Questions on fixing timing (car skipped two teeth).

[NightWalker86]

Hey guys,

So here is a quick run-down of my situation.. I bought a 96 240SX about a year ago from a guy that thought it had a blown headgasket. Turns out the motor just had a HUGE air bubble in it and he didn't know how to properly bleed it. At any rate, during his troubleshooting he took the valve cover and a bunch of other pieces of the motor apart. I re-assembled everything, bled the car, and it seemed to run fine.

However, during my first test drive I ran the car up to about 5000RPM and I felt it skip, and then loose ALL power. I had to limp it back home (luckily only right down the road). After diagnosing the issue I noticed my timing was extremely retarded (like past any visible marks). I turned the distributor as far as it would go but even then I was only able to get the car to -5 degrees. This was drivable however, so I have been using the car with this awful timing for awhile now.

Okay, now that the history is out of the way, let's move on to the good stuff haha. I finally had some free time yesterday to tear the valve cover off and take a look at the chaos that was my timing nightmare. I suspected the car skipped a tooth (I think I know what caused it as well...), but I was unsure exactly how bad it would be. Here's a few shots of the valve cover off and a look at all the chains. Pay close attention to where the colored links are, the index marks on the sprockets and idler, and also the LACK of a visible colored link anywhere near the index of the idler...





Pretty ugly huh? It looks like it skipped TWO whole teeth! Not fun. I followed a guide called "How to fix crazy timing issues" located here http://fresno240sx.forumotion.com/t2-ho ... ing-chains that basically described my exact same problem. What I ended up doing was removing the cam sprockets and chains, loosening the idler sprocket, supporting the lower chain so it didn't fall, end then turning the idler sprocket until the index mark was where it should be. Then reassembled everything.

This is what the chains looked like when I finished:



I believe I followed the guide correctly, but I am unsure if this is really going to fix anything. Can someone take a look at the pictures and tell me if they notice anything that is setup incorrectly? Keep in mind the colored chain for the idler sprocket was completely lined up incorrectly and I did NOT bother trying to fix it because I would have had to remove the whole chain. It looks like all i really did here was to rotate the idler sprocket two teeth without turning the motor. Is that really all I had to do? Thanks guys!

PS: Here is the culprit of the skipped teeth more than likely:





Can anyone tell me what the heck that was?

[compactfean]

That used to be a timing chain guide. Lol

[NightWalker86]

That used to be a timing chain guide. Lol

Mmm, I thought so lol. Anybody have any clues about the timing?

[compactfean]

My guess would be that the chain rather destroyed the guide (from chain slap), or it was intentionally removed (If so I think it would have been easier to just remove the bolts lol)
Either way id get new chains, tensioners and guides. Loose tensioner+ no guide.=skipped teeth.

[NightWalker86]

My guess would be that the chain rather destroyed the guide (from chain slap), or it was intentionally removed (If so I think it would have been easier to just remove the bolts lol)
Either way id get new chains, tensioners and guides. Loose tensioner+ no guide.=skipped teeth.

I'm guessing that the guide is what caused the chain to skip two teeth when it got jammed in-between the sprocket teeth. I removed what was left of it and dug a few shards out from inside the upper timing chain cover. Can you tell if it looks properly timed, was moving the idler sprocket over two teeth really all I needed to do?

[NightWalker86]

Does anyone have any ideas on whether or not this procedure will properly fix the 2 skipped teeth? I wont have a chance until Saturday to test everything out so I was hoping to get some confirmation before then. Thanks guys!

[liquid_cool]

#1...DUMP the oil and filter!..there is metal in there waiting to destroy your engine!..then with the pan drain plug out, take a flexible magnet tool and poke it all around on the inside and get all that you can out..the upper guide was a factory tech issue, you just remove them and never put a new one on..as for the timing..start from scratch..put #1 on tdc..make shure the cams are facing away from eachother but verry slightly upwards...now count from the pins that hold on the cam sprockets, 8 links from pin to pin..after that is done..rotate the crank backwards passing the 20 bdc mark and then forwards to it..that way all slack is out of the chain ..set the dizzy to fite #1..let us know what and how it runs..

[SX APPEAL]

Just so you know, timing chains don't "slip teeth" like timing belts often do. There's not enough flexibility in the system to allow that. More than likely they'll just break.

And that upper chain guide is completely unnecessary, Nissan tech bulletins tell you to just remove it, so it's being broken is not your issue.

Also you can't just rip the valve cover off and say "oh look the marks aren't lined up it must be off" because even on a freshly re-timed engine, the first time you rotate the reciprocating assembly around the marks are going to be off. Now obviously nothing has "jumped", that's just the result of there not being an equal number of links on the chains as teeth on the gears.

Don't ask me how many times you have to turn it over until the marks line back up again, because I've never been bored enough to sit there with my engine and rotate it again and again and again to find out. My guess is many many times.

This is why you have to do like liquid_cool said and start from scratch, re-time the whole assembly from TDC.

[NightWalker86]

Just so you know, timing chains don't "slip teeth" like timing belts often do. There's not enough flexibility in the system to allow that. More than likely they'll just break.

And that upper chain guide is completely unnecessary, Nissan tech bulletins tell you to just remove it, so it's being broken is not your issue.

