Cold start troubles

[Steverino]

My 2000 Ranger 4.0 with 82000 miles is running really roughly on cold starts, but does not die and smooths out after several minutes (less than 5). The fuel pump was new (dealer installed) less than 10,000 miles ago. The check engine light does not come on when this happens.

I have to take it in for our state pollution certification, and I doubt it will pass with his going on. So, I need to get it fixed and wonder whether anyone has some ideas of what the problem is so I can be informed when I get it fixed, whatever it is.

Thanks very much.

 

[RonD]

Welcome to TRS

All gasoline engines need to be Choked on cold start, fuel injection(EFI) can't use a "choke plate" like a carb did because there are no Jets to suck extra fuel from
Choking just means a Rich fuel mix with advanced spark timing, and HIGH idle, do you get the high idle?
EFI uses a computer choke routine to do this

This choke routine/software relies on the ECT(engine coolant temp) sensor telling the computer the true temp of the engine at key on and startup
If outside/engine temp is 70degF and with key on ECT sensor shows 120degF then not enough Choke would be applied, so rough running until engine warmed up

If the ECT sensor stops working altogether then that would set a code, but wrong low temp wouldn't set a code, computer just thinks this is a restart after maybe 30mins of sitting, not a cold start

So best GUESS, with provided info, is that your ECT sensor is reporting the wrong Cold temp
On a 2004 4.0l there will be TWO temp devices on the thermostat housing
1. ECT sensor, 5volt, 2 wires, one is a grey/red wire, used by computer
2. ECT sender, 12volt, 2 wires one is red/white, only used by dash board temp gauge

 

[Steverino]

Welcome to TRS

All gasoline engines need to be Choked on cold start, fuel injection(EFI) can't use a "choke plate" like a carb did because there are no Jets to suck extra fuel from
Choking just means a Rich fuel mix with advanced spark timing, and HIGH idle, do you get the high idle?
EFI uses a computer choke routine to do this

This choke routine/software relies on the ECT(engine coolant temp) sensor telling the computer the true temp of the engine at key on and startup
If outside/engine temp is 70degF and with key on ECT sensor shows 120degF then not enough Choke would be applied, so rough running until engine warmed up

If the ECT sensor stops working altogether then that would set a code, but wrong low temp wouldn't set a code, computer just thinks this is a restart after maybe 30mins of sitting, not a cold start

So best GUESS, with provided info, is that your ECT sensor is reporting the wrong Cold temp
On a 2004 4.0l there will be TWO temp devices on the thermostat housing
1. ECT sensor, 5volt, 2 wires, one is a grey/red wire, used by computer
2. ECT sender, 12volt, 2 wires one is red/white, only used by dash board temp gauge

Thanks very much! I haven't done anything yet, and will bring it to a shop. Have recently moved and don't know local shops well so I wanted to educate myself a little beforehand. I worried this could be like another $860 fuel pump! That was stunning, mostly parts.

 

[RonD]

A Shop would only use a MotorCraft fuel pump, which runs $400-$550 these have quality control, i.e. each pump is tested and works before it is packaged and shipped to Ford, or Parts store

3rd party brands run $100-$150, but are not tested, they usually work but............can fail within the first year, which is under warranty, but its just a pain to lift the bed or drop the gas tank again, to replace the pump

 

[Steverino]

A Shop would only use a MotorCraft fuel pump, which runs $400-$550 these have quality control, i.e. each pump is tested and works before it is packaged and shipped to Ford, or Parts store

3rd party brands run $100-$150, but are not tested, they usually work but............can fail within the first year, which is under warranty, but its just a pain to lift the bed or drop the gas tank again, to replace the pump

Mine is a Motorcraft installed by an exceptionally reputable dealer, but the price did gag me nonetheless Just don't want anyone telling me it's a fuel pump this time unless I am sure it is. I was charged over $600 for the part. Seemed to be the going price at the time. And there is miserable labor involved.

 

[RonD]

Its the fuel pump.............................lol

 

[Steverino]

Thanks very much! I haven't done anything yet, and will bring it to a shop. Have recently moved and don't know local shops well so I wanted to educate myself a little beforehand. I worried this could be like another $860 fuel pump! That was stunning, mostly parts.

I've had it into a Ford dealer service shop. Their diagnosis is that the truck has an internal coolant leak, probably a head gasket or a cracked head. Pressure testing showed only a very slight leak at the timing belt cover. The coolant was low and this is what caused the coolant sensor to send poor information (111 degrees), and why the rough idle stopped after a few seconds when the censor got coolant to get a good temp measure. Any thoughts on whether this makes sense and how to proceed? (I've posted separately that the same shop says the transmission needs to be replaced). A bummer with only 84K on it.

 

[RonD]

Yes, if coolant is low the temp measuring units won't work well because they are not immersed in coolant they are reading hot air which they are not designed to do

Like reading the outside air temp of 95deg but the asphalt on your bare feet is 120+deg, lol