Oz 2000 XLT in Limp Home Mode

[ricebubbles]

Issue is with a RHD Australian 12/2000 Ford Explorer XLT 4.0L SOHC

On a really hot day (over 40C) truck goes into Limp Home Mode (LHM) and will not drive faster than 15Kph. It is OK on other days! When it is running normally it drives and sounds fantastic having installed new timing chains, guides, valves etc. a year ago.

There are no fault codes showing with my OBDII scanner and the fuel trim values look reasonable both when it is running normally and when in LHM. The fuel pressure seems OK.

I have cleaned the Throttle Body, Air Flow Sensor and changed the Ignition Coil Pack (supplies all six spark plugs). Truck has new HT Leads.

When it was in LHM, I used a whole can of electronic freezer on the engine computer (PCM) after exposing the printed circuit board by drilling out the pop rivets and removing the PCM’s top cover, which made no difference!

I have yet to change the spark plugs but they were OK a year ago.

Any ideas much appreciated.
Brian in Australia with half the country on fire!

 

[boominXplorer]

Fuel trims are a little high. I'm not aware of any limp mode in the 2000 explorer software in the US. What is your fuel pressure while running and hitting the gas? My other idea would be mass air flow issue.

 

[ricebubbles]

Thanks for the suggestions which are very interesting especially the comment re no Limp Home Mode. I had assumed the computer was getting upset over something and limiting the speed to 15K per hour, even though there are no fault codes showing. The issue has to be either fuel or spark. When it is misbehaving it will just not drive at more than 15 K per hour. In neutral, the engine will rev to about 2,000 RPM and then misses and coughs and splutters.

The weather has now cooled off a bit with 25C day temperatures and the Explorer runs beautifully. Only misbehaves on days with temperatures over 40C. We have had quite a few 46C days recently! Thank goodness I don't live in a high fire risk area as the intermittent Ford would be a serious risk as an emergency escape vehicle.

I am going away for a couple of weeks so when I get back I will do a thorough measure of the fuel rail pressure on a cool day and when it is misbehaving on a hot day and post the results.

I did clean the MAF sensors but didn't measure their resistances. Something else I will have to do.

I did follow the Forum tips section and cleaned every connector and relay socket I could get my hands on. I like applying silicon dielectric grease to the connectors which ensures an easy insertion and extraction but more importantly keeps the air from oxidising and moisture from corroding the contacts.

Thanks again,
Brian coughing and wheezing in Australia now covered in smoke

 

[drdoom]

Sorry to hear about the fires, Brian. Best wishes to all in Australia, men & creatures alike. Take care.

 

[donalds]

Sounds like a temp sensor.
Can u test it with a scan tool if one is available

 

[ricebubbles]

Issue is with a RHD Australian 12/2000 Ford Explorer XLT 4.0L SOHC

On a really hot day (over 40C) truck goes into Limp Home Mode (LHM) and will not drive faster than 15Kph. It is OK on other days! When it is running normally it drives and sounds fantastic having installed new timing chains, guides, valves etc. a year ago.

There are no fault codes showing with my OBDII scanner and the fuel trim values look reasonable both when it is running normally and when in LHM. The fuel pressure seems OK.
View attachment 177162

I have cleaned the Throttle Body, Air Flow Sensor and changed the Ignition Coil Pack (supplies all six spark plugs). Truck has new HT Leads.

When it was in LHM, I used a whole can of electronic freezer on the engine computer (PCM) after exposing the printed circuit board by drilling out the pop rivets and removing the PCM’s top cover, which made no difference!

I have yet to change the spark plugs but they were OK a year ago.

Any ideas much appreciated.
Brian in Australia with half the country on fire!

Now that it is Summer again in Australia, this issue is driving us nuts. Truck is near enough to useless when the weather is over 35C.
Any ideas much appreciated.
Brian in Australia with half the country flooded!