i have a 2001 discovery 2. Just hit 113K miles. two weeks ago i replaced plugs wires valve cover gaskets plenum gasket throttle body gasket oil separator and i also installed a 2" suspension kit and some new tires. While i had plenum and throtle body off i cleaned both. truck ran really good. this past weekend i went on a two day off road - trail ride down dirt roads and trails. i did about 300 miles all weekend with out any problems. as i was driving home check engine light came on blinking. i pulled over and shut down and read codes. i got random misfire and catalyst damaging misfire. After i restated car it had a bit of a rough idle but no more misfire. and at higher rpm it seemed to drive fine. When i got home (70 miles later) i read codes again. i had same codes plus "Blocked idle air control". i pulled off idle air control and cleaned, also cleaned MAF sensor. when i had intake hose to throtle body off i could see the throttle body really dirty and dusty so i cleaned it as well. i also found my air filter was not seated properly and has a small gap allowing dusty/dirty air into intake. i reset the codes and still same symptoms. Can very dusty air in the intake cause some damage that will give rough idle? or is it possible the plenum has come loose after 300 miles and caused vacuum leak? can a plenum leak cause IAC code? or MAF code? only other symptom along with the rough idle the exhaust smells rich, and sounds more like "puff puff puff puff" rather than the normal - steady exhaust. im assuming this is from the rough idle, but could the dust breathed in by intake cause cats to clogg? i didnt get any catalitc codes. i have one o2 sensor that was giving bad readings. the plug got oily from leaking valve cover hense the valve cover gasket change. I cleaned up connectors when i did valve cover gasket and no o2 codes yet, but this may or may not be related. the rough idle is worse then the rough idle i got when the oil was in the o2 plug.

i have the Bosch 4.0 engine. 113K miles. my fear is all the dust sucked into engine may have damaged it. im kind of freking out with the thought of all that dust being sucked into engine for 2 days straight. about 20 hours of dusty trails worth of dust..

any thoughts?

 

Codes were for cylinder 1,4,6,7 if that helps any. Also Blocked Idle Air control valve and o2 sensor upstreat bank 2, and Mixture adaption factor FRA bank 2.

these are codes: 12, 20, 4b, 3f, 42, 44, 45, 22.

I have a Autel MaxiDAS auto scanner and the codes are not "P" codes.
The p codes were:
P1300- catilist damaging misfire
P0150 o2 sensor circuit Bank 2 sensor 1
P0505 Idle Air Control system
p174 system too lean bank 2

after last reset, no codes returned but still rough idle. i reset adaptions after cleaned idle air valve. i have check all vacuum lines (most were recently replaced) and all have no signs of damage of leaks. Im going to try carb cleaner on the plenum to check for leaks in the morning.

i hate to just throw parts at a problem but im thhinking of getting new (or used?) IAC and seeing what happens.

 

With those codes... I would check your connections to your coil pack. Make sure all wires are snug.. and that the plug wires aren't touching each other or any twisted wire pairs.... (not rover advice... general automotive). Cheap plug wires close to any two wire pair that it twisted... is bad. Twisted wire pairs are twisted to cancel each others signal out so they can get an even signal... introduce outside interference and the signals are interrupted.

Oh... and make sure all of your spark plug wires are tightened at both ends.

 

Oh... and if you have a filter in your airbox... stop worrying about the dust.... check to see if it's dirty... bang it out... and then check your vacuum lines... I personally don't understand how they are routed... but If things were good before going over bumpies... you might have cracked some.... un-metered air after the maf is bad...

 

Hi clay, thanks for the reply. Turned out one of the plugs on the coil pack was on but not clicked in. Once i found that, plugged it in properly and clicked in place all symptoms went away. You nailed it.

I guess the sea-foam treatment, cleaned IAC, MAF and throttle body, new Air Filter, and can and a half of carb cleaner looking for vacuum leaks all only help because now that coil pack plug is on right, shes running amazing again. I also degreased engine and undercarriage. With the new valve cover gaskets and a clean engine i figure i can more easily pinpoint the next oil leak. They say a land rover that doesnt leak oil doesnt have any oil lol.

Thanks again for your help. take care

 

Glad I could help. Also glad you got your oil leaks fixed. I suggest adding a fire extinguisher to your list of add-ons. Ignored the valve cover gasket for too long and could have burned my D1 to the ground.... at a gas station... 10 feet from the pumps. I've never felt so helpless...