Hi everyone, I have had this ‘96 Discovery (158k, poorly maintained, engine light on, not scanned & more), since September- and the thing is running pretty good after this last bit of work. I have been tackling suspension and drivability issues part time and recently and after a bit of action on the forum I thought I would go after the MAF and IACV cleaning, plugs, 8mm wires and the big filter/ Rotella oil service. I did this over a week or so- with plugs and wires the first night, IACV/ MAF cleaning on a different evening and the oil service a final evening. A few observations from a Rover noob but a VW semi-pro. (If that matters).

Parts- OEM Rover thermostat and gasket, Proline 8mm wires (Rovers North), Autolite double platinum’s -.035, PB Blaster, brake cleaner, 104 Octane boost (local auto parts store) and paper towels.

Thermostat- Mine was stuck open and only occasionally would register low on the gauge. Oddly, it made plenty of heat over the winter. Now it stays just below center. (Cold temp= out of range).

IACV cleaning- This single thing made a huge difference in the overall running condition of the engine - as has been stated previously here on the forum. Gone are the sucking, whishing, loud vacuum sounds my engine was making. My Chevy had a similar IACV to the D2 in that it screws in as opposed to the flange and bolts on the D1.

For your D1 bolts- you may find that your 7/32 socket wont grab the bolt. If you look at the snout of your socket you’ll notice there is a slight chamfer on the inside that allows the bolt to be easily- “received”?.. Anyway- grind that off and re chamfer the outer edge. Now you can grab those bolts.

Once its out- don’t move the pintle. At all. Don’t make fun of it, or say “gross” or anything. Only refer to it as “Sir or Madam”. This is important because we have a valve and a seat with wear. I sprayed mine with PB Blaster and set it aside (pointing down) to clean my MAF. After about 45 minutes I went back and hit it with brake cleaner. This loosens the sooty, oily carbon so it can be gently scraped off. Gently get into the base recess too- if you shoot a cleaner in there, hold it so the pintle is pointing down and spray up. You’ll eventually see a yellow seal deep in there.

MAF cleaning- Nothing new here but- after you unload a bit more than half a can of MAF cleaner in there, spray about an eighth of an inch or more of it into the cap that came on it. When that evaporates- your MAF should be dry. Put some paper towels in the intake under the butterfly and unload the rest of the MAF cleaner in the IACV hole and clean out the hole.

Plugs- For those who may not be aware- the newer plugs with iridium or platinum are easily damaged with only gapping. Use very little force with a gauge or you could break, damage or scrape the very sensitive center electrode which will cause the new plug to misfire, and is really frustrating to diagnose. The manufacturers say to use a certain type of gauge. I use feelers and a wire gauge to confirm.

104 Octane boost- Let me explain…….. With no owners manual and knowing the origin of this motor, I had expected and assumed it would take regular, and so that is what I did the first full tank with 6 days prior to service. So the booster was more to get me back to a reasonable octane level. I’m sure the fuel cleaner component helped too.

Rotella oil service- I don’t know if this is specific to the Rotella or the Rover or what, but- POUR SLOWLY!- You can’t just -“up end” a quart of oil in there like you can a VW or some other cars I have worked on. Noises in general and a slight valve noise are gone. Might be a little more aggressive than I need- so I’ll be looking into this. I’ll keep the big filter though.

Test Drive- After you do the IACV- make sure you can drive for about a half an hour the first time before you turn the engine off. Your computer will need to adapt to the change- (this is why you didn’t move the pintle), and your rig is gonna’ run poorly for a bunch of hot/cold cycles. Don’t worry if it starts weak or revs a little high at startup for awhile.

Don’t do what I did- I jumped in and went right to the gas station. - ran good but after I got gas I had to crank it forever. Embarrassing. This went on for about seven minutes at a busy gas station. After it started it went straight to 2500 rpm and stayed there. (3” open chamber exhaust). Stymied, I shut it off and re started and it did the same thing. I couldn’t figure out how I was gonna get it into gear. The third time I started it in neutral and pulled it into drive before it revved too high. It was fine awhile latter.

