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Discussion Starter #1
I’m at a dead end with my ‘94 NAS. Truck seems to run fine but once driven for 30 minutes or so it will no longer idle. It will start right back up but then dies in seconds. I’ve replaced iacv, distributor, ignition coil(s), chicklet, plugs, wires, O2 sensors, fuel pump, fuel filter and I’m sure a couple others things I can’t think of at the moment. It’s been to two shops, one of which is pretty familiar with Defenders. Any suggestions on what road to go down next?
 

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Have you been through the manual? Have you trying adjusting the base idle?
 

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Discussion Starter #5
Have you been through the manual? Have you trying adjusting the base idle?
I have been through the manual and used it to reset the base idle...don’t recall if I’ve done absolutely everything in the manual I’d have to go back and look.
 

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Try an old school trick? With the engine idling cold and as warm as you can get it without stalling spray the intake , engine , everything with carb cleaner or starter fluid .

Listen for changes in rpm , use this to pinpoint a possible air leak .

Don't burn your truck down
 

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Discussion Starter #7
Try an old school trick? With the engine idling cold and as warm as you can get it without stalling spray the intake , engine , everything with carb cleaner or starter fluid .

Listen for changes in rpm , use this to pinpoint a possible air leak .

Don't burn your truck down
I did spray it down with some carb cleaner...I didn’t go too crazy on it though. More than happy to give it another try.
 

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Discussion Starter #8
Another odd thing is that numerous coils were put on (various brands) and one coil had the truck consistently running much longer than any of the other coils....not sure if this is telling me something or not??
 

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Are you saying it won’t idle at all or it just does when you stop? The base idle setting should be what sets the warm idle. The idle air control is only used when a bit more is needed for a short period.
 

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Discussion Starter #10
Are you saying it won’t idle at all or it just does when you stop? The base idle setting should be what sets the warm idle. The idle air control is only used when a bit more is needed for a short period.
It idles fine when “cold”. Drive it around a bit, let it sit for 20 seconds and then dies. Start it back up, idles for 20 seconds then dies.
 

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Check fuel line pressure continuously from starting to stall. Its possible your pump is on its last legs and unable to keep up with demand.
 

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Discussion Starter #12
Check fuel line pressure continuously from starting to stall. Its possible your pump is on its last legs and unable to keep up with demand.
I personally have not checked that but a shop did...fuel pump is new. I will do that test though.
 

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Any specific location to look? I’ve not noticed anything.
Since you observed a coil anomaly to the symptoms, I'd start with the ground for the coil. Then I'd probably Google every conceivable combo of coil, ground, & stalling. Then look at the condition of the grounds related to anything involved in keeping a started engine running? And if it's actually more like 3 minutes than 30 minutes, I'd try a new coolant temp sensor if nothing else gives you your fix...

Did the more successful coil installation happen to occur during a cold snap?
 

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Discussion Starter #16
Since you observed a coil anomaly to the symptoms, I'd start with the ground for the coil. Then I'd probably Google every conceivable combo of coil, ground, & stalling. Then look at the condition of the grounds related to anything involved in keeping a started engine running? And if it's actually more like 3 minutes than 30 minutes, I'd try a new coolant temp sensor if nothing else gives you your fix...
Thanks, will look into. Coolant temp sensor has been replaced, one item I forgot to mention. Fuel pressure regulator new as well...
 

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I personally have not checked that but a shop did...fuel pump is new. I will do that test though.
My last fuel pump lasted four years and failed on during an off road weekend....

Attach a pressure sensor. Record pressure prior to start up. Start it up, and let it run until it stops, recording pressure at regular intervals

Problem solving is best done one step at a time methodically.
 

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Discussion Starter #18
My last fuel pump lasted four years and failed on during an off road weekend....

Attach a pressure sensor. Record pressure prior to start up. Start it up, and let it run until it stops, recording pressure at regular intervals

Problem solving is best done one step at a time methodically.
Thanks, will try to test that this weekend.
 

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It idles fine when “cold”. Drive it around a bit, let it sit for 20 seconds and then dies. Start it back up, idles for 20 seconds then dies.
Then I do not understand that you have set the base idle. The whole point of adjusting the base idle is to get a smooth idle when the engine is hot.

Beyond that you need to go through the whole test sequence. Download the RRC manual. It has a nice step by step procedure to get it checked and adjusted. It should only take an hour.

Check the temperature sensors. Set base idle properly. Check for vacuum leaks. Make sure the ECU is getting an RPM signal.

A bunch of the stuff you replaced has nothing to do with idle.
 

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Discussion Starter #20
Then I do not understand that you have set the base idle. The whole point of adjusting the base idle is to get a smooth idle when the engine is hot.

Beyond that you need to go through the whole test sequence. Download the RRC manual. It has a nice step by step procedure to get it checked and adjusted. It should only take an hour.

Check the temperature sensors. Set base idle properly. Check for vacuum leaks. Make sure the ECU is getting an RPM signal.

A bunch of the stuff you replaced has nothing to do with idle.
Thanks for the feedback. I followed instructions for setting the idle, more than willing to give it another go. Most items I’ve replaced have had similar symptoms to what I have (at least by reading tons of other posts). I’ve got the RRC manual now and will continue to explore.
 
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