Compression for 03 Disco 4.6?

[dagdisco03]

I have the RAVE CD but I'm not seeing what the correct compression reading should be?

[Toowild78]

4,554 cc 4.6 liters 8 V front engine with 94 mm bore, 81 mm stroke, 9.4 compression ratio, overhead valve and two valves per cylinder

[dagdisco03]

Thank you for the quick response but what I'm not able to find is the PSI or Bar reading I should see when doing a compression test with a gauge screwed into a spark plug hole. A wild guess would be something like 175 psi?

[Paul Grant]

More than anything else, what you want out of a compression test is consistency between the readings on the cylinders. It is far better to have all eight cylinders having compression within 10% of each other than to have seven showing 170 PSI with one blowing 120 PSI. Ideally, all eight around 150-160 PSI and you should be very happy.

[Disco Mike]

Why are you asking, do you think you have a problem, if so what?

[dagdisco03]

I'm still getting misfires and it seems like a sensor adjusting values out of range to me. New OEM Champ double plat. plugs and 8 mm Magnecor wires, In drive it will not go over 3500rpm with WOT. You can here the misfire pings like its a timing issue. 91 Octane always. I was hoping someone would understand the fuel trim on bank 1 and 2. -16% on bank 1 and +13% bank 2 seems extreme to me but I don't know what that is telling me. I always pull P0301 and P0305 is pending. I also think its odd that the 2 are the upper left terminal of each coil or same position coil 1 and 2. I'm not sure if that is random or if it means something? I did the compression test 1 = 158 psi, 3 = 153, 5 = 155, skipped 7 since it was hard to reach and not throwing codes, 2 = 160, 4 = 155, skipped 6 and 8 figure they must be close. I know we don't like short cuts but the codes are on 1 and 5 and all seem to be very close. I also bought a new upstream 02 sensor and placed that on bank 1 where the misfire is occurring. I then swapped the rear/downstream 02 sensors from bank 1 to 2 so I could see if the issue would move to bank 2. I had the battery disconnected for 30 to 40 min and also reset codes before disconnect. Connected all back up and took it for a ride around the block. Flashing CEL returns within 2 miles. I will be testing injector and timing next. It seems to me that something is telling the system to retard the timing over 3K RPM. I'm not to sure what adjustment I really have for timing on here if any. Also with the plug out the coil fires the plug like crazy if that matters. I think the coil is good.

Freeze Frame Information https://www.canobd2.com/Images/Diagn...tonOnBrown.gif Parameter Description Value DTC for which Freeze Frame was Stored P0301 Fuel System 1 Status Open Loop - due to detected system fault Fuel System 2 Status Open Loop - due to detected system fault Calculated LOAD Value 24.31 % Engine Coolant Temp 201.20 °F Short Term Fuel Trim - Bank 1 0.00 % Long Term Fuel Trim - Bank 1 -16.41 % Short Term Fuel Trim - Bank 2 0.00 % Long Term Fuel Trim - Bank 2 13.28 % Engine RPM 2,594.50 rpm Vehicle Speed Sensor 68.35 mph

Additional freeze frame Bank 1 -14.xx%, Bank 2 +12.xx%This was from highway today.

[dagdisco03]

Also ran with MAF unplugged and I pull 2 MAF codes but only misfire on 1 and 5 still. People were saying if the MAF is bad I should misfire on both banks. This is not the case when it's disconnected. Also the truck runs the same with the MAF unplugged or plugged in nothing changes. I'm planning to swap a few injectors next to see if that is an issue. Just a PITA to move an injector to test since I need to pull the upper intake on the Bosch engine to reach them.

[Disco Mike]

Don't go screwing with your injectors, D2 injectors hardly ever fail compared to the D1's and you would be getting a 201 and 205 codes, plus some cat codes for all the excess fuel.
Have you pulled those plugs, what do they look like?

[dagdisco03]

Yes the plugs are new OEM Champ double platinum. I had Bosch +2 in before so I expected this to all go away after replacing the plugs with OEM and new Magnecor 8 mm wires but there was no change in the issue. I've also swapped the wires and plugs to other locations and issue stays on 1 and 5.

[Disco Mike]

Time for a leak down test on those 2 cylinders.
How about carbon misfiring, how do the plugs from those 2 cylinders look?

[p76rangie]

This is from an earlier thread:

This is a post by a friend on another forum about some O2 codes he was getting on a D2.

"I had 3 error codes logged on my ECU, P0171 (bank 1 lean), P1171 (both banks
lean) and P1174 (both banks rich).
Ever since the 2nd time the engine was rebuilt at Range Rov, I kept getting
variations of these logs in my ECU. Every time I clear them, they come back.
So thinking it was the O2 sensors perhaps, I took it to MLR for them to diagnose
with the Testbook.
When they reset engine adaptations, the V8 ran like a dog. Turns out the MAF is
fault and the ECU has been adjusting trims to compensate. Makes no sense to me,
but in searching through the internet, someone else in the USA is saying too
that if the MAF goes, usually Bank 1 on the V8 starts getting lean error codes.
Anyway, new MAF (rrp $320) solved the problem.
The old MAF looked like it had been dunked in dirty muddy water. "

[dagdisco03]

I ran through all of the vacume tests and all looked very good to me at most .25" movement of the needle but near as still as possible. Each test had a just what was expected for a good running engine. Idle is low to me but still made 17. no needle tickes of 1 to 4 " on anything and the blip tests were correct as well as 3000RPM tests and blockage tests. No bad results. I ran the truck down the road and pushed it in 2nd gear and was able to pull 1300, 0300, 0301, 0303, 0305, 0307 for codes. So getting it to 4500RPM pulls misfires on all bank 1. Also did vacume tests on PVC and those were good as well. I have not been under to check the CKPS. It's running so good after all these cleanings and parts but the misses won't go away.

[dagdisco03]

I'm trying to figure out what to try next studying the RAVE CD info the codes pulled are only listed for bad fuel injectors and no where else. My issue is the system goes to open loop fueling with bank 1 full lean and bank 2 full rich. The open loop fueling with one rich bank and one lean bank seems to be related to the O2 sensors as far as the RAVE is concerned. With no code for bad O2's I'm not sure if the RAVE CD is leaving out a lot of possibilities? I feel fairly confident that the vacuum test and compression tests confirm that I do not have major mechanical failures and this is electronics making adjustments.

[Disco Mike]

I have heard of a few people having one bank, full lean or full rich, but have never heard what they did to fix it.

[Prodigy999]

sounds like you have some sticking valves or a broken camshaft (yes I have seen it)