I have a 1999 disco one with 108,000 miles. Need help with possible rough running issues. Former history of vehicle is unknown. I have owned 6-8 months and cannot figure out what ails it. There is a "dead" spot in throttle from about 2000 -2300 rpm. Runs ok after downshift and at higher rpms. Have noticed terrible fuel mileage (7-8 mpg).

Thus far, have replaced spark plugs, fuel filter, maf sensor, two o2 sensors, throttle position sensor. Still throws code saying - failed to switch to rich - bank a, and excessive emissions. Check engine lite only recently came on - ran rough before without setting check engine lite.

Have checked thoroughly for vacuum leaks, sensor leads (knock, crank position, etc.). (Seems to really run very lean - has buried temp gauge twice intermittently). Fuel pressure checks out as strong and responsive once revs build. Any suggestions on what I might be overlooking??

 

That sounds like a bad TPS.
Did you buy anew one or used?
Using a live OBDII scanner and the engine off you can read the TPS values and see for sure if it is working correctly.

 

and at minimum it won't be 0%, mine is like 9%

 

i bought a new tps, but it was not from land rover. ill have to look to find paperwork on where it came from. what should values look like - i do not have a shop manual.

 

i do have access to a live obdII scan tool - i just have not had time to download the land rover specific date to it, or read the directions. a friend loaned it to me. he had it hooked to rover while driving and i think i remember him saying that he did note numeric values from tps - i just cannot remember what the were. one specific thing he said that i thought odd was that timing advanced to almost 40 degrees when coming under load. and it is intermittent problem - we are wondering if it is a bad ecm/ecu, or bad connection somewhere in harness. it is a frustrating trouble shooting problem thus far

 

In a 1999 the timing is controlled by the ECU independently for each cylinder, so you can have eight different advance settings, all at the same time.

 

sooner or later you'll probably have to do this anyway...so eliminate a possibility now by unhooking the battery and removing the ECU...put it on a clean workspace and remove the cover(s) ....to make sure that it's DRY and clean inside.....water has a way of getting in there and causing all kinds of trouble ( dry it out and reseal it )....its happened to many of us here..it doesnt take long to check..and best of all , its a cheap fix / insurance...good luck

 

thanks for all your recommendations to date!! finally located engine ecu - read somewhere it was inside vehicle, but later found it outside in engine compartment under window washer reservoir. the ecu/ecm looks to be a replacement (used) as it has numbers painted on it as i commonly see on used parts from salvage yards. Thinking i may have an ecu/ecm problem, i inquired with an internet ecu rebuilder (aes), who informed me that they charge $525 to refurbish my unit. however, they indicated that if this ecu/ecu was not vin matched to my truck, it may exhibit similar problems to what i am having. as i understand, the only way to match this vin to my truck is to take the unit installed in the truck to land rover. I am going to read the vin from the obd scan tool and assume that if it matches the vin plates on vehicles it is set properly, or unlocked.

i am also assuming that if it was not matched to vehicle vin when installed that the truck might indeed run, but could be exhibiting the problems i am seeing?

any suggestions or thoughts appreciated.

 

Yes a bad/unmatched ECU can exhibit run problems.
It could also have water inside it.
Remove it, open it, dry it, seal it with silicone, put it back.

 

removed ecu - inside looks good-no burned or visibly damaged areas. it was dry. i tried pulling vin from vehicle with obd2 scan tool, but it informs me that it is not a supported function to look at vin with scan tool. so, my question is, do i have to now go to land rover to have them check to see if ecu has been matched to vin of vehicle? or do i just need a fancier scan tool. it reads as if there is no way to read it - i don't know if it is vehicle related or scan tool related. also, now have new error code popping up - p0340. scanner says: "camshaft position sensor a circuit (bank 1 or single circuit). that is the first i have seen of that one. also showing P1316.

previously, i had codes p1137, and p1316. this is first time for p0340. if ecu is not "set" for vehicle can i even trust the error or check engine codes??