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Discussion Starter · #1 ·
Just purchased a 2000 Discovery II. Storted with a too lean code, then O2 code, then misfire codes. Now it is running like crap and I got a blinking service engine light once (came on at cranking and went off once in drive and in motion). We are pretty sure we have a fuel regulation problem. Just not sure where to start O2 sensors? Fuel pump? Fuel injectors? MAF?
 

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Just purchased a 2000 Discovery II. Storted with a too lean code, then O2 code, then misfire codes. Now it is running like crap and I got a blinking service engine light once (came on at cranking and went off once in drive and in motion). We are pretty sure we have a fuel regulation problem. Just not sure where to start O2 sensors? Fuel pump? Fuel injectors? MAF?
Plug in the OBD & report back with fault codes.
 
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It also wouldn't hurt (or cost anything) to look over the plastic pipes/lines/fittings & test for vacuum leaks.
 
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Discussion Starter · #5 ·
P0130 O2 Bank1
P0171 Bank 1 Too Lean
P1174 Bank 2 Too Lean
P1171 Bank 1 Too Lean
P0150 O2 Bank 2
P0174 Bank 2 Too Lean
P1230 Pending Fuel Pump Relay open circuit
P1590 Pending ABS Rough road signal
P0300 Pending Random Misfires
P0303 Pending Cycle 3 Misfire
P0307 Pending Cycle 7 Misfire
 

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Discussion Starter · #7 ·
Cleared Codes and Pulled them again... slightly different and now I'm getting a backfire every now and then.
P0174 Too Lean
P0171 Too Lean
P1174 Too Lean
P1171 Too Lean
P0300 Randomly
Po307 Cyl 7 misfire
P1300
P0305
P0306

We've been told maybe MAF but it tests fine. Also told maybe crank position sensor. I keep thinking fuel pump.
 

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There is a valve on the fuel rail; put a gauge on it and check for vac leaks @ the intake.

Cleared Codes and Pulled them again... slightly different and now I'm getting a backfire every now and then.
P0174 Too Lean
P0171 Too Lean
P1174 Too Lean
P1171 Too Lean
P0300 Randomly
Po307 Cyl 7 misfire
P1300
P0305
P0306

We've been told maybe MAF but it tests fine. Also told maybe crank position sensor. I keep thinking fuel pump.
 

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Discussion Starter · #10 ·
So, after cleaning the MAF, the idle air control, and checking for vaccumm leaks. No major leaks but I'm convinced they all need to be replaced - just sloppy fittings. Tested the intake pressure incase to get a feel for the cats (5 at idle, 9 @ 2500 RMP, throttle response from 5-15, bounce back to 5 like you would expect).

Non longer throwing ANY codes YET. Driven it about 10 miles. Driving smooth now but still idiling kind of rough. NONE of the backfires we got at peak (that prompted the parking of it). Thoughts?

Only reason I haven't checked the fuel pressure yet is dreading pulling the intake off. Really dreading it.
 

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Discussion Starter · #11 ·
So, after cleaning the MAF, the idle air control, and checking for vaccumm leaks. No major leaks but I'm convinced they all need to be replaced - just sloppy fittings. Tested the intake pressure incase to get a feel for the cats (5 at idle, 9 @ 2500 RMP, throttle response from 5-15, bounce back to 5 like you would expect).

Non longer throwing ANY codes YET. Driven it about 10 miles. Driving smooth now but still idiling kind of rough. NONE of the backfires we got at peak (that prompted the parking of it). Thoughts?

Only reason I haven't checked the fuel pressure yet is dreading pulling the intake off. Really dreading it.
Forgot to mention we replaced the CPS too.
 

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So, after cleaning the MAF, the idle air control, and checking for vaccumm leaks. No major leaks but I'm convinced they all need to be replaced - just sloppy fittings. Tested the intake pressure incase to get a feel for the cats (5 at idle, 9 @ 2500 RMP, throttle response from 5-15, bounce back to 5 like you would expect).

Non longer throwing ANY codes YET. Driven it about 10 miles. Driving smooth now but still idiling kind of rough. NONE of the backfires we got at peak (that prompted the parking of it). Thoughts?

