# Hard start, runs rough and won't idle HELP!!!!!!



## kenv1 (Jan 14, 2010)

I just bought this 97 Passat. On the way home with it the thermostat went out. I replaced it along with the housing. All was well until I hit a large bump in the road. The car died and I was barely able to get it started and back home. Now when I can get it started it dies immediately. Occasionally I can get it to keep running by holding it around 2000 RPM, but it runs rough, misses and back fires. I replaced the fuel pump relay, plugs and plug wires. The hose from the PCV to breather was shot so I replaced the intake boot. I can't find any loose wires and VAG-COM is not showing any faults. I blew out the fuel lines today thinking a blockage, but no help. I am about to pull my hair out and at this point it has become a puzzle and I have to figure it out. I hate to take it to a mechanic, but may have to yet which would spoil my fun and success for figuring it out. Any suggestions???????http://forums.vwvortex.com/zeropost?cmd=newtopic&id=34#


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## O_o (Nov 12, 2009)

*Re: Hard start, runs rough and won't idle HELP!!!!!! (kenv1)*

Sounds like you might have a dud ignition coil, but try cleaning the throttle body and putting some injector cleaner in your gas tank and see if that helps. If it doesn't, then you at least have a nice clean TB and injectors. http://****************.com/smile/emthup.gif


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## kenv1 (Jan 14, 2010)

*Re: Hard start, runs rough and won't idle HELP!!!!!! ()*

After running rough awhile the catalytic conv got really hot and I loosened the center console to make sure nothing was burning. When I started it with the console loose it started fine and idled like normal for a few minutes then died and same problem all over. So, today I loosened the center console and poked around. Once again it started easy and idled great for about 10 minutes then sputtered and died. Any suggestions before I pull out what little hair I have?


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## tryin2vw (Dec 30, 2006)

*Re: Hard start, runs rough and won't idle HELP!!!!!! (kenv1)*

Check for a vacuum leak.


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## No self control (Oct 13, 2008)

*Re: Hard start, runs rough and won't idle HELP!!!!!! (kenv1)*

The first thing you should do is scan your car with vag com. If you can't use vag com then have it scanned with an OBD2 scan tool and report back.


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## kenv1 (Jan 14, 2010)

I scanned with VAG-COM and the only fault is an intermittant low voltage at the Mass Air Flow. What could be loose in the dash behind the radio or center console that could cause this? When I wiggle wires in that area and pull the center console I can get the car started and it will run OK for several minutes and sputter and die. Then if it sits a few minutes and I wiggle again the same thing.


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## No self control (Oct 13, 2008)

*Re: (kenv1)*

What is the production date of your car and the trouble code number? I will need this information to accurately diagnose your car, however based on what you said I would first check the power supply relay. Main relays fail but the contacts on the back of them often become corroded and are more likely to cause any problems associated with the relay.With multi-system faults you need to check power, ground, main relay, and the ignition switch. Now would be a good time to buy a decent DVOM if you don't already have one. Next inspect the wiring harness where it passes through the fire wall. Wires often become chafed causing them to short out. Next check the routing of the harness around the engine bay looking for abrasion and tension on the wires, pay close attention to the area around the trans axle. Next check all of your ground wires for corrosion, you will need to remove the battery when you do this. Bad ground connections have been the source of many strange problems on these cars, however I don't think your problem is ground related. You will need to get a service manual with wiring diagrams in it. Bently manuals are the best but a haynes manual will work for this. Good luck ! 

_Modified by No self control at 10:17 PM 1-16-2010_


_Modified by No self control at 10:30 PM 1-16-2010_


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## kenv1 (Jan 14, 2010)

According to the label the production date is 2/97.


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## kenv1 (Jan 14, 2010)

I got it to start today and it idled for a little while. When it died I noticed a fairly loud whine/whisle noise coming from somewhere near the throttle body, but it quit before I could track it down further. It seems to be starting easier, but hesitates on acceleration real bad.


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## O_o (Nov 12, 2009)

*Re: (kenv1)*


_Quote, originally posted by *kenv1* »_When it died I noticed a fairly loud whine/whisle noise coming from somewhere near the throttle body, but it quit before I could track it down further.

