# 1987 Sentra engine power issues



## Jcs1989 (Jan 7, 2017)

I have recently came across a very clean 1987 Sentra sedan. Unfortunately it's an automatic. The car is is close to immaculate. 117xxx original miles clean vehicle history. Problem is it's acting as if the car has no power. It has the e16s. It will crank an idle. But when you put it in gear the idle drops to 300rpm an you can push the gas to the floor an just chugs hardly moving. If you stop while in gear it will die. I'm no professional mechanic. But I've replaced the timing belt thinking it was stretched. No difference. To me it seems as if it has an issue with spark timing. Or has a blown head gasket. But it barely smokes. The smoke that does come out of it is a bluish. Would the Map/vac sensor cause this ? If it failed. I used to have a 1990 Sentra that had a maf on it i had unplugged it an it did the same. Ran like it had no power at all. An I plugged it back up an it would smoke tires. Anyone have any ideas what this could be. I'd really like to get this see little Sentra back on the road where it belongs... Thanks


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## Car guy (Mar 31, 2016)

The distributor cap and then the plugs would be my first checks.

But, also ...

The E16S uses the richer solenoid during start and cold run; it then switches over to the AFR solenoid (and ceases using the richer solenoid then); there also is a mixture heater under the carb (on top of the IM) which only runs until the car is around 140' (as I recall); you can feel it switch on and then off by placing your fingers on its relay housing inside the rectangular p's side relay box; that would tell you a lot - it would tell if you if the CTS is working and the mixture heater is running and ceasing to once warm.

The ECU does monitor the neutral safety switch on the trans (which could explain two of your symptoms). The ends (internal to the trans) of those wear over time and the signal suffers as a result. 

When you changed the belt, did you change the spring-tensioner and the spring? Did you ensure the new belt lined up EXACTLY where the old one did on the cam and crank teeth? Did you count and mark belt teeth?

There is no MAP, per se, on the E16S; there is a barometric pressure sensor on the firewall, though; normally, the car will run fine without this even connected. There is a small black/red vacuum diaphragm just upstream of the BPS; it can clog; if removing it, before to orient it in the same manner it came off.

The TPS is on the p's side of the carb, and could explain 2 of your symptoms; it has a teeny circular cap on it, and if you gently lift up the throttle plate right there, you should be able to hear if the TPS is clicking - signaling to the ECU that you did in fact push on the gas pedal (when the RPMs dropped); worth doing a 10-for-10 test on it.

There also is a small vacuum cap on the vacuum cut solenoid on the p's side of the engine; it sits vertically; it splits open and causes the car to stall out; would definitely check it with a high lumens light aimed at its base; think it's 3/16".

There also are 50 vacuum hoses on the E16S. 

The carb gaskets do fade over time and the carb channels do need cleaned out; usually, the jets do not need replacing; just cleaning; and note there are 3 carb chambers when disassembling with 2 bolts from above and 2 from underneath; would recommend against disassembling unless all gaskets, filters, o-rings, and the float are in-hand. 

And, the EGR valve can stick; lift the valve up with your middle/index fingers under its lip and see if the valve immediately re-seats.

Let us know how things proceed.


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## Jcs1989 (Jan 7, 2017)

I replaced just the belt. But the tensioner seemed recent an so did the belt I replaced. Like I said the car only has 117xxx miles. So it may had just been replaced. I'm the third owner of the car. The second owner said the carb had been recently rebuilt. I may have to check the few things you've mentioned. Specially the deal with the trans. Like I was saying it is an automatic. Not sure if these have neutral safety switchs. But I will check the points. That would make sense. If the ECU thinks the car is in park. It wouldn't want to pull in gear. But as far as the choke an most the electrical components in or on the carb I'm pretty sure they are all working. But it does seem to want to run super rich warm or cold. I've pulled plugs to check an seems cylinder 2 has white on the plug. The rest are super blacked out. The engine seems to be a good one. Whatever the issue it has to be simple. The second owner also told me. He was driving the car to work one day when this issue suddenly happened. An was able to limp it home. What could cause a sudden huge loss of power ?


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## Jcs1989 (Jan 7, 2017)

I will also check the TPS as I didn't realise these had one on the carb. Since it does seem to be more of a spark timing throttle issue. That would be the best guess. When I push the throttle pedal in park. It stunts then revs. But revs like a jalopy. An sounds like its out of time. But mechanically it's dead perfect. So it has to be something electronically controlled or operated.


