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Demoster

Losing my faith in my s13

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So here goes. My hell machine isn't working too well. The symptoms are as follows.

Fluctuating idle at the lights, so revs between 100 and 1000rpm

Fuel consumption is around 20L/100 I know I should expect a gas guzzler but this is a little over the top

More carbon and overall black stuff coming out of my exhaust than a diesel truck.

Whether it means anything my voltmeter gauge fluctuates with the rpm

Got the idle control valve cleaned out, same as the injectors, and fuel tank,lines and filter. The mix is obviously very very rich.

Any help is valued. If your very helpful I'll try make a case or something head your way as a thank you!

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Silly question, could that be responsible for lack of fuel vacuum? When I go to fill up no hissing noise... I'm an apprentice panel beater not mechanic so excuse the simple-ness

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N/A cars still have vacuume lines mate. As said above, afm, spark plugs O2, sensor maybe?

Edited by Captain Wow

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listen,

spray soapy water and look for bubbles

spend $20 and replace all the vaccume lines with new ones front autobarn (only use 2 sizes so just take a sample)

check they are going to the right spot

S13 SR20DE.jpg

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things to check..

 

1. plugs.. are all cylinders running rich ? (fkd injector, injector oring, rail insulator, potential spark issue(backfire ? ))

2. Fuel regulator.. is your fuel pressure ok ? (too much fuel pressure)

3. Sensor issue..

3a) AFM voltage too high

3b) engine temp sensor not working

3c) throttle position sensor

4) cold start issue (throttle bypass) common on the NA sr..

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Alec, just give up and sell it to me cheap.

 

I mean, last time you spoke to me, your description sounded like it's running on 3 cylinders. Have you done anything to check that it's not the case?

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Demoster, a little history of the car would be good. Has it ever run well? What changes have been made? When did the problem start? How did the problem progress? Etc.

chris2712au summed it up fairly well. The issue is clearly over-fueling, which can occur due to a variety of reasons.

 

Here's my expansion on what's been said, to give you a better idea of what you can do.

 

A. Injectors flowing too much fuel despite being triggered correctly by the ECU

I had similar problems to what you've described when I accidentally put injectors that had been high-flowed (or were simply f**ked) on my replacement SR20. Used a tonne of fuel, ran like a dog and had no power.

A failed FPR could also cause this by forcing too much fuel through the holes. A failed fuel pump, blocked pump filter, bad pump relay, bad pump wiring or screwed fuel filter could cause an erratic idle. A blocked breather fuel tank pipe (attached to the bottom of the charcoal cannister) could also cause some problems.

 

B. Injectors working correctly, but being triggered to flow too much fuel

This will be caused by incorrect sensor input, or incorrect ECU commands. A good starting point of testing is to buy a Nissan Consult Cable, hook it up to Consult on a laptop, then confirm the sensor input numbers are appropriate. The sensors in question are Oxygen Sensor, Temp Sensor [for ECU], Mass Air Flow Meter, Idle Air Control and Throttle Position Sensor.

The MAF and IAC can be cleaned, although a better option is to borrow a known working MAF and test. Testing the oxygen sensor involves replacement, as does the Temp Sensor. The TPS can be tested using a multimeter, for which instructions can be found in the Nissan Service Manual.

As for ECU, if the car is stock and untuned, the best test is to swap in a known working stock ECU.

 

C. Fluctuating power causing an errratic idle

It's a fact that the SR20 alternator is too small for a modified car. Add anything that draws more power (thermo fans, amp, fuel pump) and you could lose all the power headroom you had, should your alternator be on the way out (which many are after 20 years of service). It's important to understand that alternators don't necessarily just fail, sometimes the regulators go bad and they can perform erratically, causing a weird idle and other odd characteristics. In itself, this wouldn't cause an overfuelling situation, however it can be a contributing factor to unstable performance, as it messes with the ECU and coil-packs, hence spark plugs.

 

D. Weakness or absence of spark

No spark means no combustion, and a weak spark can fail to combust all the fuel, dumping it on the oxygen sensor in the same way that overfuelling would. An easy first step is to change the plugs with NGK cheapies, which work just fine.