Did it quit gradually, kind of like a vacuum leak? That could throw a MAF code. So could a dirty/failed MAF sensor. Try cleaning it with some electronics cleaner, and check for a vacuum leak.


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## kenv1 (Jan 14, 2010)

Here is the latest. I got it started last night and it idled and ran fine for about 20 minutes then sputtered and died. I was able to restart it, but would not hold idle and it became more and more difficult to start. This morning it would start, but immediately die. The only way to keep it running was by pumping the accelerator and then it was running really rough. Occasionally I could let off the accelerator and it would hold a low idle, but if I pressed the accelerator it would die.


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## kenv1 (Jan 14, 2010)

I forgot. The whining sound quit abruptly. It didn't sound like a vacuum leak, but more like a mechanical whirring sound. That happened again last night also.


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## O_o (Nov 12, 2009)

*Re: (kenv1)*


_Quote, originally posted by *kenv1* »_I forgot. The whining sound quit abruptly. It didn't sound like a vacuum leak, but more like a mechanical whirring sound. That happened again last night also. 

Huh. Thought I'd replied to this already... Must have been hallucinating...

__
Image uploading. Refresh page to view









Anyway, did it sound like it might have been the SAI pump? If the relay were fubar, it could turn itself on and off randomly. The O2 sensor would then confuse the ****e out of the ECU, and the a/f mixture would be all over the place.
I'd still check the easy stuff before trying any such hare-brained ideas: ignition, MAF sensor _(for which you have a code)_, TB, vacuum/intake leak(s) (_which normally throws a MAF code_). Even if one of those is not the primary cause, if any of them is not working properly, it would be a contributing factor.
If it were me, I'd start by sniffing for vacuum/intake leaks. Cheap, easy, and likely.


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## kenv1 (Jan 14, 2010)

So,if I unplug the connector from the throttle body the car starts and idles, but only around 500 RPM. If I touch the accelerator it dies. If I plug the connector in it dies. If I try to start it with the connector plugged in it is hard to start and will not idle. I can't find any bad wires. Is this the TPS? It has more than three contacts, but is the only electrical connection on the throttle body.


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## O_o (Nov 12, 2009)

*Re: (kenv1)*


_Quote, originally posted by *kenv1* »_Is this the TPS? It has more than three contacts, but is the only electrical connection on the throttle body.

The stock 8-pin connector is for the TPS + IAC. What you describe makes perfect sense to me: the idle speed will be low because the IAC will not stop the throttle from closing completely, and it will die when you touch the throttle because the TPS is not asking the ECU for more fuel.
When I said "check the TB" what I really meant was "take it apart and give it a good cleaning." I'd check the other things first though, because they're easier and quicker: try running it with the MAF sensor disconnected, spray some ether around looking for vacuum leaks, and check for a nice bright blue spark, keeping in mind that it's not a guarantee the coil is good.


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## kenv1 (Jan 14, 2010)

I disconnected the MAF connector and no change. I can't check for for vacuum leaks because the car will start, but immediately dies. The only way it will sometimes stay running is with me pumping the accelerator or with the TB connector unplugged and then it only barely idles and soon dies.


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## kenv1 (Jan 14, 2010)

I looked inside the TB as best I could and it has very little in the way of deposits and a rag wiped around comes out clean.


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## kenv1 (Jan 14, 2010)

OK, so, I got it started and kept it running by pumping the accelerator like crazy. The first few times when I let off it died. I reved it to around 5000rpms a couple times and let off and it idled rough at first and smoothed out and kept running. It idled for about 15 minutes and started to sputter. I reved a little more to around 2000 RPM and let off and it idled. It starts pretty easy now, but it has done this before so I don't know how long it will last. When it runs it is still sluggish when I push the accelerator. I am almost ready to call for an old priest and a young priest and get out the pea soup because I am not certain the thing isn't possessed.


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## kenv1 (Jan 14, 2010)

I got to thinking that this was more of a problem when the engine was cold so I disconnected the blue coolant temp sensor and it started right up and idled. Not the best idle it was a little low and rough, but it didn't die right away. I have ordered a sensor at my friendly NAPA store and am picking it up this afternoon. If an $* part fixes this I don't know if I should be happy or really pissed







.


