Looking for Advice on P1172 and P1175 Codes
 

So, I'd like to know what all I should consider checking with these two codes.


I know they typically refer to the MAF sensor, but I've tried several different MAF and still getting the same cold start issues.


I've checked all vacuum related lines. Cruise works great. Nothing odd aside from a nipple on the passenger side of the plenum that has no hose attached. It's right below the other two vacuum hoses that connect to the top of the plenum. Year is a 99.


My intuition is leading me to believe it may be the injectors or injector seals. Is that possible with these two codes? I think it could be the injectors because I believe there is a loss of air somewhere in the vacuum system which is causing the rough idle on cold starts.


Otherwise everything is great after about 1500 recent miles. Once started and warmed up, she runs quiet and cool.


Just need some assistance pinpointing the vacuum codes.


Thanks for any help.

I would start it up cold and pour some water along both sides of the lower intake manifold. Leaking intake gaskets is a pretty common problem on lots of vehicles. If it's leaking, you'll hear it sucking in the water.
If it doesn't suck in water, it's possible that your IAC valve isn't working correctly.
Also, if your coolant temp sensor is giving an incorrect temperature, that can also cause rough running at certain engine temps.

I will try the water hose method. Wouldn't I get the same effect by spraying starting fluid around the intake gaskets and be able to diagnose that as the problem if the rpms increase?


I recently cleaned the IACV, but there is still visible carbon deposits. If I could dismantle the iacv, I feel like I could get it completely clean, but the scrrews that hold the assembly together have epoxy over them. I may have to buy a new one.


I guess I will try that before digging into the injectors. I wish I had checked the injector seals when I changed the plug wires, but I didn't want to create a new problem.
Thanks for the suggestions.

Usually a good idea to search for & look at the LR code description versus generic in the manual. Doubt IACV or intake leaking causing a rich condition.

From injectors section:
......

I also see a rich system can cause an O2 sensor to throw a code. I have been thinking my problem could possibly be clogged cats. Maybe that mixed with injector seals or bad injectors. It's just my guess based on the mileage and some recent hard driving after mostly being used for day to day short commutes.

Oh wait a minute, I misread your post. I read vacuum leaks, rough running on startup and I didn't pay attention to the codes in the heading. I apologize for that.
No you don't have vacuum leaks, or at least that's not your problem.
I would check out the coolant temp sensor. If the maf is good and it runs good when warmed up. Connect a scan tool and watch the coolant temp from cold start all the way through warm up. I usually graph the reading so if it drops out or changes erratically you'll see it.

No problem. I will switch to graph. That's a good idea.


So far, the temp gauge doesn't have any wild swings, and it levels off to about 194f once warmed up.

It's just one possible cause of temp specific problems.


You could always try unplugging the maf on a cold start an see if it runs better.
I don't think clogged cats would be the problem. I would think that would make it run poorly at any temperature. Not that I would rule it out completely without looking into it further. But I would start with fuel and air first.


What do the fuel trims do as the engine warms up? Do they start going back towards zero?


Also, don't forget the intake air temp. That can sometimes cause some trouble too if it's not accurate. I would go through all the data pids while the engine is cold and see if anything looks out of place.

So, I started digging around. Checked oil breather hoses, noticed I didn't latch the air filter box last time I was in there, and then noticed an oil leak.


The oil leak led to further inspection and I noticed the flywheel plugs are no longer there. Couldn't tell you how long it's been like that.


Now I have a lot of cleaning to do and have to figure out a substitute for the plugs until I can buy them from a local parts store or order new ones.


I will continue to update as I diagnose and fix.

It's only one flywheel plug missing. Thought the other was gone, but it's still intact.


I think I will do an induction cleaning and engine oil clean. Then plan to drop the oil pan, clean out any grime and replace the oil pan seal.

I may also pull the intake apart so I can clean it and check the injector seals.

Injector seals would make it run lean, so that's probably not an issue.
What is the TPS reading at idle?
You could try cleaning the throttle plate. Sometimes if you get enough carbon build up in there it can stick the throttle open a little bit. The computer sees an open throttle from the TPS and starts adding fuel, but it's actually closed against the deposits. You may have to remove it and really clean both sides good.

I just checked the throttle plate only finding a little oil residue, but no buildup or varnish.


I will let you know what the readings are after cranking it back up.


Do you think it's okay to crank it without the flywheel grommet?

As long as there's nothing in the way of the flywheel, I don't see why not.

Here are my readings:


intake temp: 76f start 96.8f after 10 mins


fuel trim: -1.6 - 0 at idle, both sides


maf: 6.1


vac: -10


o2: .1 and jumps to .8


coolant temp: 76f at start, 194f after 10 mins.

There's something up with the extra nipple below the oil separator line on the plenum.


When I plug it, she idles sort of normal. When I remove the plug she starts bogging down and will stall if I don't hit the throttle.

Which fuel trim reading is that? Check the long term and short term fuel trims. They should both be within +/- 10%. Anything over that and there is a problem.
On the MAF sensor reading, try doing a couple snap throttle tests. Open the throttle all the way and quickly release. The reading should spike briefly.

I'm not sure exactly what this is. Is it missing a plug, or a vacuum line?

There's a small nipple below the oil separator line and the vacuum line with the red quick release on the top passenger side of the plenum.
It's been like that since I bought it. I made a plug out of electric tape to seal it. I've asked on forums before what it goes to, and no one knows. It's a 99 model D2.

