# 1990 Sentra Timing Issue?



## djd100 (Aug 9, 2015)

Hi all...

Our 168k mile 4-Speed Sentra (no AC or PS), just failed smog here in CA due to the timing showing 36* BTDC advance at idle (with the TPS disconnected)? It made the tailpipe numbers fine, runs great on cheap gas, never pings etc.

However, when I timed it to 7* BTDC base advance per the emission's sticker (idle set to 800 RPM - TPS disconnected), it's obviously too retarded as it's down on power and tip-in driveabilty has worsened etc.

Could the Harmonic balancer have slipped causing the timing marks to be in space? 

This happens on High Performance Chevy V8's with OEM Balancers all the time, but I don't about Nissan Sentras, plus we don't race this car so it never sees high RPM etc?

I also found that when it was indicating the base advance or 36* BTDC the distributor was adjusted to max advance (to the end of the adjustment slot)? I have never adjusted it and we've had the car since new, so the last people who were in there were these same shop people who failed it, but who passed the car 2 years ago?

I doubt it left the factory with the distribtor set to max base advance, and I've never changed it until now?

Weird huh?

Any thoughts?

TPS Idle Switch?

Thanks in advance!


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## djd100 (Aug 9, 2015)

Confirmed the balancer as not slipped today by manually bringing #1 to TDC etc.

Confirmed TPS/Idle Switch as good as well, and it's going into idle mode whrn the throttle is lifted.

Crank Angle Sensor?

Again runs pretty good excepting tip-in and WOT with timing set to 7* BTDC (TPS unlugged), though tip-in is perfect and there's more power when the dizzy is advanced?

Thoughts?


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## smj999smj (Jan 1, 2006)

Any chance the timing chain jumped a tooth? That used to be a common occurrence on the GA16i and KA24i with the original plastic timing guide. The oil channel to the chain tensioner would get debris in it, restricting the oil flow to the tensioner at start up. The slack in the timing chain would beat up the top of the plastic, fixed chain guide until it broke and then the timing chain could jump. If it jumped one tooth, the engine would still run, but with decreased power. Since the distributor was driven from the cam, the ignition timing would retard about 8 degrees. Sometimes people would adjust the distributor all the way to the end of the adjustment slot to get the ignition timing close to spec and the engine would run better, however the mechanical timing of the engine (cam to crank relation) would still be retarded. Around 1995, Nissan came out with a metal-backed guide to replace the plastic guide.


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## djd100 (Aug 9, 2015)

Hi, thank you for the reply!

Yes, I had thought about that though the car runs fine and passes smog etc with more timing added, so maybe?

It does have the dreaded timing chain tensioner noise when first started every every (and has for the last 30K miles or so), just for a couple of seconds though, and after the initial start of the day it's quiet for the rest of the day.

Can I check this without pulling the guides and timing chain, (wouldn't see the bottom gear this way)?

Thanks again...



smj999smj said:


> Any chance the timing chain jumped a tooth? That used to be a common occurrence on the GA16i and KA24i with the original plastic timing guide. The oil channel to the chain tensioner would get debris in it, restricting the oil flow to the tensioner at start up. The slack in the timing chain would beat up the top of the plastic, fixed chain guide until it broke and then the timing chain could jump. If it jumped one tooth, the engine would still run, but with decreased power. Since the distributor was driven from the cam, the ignition timing would retard about 8 degrees. Sometimes people would adjust the distributor all the way to the end of the adjustment slot to get the ignition timing close to spec and the engine would run better, however the mechanical timing of the engine (cam to crank relation) would still be retarded. Around 1995, Nissan came out with a metal-backed guide to replace the plastic guide.


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## smj999smj (Jan 1, 2006)

The "death rattle," as I call it, is never good. If you remove the valve cover, you can use a flashlight to see the top of the fixed guide. If it's the all-plastic guide and it's broken, you'll be able to see it. If the guide is broken, you'll need to tear the front of the motor apart, anyway, so it's a good time to replace the timing set and then you'll also be able to get a good look at the engine timing. Another thing you can do without pulling anything apart is to do a compression test and compare with manufacturer's specs.


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## djd100 (Aug 9, 2015)

Hi, thanks for the reply!

Drive-ability was good until yesterday when it died coming to a stop sign, and it has run like crap since (rough idle, down on power etc).

Back to basics today, plugs, compression, and the tensioner noise seems worse so I'll look in via the valve cover as well, thanks for the tip.

We're in CA and can get $1K to recycle the poor car which we've owned since new (it's been a great car up until 150K miles or so), so this might be time?



smj999smj said:


> The "death rattle," as I call it, is never good. If you remove the valve cover, you can use a flashlight to see the top of the fixed guide. If it's the all-plastic guide and it's broken, you'll be able to see it. If the guide is broken, you'll need to tear the front of the motor apart, anyway, so it's a good time to replace the timing set and then you'll also be able to get a good look at the engine timing. Another thing you can do without pulling anything apart is to do a compression test and compare with manufacturer's specs.


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## djd100 (Aug 9, 2015)

Confirmed that the static timing chain tensioner towards the front of the car has self-destructed (metal on metal, timing chain hitting block witness marks etc), though the movable one on the other side looks relatively ok?

is this the common failure?

Will try to confirm if the chain jumped a tooth by manually bringing #1 to TDC and eyeing the cam sprocket mark?

How hard is the timing chain R&R in the car? Any tips?

Thanks...


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## djd100 (Aug 9, 2015)

Confirmed the timing has not jumped a tooth, and compression is good.


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## smj999smj (Jan 1, 2006)

The fact that the guide is broken means the chain is slacking and could be creating havoc with the ignition timing. It was a fairly common failure 20-years ago when these engines were more common, but since the GA16i was only in the US for about 2 years until it got replaced with the GA16DE, you don't see them too much these days. However, you do see it occur a lot on the KA24E, which was in use a lot longer and in more models. Timing sets are available at Rockauto.com with new gears and chains, etc., and I don't believe they are expensive, but I would stick with a well known and reputable brand. The job, itself, is only difficult because of the lack of room between the front of the engine and the passenger side engine compartment. The engine will need to be supported as the oil pan and cross-member need to be removed. You can probably find repair directions in the free repair guides at Autozone.com if you don't have a manual. You don't need to remove the cylinder head, if it says anything about that.


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## djd100 (Aug 9, 2015)

Thank you for the help, much appreciated!

Well, since the CV joints, struts, and shocks were on their way out too, as well the rear brakes getting low, the CAT, plus the torn up seats and carpets the wife decided a newer car with more features was the way to go.

We got a 75K mile, two owner always garaged Chevy Cavalier with the base motor and 3 sp auto, AC, real clean like show room inside and out aside from some minor scatches and sun fading etc. 

I'll need to do some ABS work as it's showing an intermittent ABC Controller Solenoid Relay code but the ABS is still working at this point. 

We'll be recycling our old Sentra it seems (CA gives us $1K for it). That seems like a waste as all those good parts will not be available, but that's life here in CA where's it's harder and harder to smog the older cars.

Take care all...


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