95 DISCO 158,000, working thru service list....

Good Morning you LR nuts. Need some diagnostic expertise please.

Last Friday noticed a 'rough' idle at start. This continued for approximately 3 miles or so before it 'smoothed' out. Drove around town etc. with no issues. Started and ran fine. Saturday morning started up again with the rough idle and check engine light. Again rough but not erratic. Cut if off and left it sitting for the day, other stuff going on with youth football and basketball. Diagnosing on Sunday I found (2) missing exhaust manifold bolts and all remaining minus (2) were loose to the point of pretty much tightening with hand until I had to wrench, tightened those up.

Started up, check engine light gone. No codes at this point. Obviously ran a bit better after the exhaust manifold bolts tightened. Still has 'rough' idle. Checked coolant level, added just under have a jug to the expansion tank. Still have rough idle for approximately 3-5 miles before it 'smooths' out somewhat. Took air filter assembly out, etc. back to the plenum chamber (did not unplug any electrical connections to air flow sensor) **Did note the throttle disc 'area' had a couple of ports, one forward and one rear, that had 'oily' deposit, cleaned with carb cleaner**.

This rough idle immediately has me thinking head gasket. Although no lose of oil whatsoever. This is, as all of you Disco guys know, the latest in the never ending diagnose and chase down weekends upcoming. Just glad it's a long weekend for me.

Thoughts gentlemen??

All you Jarheads, Squids, Spoiled Air Force dudes, Coasties and especially you Seabees (Veteran here). Woo Rah!! Have a great day on Friday...

 

Does your version have the built in code reader small display box under the seat? See Land Rover FAQ - Repair & Maintenance - Range Rover for how to read it and what codes mean. Would reset by removing bateery wire for say 5 minutes.

Most likely some sort of emmision related code. Intake manifold bolts might need snugging up as well.

 

Yes under the seat Buzz. No codes. Just rough idle with what seems to me like a loss of power until it 'warms up'. What would be an investigative direction for rough idle and loss of power??

 

vac hose leak, for one.

 

You mentioned your coolant was low, you may have a blown head gasket leaking into one of your cylinders over night which will cause a rough start/idle, pretty common issue.

 

A good point, and this would show up as some white smoke out the tail pipe, perhaps some "steam cleaning" of the spark plug (inspect), or coolant test not holding pressure.

 

Going to replace plugs this weekend, if I have a "clean" one, could be HG correct? No smoke coming out at all. Would the symptoms subside after the vehicle is warmed up??

 

HG can do strange things depending on temperature. Here is a pix from another member, this one was a massive leak, but plug still dark. So the answer is maybe.

 

After sitting all night or day start it and then go to the tail pipe and sniff, does it smell sweet?
If the coolant level drops again it is a bad head gasket, you do not always get water in the oil, like when it only leaks into the cylinders and burns off after starting first thing in the morning.
I am going to agree with Mike and say you have a bad head gasket.

 

I had read the smell the tailpipe on another post and did that the day after the rough idle was noticed. Certainly not a sweet smell of coolant, much more of a 'rich fuel' smell. If HG is issue, would the loss of power 'go away' once the LR has warmed up?? That part is confusing to me??