Next, you can test the strength or existence of the spark. Remove the fuel pump fuse and crank the engine a few times to remove fuel and pressure. From there, remove the plugs and find a spark plug lead that fits them. Remove the opposite boot and jam that end in a coil pack, connect a jumper lead to the engine block and the thread of the spark plug, pop it all on a block of wood to avoid a short, then have a beautiful assistant crank the engine. Check for a strong spark, then repeat for all coilpacks. If you test all the coilpacks and corresponding plugs, it will be clear if any suck and need replacement.

 

E. Vacuum issue

A lot of devices on the engine are operated by manifold vacuum (throttle closed), most notably the FPR. The easiest way to be confident all is well is to just buy a bunch of rubber vacuum hose from Repo (not silicone hoses becuase they collapse with heat), then replace all the vacuum hoses in the bay. They're 20 years old; no reason not to. As for larger hoses, remove any clamps and check them thoroughly for cracks or splits.

Edited by pmod

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Is it ok when you start it when cold? and then just gets worse as it warms up? If so then it's the engines ecu temp sensor telling it it's still cold and running full rich. This works independant of the gauge so the temp gauge can still read normal even if the ecu still thinks it is cold, very common.

The timing, tps and idle all need to be adjusted spot on or it will hunt like that, but not use all that fuel.

O2 sensor will also screw with your mixtures

If it's fluctuating between 12v and around 14 then it's just the alternator won't charge on 100rpm, normal. If it goes lower than 12v then your battery is probably weak.

You are using roughly double the fuel I would expect.

As PMOD says, find someone with nissan consult or ECU talk and plug it in. That will probably diagnose the problem in 5 minutes. Even a trip to a mechanic that has consult will be cheaper than guessing and changing stuff that aint broke. Or ECU talk is available of the net for around $100, best diagnostic tool ever for these things.

 

The insert in the fuel filler neck is probably not sealing properly, do you get a fuel smell around the cap? remove insert and reseal, but thats not the running problem.

Edited by Moneypit

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Not sure about the voltage fluctuation, but I would echo others in suggesting that it may be related to your AFM. Give the element a clean with some contact cleaner and see how you go.

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http://www.plmsdevel...etup_tips.shtml

 

try the below - 30min max, use a contact cleaner from repco or supercheap

 

9. Airflow Meter Cleaning

 

Dirty airflow meters are becoming quite common now that most SR's have quite a few k's on them. They become dirty due to normal airborne crud and from oil mist that naturally occurs in the inlet tract. Oiled foam air filters will dirty them quicker than anything else. But nobody uses them anymore (ahem...).

Symptoms can be hard to fathom as sometimes they will cause the engine to run lean, other times rich. I've seen both. Fortunately the sensing elements in SR AFM's are easily removeable and quite easy to clean. R32/Z32's can be cleaned but not quite as easily because the sensing elements are not a bolt-in job. Most contamination can be removed using a fine brush (as used for painting models etc.) and solvent such as acetone or contact cleaner.

 

clean_afm_1.jpgclean_afm_2.jpgclean_afm_3.jpgclean_afm_4.jpg Remove clip Remove connector Unscrew element Remove element

 

 

 

clean_afm_5.jpg Clean element using a fine brush and solvent. Acetone is good. Or almost any contact cleaner will do. Be careful not to damage the sensing elements.

 

Inspect the two elements under a really good light. An eyeglass helps here (about $5 from Jaycar - the one used in the photo is actually a lens from an old scanner!). They should look like a shiny glass bead with a fine wire wrapped around it. There's often black crud evident. clean_afm_6.jpg

 

clean_afm_7.jpg Crud = bad.

 

 

 

Put it all back together, congratulate yourself on a job well done and shout yourself a beverage for being smart enough to clean your AFM. Instead of declaring it broken and throwing it in the bin like workshops all over the world do. clean_afm_8.jpg

Edited by george.k

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Demoster, a little history of the car would be good. Has it ever run well? What changes have been made? When did the problem start? How did the problem progress? Etc.

chris2712au summed it up fairly well. The issue is clearly over-fueling, which can occur due to a variety of reasons.

 

Here's my expansion on what's been said, to give you a better idea of what you can do.

 

A. Injectors flowing too much fuel despite being triggered correctly by the ECU

I had similar problems to what you've described when I accidentally put injectors that had been high-flowed (or were simply f**ked) on my replacement SR20. Used a tonne of fuel, ran like a dog and had no power.