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## Car guy (Mar 31, 2016)

Good info. Sometimes the distributor cap's 4 brushes can have the white carbon build-up gently scraped off to fix things (or improve until the cap can be replaced). If the brushes have a significant concave to them after cleaning (deeply worn from all the firings), time to replace the cap. Blow out all the carbon debris (or use a slightly damp paper towel to wipe up the teeny white particles inside the cap) once the brush surfaces are cleaned. Also, worth pushing on the cap's center spring brush to ensure it bounces back. While the cap is off, just do a visual to ensure the dizzy isn't leaking oil internally and out the seal.

Did you ohm the plug wires and coil wire?

Wasn't referring to the choke, per se; but, the choke is on the top near the front end of the air intake; removing the end-most plastic intake and looking up inside the metal housing should reveal if the choke is lifting when the car is first started cold and then lowering/re-seating as the temp-sensor in the air housing warms.

Running without complete combustion could be dist cap brushes (badly worn) (causing fouling plugs) or aged/worn plugs or the carb's AFR o-rings failing (one top and one bottom, in the fuel bowl). If it went too long, cat likely affected.


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## Jcs1989 (Jan 7, 2017)

That was the first thing I checked was the distributor cap. It was pretty corroded with the white build up on the contacts. Also the rotor was rusted. Cleaned both no difference. It definitely needs a fresh cap. The plug wires are new. I checked for spark at each wire end using a plug. And they all sparked really good. But a couple were erratically sparking. Not sure why that is. Thanks for all the ideas on things to check. It's extremely hard to find any info on these engines. Oh an I checked for the TPS sensor on the carb and it doesn't have one. Jus the view glass for the float.


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## Car guy (Mar 31, 2016)

The TPS should be there, to the lower left of the sight glass. It is a switch (not a sensor) on this car. It is a small rectangular plastic housing with that small circular cap where the contact is made and released, upon each gas pedal depression/release.

If the rotor is worn (and not replaced since the cap would have been) and the concaveness exists on the brushes, the spark is having to work too hard to jump all the "gaps," explaining the plugs.

Did you clean the plug ends when they were out?

Are the wires OEM or aftermarket?

Sounds like new rotor, new NGK plugs (BPR5ES-11), and new cap should remedy, unless cat back-pressure has ensued.

There is a BPT valve that monitors (exhaust) back-pressure and is connected to the EGR valve. Small metal pipe runs between the two. If that pipe becomes carbon'd up, must be cleaned out (thoroughly). Small hose on that pipe also. The BPT valve has a circular outer air filter that gets clogged also (not replaceable without the entire BPT valve). 

There are (at least) 7 air filters on the E16S.

Oh, and how does the small rectangular PCV filter (in the air housing) look? White (clean), slight dirt, or oily circle?


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## Jcs1989 (Jan 7, 2017)

Also just wanted to say the gas tank has been replaced the fuel pump is new. The fuel flows freely from filter(had to replace a line) the eye glass float level seems good.


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## Car guy (Mar 31, 2016)

Should mention to take CARE when loosening the rotor bolt and dizzy cap screws. Knew a guy who stripped both. Of course, you have the cap off now, so you got safely past that with the phillips screw driver (different lengths for each side). The cap is "keyed," so the new one will only go on one way - the screws will only line up when correctly positioned. But, the plugs must be on the cap 1-3-4-2. If that is wrong ...


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## Jcs1989 (Jan 7, 2017)

Yes I went as far as taking the dizzy off the engine an checking cleaning the electronic pick up inside the distributor. But it's very clean. No oil or residue inside the cap. An the pickup seemed OK. But when I get the chance I'm going to the local pull apart. An checking to see if there is any spare parts I can accumulate. Coil, distributor pickup, and vac sensor. An I did find the TPS it was hiding behind the carb a little. I appreciate the tip on location.(I would have never found it.) Also it seems OK. Looks like it's just a button that clicks when throttle is depressed. Maybe the sensor itself isn't any good. Also a part I plan on getting..


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## Car guy (Mar 31, 2016)

The dizzy uses a 360' photo-LED slit plate, with slits for each TDC. Highly reliable.

