Hello, I have a 98 Discovery. Over all its in fairly decent shape. It was running ok when I first got it, but did have a not so smooth idle. I squirted some Kroil around to see if maybe there was a vacuum leak, but that didn't seem to reveal anything. Replaced the Idle air stepper, didn't make a difference. Messed with the MAF by disconnecting it and it idled nice, but when you gave it throttle it would stumble. Plug it back in and it would die. Got a cheapo from Ebay and put it on, and it ran worse. I put the old one on and decided I would live with the funky idle. It was running ok. I got a Lucas MAF from a guy and put it on to see if that would make a difference, but it didn't.
The other day I decided to pair the Home Link to my garage door and that was a success, but now the truck barely runs. I don't know what that could possibly have to do with anything, probably a coincidence. Put on a more expensive MAF, but still no joy.
So far I have replaced the MAFx3, Crank Position Sensor and the Idle Air Control. I replaced the plugs somewhere in there and it ran for a few minutes, then went back to the barely running scenario. The plugs were badly fouled and smelled like fuel. I pressed the schrader on the fuel rail and fuel squirted out. When I put the key in III I can hear the fuel pump run for a few seconds and then stop. I disconnected the fuel line at the filter and turned on the key and fuel would pump out for a few seconds, and then stop. Don't know if that's normal.
Only code I get is a pending code for the MAF Low Voltage or bad MAF, ( don't remember what it is P0102 maybe) but I think that's because I unplugged it.
I have also tried to use that GEMS Utility to reset the adaptive values, but it still will barely run. I disconnected the battery and removed the ECM for inspection, but other that a little corrosion on some pins in the small black connector it looked ok. Removed one of the covers and I saw no sign of water intrusion. Anyway I guess I should get used to being at my wits end.

 

First things to do are ...
1. get an obd dongle and a smart phone app to see what some of the sensor readings and fuel trims are doing (OBD fusion or Torque) https://landroverforums.com/forum/di...02/#post581013
2. You'll probably need to get new plug wires. Easy job and reasonable cost from Kingsborne. </title> <meta name="robots" content="index, follow" /> <meta name="GOOGLEBOT" content="INDEX, FOLLOW" /> <link rel="canonical" href="https://www.kingsbornewires.com" /> <link type="text/css" href="//ajax.googleapis.com/ajax/libs/jqueryui/1.8.4/theme choose 8mm in your favorite color.
3. I suspect fuel pump getting weak so getting a true fuel pressure reading at the rail will help hasten the diagnosis. Your local parts house might have these available to use/rent.
4. grab all the workshop manuals from the google drive link in my signature
5. Run some Techron injector cleaner though your next tank of gas
6. post in the Discovery 1 section of the site so you'll get more/better eyes on your situation and have it resolved more quickly/easily. You are currently in the 'general tech' section

lastly, it isn't clear to me what the current running status is. Running ok and idling poorly? Not running?

 

Walt, Are injector cleaner additives a good thing to do occasionally? I’ve never run anything through mine but haven’t felt the need to I used to run some Lucas through my first one about once every three months, as a preventative measure.

 

Thanks for your reply. At the moment it won't run. It'll fire, stumble around at about 400 RPM, then die. If I mash on the gas it'll rev up, but as soon as you let off the pedal, it dies. I did read through the RAVE pertaining to the GEMS and answered one of my questions about the fuel pump. It is designed to run briefly when the key is switched on to prime the system. I will put a guage on the rail. Should it be done running or just with the key in III? I don't see fuel supply as a problem, since my plugs are black and smelly of unburnt fuel. I'm leaning toward timing. But I will check the pressure. Also, it'll idle somewhat better (@ 700rpm) with the MAF disconnected, but as soon as it's plugged back in it dies. I would think that would indicate the ECU is relying on it's fall back values to compensate for the faulty/ missing sensor.
My next move I plan on taking is getting down to the cam position sensor and clean it off. It's pretty grimey down there, so maybe the connection is faulty. I will be removing the plugs again and either clean them or replace them. I have a replacement fuel regulator too. I'll replace that if the Cam PS is inconclusive.
I have a dongle, as well as a cable reader and I can only find a pending code of P0102. I did download the GEMS reader app and it reports 0 airflow and 0 fuel flow rates, of course because it's not running. I have attempted to apply the adaptive values change to the app when it prompts me to do so, and I am assuming that it is doing that, but there ids no message to say it was successful. I had to watch the numbers change (idle, etc.). It is reading my ECU because it reports the VIN.
Once I do those things I will proceed accordingly. I would really love to get this little beast on it's feet again.