A failed FPR could also cause this by forcing too much fuel through the holes. A failed fuel pump, blocked pump filter, bad pump relay, bad pump wiring or screwed fuel filter could cause an erratic idle. A blocked breather fuel tank pipe (attached to the bottom of the charcoal cannister) could also cause some problems.

 

B. Injectors working correctly, but being triggered to flow too much fuel

This will be caused by incorrect sensor input, or incorrect ECU commands. A good starting point of testing is to buy a Nissan Consult Cable, hook it up to Consult on a laptop, then confirm the sensor input numbers are appropriate. The sensors in question are Oxygen Sensor, Temp Sensor [for ECU], Mass Air Flow Meter, Idle Air Control and Throttle Position Sensor.

The MAF and IAC can be cleaned, although a better option is to borrow a known working MAF and test. Testing the oxygen sensor involves replacement, as does the Temp Sensor. The TPS can be tested using a multimeter, for which instructions can be found in the Nissan Service Manual.

As for ECU, if the car is stock and untuned, the best test is to swap in a known working stock ECU.

 

C. Fluctuating power causing an errratic idle

It's a fact that the SR20 alternator is too small for a modified car. Add anything that draws more power (thermo fans, amp, fuel pump) and you could lose all the power headroom you had, should your alternator be on the way out (which many are after 20 years of service). It's important to understand that alternators don't necessarily just fail, sometimes the regulators go bad and they can perform erratically, causing a weird idle and other odd characteristics. In itself, this wouldn't cause an overfuelling situation, however it can be a contributing factor to unstable performance, as it messes with the ECU and coil-packs, hence spark plugs.

 

D. Weakness or absence of spark

No spark means no combustion, and a weak spark can fail to combust all the fuel, dumping it on the oxygen sensor in the same way that overfuelling would. An easy first step is to change the plugs with NGK cheapies, which work just fine.

Next, you can test the strength or existence of the spark. Remove the fuel pump fuse and crank the engine a few times to remove fuel and pressure. From there, remove the plugs and find a spark plug lead that fits them. Remove the opposite boot and jam that end in a coil pack, connect a jumper lead to the engine block and the thread of the spark plug, pop it all on a block of wood to avoid a short, then have a beautiful assistant crank the engine. Check for a strong spark, then repeat for all coilpacks. If you test all the coilpacks and corresponding plugs, it will be clear if any suck and need replacement.

 

E. Vacuum issue

A lot of devices on the engine are operated by manifold vacuum (throttle closed), most notably the FPR. The easiest way to be confident all is well is to just buy a bunch of rubber vacuum hose from Repo (not silicone hoses becuase they collapse with heat), then replace all the vacuum hoses in the bay. They're 20 years old; no reason not to. As for larger hoses, remove any clamps and check them thoroughly for cracks or splits.

 

well it ran like crap for a while, i changed the fuel filter, cleaned injectors etc etc (all the mentioned fuel related stuff) and then it ran like a champ! i did a few electrical modifications i.e sub, amp and put in two gauges, it fell apart. i was thinking from the start alternator problem, but everyone i talked to told me i was a moron. i noticed how fast the amp gauge would drop at the lights which makes me think under idle it draws more power than it produces... as for the glutenous fuel problem ill just start fixing everything... as you said its a 20 year old car so things are going to fail.

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Interesting. I recently had alternator problems prior to the engine failing (unrelated issue). When it was actually capable of starting and running, it idled badly and seemed like it was running rich. Replacing the alternator improved the situation and allowed me to start the car after shutdown, but the replacement was only slightly better than the failed one.

 

From what I can tell, with some fab work on the brackets, a VQ30 alternator from a Maxima can be made to work, as it should be the same as the Nissan Quest in the US. Cheapest way to fit a 125A alternator.

http://zilvia.net/f/...y-bolt-kit.html

I have not yet looked into this with any seriousness, but it might be worth your time investigating it. Apart from the bracket work, the pulley has one more rib that is unused by the SR, although people apparantly don't have problems running it this way.

Edited by pmod

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Check the continuity on the amp etc. May not be earthing super well. In fact, just do a small earthing kit. Will cost you less than 50 to put one together, and not only might it fix your issue, but you could also gain a bit of response while you are at it.

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