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## O_o (Nov 12, 2009)

*Re: (kenv1)*

I've never heard of a bad ECT sensor causing the car to run as rough as you describe. Usually it just makes it hard to start, and/or you get poor fuel mileage, cuz the ECU thinks the engine's cold. I'll keep my fingers crossed for you though...

_Quote, originally posted by *kenv1* »_I can't check for for vacuum leaks because the car will start, but immediately dies.

Right, of course. Duh. You'd have to pressurize it then, which isn't really a DIY if you don't have an air pump or compressor...


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## kenv1 (Jan 14, 2010)

Well, everything seems to help a little. Now it starts every time which is new. After it starts it idles at about 500 RPM for around 10 seconds and dies. If I pump the accelerator it will run, but I get a lot of backfire like noise. If I hold the accelerator steady or let off it idles at 500 for a few seconds and dies.


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## O_o (Nov 12, 2009)

*Re: (kenv1)*

I think someone suggested this already, but maybe your TPS went kablooey. I don't know the pin-out on the connector, but if you can find it, and have a DMM, you can do a few quick and simple tests on it. You shouldn't need to have the engine running, just the key in the run position. First, make sure you have the right supply voltage (probably 5V, but check a repair manual for the spec). When closed, the TPS output is usually 1V, and at WOT, it should be whatever the supply voltage is, and it should vary linearly between those. Anyway, if you have a repair manual, it should have a TPS troubleshooting walkthrough.


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## kenv1 (Jan 14, 2010)

Here is today's tale. I thought I'd check for loose connections so I pulled the battery and everything looked OK. I pulled the center console and, just like the past two times I had, the car started and ran like a dream --- for about a minute. Then back to the usual turn the key tries to start then immediately dies unless I pump the accelerator. Then I disconnected the coolant temp sensor (blue 2 pin) turned the key and it started and idled. The idle was a little rough so I disconnected the MAF and the idle was better. Now it starts every time, but if I rev to 2000 RPM or so and let off it sputters and dies. Does anyone know an exorcist??????


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## dangerous_dave (Jun 28, 2006)

*Re: (kenv1)*

you disconnected the fan temp switch if you disconnected a 2 pin connector. coolant temp sensors are 4 pin.


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## kenv1 (Jan 14, 2010)

Oh, I was just going by how the part is listed at NAPA and Autozone. With it disconnected the fan still comes on at the correct temp.


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## O_o (Nov 12, 2009)

*Re: (kenv1)*

You say you scanned with VCDS. Do you have one, or can you borrow one for more than a quick scan? If so, monitor/log the following:
* engine speed. 
* MAF
* manifold absolute pressure
* fuel pressure
* a/f and/or lambda
* throttle position (if possible - I can't remember)
* anything else you suspect could cause your problem
Also, just for giggles, count the misfires. There will always be a handful. I think the VCDS will tell you how many is too many.
If all looks normal, then I'd say your ECU is toast, and either needs to be reprogrammed or replaced, or (less likely) that you have a timing problem, possibly the exhaust cam hopped a link.
I'm starting to get p1ssed off by this one. I can only imagine how




























you must be...


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## kenv1 (Jan 14, 2010)

Great minds must think alike. This morning I reset the ECU, did a TBA and, you guessed it, purrs like a kitten. I drove it and came home. I tried to restart and same problem. Reset and TBA and all is better. I just ordered a replacement from Ebay so I hope this fixes it. If not it's off to church to either get a priest or confess to setting the damn thing on fire and using it for target practice.


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## O_o (Nov 12, 2009)

*Re: (kenv1)*


_Quote, originally posted by *kenv1* »_Great minds must think alike.

... and fools seldom differ. ;P
I hope it works, but let us know either way.


_Modified by  at 12:26 PM 2/2/2010_


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## kenv1 (Jan 14, 2010)

I had the ECU out since yesterday and put it back in today and it started and idled great so I am even more convinced that it is the problem, but I am still waiting on the replacement to arrive. Thanks everyone for your help this was making me crazy.


