Idle Problem 1994 Subaru Legacy

[Jessekrs123]

Ok, so here it goes. I recently rebuilt my EJ22E. After the rebuild the car ran very well for 800 miles, then I had a bad ground that would disable spark, but I fixed that. Now the car cannot idle to save it's life. I am getting code 24 for the IACV, but I replaced that and I am still getting the code and it is still idling badly. When I start it up, it will idle high at like 2,500 rpms, then it will slowly drop to 1,500 rpms, then it will instantly drop to like 1,000 rpms and the idle will surge and the car sputters. I checked everything, the TPS and MAF and everything checks out ok. I am thinking there might be a problem with the ECU and I am looking for a datalogger to possibly pinpoint the problem. Anybody ever have this happen to them before? I am stumped, I cannot figure this out.

[porcupine73]

Do you have any vacuum leaks anywhere?

[Legacy777]

Welcome to the BBS.

If you've cleared the code for the IAC valve and it's still showing up after you replaced the valve with a known working valve, I would check the continuity of the wiring from the IAC valve to the ECU. If all checks out good, then it may very well be an issue with the ECU.

[Jessekrs123]

Just today I got a new charcoal canister because Subaru looked into the code history and said I had 1 for the IACV, and 1 for the charcoal canister. I put in the new canister AND the stock airbox back on and now the car runs fine. I just have to wait and see if the problem comes up again. Most of the time the problem will go away for maybe a week, then it will come back randomly usually on Sundays. I am on NASIOC, so I am not new to forums, but I figured this site would best fit my car. ALSO, I looked into the ECU on my car, and although in my Hayne's Repair Book it says that the ECU is located on the left side under the passenger kick panel, MY ECU is located on the driver's side right behind the hood release latch. It says in my manual ALL subaru ECUs are on the right side. Does anyone else here have their ECU on the driver's side?

[vrg3]

Hmm. The purge code is actually tripped by the solenoid valve, not the canister itself. If that code comes back you'll probably have to replace the canister purge control solenoid valve.

As you've found, the Haynes manual is pretty lousy. All first-generation Legacies have the ECU where yours is.

[Jessekrs123]

OK, at this point I am beginning to lose all hope with my car. It was driving wonderfully last night, and when I went to start it up this morning, it was extremely difficult to start. I did have a grounding issue which was fixed, and it was like that grounding problem came up again. A couple months back, my car would randomly lose control for the ignition, and I would lose spark and break down. I noticed that the shield wire for the knock sensor had power in it, so I grounded that wire and the car ran again. So the ground problem was fixed, but then came the idle problem which I have not been able to fix. Could this have anything to do with my ground from the shielding wire? At this point I am contemplating on whether or not I should tear my interior apart and thoroughly inspect the wiring harness in hopes of coming across a bad ground or a damaged wire. I really do not want to do this because it is a major PITA, but I really want to just have my car run good without having to effing worry about it all the effing time. My dad says I should sell it, but I have put way to much time and money into this thing to just get rid of it. Plus it is a FWD 5 Speed 1st Generation Legacy Sedan with bad transmission bearings and 149,000 miles. I feel I would only be able to sell it if I were able to find another person like me who ABSOLUTELY adores first generation legacys. What do you think I should do? Do you think my harness might be broken somewhere and that fixing all the possible bad connections and grounds that my car will finally run for me everyday with no problems? I have owned 2 other first generation legacys and I have had never experienced problems with them like I have with this car. I JUST WANT MY CAR TO RUN WELL. I WILL redo the harness if I can get some more input. I have done everything to this car myself with help from my father, it was good bonding time when we worked on it, but now he just gets pissed off everytime I mention it and I just want my car to run. Haha, I do not know what it is with this thing but I just drove it around for like 1 hour no problems. I could not start it up, I plugged the diagnostic wires in and it started right up. Then I shut the car off and took the wires out and started it back up. It was idling fine and driving wonderfully. I am sure the problem will come up again but this thing is just unpredictable.

[vrg3]

First, I'm sorry this problem is so frustrating.

Second, please try to organize your writing into paragraphs. It'll make it a lot easier to follow your posts and to help you.

Third, what do you mean when you say "I noticed that the shield wire for the knock sensor had power in it, so I grounded that wire and the car ran again?" Can you explain that in more detail?

Fourth, porcupine73 suggested you might have some vacuum leaks. Have you searched thoroughly? You say you checked out the hoses and stuff, but it could be a leak in the brake booster, or a bad intake manifold gasket, or throttle body gasket, or IAC valve gasket.

Fifth, what exactly happens when it fails to start? If you're having problems with spark, maybe you should look at the ignition system -- coil, ignitor, plug wires...

Hang in there.

[Jessekrs123]

3. When I bought the car, the shielding wire that surround the wire going to the knock sensor was just out in the open. The car ran good for 800 miles, then my spark was lost. When my car was without spark, I grounded that wire to the transmission and I got my spark back. Here is a video of what I am talking about.
http://www.youtube.com/watch?v=EDoBJ321WjY

4. When I rebuilt the engine, every single gasket was replaced EXCEPT for the headgaskets, so I do not believe that there is a leaking gasket somewhere, all the gaskets besides the headgaskets only have about 1,500 miles on them.

5. Luckily I had a bunch of ignition parts from my old legacy, so when this problem did occur, I had extra ignition crap that I could test on my car. I replaced the coil pack, igniter, wires, plugs and still no luck. Once that shield wire was grounded, the ignition system worked no problem.