The Rover is running great after the service but the engine light remained on. As I had said, I didn’t scan it previously knowing the engine was running poorly and I needed to get some sort of baseline. The following stored codes remained in this order-

P1193 Oxygen sensor heater circuit open downstream
P0300 Misfire on multiple cylinder
P0304 Misfire on 4
P0303 Misfire on 3
P1316 Misfire excessive emissions fault
P1314 Misfire catalyst damage fault bank B
P0113 Air temp high out of range fault

I was looking in the Rave for awhile to identify the codes. After going back and fourth I see that the diagnostic codes are- “not included in this publication”- which is handy.…… I mean- why would you include the information to repair the vehicle in the service manual? I guess I need the GEMS for that…

I cleared the codes and re scanned. (0) codes found. Engine light off. This is odd considering the 1193. I would have thought I would have needed to trace that. I left it for the night and drove it the next day to two places, (for less than a hot /cold cycle really)- perhaps 1.5 miles. Latter that night I took it out for another short drive and the engine light remains off. If there is any change I’ll let you know.

Thanks again to all the contributors to the tech section and the forum. I went through many searches and posts and even prepared for the worst and went through all of- “War on misfires”, (thank you Eric and contributors to that post)! Glad I didn’t have to go through the harness or deal with crank trigger shielding- gross! (whoops….)

I’m going to let it be for awhile now. That is a lie.

Thanks,
Greg

 

Some codes take multiple drive cycles to re-appear. Here's a link to the GEMS manual.

 

I know. As of today I think I have about six hot/cold. Scanned again earlier and nothing new or aging. Waiting though....

 

Don't want to rain on your parade, but I would bet you're not out of the woods yet.

Keep your fingers crossed. That trouble codes for the O2 heater will probably be back.

What did the removed plugs look like.

I ran the ProLine wires before I got my new NGK's, I had a end pull off the ProLines and also had one come off the NGK as well.

Best wishes with it.

After the initial cleaning , you can cycle the key a few times to run the fuel pump to ensure enough gas gets to the intake to reduce long cranking.

They also say not to attemp extended cranking as you can do damage to the CATS.

Welcome Aboard.

 

Actually, I thought that 1193 would have been back already as I took no steps to remedy that particular issue.

Plugs were only mediocre but very old and had more rust than I would have liked to see- one was not fully seated. They were Bosch doubles and all consistent in color. None wet or oily. Just carbon grey.

Proline's seem okay for me. I have a spark plug boot plier so no problems there- yet.

Fuel pump cycling should not have been a problem. After the initial start- (a regualr quick twist of the key) it started right up but hunted for about ten minutes before settling down. After that, I idled it for about five more min and shut it off. Then after a few checks- I went to the gas station.

In reality- it was perhaps several regular cranks. Nothing too long- If you have ever had a problem at your local station- you know what I mean.

It should be noted that I was not on a crusade to abolish these codes. I was looking for a baseline and to help others that might be in the same boat. I did'nt even scan it before I started. I just wanted it to run well, get a little better than 8 mpg and not do damage. I don't really care about the engine light- (although its nice when you don't have one) 'cause here in Mass- a '96 is exempt.

Thank's Danny- and don't worry- I'm sure I'll have to get to that 1193. Just not today. Gotta go- Good luck all
Greg

 

Hi everyone. So, after one week nearly to the hour- the engine light came back on. This wasn’t totally unexpected as- after driving the Rover for the week I realized that it wasn’t running quite as good as I had thought. Better for sure- but still off. It seemed a bit anemic and made a lot of noise and fuss going down the road but not so much power. Over the week the Rover did 170 miles to the half tank mark. A quick calculation reveals a little over 13 miles per gallon over that 170 miles around town.
I scanned for codes on the 14th - one week latter and have the following codes in the following order-

(Code History-)
April 7th
P1193 Oxygen sensor heater circuit open downstream
P0300 Misfire on multiple cylinder
P0304 Misfire on 4
P0303 Misfire on 3
P1316 Misfire excessive emissions fault
P1314 Misfire catalyst damage fault bank B
P0113 Air temp high out of range fault
　
April 14th
P0158 Oxygen Sensor High Voltage *codes* BD
P0304 Misfire on Cylinder 4
P1316 Misfire Excessive Emissions Fault
P0158 Oxygen Sensor High Voltage *codes* BD (pd)¬ I think this is aging.
P0138 Oxygen Sensor High Voltage *codes* A D


Looking at the code history I can see that the red codes have reappeared and that bank B is still a mess. Also- I can see I should be watching my cats and o2 sensors. At this point I also suspect a coil. So it’s back to the daily for now.
A few days latter and I’m back at it. I like to keep it simple. And while- generally I think my vehicle has every problem that you all post, (and it does), I hate to jump to conclusions about expensive parts. So I started looking around. On inspection I see the no 4 plug is arching to ground and has left a nice carbon trace on the plug insulator. I check them all- and this only exists on 4. I notice my new 8mm wires- like many spark plug wires I have used in the past are common in that they don’t “clip” to the end of the plug like I expect an interference fit to act. The number four plug boot is holding the connector at zero around the plug end, not contacting- but arching out. I took care of this like I have in the past- I crimped them all, (say what you will), and tightened the -now loose for some reason- screw on ends. By now I’m out of time- so I clean up, check everything again and wipe down some leaks underneath. I’ll look over the o2 sensor wiring another time.