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## kenv1 (Jan 14, 2010)

I put the new ECU in and it started right up and even though the idle was a little rough in the cold it ran pretty well. Once it got to temp. the idle smoothed out and it idled fine for around 1/2 hour. I got to the end of my driveway and it quit. Right back to the same old crap. I disconnected the battery for a few minutes and it started right up and was fine. This went on several times and then all ran well for awhile. I drove for about 15 minutes with no problems. After I stopped back at home and started again I went through the same cycle. I did discover that pounding on the steering wheel and dash while calling the car a dirty whore had no effect other than make my hand sore. My current thinking is TPS, throttle body or some combination of the two. Oh, and the excorcism is still on the table.


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## kenv1 (Jan 14, 2010)

I got in this afternoon and it started like normal. I took it out for a drive and went up and down my road several times with no problems. Then it came back the only way I got back was by wildly pumping the accelerator. If I reset the ECU by removing the battery, connecting the cables and turning the switch to on for several seconds then reconnect it will start and run, but soon quits again. In the engine compartment by the battery is a black electrical component with two fuses a 7.5 and a 20 amp. The 7.5 was blown. There is a blue connector on the back of my fuse box and when I plug it into the blue plug the same fuse blows. I had noticed this connector loose when I first encountered this problem and reconnected it then. What is this fuse for and could this cause these problems?


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## tryin2vw (Dec 30, 2006)

*Re: (kenv1)*

Can you post a picture of where you are describing? The only thing I remember by my battery is the ECU control enclosure.


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## kenv1 (Jan 14, 2010)

I figured out what the part is. It is the electric fan control. Does anyone know what size fuses it is supposed to have? There are two. Currently they are 7.5 and 20 amp.


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## tryin2vw (Dec 30, 2006)

*Re: (kenv1)*

You have a 2 speed fan with two fuses. One should be a 5, the other a 30, the way I am reading my bentley. Could they have been accidentally reversed?


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## O_o (Nov 12, 2009)

*FV-QR*

Suckando!
Why would it run rough with a blown fan fuse - especially if it's the low-speed fuse? Maybe there is a wiring problem with the ECU? A bad input/reference voltage, or ground?


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## kenv1 (Jan 14, 2010)

I didn't figure that had much to do with the big problem I just happened to notice it. At this point any victory no matter how small is good. I have a new throttle body coming today. I'm going to put it on tonight and see what happens. I think my new plan is to replace every part one by one until I have a new car. This thing is MAKING ME CRAZY!!!!!!!!!!! I'm thinking that the TPS is fried and it gets the signal to accelerate, but not idle or run at a steady speed and that is why it will run if I pump the accelerator, but dies if I hold it steady. I did find several broken wires in the harness coming from the fan control and when I connected them all back I started getting a voltage high at terminal 30 code and the fuse still blows.


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## O_o (Nov 12, 2009)

*Re: (kenv1)*

You can check TPS operation very quickly with a DMM and VAG-COM. First, log TP with the V-C. If it's what you expect, the ECU is getting the correct throttle position, and the TPS is fine, and you can look elsewhere. If the log looks wrong, you would next check the TPS input and output with the DMM. If those are both OK, then it's a wiring problem. If not, then your TPS is indeed fubar. Beats throwing parts at it and hoping for the best.


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## kenv1 (Jan 14, 2010)

*Re: ()*

Except at this point throwing stuff at is is the only satisfaction I get. 
_Modified by kenv1 at 2:36 AM 2/5/2010_










_Modified by kenv1 at 2:39 AM 2/5/2010_


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## O_o (Nov 12, 2009)

*Re: (kenv1)*

I'd watch, but I am the last remaining person on Earth who does not have a Facebook account.


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## kenv1 (Jan 14, 2010)

*Re: ()*

I forgot I had a you tube account try these.
http://www.youtube.com/watch?v=joE7cZT1vF4 
http://www.youtube.com/watch?v=nu5rtBBhpTU
http://www.youtube.com/watch?v=xwbHS8b3y-c 
http://www.youtube.com/watch?v=ZMJIefGfmK4
http://www.youtube.com/watch?v=K2dyzaxmpew 
For your viewing pleasure. This is with me pumping the accelerator and, believe it or not, is a vast improvement with the new throttle body installed.