Well, I bought the car for $800, it needed a new clutch. The previous owner was a woman driver from a foreign country who completely burnt out the clutch after driving it 400 miles XD. I love 1st generation legacys. I pledge that Subaru will be the only manufacturer that I will buy from. Me and my father know Subarus very well, it just sucks when there is an electrical problem because it is just ridiculous to pinpoint the cause. I hope to go to school to become a mechanical engineer for Subaru, or if that doesn't work out then become a Subie Tech, in which I am already somewhat training for.

[vrg3]

I can't watch YouTube videos at work, but --

I think you're absolutely right when you think this is a bad ground. Nothing about the knock sensor should be able to make you lose spark. The sensor shield is supposed to be grounded by the ECU; inside the ECU's case the "knock sensor shield" contact is connected to ground.

But, if the ECU wasn't grounded, then the knock sensor shield would be floating, and when you connected it to ground you provided a ground (albeit a poor one) for the ECU, allowing it to function.

First, undo your grounding of the knock sensor shield. That's just going to cause problems.

Second, check the ECU's main ground. It's two ring terminals attached to a bolt at the rear driver's side of the engine -- if I remember right it's on the intake manifold by the fuel rail. Remove it and clean the bolt, ring terminals, and grounding surface. I'd use a steel wire brush on the bolt and sandpaper on the flat surfaces. Then use copper anti-seize compound on the bolt as you reassemble it securely.

Maybe you just forgot to bolt that up when you did your rebuild!

[Legacy777]

Watched your video.....yeah that shield wire should not be touching anything.

I second the ground issue. Vikash is correct regarding the ECU ground location. There's no need to tear apart the interior to check grounding. The ECU ground only goes to the intake manifold.

Also, if you don't have a multimeter, I'd suggest getting one. It's an invaluable tool to troubleshoot problems like this. Additionally, wiring diagrams provide a lot of help. Check out this thread if you haven't seen it yet.

http://bbs.legacycentral.org/viewtopic.php?f=12&t=14485

[Jessekrs123]

Yes I have a multimeter and I know how to use it, but I think 777 and vrg got it. VRG, when I checked out the ground that you were talking about, to my suprise, IT WAS LOOSE!!!! I attempted to tighten the bolt that was holding it down but it was as tight as it got! I then grounded that ECU ground to something else that would tighten it better, I took the knock sensor shield off it's ground and VOILA. My car is running exceptionally well and it now idles like it should. Thank you very much VRG, this seems to have solved my problem for now, only time will tell if the problem comes up again, and I really hope it doesn't, I hope that this will permanently fix my problem. Thank you so much, if I could I would buy you guys a steak and some beer. Thank you so much for your help.

[vrg3]

Woo hoo!

You grounded it to another threaded hole nearby, I imagine? That should do fine as long as you secured it well. The most important thing is for all the ECU's grounds to be the same.

[Legacy777]

Yeah I am going to follow up on the same thing. Ideally, you want the ECU ground to be the same spot. It doesn't hurt to also add an additional ground lead from the ECU ground to the negative lead on the battery.

From the testing I have done, I've found small variances in grounding locations between the intake manifold/ECU ground spot and battery. Tieing those two together may help.

[kleinkid]

Josh--what do you mean by saying that ideally the ECU ground should be the same spot? Same spot as what? Does it have to be at that bolt hole on the back by the fuel rail? On my '94 I found it bolted to the intake manifold up towards the front. If that is OK, I will run a ground from that spot to the neg batt. terminal. This car has wild idle.

[Legacy777]

I meant it should be on the manifold near where it originally was. I didn't word that well.

As long as you have the ECU ground on the intake manifold in a good spot, you should be ok.

[Jessekrs123]

This is where I relocated the ECU ground.



It is on the intake manifold, bolted to the vacuum hose bracket. The car runs fine with it here so this will be the ground. Problem solved

[kleinkid]

That is easy to get to. Down below there by the fuel rail is harder to get at.

[Legacy777]

I would suggest putting the ground directly up against the intake manifold. Also, if you haven't, I would also suggest sanding down the paint so the ground terminal can make good contact with the intake manifold.

[Jessekrs123]

Sorry to resurrect this thread but, 777, I just sanded off the paint on the intake manifold and put the ground directly on the manifold because my car has been very hard to start in the morning. I have to crank it for at least a minute for it to get going, so I figured, hell, maybe that ecu ground could be better. I'll see what happens tomorrow but in the morning I go to start it for work, it has been like 50 degrees the past few mornings, and it takes a minute of cranking to start. Then after 8 hours of work I come back to the car, it has been sitting in the sun and its nice and warm, but still a cold start and it starts up fine, just with some chirping from the power steering. Hope this makes it easier to start.

[Legacy777]

If you are still having starting issues, you may need to replace the coolant temp sensor.

[Jessekrs123]

After grounding it to the intake manifold, it does start up a lot easier, but still takes some cranking. I replaced my coolant temp sensor during the build, and I did recently check and the resistance is in range. I'm going to the store to get some wire and I am going to do my own grounding kit from the Neg terminal to this ground, intake manifold, throttle body, and alternator and see if it runs any better.

[gilbert]

Thanks for this thread and the posts on it its made me not ask the idling question but follow what
is done by others, got a problem solved, am sure its helping many others.

[Legacy777]

Glad it helped you out.