When did you slide the dizzy out from the camshaft? Before or after the jalopy running? 

And, did you reset the timing to 7' BTDC after re-installing the dizzy, using a timing light?

Was the idle RPM back to 800 then?


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## Pnw (Jan 7, 2017)

Check your cat could be plugged also bad o2 sensors with create acceleration problems but I would bank on a plugged cat it won't let the exhaust flow properly which will allow a good idle but will bog and die with acceleration


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## Jcs1989 (Jan 7, 2017)

It has been running like a jalopy since I bought it. Nothing I have done has made any difference in the way it runs. I have gutted the cat so that's not the issue. Although I regret doing so because it was spotless an looked brand new. Also didn't make a difference in the way it ran.


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## Pnw (Jan 7, 2017)

does it throw any codes?


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## Pnw (Jan 7, 2017)

Could be a bunch of different things could be a temp sensor if the computer thinks the engine is cold it'll bog down when you raise the rpms like a said could also be o2 sensors but most of the time bad o2s will be make a pop and backfire it could also be a bad knock sensor


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## Jcs1989 (Jan 7, 2017)

When i purchased the car I was told by the 2nd owner he had been driving it to work one day when. All of a sudden it fell flat on its face. And he had limped it the rest of the way to work an then home. And he's also tried diagnosing the issue an was never able to figure it out. It will sit an idle fine. Just when you give it throttle it revs like a jalopy. And when put in gear it idles down very low. You can push the gas pedal all the way to the floor an it just chugs up to about 30mph. Taking several seconds to get there. As far as I can tell it has to deal with the spark timing. Thats all I can diagnose for now. I'm going to replace the distributor cap. But would that be the reason it has or is acting like it literally has no power ? Lack of compression?


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## Pnw (Jan 7, 2017)

Yeah try doing a compression test then a leak down anything over like 160 is decent compression and anything over a 10-12ish difference in cylinders is a sign of a blown head gasket. Does it blow any smoke out the exhaust? And I'm not expert but do have a lot of experience working on different cars and trucks and I honestly doubt it would have to do with spark. Any problems spark related don't just happen over night there's signs Long before anything serious like power loss happens. Been there done that and spark is almost never the problem.


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## Pnw (Jan 7, 2017)

although could be a miss fire from a lose plug wire or spark plug not tight all the way


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## Jcs1989 (Jan 7, 2017)

It does smoke out the pipe. A bluish smoke. It definitely could have a blown head gasket. There is signs of it in a few areas of things. Before I go any further I'm gona pull the head an replace it. Then go from there. Thanks guys for all the help. I will reply later with an update on how things are with the new head gasket. An fresh fluids.


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## Pnw (Jan 7, 2017)

Good luck hope all goes well


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## Car guy (Mar 31, 2016)

There are no knock sensors on the E16S (had AB), no OBD, only 1 O2 (and just a 3-wire) (not even operating when the error occurs), the cat has AIV, and the mixture heater test above quickly assesses CTS. 

It's none of these issues. 

Won't know further till rotor/cap/plugs replaced, and 7' timing confirmed (since dizzy moved). And, then, new coil, before doing any head work.

Would not bother pulling head, till the above are new and tested.

The E16S was quite susceptible to poor gap jumping, when ignition neglected.

It did just what you describe.


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## Pnw (Jan 7, 2017)

Lol chill dude I highly highly doubt the cap and rotor and/spark plugs are going to create that huge of a power loss unless they are literally completely toast and there is nothing left of them. Pull the spark plugs out connect them to the spark plug wires set them against the valve cover so they ground and have someone turn the ignition if you see a spark there is enough spark to run a good running engine.


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## Jcs1989 (Jan 7, 2017)

I've tested each plug at each wire. I took all wires off an stuck a plug in each one an tested for spark. It's firing very good on all four. Except seems somewhat erratic on cylinder 2&4 like it's sparking a popping spark not a solid flash pop spark. Could've been where the plug was jus sitting on the engine for ground. All wires were placed at the correct cylinders. When reinstalled. I'm stumped. The only other thing besides spark timing I can think of. Is part of the head gasket failing in-between cylinders letting compression slip into the cylinder next to it. Causing a miss fire. With rpms up at about 2k it will hold a steady rpm . With no missfire. It just won't pull in gear. But as car guy says it needs a few things replaced before further diagnosis. .


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