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## O_o (Nov 12, 2009)

*Re: (kenv1)*

One of these days I'll probably have to succumb to the evil of Facebook, just not today... Anyway, my sound card and speakers are pretty crappy too, but I was able to hear what sounds to me like yer basic garden variety sputtering.
I just re-read most of this thread, and you never mentioned if you checked the MAF sensor/wiring. Do you still have a code for an intermittent signal? If so, I would log MAF and RPM when the engine runs OK and when it runs rough before doing anything else. If it's only intermittent when it's running rough...


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## kenv1 (Jan 14, 2010)

I thought this was interesting. Just for giggles I hit it with a blast of starting fluid and it started and ran well til it ran out of ether. I checked again and it has good fuel pressure, but I changed the filter anyway. No change. I still think I had to have knocked a connection loose somewhere when I hit that bump. So what connection could have to do with fuel delivery that isn't the fuel pump?


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## O_o (Nov 12, 2009)

*FV-QR*


_Quote, originally posted by *kenv1* »_So what connection could have to do with fuel delivery that isn't the fuel pump?

Mass. Air. Flow.


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## kenv1 (Jan 14, 2010)

Wouldn't it be better or at least different with the MAF unplugged if that were the case? Now it is the same either way. My other problem is that I can't test the damn thing if it wont run. I'm headed to the salvage yard Saturday maybe I can find one there that is a little cheaper than the ones I have seen thus far. I also want to replace the connecter. The wires are a lilltle chafed right where they enter the plug.


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## O_o (Nov 12, 2009)

*Re: (kenv1)*

Hmmm. I'm not sure what happens when you disconnect the MAF sensor, but I think it goes into limp mode, which would at least be better...
Maybe you busted up your ignition coil? Lighter fluid doesn't need much of a spark. You need to take some logs to try and pinpoint whether it's fuel or ignition...


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## kenv1 (Jan 14, 2010)

Update, I changed the MAF connector since it had some frayed spots on the wiring. I also replaced the coil pack. When I turned the old one over I noticed a medium sized crack on the bottom. Since I am cheap and refuse to pay over $200 for a VW coil I used a ford coil and some red neck engineering and found directions on line to convert it. I picked up some used plug wires from the salvage yard from a Lincoln and once everything was in place I adapted the throttle and it idled and ran pretty well. I drove it for awhile and it started acting up again. When I checked one of the new plug wires had broken. So I had already ordered Ford EDIS ends so I can fit VW wires to the new coil. When they come in I am replacing the plugs and wires and, if today was any indication, I may have a solution. I'm keeping my fingers crossed.


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## kenv1 (Jan 14, 2010)

*Re: (kenv1)*

I received my new wire ends in the mail and quickly changed the plugs and wires. And, you guessed it IT STILL WOULDN'T RUN. If I gave it a blast of starting fluid it would start and I could keep it running if I could catch it at the right time and give it a little gas. The difference is that now I don't have to pump the accelerator and it doesn't miss and sputter. As long as I hold it at around 2000 RPM it will run nicely, but if I drop below that it dies. I changed the wiring to the MAF sensor and stopped getting that code for awhile not it only comes back occasionally and makes no difference in the way it runs whether the code is there or not. I did notice the other day when I had it running a little that if I cleared the codes the idle would surge momentarily. I have also found that if I disconnect the battery and reconnect and allow the throttle body to adapt itself it runs as I described above. If I use VAG-COM to adapt it will not run at all. I also noticed in my Bentley manual that the injectors and MAF sensor are on the same wiring diagram so I am going to check that harness and see if it is broken somewhere. I just wish it wasn't so damn cold and we didn't have a foot of snow.


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## kenv1 (Jan 14, 2010)

*Re: (kenv1)*

Success at last. I had plugged in the MAF sensor I got at the salvage yard and sat it in the intake the other day (it was from a 4 cyl so the housing was different) and had no change. That was before I changed the coil. After I changed the coil and nothing changed I had a Clak Griswold moment and punched and kicked things for awhile. So today I sat the MAF back in the intake and tried again. This time it started and ran pretty well. I drilled out the bolts on the new MAF and put the sensor in my housing and mounted it up. It ran pretty well. Now I am throwing codes for coolant temp sensor and intake air sensor as well as a P1580 throttle actuator malfunction. I am guessing the sensors are the cause of my current surging and rough idle after warm up so I am going to check my connections and test them and replace if needed. Thanks for all of your help.


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