it is not the Head Gasket that is causing the white smoke. The tests were done to verify this. The smoke is white and has a strong gas smell. This car also has no cats (I got it like this) and it was sitting for years, like it looks like at least 3+.

Now, whenever I start up the car, it doesn't emit any smoke until I would say 15-30 seconds later when the engine is starting to warm up and then it dies down and then it becomes more once it reaches optimal temperature. I think this has a connection to my next problem.

The other problem is when I drive it around the block, randomly in gear the car will decide it doesn't want to rev anymore and I can't shift into any gear anymore since the revs are not high enough. Turning the car off and then back on like 2 minutes later and the car is fine to rev and shift again until it doesn't want to rev again. When in idle for hours though, this rev problem doesn't happen.

I have replaced the spark plugs, battery, fuel injectors, fuel pump, fuel filter, oxygen sensors and air intake. Odb2 has no codes other than the downstream sensors because of the no cats. I have mechanical friend as well that can't figure this out...

wmburns said:

I would want to know what the long term fuel trim (LTFT) bank 1 and 2 values are. Especially right before and during the problem.

Do you have an ODB2 scanner?

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Yes I do have an OBD2 scanner. No codes other than the downstream for the no cats. I'll get the data tomorrow and then post them here.

wmburns said:

I would want to know what the long term fuel trim (LTFT) bank 1 and 2 values are. Especially right before and during the problem.

Do you have an ODB2 scanner?

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Idle: (idle numbers are around the same as driving in gear before operating temperatures and before the throttle cuts out)
STFT1 20-30
LTFT1 0.0
STFT2 20-30
LTFT2 0.0

When throttle cuts out without optimal temperature:
STFT 0-10 without pressing throttle
20-35 when press throttle and it goes up to around 2,000 RPM and drops down again
LTFT always 0.0

1 AND 2 are the same here

When throttle cuts out with optimal temperature:
STFT -4 TO 2 (they're the same for both)

LTFT1 25.0 and then drops to 3.9 if I press the throttle to 2,000 RPM and then drops down to idle

LTFT2 22.7 and then drops to 0.8-4 if I press throttle to 2,000 RPM and then drops down to idle

Fuel pump is very loud and can be heard over the engine when engine starts outputting a value other than 0.0 for the LTFT

Also when getting this data, the exhaust smoke is a bluish white since it was puffing out more smoke, leading to me believing that the valve seals are the cause of the smoke.

wmburns said:

What is the model year of this Mustang?

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It's a 1996 Mustang GT with only ~97,000 miles on it.

wmburns said:

With a LTFT of +25.0 the PCM is adding a TON of fuel and wants to add even MORE (hence the the DTC).

But.......Think about it. The strong fuel smell from the exhaust says, "motor is actually running rich". What are some examples of things that might cause this?

• Exhaust leak before the front O2 sensors. The unmetered air will make the O2 sensors "think" the motor is lean thus adding fuel.
• bad O2 sensors. O2 sensors stuck lean. Use the ODB2 scanner to look at the "switches" above and below the line.
• Bad PCM

It bothers me that for a motor running sooooooo poorly why are the LTFT's ever zero? Unless the PCM is dropping out of closed loop into open loop mode. This is something that can be monitored to see IF true.

Since you have an ODB2 scanner looking at some of the operational PID's. Monitor other PID's such as MAF, IAT, ECT, fuel pressure, open/closed loop to see what also might be changing when this problem occurs.

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It honestly might be that it is dropping out of the closed loop to the open loop, but it seems to take a long time to do so (around the time when it is reaching operating temperature).

I'll check for any exhaust leaks, but I highly doubt that there are any leaks before the upstream sensors because of the lack of smoke anywhere else other than through the end of the exhaust.

The upstream O2 sensors are brand new Bosch sensors that I replaced last week. I didn't bother to touch the downstream ones since the car has no cats; I thought it was pointless to go replace them.

I'll get the rest of the data tomorrow morning and then post it.

wmburns said:

Don't make the mistake of thinking that just because a part is new that it actually works. What if there's a wiring fault between the O2 sensor and PCM? Or what if the O2 heater isn't working? Especially if this causes you to ignore a possible problem source. Use the power of the ODB2 scanner to find out without guessing. Verify that the O2's are actually switching.

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The oxygen sensors for bank 1 sensor 1 and bank 2 sensor 2 goes between 0 and 1 depending on how much throttle I use when the throttle hasn't gone out so I guess that they are in working condition.

However, when throttle cuts out, both of the upstream sensors do not exceed around 0.085.

The system does in fact move from an open loop to a closed loop, and does start using the data from the o2 sensors it seems like.

ECT just seems to stay at 90-97 with throttle gone or not.

IAT goes to around 45-50 degrees Celsius when throttle cuts out.

MAF goes to 30-50 g/s when pressing on throttle and then the car jumps forward a little, seems like it will stall but then doesn't and goes back up to ~900 to ~1,100 RPM when the throttle cuts out.

There is no fuel pressure percentage on the OBD2 scanner so I think I may have to go get a kit and test that to see.

I should also say that someone that got to see and listen to the car has said that it might have a bad distributor due to the sounds it makes. However, I wanted to verify if that could make sense since the car operates just fine when not in gear and moving.

wmburns said:

We may have a problem here.

The max O2 sensor voltage should be 0.9 volts. The "neutral zone" is between 0.6 and 0.4 volts. Less than 0.4 volts is lean. Greater then 0.6 volts is rich. Sooooooo unless the O2 sensors are switching above 0.6 volts and less than 0.4 volts they are NOT working correctly. Especially if you actually mean 0.1 volts instead of 1.0 volts.

IF the O2 sensor is always returning a value of 0.1 volts, this says to the PCM, "I'm lean. More fuel". Which if true, I would look at the O2 heater circuit.

Or if this car has an after market exhaust, has the O2 sensor been moved? Perhaps too far down the exhaust?

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The car has a magnaflow exhaust, straight piped. Both of the sensors are at a little bit down after the bend from the exhaust manifold. So yeah, I believe different from the stock area since I can easily get to them.

Oh and no I didn't make a mistake with the 0 and 1 values. And this morning when I went to use the OBD2 tool again, this time the I/M readiness actually put out an X for O2S and HRT and EGR.

Could the oil that is burning also be causing a problem with the o2 sensors as well?

And basically, I need to check the heater circuit for the o2 sensors since it is running very lean when the throttle cuts out?