On the first start it cranks quickly and runs noticeably stronger and smoother. The exhaust note is now consistent as opposed to having a lope, or a- 1234,1234,… beat.
On the test drive I put it in gear and took my foot off the brake and it had much more power and was much more eager to move.
For now- I have cleared the codes, filled the tank again and I’m going to see what happens. I’m sure I’ll see some o2 sensor codes next time but that’s for latter. Any suggestions on what those o2 codes are all about is greatly appreciated as I don’t know their exact meanings or solutions- but have read that wiring can be an issue.
Good luck all.

　

 

The O2 Sensors have a heated element that is required to function correctly for them to work properly. The O2 is the main input signal for the ECU to correctly control the lean/rich aspect of the fuel injection. The Discovery ECU can alter each individual cylinder based upon inputs to the ECU.

I learned this by dealing with mine for an extended time frame, not having a good understanding of the system initially. If one side is out of whack, that entire bank will be negatively impacted.

Bottom line is: Until you have good O2's on both sides. You will continue to have all sorts of problems related to misfires that are basically caused by out of whack (technical term) O2 sensors. Buy the correct new O2's and your problems should diminish significantly.

Ignore the O2's and you are chasing symptoms/effects instead of causes. I did that for quite a while as have many others.

I also avoid using the plugs that have the little screw on caps. They do tend to vibrate loose and if you are having misfires, that increases the vibration levels at the engine area, thus the screw on caps will tend to loosen. Why some of the plugs have those and others do not is not really clear to me.

The plain old copper Champions work fine if the other items are taken care of. Using the higher priced plugs with the exootic materials for tips will not resolve misfires that are caused by bad inputs to the ECU from bad O2's. Again that is an effect, not the root cause.

I have also noticed differences in the diameters of the top electrodes on various spark plugs and recently had a problem with the diameter of the insulator body on some new NGK plugs being too large so I xchanged them for the old fashioned basic Copper Champions. That is what came in these engines initially and they work fine and only cost about two dollars each compared to several dollars each for some of the more exotic"high performance" plugs.

Exotic plugs may be required or beneficial in some of the more modern engines of today. In the old Buick/LR engines in our Discoveries, it is not going to gain anything.

The above information is not just an opinion, it is the result of actual experience not only by me but by several other members of our LR Discovery One community. I hope this information may serve to help you and any others with similar issues with the vehicle.

Try it and see for yourself. Let us know the results.

 

Thank's Danny- all points noted & agreed. What I'm trying to rule out is a malfunction say- in the wiring, or other things before I throw the parts at it. I am very cautious about that as in my younger days I could be accused of throwing parts at a problem when perhaps a good ground strap cleaning or vac hose replacement might have solved the problem for much less work, expense and headache.

Hopefully I'll be able to get under there this week and check the wiring for the o2s.

On the same note- on the weekend, I was "snugging" my valve covers and plenum bracket/hold down thingy. When I was done, I fired the engine and it immediately threw a CEL. Well, I knew I messed something up. So I started looking around and noticed a faint vac leak sound. Eventually I got around to the small FPR > plenum vac line- poked it with my finger and it was wasted. Cleared the codes again and will keep looking.

 

When I first bought mine (early 2007), the two hoses that go from the top of the valve covers to the intake were in horrible condition. The one on the passenger's side was flaking apart internally and gummy feeling.

Those two hoses are a different diameter on each end (great Design) so to get a good fit, you almost are forced to buy the correct hose. I tried some I had on hand, but ended up getting new ones from AB for the correct fit.

Recently I was down to just an occasional P1316. At advice of another forum member, I pulled the line that goes from the charcoal cannister/purge valve to the plenum port under the MAF line. I capped that port and the P1316 has not returned.

Performance also was immediately improved. It runs like a stud stallion compared to a sick pony, try that you may like it!

 

I practically had a the same codes.

Make sure you check your hose from the vacuum advance all the way to the firewall.

I had some dry rooted and it leaked...fixed it..no more light