Only reason I haven't checked the fuel pressure yet is dreading pulling the intake off. Really dreading it.
Options:

1. Sell it broke.

2. Pay a mechanic.

3. Spend 45 minutes and pull intake/coil pack.

If you do #3 , you should take the opportunity to replace the ignition wires with one of the better options.

P.S. I don't know what you cleaned the various pieces with, but the MAF on these trucks doesn't respond well to cleaning sometimes and the IAC isn't something that should be cleaned. Be aware for new issues in these areas
 

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So, after cleaning the MAF, the idle air control, and checking for vaccumm leaks. No major leaks but I'm convinced they all need to be replaced - just sloppy fittings. Tested the intake pressure incase to get a feel for the cats (5 at idle, 9 @ 2500 RMP, throttle response from 5-15, bounce back to 5 like you would expect).

Non longer throwing ANY codes YET. Driven it about 10 miles. Driving smooth now but still idiling kind of rough. NONE of the backfires we got at peak (that prompted the parking of it). Thoughts?

Only reason I haven't checked the fuel pressure yet is dreading pulling the intake off. Really dreading it.
Are those numbers you quote in the first paragraph vacuum reading?...if so. . I would expect 15 or more inches of vacuum at idle close to the same at 2500
You also mentioned earlier that the m.a.f. Was "tested" . How? By who?
I completely agree cleaning is not advised for m.a.f. Sensors or idle air bypass valves. Makes them angry!?

Sounds like the m.a.f is the one substantial change you have made (even though it was not a recommended one) and now you don't have codes resetting.
Am I right?

I have had m.a.f. Sensors do some really stupid weird stuff.
The most memorable was a couple years ago , during expressway / highway driving,

Sudden loss of power , no acceleration but kept running. Engine light on and flashing, (no it didn't overheat and crank sensor had recently been replaced) 30 miles per hour was about all I could get out of it!

After getting it off the highway to a safe place to stop, I checked and had numerous missfire codes on both banks, O2 sensor codes (lean codes as I recall)
Did some basic checks under the hood. Nothing obvious???
Decided to pop the air filter box top off and while doing so, disconnected the m.a.f. It instantly ran better!
Figuring that maybe I was onto something, I removed the m.a.f. Inspected for anything unusual, foreign material etc. Nothing obvious.
I blew through the bore and decided to give it a try. Put everything back together and cleared the codes (I always keep my autel scan tool with me).
Truck ran fine! Drove another 40 miles to get home. Switched out the m.a.f with a spare and never had similar problems again!
I figure it was a bad m.a.f. Sensor............ but I guess it could have been a bad connection as well.
Either way it was m.a.f. Related
 

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Discussion Starter · #14 ·
Options:

1. Sell it broke.

2. Pay a mechanic.

3. Spend 45 minutes and pull intake/coil pack.

If you do #3 , you should take the opportunity to replace the ignition wires with one of the better options.

P.S. I don't know what you cleaned the various pieces with, but the MAF on these trucks doesn't respond well to cleaning sometimes and the IAC isn't something that should be cleaned. Be aware for new issues in these areas
Cleaned the MAF with MAF cleaner as instructed and seemed to have no adverse reaction from that or from cleaning the idle control valve. I know you are right on the intake manifold removal. Pullint it this weekend. The guy who sold it to us replaced the plugs and gaskets but I don't think he replaced the wires. I can also HEAR a vaccum leak under the hood but can't find it. I think it is behind the manifold.
 

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Cleaned the MAF with MAF cleaner as instructed and seemed to have no adverse reaction from that or from cleaning the idle control valve. I know you are right on the intake manifold removal. Pullint it this weekend. The guy who sold it to us replaced the plugs and gaskets but I don't think he replaced the wires. I can also HEAR a vaccum leak under the hood but can't find it. I think it is behind the manifold.
Sometimes if you look at that MAF the wrong way it'll set a code. It's the same Bosch internal piece as used on lots of other vehicles, but for some reason, they become super-sensitive on the Rover. Various cleaners can cause rubber seals and gaskets to swell. There's no instruction on cleaning the IAC so no spec cleaner. I do know that carb cleaner ruins them.

