A couple of years ago, my first post on the forum was about the problems I was having with a 1997 Disco I that I had driven and been professionally serviced for more than 20 years (and added 240K miles), but we are now more than 150 miles from a dealer or respectable Indie. It was backfiring, running rough at idle and at RPM, and throwing a number of codes that didn't make any sense to me. The Indie who had been maintaining it for several years opined that the MAF was at fault and would cost $1500 to replace with OEM and that aftermarket would do no good. In short, I bought the story and the $1500 MAF, replaced it and it did no good. This lowered my confidence in this Indie substantially. This resulted in the Disco sitting in my shop for over 2 years while I worked on other projects. I got back to the Disco a few months ago and decided I would download the RAVE and take some old school measurements like compression, leak-down, vacuum, fuel pressure and so-forth. Anyway, I found that most of the numbers looked very good for that age engine, but the injectors were dirty, and the primary on (at least) one coil was defective. After I cleaned the injectors and replacing the coil pack, the scanner numbers were on target and the truck ran just great! Now, I am having some problem where the engine runs fine at idle-- and through the rpm range until it heats to operating temperature and then still runs fine to about 1500 rpm, then hesitates then surges. The code shows "Cam Position Sensor" error. Since the scanner track shows this same #1 cylinder timing changes, I plan to change out the cam and crank sensors. (I cleaned the cam sensor and it didn't help) Since the truck has so many miles, I wonder if maybe I should also replace more sensors (and which ones)?

 

Coolant temp sensor (right there on the t-stat housing) is one that is easy and cheap (my favorite kind). IACV is notorious for crapping out but doesn't sound like your issue. How is the fuel pressure (fuel pumps are often problematic)?

 

Thanks for the quick response, good suggestions! I had some overheating problems this summer and changed the thermostat-- but forgot about the sensor! ( I also flushed the system, new coolant, new evaporator fan assemblies, and other, before I replaced the viscous clutch which solved that specific problem-- which maybe could be in a new thread someday) I keep reading stories about the IACV, but I don't know what all the symptoms could be. The RAVE does not seem to be too clear. Howevever, in the cases where there are thermal dependencies, an old thread I just read on the "Related Threads", triggered me to start looking at the heated O2 sensors. They may be a cause since they don't activate until the engine warms-- which is when my engine starts acting up. Fuel Pressure Key ON: 35 PSI, 1500 RPM: <40 PSI Maybe a little low?

 

that fuel pressure is OK.

IACV fail typically means it won't hold idle after running. Like, get off the highway, waiting for the light at the end of the ramp, won't hold idle unless you put it in neutral and add some throttle. Again, I don't think that is your issue.

O2 sensors could be a possibility. Do you have a OBD real time data reader? If not, get one. Best $25-50 you'll ever spend. You'll be able to see the O2 voltage and fuel trim in real time.
You'll also see the outputs from sensors like the coolant sensor. If nothing else, it will help you rule a bunch of stuff out. https://landroverforums.com/forum/di...02/#post581013

 

I have an "OK" scanner that I bought a few years ago brand CareCar, that nobody recognizes. It works pretty well and will take the sensor data and plot 2 channels at a time-- and is pretty easy to use. Except for the Disco, I usually work on old pickup trucks 1960s, 1970s. (no computers)