 

I also failed to mention that I checked the wires between the ECU and the MAF. I got 12 volts on the brown or orange wire with the key on and my meter both grounded to the block as well as to the black/ red wire. I used the black /red from the MAF as well as the one from the TPS and the IAC stepper. I have not done so on the Cam PS yet. If I remember correctly, all those sensors grounds are connected somewhere on their way to the ECM. That's if I read the crazy wiring diagram correctly. I'm just so puzzled because there was no real thing to cause these problems. Like I said the last thing I did even remotely related to electrical inputs was programming that Home Link thing for my garage door.

 

Stilruns, my son (the main driver these days) and I perceive better performance with the periodic use of injector cleaner. Once every 6-8 weeks I'll throw a bottle in the tank while I fill up.

Bob, will it remain at idle with the MAF dis-connected? Check fuel pressure should be mid 30's. "Timing" is all calculated by the ECU so knowing what the sensors are saying can help reveal the issue.

 

Hello Walt, Yes it idle pretty nice with in disconnected. Not now, because the plugs are all fouled again. After lunch I plan to clean up the first set and reinstall them. Before lunch, I swapped Idle Stepper motors, and pulled the cam PS out and cleaned the connectors and the end of the actual sensor. I didn't see any obvious sign of damage to the wiring or connectors. I don't have a replacement for it so I just put it back in. Still won't idle. Step on the gas and it will run, but like I said the fuel mixture is very rich and the plugs foul quickly. It barely wants to run at all now, so out with the plugs.

I checked the fuel pressure with my newly acquired test gauge from harbor fright and it was near 40psi. Even with the fuel spewing from my loose connection.

 

OK. So you replaced your IACV (stepper motor). It is running rich. And fuel pressure is good.

Rather than throw a bunch of parts at it (which I don't think it needs), I'd first attempt to reset the adaptive values stored in the ECU. robertf has developed an app which will talk to the ECU or you can pay a dealer to do it if they still have a Testbook.

The ECU 'learns' how to best manage the fuel mixture and timing based on the sensor inputs. It progressively 'learns' the best way to develop power from the engine. In doing so it stores some constants which it uses in successive cycles. The app clears these constants (aka: adaptive values) basically re-setting the ECU to a blank slate as if it were 'day 1' of your truck.

Here is a thread which explains it and links to discoweb for further explanation. In post #19 robertf points to an Android version he developed in addition to the windows version.

https://landroverforums.com/forum/di...33/#post598538

 

Hello Walt. Yes I used the GEMS Utility to try and reset the adaptive values. I assume they were done, just by closely watching the number change when I select Save Changes, but the truck still runs like crap. If there were a message or something that let you know the changes were successfully mad that would be great., but Im no computer wiz, so i'll take what I can get. Yesterday I sandblasted the first set of plugs with my old plug cleaner and reinstalled them, but it made no difference. It tried to start, and as before it would only run with the pedal depressed. Rich mixture smell from the exhaust, but a new twist was added. I would hold the accelerator down to try and maintain a constant 2500 or so RPM, and the engine would rev and fall as if I were pumping the pedal. I was holding it in one place.

I am wondering if the ECU has not experienced some failure. As I said this condition started as if a switch was flipped. I had just come back from DMV and the tire shop. No overheating, no surging or any oddball antics. I was cruising down US 1 at 60-65 without incident. I pulled into my driveway, shut her down, decided to program the garage door opener, started it again and it was running like poo.

I am not one to give up on things, but this is testing my resolve .I cant figure out what I could be missing here.

 

Also, different from before was the fact that it would not idle any different (as in not at all) with the MAF connected or disconnected. I am the proud owner of 4 different MAFs for this beast. I think i'll check the wires again to be sure there it not a shunt or open circuit. Aside from that I am considering binning the GEMS and replacing it with my old Holley Pro Jection unit and a Megajolt system.