If you're going that far, I'd suggest doing the intake gasket. They are known to leak coolant in the rear and occasionally some vac leaks as well.. If you do, pre-fit it and torque it down to stretch it a bit. Place the valley end clamp bars on and snug them but don't tighten until the main bolts are torqued. Then remove, light silicone on just the bottom surfaces, then install and torque. Let it set, then remove and silicone the top surface. Take your time and use just a very light amount. If you have good mechanical skills, it can be done in one shot, but it's a bit tricky.

Torque is very important on these bolts- especially the upper plenum bolts, which also require loctite. Omission is common and also the result of alot of vac leaks. And broken bolts- they're very long and skinny.

You're going to need to do VC gaskets if you pull the intake. If they haven't been done recently they're probably hard as a rock and leaking. Every one I've ever seen is a little smaller than the opening. Set them in the sun and warm them, then glue them to the cover. You can use some clamps or bolts and washers to hold them in place while it sets. If you don't, they'll just leak.

If you're not in a hurry, get a kit and replace the screens in your injectors and the o-rings as well. It's an easy job and cheap ($25) insurance. And you're right there anyway. Be careful re-installing the fuel rail- it's easy to nick an upper o-ring on re-assembly. Ask me how I know.

I know- just think of your Rover as your old, favorite sweater with a loose thread. You pull just that one and next thing you know, you're holding a giant ball of yarn.
 

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One last thought- if the truck has SAI, you should be soaking those head adapter connections at least a couple days beforehand with a good penetrant. The will bind not only between the nit and the adapter, but the nut on the tube. If they do, they'll twist the tube.
 

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Discussion Starter · #17 ·
Sometimes if you look at that MAF the wrong way it'll set a code. It's the same Bosch internal piece as used on lots of other vehicles, but for some reason, they become super-sensitive on the Rover. Various cleaners can cause rubber seals and gaskets to swell. There's no instruction on cleaning the IAC so no spec cleaner. I do know that carb cleaner ruins them.

If you're going that far, I'd suggest doing the intake gasket. They are known to leak coolant in the rear and occasionally some vac leaks as well.. If you do, pre-fit it and torque it down to stretch it a bit. Place the valley end clamp bars on and snug them but don't tighten until the main bolts are torqued. Then remove, light silicone on just the bottom surfaces, then install and torque. Let it set, then remove and silicone the top surface. Take your time and use just a very light amount. If you have good mechanical skills, it can be done in one shot, but it's a bit tricky.

Torque is very important on these bolts- especially the upper plenum bolts, which also require loctite. Omission is common and also the result of alot of vac leaks. And broken bolts- they're very long and skinny.

You're going to need to do VC gaskets if you pull the intake. If they haven't been done recently they're probably hard as a rock and leaking. Every one I've ever seen is a little smaller than the opening. Set them in the sun and warm them, then glue them to the cover. You can use some clamps or bolts and washers to hold them in place while it sets. If you don't, they'll just leak.

If you're not in a hurry, get a kit and replace the screens in your injectors and the o-rings as well. It's an easy job and cheap ($25) insurance. And you're right there anyway. Be careful re-installing the fuel rail- it's easy to nick an upper o-ring on re-assembly. Ask me how I know.

I know- just think of your Rover as your old, favorite sweater with a loose thread. You pull just that one and next thing you know, you're holding a giant ball of yarn.
Can you tell me the torque requirements and sequence for the upper intake manifold? I am having trouble finding them and getting some conflicting information.
 

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Discussion Starter · #19 ·
So we think we narrowed it down to a vaccum leak on the upper intake manifold at the front passenger side elbow. Replacing those gaskets. Anybody know the torque specs on that??? The gasket is part ERR6622.
 

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Discussion Starter · #20 ·
Thread Update: Problem Solved
Thank you to those that helped and an update incase it is helpful to anyone else searching threads. We found the problem. The o-rings had to be replaced and the injectors cleaned (injectors cleaned were prob a bonus). O-rings were bad for sure. Stopped the air leak by replacing all of those and once the air leak was fixed the idle returned to normal and the misfires went away. 40+ miles down and no Service Engine Soon light or codes. Happy Rover Owner.
 
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