Tuning up the new car (90 240) Bucking Kicking

[NC 240 SX]

Ok, its new to me...lol She's completely stock (for now) has 164k on the speedometer, an older couple owned it since it was new and when the oil and coolant began to mix they were told they needed a new engine so they junked it. Well, I got it for a good price and figured some fixing up would make it a great car my son...no rust, interior is in great shape etc.

Anyway what I have done to it so far. I first pulled the head and had it milled .008, new seals, new head gasket kit etc. Still not fixing the problem I discovered the timing chain was missing one of the guides and chewed a hole in the timing case. So I replaced that and put in a timing chain kit, new water pump, thermostat, plugs, wires, distributor cap, and rotor. Set the timing at about 18 degree BTDC. Idles set at 700 rpm.

While idling she sounds like a cammed V-8, kind of rough. On the road, in lower gears she's still rough, but when opening it up getting through the gears at higher rpm's she smooth's out pretty nice. At about 4,000 rpm's she starts to cut out. When you are crusing in slow speed limit area's 2d gear etc, she buck and kick...not backfiring like the timing is off or anything, just acts like its choking. Also, get a valve tapping noise during excelleration, almost like a timing issue, but I checked it again and its on. Any idea's on what we can do to get her running smoother?

One thing I haven't changed out is the fuel filter, but I'm going to do that tomorrow. It really doesn't seem like a fuel problem, but I'm still some what new to imports as far as tuning and working on them so any help would be greatly appreciated. Sorry for writing a book, I hope it all makes a little sense.

[Grendel]

Have you changed plugs, wires, and rotor/cap? I just did that and it fixed a similar problem. Mine used to buck under full throttle a lot, and once I changed those it seems to have fixed it.

Now I just gotta fix the other 10,000 things that always pop up

-Grendel

[J_Spec_NiTeMaRe]

it sounds like it's a spark or timing problem. if youre sure that youre firing at the right time, then see if your injectors are clogged, or maybe you have a few sticky valves. when the head gasket blew (which caused it to get oil and coolant together), you probably got alot of oil and coolant into your combustion chamber. this can deposit onto everything in there, causing a circus of problems, it can even foul your cat and 02 sensor. try some simple fuel additives after you replace your pump and check your injectors. also, do a compression check and see if youre normal and even in all of your cylinders.

[canisay182]

1 of mine did that for a while i just changed the o2 sensor. oh and the broken timing chain guide didnt need to be replaced they break all the time and are not a nessesary part the timing chain is controled by oil pressure so if you ever get low oil pressure it will get broken agian. also try checking the fuel sys, and plugs all the stuff the other members posted

[NC 240 SX]

Thanks for the input! I'll be busy all weekend tweaking on it. Hoping to get a service manual here in the next week or two to help get familiar with the engine and learn where all the sensors and stuff are at. What do you guys think of removing the AVI (?) I think thats what its called, and a really dumb question, where is the map sensor? Is it located at the end of the intake near the filter box? How do I go about cleaning things like that up, with carb cleaner or something similar?

I had to replace the timing case so I figured while I was in there I would put in the timing chain kit just to be safe. I had no idea the guide wasn't necessary, I'll definitely remember that, thanks.

Sorry for the noob questions, but after all, I'm a newbie to the 240's! lol And I do appreciate your help greatly! One day I hope to be able to share and help others just as you all do. Thank you.

[DWF Engineering]

You changed the timing chain, right? Are you sure the cam timing is correct? On many OHC engines I've messed with, the timing cam timing was easy to do incorrectly. If you're still having problems with it at present, take all four spark plugs out and discribe the appearance of the ceramic insulator to me in as much detail as you can. From the appearance of this we should be able to determine the combustion temperature, air fuel ratio, and what contaminants are in the combustion chamber. This could give us some more ideas as to what the problem is.

[Soyo]

wow... that could be like 10 different things probably... I'd say your best bet is find someone who knows imports or just engines in general, or take it to a shop that does free check-ups... just find one of those little shops and it'll either befree or really cheap

[markheth]

FYI: The timing chain guides are 100% necessary on this car. The left side one is the one attached to the tensioner (and yes, it does run on oil pressure), and the right side one is plastic... this is the reason they break.

The stock chain guide on the 89 240sx was 100% plastic, so when it broke, bad things happen (like the chain rattling it's way through the water pump wall)... which is exactly what happened here.

