Okay guys, I just picked up this 97 Discovery SD with 108,000 miles. It had several check engine lights. It had thrown codes P0300, P0307, P0305, P1313, P1496. On the drive home from where I purchased it, after about 20 minutes of driving the Rover started doing a thing where it would feel like it lost all power for a split second, RPMs drop 1000 and then go back up and power is back. Once it started it seemed to be very consistent (see YouTube link for video example of this "hiccup". I took it home, put in new Champion Copper Plus plugs, NGK 8mm plug wires and tested the coil packs which had all 4 gone bad, replaced them. I went to AutoZone to have the check engine light cleared. As soon as I left the Did a smoke leak detection and found the crank case breather hose was basically disintegrated and a vacuum hose had been disconnected on the right side of the plenum. Connected those and cleared the codes. No check engine light or code has come back and I've driven almost 184 miles since clearing. Rover passed emission (although the EVAP and Catalyst systems were not ready but Utah allows two systems to not be ready and pass). I did a smoke leak test again and the only smoke coming out is now right out of here, where the throttle assembly enters the plenum. What can I change on the throttle assembly to eliminate this leak? Here is the link for the power loss issue.


Also there is this vacuum line that exits the vacuum cannister on the throttle assembly, goes to a T fitting, enters the firewall and the other T runs along the left fender and just sits alongside the air filter. I would have assumed this hose would have plugged into the air filter but the air filter has no vacuum port. Does anybody know what I should do with this end? Does the end that goes in the firewall connect to anything? I pulled on it gently and it moves freely as if it is not connected to anything. I feel like I am still having vacuum issues because when I let my foot off the gas, the rpms drop 1000 and then go back up which is different than the power loss issue in the YouTube link above.





Any help would be appreciated!

 

The hose you are holding is for the cruise control pump that usually no longer work on the D1's you can upgrade it. As for the tachometer bouncing up and down commonly caused by the alternator going bad or loose connections. i don't see the loss of power since your speed seems to be stable. Check your alternator, grounds, and battery connections.

 

Hi, Surfish. The front cruise control tube goes to a small electric vacuum pump up front behind the headlight and under the jack storage location. The back tube through the firewall goes to the brake pedal switch to turn off the cruise when the brakes are touched. I fixed my cruise control by replacing the tube, but the cruise module also needed work due mainly to some really weak soldering on the circuit board.

As for the vacuum leak at the throttle plate shaft, there are seals there, but I think I would try some light oil, like 3-in-1 first. That might help the seal swell a bit and stop the leak. A thick oil (or even grease) might be enough to seal too. Looks like the throttle assembly, springs, and linkages could use some cleaning and lubrication anyway.

Looking at the overall condition of the engine bay, I would clean up the throttle plate and the air bypass passages, and remove and clean up the idle air control valve. That might help the loss of power issue if the IACV is gunky or blocked. The air inlet part of the engine can get really dirty because of the crankcase vent. Give it all a good internal cleaning to help reliability, gas mileage, start up, and idle. Make sure the throttle position sensor stays in the same position (don't rotate), otherwise you could get the high revs issue after initial restart and need to reset the ECU (forum threads tell how to do that). That end of the throttle plate shaft also has a seal and bearing.

Good luck. These trucks need a little tender loving care sometimes.

 

Icannap1....upgrade the cc pump? tell me more. Is there a modern replacement that will do the job?

Alternator is the first check. Agreed

Welcome to the Disco club. The first things to do are to get a wireless OBD to read codes and monitor live sensor readings. This will help diagnose problems when they appear and it will be the best $30 you have ever spent.
https://landroverforums.com/forum/di...02/#post581013

And download all the service manuals from the google drive linked in my signature.

 

Thank you for the ideas! I will definitely do the cleaning.