I don't know if mine has that. The '99 is different from mine, I think.

The maf spikes when I open the throttle all the way.


Those are the long term fuel trim readings. Short term seems normal too.


I think I might ask Dave at AB what the extra nipple is. He has helped me with some issues before.

The left one is for the valve cover breather. (I know the clamp is loose BTW)
The right is the brake booster.
And below is the plugged nipple on my 2001.

https://cimg0.ibsrv.net/gimg/landrov...d99737cde2.jpg

That's the one in talking about. Maybe I need a better plug than my homemade version. It ran for many miles without one, but I've had it plugged for the last 4k or so.


Anyone have an idea what it's purpose is.


Thanks for the photo. I was going to upload mine once I got to a better signal area.

I have never seen a DII with anything hooked up to it?

Auto parts stores sell assorted plug kits that have a few different sizes.

Or you can a piece of hose from somewhere about 3" long and stick a golf tee in it for now?

So, I just drove to the parts store. On the initial cold start it was rougher this time. Fuel trim hit 25 on startup. Same with short term. They leveled back to around 0 after warming up and after driving hit 25 again, then back to zero once I parked.


Any ideas?


I'm still thinking the vacuum is draining somewhere. Might try a new filter. I dunno.

Is that positive 25%?

Yes, ➕ 25%.

Okay, then you should have lean codes. If that hole is leaking vacuum, that's probably the whole problem.

I'm going to find a plug for it somewhere today. I won't know until tomorrow morning's cold start if that is the fix.

That's really strange that you got rich codes.

I have a vacuum tube connected to that nipple, just saying.

Okay, so this morning I got a better start out of her, but still rough. It's just been bothersome because once warmed up, I feel like she is running better than ever.


One odd thing I noticed though this morning was when the ignition was clicked to acc, the intake temp reading was -40f. After cranking the car, the temp adjusted to what looked normal.


My plan at the moment is to put in an order on AB for a intake temp sensor and flywheel grommet. Then plan to do an induction cleaning and all of the breather hoses, tbi, and pretty much anything else connected.


I also still need to find an actual plug for the plenum nipple. Maybe AB can throw one in my order.


Again, I will update as I learn more.

Where does the other end connect?

Also, can someone tell me if this part: [Linked Wrong Intake Temp Sensor] is the intake temp sensor I need?

If you have secondary air injection, there is a tube that runs from the SAI to that nipple. If you do not have SAI, the should just be a cover. Discorey, do you have SAI? I don't think you do based on this thread. If you don't then that is wrong sensor you posted the link to. The photo that Backin a 88 posted is showing no secondary air hose, just a cover. If your setup is the same as his, you don't have secondary air and that would be the wrong temp sensor for sure.
Take a look at what SAI looks like:
http://www.roverlandparts.com/2ndair.aspx

This might help you sort things out better.

I do not have SAI.

I noticed after you asked whether or not I had SAI that I linked the wrong sensor.

I called AB, and asked if they have the one I need in stock. Brian that I spoke with said they don't get many asks about that sensor, so he asked what I had diagnosed that led me to that. So, I went through everything I'm currently dealing with, and he thinks it could be the IACV. So, now, I'm on the lookout for a new IACV.

I'm hoping to try one if I can find it at a Pick N Pull before buying a brand new one to see if I notice any differences.

I found a new Bosch OEM IACV on amazon for $174..

Is there a chance I've got a plenum for a SAI D2, or did all D2 plenums come with this nipple and some were capped?

Thanks for everyone's help. I will continue to update once I get the proper diagnosis and fix.

I had trouble with the IACV as well. I'm not saying this is a good idea but it seemed to help. I bought two cans of brake part cleaner and a 1 quart paint can. I very carfeully sprayed the parts cleaner into the can. It is a common practice for scale modelers who want to use their own airbrush instead of the spray can. I sprayed enough into the can that I could immerse the openings of the IACV and let it soak. I would pull it out, clean it and repeat the process a number of times. It really got the carbon buildup out and seemed to help the performance. I will grant you that I had done a bunch of other things like replacing the vacuum lines and PCV purge valve, but it seemed to make a difference. As you seem ready to go the PNP or buy one route, how much damage could you do? I make no warranties or guarentees.:dunno::dunno:

Seafoam is really good at breaking down carbon deposits. I use it to clean throttle plates on newer cars that have coatings around where the plate seals on the intake. It breaks down the carbon, but doesn't damage the coating. I would think it would be safe for use on the IAC.
As long as your temp is normal when the engine starts up, I wouldn't worry about the IAT sensor. The IAC may not be opening all the way on cold starts. It should flare on startup and then slowly come down to a normal idle.

So, I'm cleaning the IACV now. Still getting some tiny little bits of carbon coming out. Alternating between soaking in seafoam and spraying out with starting fluid.

The flap inside the IACV moves freely if I depress it with a screwdriver and goes back into place when I remove the screw driver, but it's still sort of floppy in the housing. I hope that is normal.

That's probably okay. As long as it is capable of opening all the way with no obstructions. If there was enough of a buildup behind it that it couldn't open up all the way. You would almost certainly have problems on startup. Especially cold starts.
I hope that's all it is. It's always nice when you can fix things without spending money on parts.