The replacement chain guides have a metal backing to them, which will eliminate the chance or the chain going through the wall again, but still have a plastic casing which can break, and become noisy.

After you mix antifreeze and oil, I would think about changing the oil pump, to ensure water was not sitting inside the oil pump causing nasty things to happen.

I have the same problem with my car, and have replaced the timing chain... but I have low compression in the third cylinder, and suspect a bad intake valve. I am about to pull the head and grind, etc...

[KenOhki2112]

Originally Posted by markheth

FYI: The timing chain guides are 100% necessary on this car. The left side one is the one attached to the tensioner (and yes, it does run on oil pressure), and the right side one is plastic... this is the reason they break.

The stock chain guide on the 89 240sx was 100% plastic, so when it broke, bad things happen (like the chain rattling it's way through the water pump wall)... which is exactly what happened here.

The replacement chain guides have a metal backing to them, which will eliminate the chance or the chain going through the wall again, but still have a plastic casing which can break, and become noisy.

After you mix antifreeze and oil, I would think about changing the oil pump, to ensure water was not sitting inside the oil pump causing nasty things to happen.

I have the same problem with my car, and have replaced the timing chain... but I have low compression in the third cylinder, and suspect a bad intake valve. I am about to pull the head and grind, etc...

The timing chain guard breaking is not a problem, the noise lasts a few seconds when starting the car up, and doesn't really pose a threat to your car. Mine has made that noise for about 50,000 miles, my timing chain is still fine. You will be hard pressed to find a 240 with 60K+ miles and factory guards that does not make this sound.

(S13 240sx btw.)

[markheth]

The timing chain guard breaking is not a problem, the noise lasts a few seconds when starting the car up, and doesn't really pose a threat to your car.

If you have an 89 or early 90, it is a potentialy disasterous situation... As I mentioned, if the chain guild is 100% plastic, and missing, the chain will eventually eat through the wall to the water pump... Mine was 75% of the way there after 60000 kms of rattling noise.

I have seen cars where this has eaten all the way through... its not pretty... imagine all of your antifreeze emptying into your oilpan.

Nissan agree'd this was a problem, and fixed it in 1990 with the guides being metal with a plastic casing. This can still be noisy, but not dangerous.

After putting the new guards on, my chain is 100% quiet now, and the car runs smoother (other than the valve problem i am having).

I imagine high oil pressure makes up for the extra tensioning that needs to take place when the right guide is missing, but I personally would not put so much faith in an ageing oil pump.

If you have a 1990, there is a good chance your guide was 1/2 metal already... anything newer than that is a guarantee.

1989... if it has not been replaced... something to add to the "todo" list.

You can check easily by opening the valve cover, and looking down along the chain to see if the guide is there. It's not a terribly hard job to do, just takes some time... I had to lift the engine 2 inches to get the oil pan out (which was full of plastic pieces from the broken guide). And the timing chain kit is around $100 or less.

[KenOhki2112]

Mine is a 90' and Nissans offical reponse to the timing chain guard breaking was: "There will be no recall because this condition is not detrimental to the vehicle." I'm pretty sure the 1990's had a plastic guard too, I was my understanding they swiched the guards after the SOHC was gone.

I say fix it to get rid of the noise, but I've never heard of the chain taking a bite out of the water pump O_o

50K miles and going strong.

EDIT: Although I still feel this should have been a recall.

[markheth]

I've never heard of the chain taking a bite out of the water pump O_o

The original post had the same problem...

I discovered the timing chain was missing one of the guides and chewed a hole in the timing case.

Mine was 195,000kms before i replaced it... i imagine at that rate, it would have been 230,000kms before it ate through.

And I agree, it should have been a recall, as it has proven to be detrimental to the vehicle as my dealership has confirmed due to the amount of chains they have replaced (for about $700).

Nissan was lazy on this one, trying to save some money on recall's.

P.S. When I Changed mine, it was because it was rattling all the time, not the usual start up rattle. After 1 week of constant rattling, i knew something was up.

[KenOhki2112]

Originally Posted by markheth

P.S. When I Changed mine, it was because it was rattling all the time, not the usual start up rattle. After 1 week of constant rattling, i knew something was up.

Yeah, thats a little different, If the guard is gone and the chain is not tense due to a oil pump problem or something not working very well, it probably will bork every thing up. If that happens definatly replace it.

If it's just start up rattle it shouldn't hurt anything.