4.3gxi bad temp sensor?

[happychapboater]

I’ve been having issues with one of my engines in that it is stalling at idle and sounds like it’s searching. I just got the tech mate device and have been comparing between my two motors. I noticed that the good engine’s temp while it’s cold now is at 70 degrees, while the other engines sensor is saying 85. I swapped sensors between engines and re-read the tech mate and the sensors showed the same readings.

Could this be that it’s a bad temp sensor and causing the stalling?

 

[Scott Danforth]

doubt its the temp sender causing the issue.

did your temp follow the sender or stay with the motor, your post is not clear there.

hunting at idle is usually the IAC. what is the IAC showing on both motors.

 

[happychapboater]

doubt its the temp sender causing the issue.

did your temp follow the sender or stay with the motor, your post is not clear there.

hunting at idle is usually the IAC. what is the IAC showing on both motors.

The coolant temp followed the sensor when I swapped them. The main problem has been to get the engine to not stall after 10-15 seconds without giving it some throttle to warm up.

 

[alldodge]

The coolant temp followed the sensor when I swapped them. The main problem has been to get the engine to not stall after 10-15 seconds without giving it some throttle to warm up.

That sounds like the IAC as Scott mentioned

 

[happychapboater]

That sounds like the IAC as Scott mentioned

I replaced the IAC first and that hasn’t corrected the issue unless it was a bad IAC. I also swapped IAC between the two motors and it still stalled.

 

[alldodge]

I replaced the IAC first and that hasn’t corrected the issue unless it was a bad IAC. I also swapped IAC between the two motors and it still stalled.

Which other sensors have you swapped?

Measure 5V reference voltage on the MAP or TPS

What voltages does Techmate show for TPS and MAP?

What is your fuel pressure at the rail?

Don't think it's the temp sensor right now

 

[happychapboater]

Just throttle and IAC I’ve tried swapping. IAC position is 120.

5v for both were 4.7-4.8v with engine off, key on. Tech mate shows map volts 4.23v, tps .74v.

Fuel pressure was at 50psi for high pressure and 10psi for low pressure. It has a brand new high pressure pump just put in.

 

[Scott Danforth]

IAC should not be open that far. usually about 40-50

the 5.0 being read at 4.23 means something is drawing down the 5.0 reference. could be a bad ground in the harness

 

[alldodge]

Motor of voltage for TPS looks good, MAP is a bit low, should be closer to 4.9 but 5V ref is a tad low

Once started the MAP should be around 1.4v

With IAC counts so high there is to much air for the fuel.

Might move the bad running ECM to the good motor. Don't move the good to the bad,

 

[happychapboater]

IAC should not be open that far. usually about 40-50

the 5.0 being read at 4.23 means something is drawing down the 5.0 reference. could be a bad ground in the harness

The IAC on the good motor was showing 130 for the value with key on, ignition off.

 

[alldodge]

The IAC on the good motor was showing 130 for the value with key on, ignition off.

Good point, have motor running

 

[Scott Danforth]

all readings need to be engine running. very few are KOEO

 

[happychapboater]

all readings need to be engine running. very few are KOEO

It’ll be a couple days until I can test that when it’s finished getting painted.

 

[happychapboater]

Boat got back into the water yesterday. Motor is still stalling. I changed out the IAC with a Delphi one. MAP 5v reference still reading 4.8 with the engine off. 4.25 on the tech mate. When the engine started and before stalling, went down to around 2.0v. IAC was around 80-100. I also put the bad ECM on the good motor and that ran fine. I also swapped MAP sensors and it still stalled also.

all readings need to be engine running. very few are KOEO

 

[alldodge]

5v ref is low, wonder if it's a bad connection, bad sensor, or bad ECM

 

[happychapboater]

5v ref is low, wonder if it's a bad connection, bad sensor, or bad ECM

Where would the 5v come from? The contacts look clean. I moved the bad ECM to the good motor and it ran fine. I also disconnected the MAP sensor and it ran well.

 

[alldodge]

The 5v Ref comes from the ECM
Now it could be it is at 5v it's just your meter, but if you see 5v on the other motor than that's not the issue

 

[happychapboater]

The 5v Ref comes from the ECM
Now it could be it is at 5v it's just your meter, but if you see 5v on the other motor than that's not the issue

The other motor was showing the same 4.8v and similar numbers in tech mate also. I have a better meter I can double check with the voltage later this afternoon.