Ok guys I have a 98 discovery1 I bought 3 years ago w/136k miles I have now 173k on it now. Some days runs good but lately have issues. I'll start by saying great compression, new parts ( IAC, plugs, wires, throttle position, water pump, temp sensors, fans electric and clutch, thermostat, belt, battery, on 2nd radiator, crank sensor and wiring, both mufflers, decats, trans filter, u joints, brakes, and bushing ) that all in last year. Lately check engine with low flow bank 1 cat. After I had old muffler welded up. So new muffler and just decat this weekend. The rover is still running rough lack of power. Before it would back fire and fall on its face after it warms up. Its running better but not right like when I first got it. The on going issues I gave up on with new computer and now have old one back in it has high idle when cold start after warm up shut off start up and regular idle. The computer read -32 in Florida when its 90 out. So after new Temp sensors and tried new computer didn't work I live with it. But need ideas for this latest issues! Other wise been a great vehicle and only have $2500 into with purchase price 3 years ago.

 

if you havent already
replace the crankcase to intake hoses (2 of them) spray out the intake, butterfly valve, MAF, remove the IACV and clean all the carbon out.
run some seafoam thru a tank of gas

search high idle and seafoam - tons of stuff on here

the high idle program worked for me though I know not everyone has had luck

 

Ok I will do that I did once before when I replaced the IAC, but didn't do anything with hoses. When it does this like today when I went to store came out doesn't run right and back fires. Had to spray carb cleaner to get it to stay running after I get it to 3k rpm it stay running and cleans up.

 

Hmmmm.. you many have checked some of these things out but:

Did you ohm out the temp sensors (the old and new ones) to see if they are reading what they're supposed to be reading? You should be able to find a table that'll tell you what reading you should get at a certain ambient temp. If they do read correctly, try ohming out the wires at the computer connector to ensure it's getting the right reading, and not shorted out somewhere. If it thinks the temp is wrong it'll run rough. I had that happen with my truck and the sensor had only drifted like 12-15 degrees.

Have you tried swapping the O2 sensors around? It reads off the upper sensor.

Vacuum leak?? Once you know the temp sensor is good and it's not the O2, check vacuum. Go around it with an unlit propane torch (valve slightly cracked open) and a hose on the end and move the hose around the top of the intake in various places to see if it smooths out, indicating a leak. You can spray carb cleaner or ether as well..

Fuel pressure correct?

Possible water in the tank (don't laugh - I wasted a lot of time and money on a vehicle once only to discover it was just water in the tank!!). Took a couple tankfulls and several containers of fuel water remover to finally work it out, but it was indeed the problem.

Bad coils? (common) Do you have clean spark at all plugs?

Bad computer ground ...proper voltage to computer? In my GM manuals they make a big deal in several places in the computer troubleshooting trees about ensuring proper computer voltage and ground before getting deep into the other tests. Apparently lot of inexperienced Service Techs spend time chasing wierd behavior problems due to relatively basic poor voltage/ground issues.

That's all I got for now..

 

Well checked all sensors and used dialectical grease on everything. Cleaned everything I could did induction cleaning. Still have high idle when cold but after it sits and is warm it will not start with out mis firing and back fire. Shoot carb cleaner across intake and it will fire up run rough until around 3k rpm then it clears up! It ran great for 1hr on the way home today then started doing it again. I get ohms change on sensor when I spray air acrossed Sensor to cool down. They warm up they change I other direction. Checked grounds so what next!! It's a great truck when it runs great

Fuel sender started acting up so I think bad wire on sender because I checked outside wires. And I get a weebal wobble in suspension and wobble in wheel once while. I replaced bushing in sway bars but everything looks good and it tight. I ordered tie rod ends and 2 boots are shot when I was looking for a reason.

 

MAF sensor perhaps?

 

Ok what computer scanner to buy so I can reset valves and change tps and air temp? I only have obd2 right now

 

Ok guy I have gone through everything again found nothing. I got fed up so order new ( maf, tps, iac, fuel temp, air intake temp, engine coolant temp, intake vacuum hoses, coil pack, plugs, wires, fuel filter, air filter ) still have high idle actually its higher now 2500rpm. I turn on ac and it will lower to 1500-1800rpm. It still spits and sputter after warm start up but doesn't stall out so far. No check engine lights. I don't have any place in my area to flash computer to reset only have rover dealer 2hr in each direction and way to expensive. Any ideas?

 

Thoroughly clean IAC bore, with all the pounding from the pintle a good deal of tar builds up in there. With a new IACV you most likely may need to get the adaptive values reset.

 

https://landroverforums.com/forum/di...acement-83233/

^Yep, my thought too. If I threw that many parts at a simple problem at work they'd kick me out the door.......