Also you can't just rip the valve cover off and say "oh look the marks aren't lined up it must be off" because even on a freshly re-timed engine, the first time you rotate the reciprocating assembly around the marks are going to be off. Now obviously nothing has "jumped", that's just the result of there not being an equal number of links on the chains as teeth on the gears.

Don't ask me how many times you have to turn it over until the marks line back up again, because I've never been bored enough to sit there with my engine and rotate it again and again and again to find out. My guess is many many times.

This is why you have to do like liquid_cool said and start from scratch, re-time the whole assembly from TDC.

The chain definitely skipped, during the first drive it was running like a champ and then it lost ALL it's power. The colored links were off by two teeth upon disassembly. I now know this is the result of the upper chain guide breaking off and falling down in-between the teeth. Who knows how weak it was or what the previous owner had done; this was my first test drive after fixing the cooling issue. This ground it to hell and caused it to skip two teeth. I do agree with you that it is very unusual for chains to skip and I will also agree that they would more than likely break instead. However, in this case it did happen and it has happened to multiple other people with 240s.

What results is the exact same scenario as I am having and as the person in the link I posted is having. The chain skips a tooth or two and it causes you to have to crank the distributor ALL the way over to just get it to start. It still won't be at factory timing though and in my case I could only get it to -5 degrees I believe. I followed the remedy listed in the link on my first post and it makes sense, sort of. But I was just looking for confirmation of the work done/of anyone else who had the same issue happen.

As for retiming the entire assembly, well that will be my only other option if this fix doesn't work. Ideally though I would like to avoid that as time and space are very limited with college and being stuck in an apartment for the time being. I will update this post once I am to the point of being able to test whether this worked or not. My other issue was the intake mani coolant pipes being corroded and leaking. Updates to come.

[SX APPEAL]

Maybe my earlier post came off as joking or something so I'll reiterate, IN THE PHYSICAL UNIVERSE THAT WE OCCUPY, THE UPPER TIMING CHAIN ON A NISSAN KA24DE CANNOT "JUMP TEETH." Even with the upper tensioner completely removed, there is not enough slack in the chain for it to allow the cam or idler gears to move independently from it without breaking it. Try it if you don't believe me. Take the tensioner off your upper chain and try to pull enough slack to get the chain to skip teeth on any of the gears. ITS IMPOSSIBLE. And its not going to stretch like a belt would, timing chains don't stretch, they break. It's easy to mistake the appearance of the timing being off, due to the phenomenon I explained in my earlier post, which you must have misunderstood or just flat out didn't read. This is most definitely what happened with the "multiple other people with 240's" as well. The link you posted is just a tutorial of how to set valve timing on the KA, its straight out of the FSM. The guy in that thread isn't saying the timing jumped, he's saying it was wrong from the beginning.

I'm not saying this to be an ***hole, and I'm not trying to insult your intelligence. I can see how you would think the timing has slipped, but that's just not the case. I'm just trying to save you a lot of time and busted knuckles chasing down problems that don't exist. I'm looking at the very first picture you posted, your timing is correct in this picture, I promise you that. Now if you have moved the upper chain in relation to the lower chain since that photo, which it appears you have, then your timing is now off. You need to rip the front cover off and re-time the whole valvetrain from step one. Good thing you have that tutorial.^

Also it seems you're getting valve timing and spark timing mixed up, they have NOTHING to do with each other. Valve timing is mechanically set with the chains and gears in the valvetrain, spark timing is set by the position of the distributor but is also variable (within the certain window allowed by the physical rotation of the distributor) controlled by the ecu. Now there are a few different parameters that control spark timing, coolant temp is a major one. So say your CTS took a s*** and the ecu got an "off the scale hot" signal, it would pull all your timing, and you would have no power. Just one possibility, there are others. All I'm trying to tell you is that the engine is (was) mechanically sound and that the valve timing wasn't your issue. It is an issue now however... My hypothesis would be that you have a sensor issue somewhere that's causing your ecu to retard your spark timing and make it run like a dog.

[NightWalker86]

Maybe my earlier post came off as joking or something so I'll reiterate, IN THE PHYSICAL UNIVERSE THAT WE OCCUPY, THE UPPER TIMING CHAIN ON A NISSAN KA24DE CANNOT "JUMP TEETH." Even with the upper tensioner completely removed, there is not enough slack in the chain for it to allow the cam or idler gears to move independently from it without breaking it. Try it if you don't believe me. Take the tensioner off your upper chain and try to pull enough slack to get the chain to skip teeth on any of the gears. ITS IMPOSSIBLE. And its not going to stretch like a belt would, timing chains don't stretch, they break. It's easy to mistake the appearance of the timing being off, due to the phenomenon I explained in my earlier post, which you must have misunderstood or just flat out didn't read. This is most definitely what happened with the "multiple other people with 240's" as well. The link you posted is just a tutorial of how to set valve timing on the KA, its straight out of the FSM. The guy in that thread isn't saying the timing jumped, he's saying it was wrong from the beginning.

I'm not saying this to be an ***hole, and I'm not trying to insult your intelligence. I can see how you would think the timing has slipped, but that's just not the case. I'm just trying to save you a lot of time and busted knuckles chasing down problems that don't exist. I'm looking at the very first picture you posted, your timing is correct in this picture, I promise you that. Now if you have moved the upper chain in relation to the lower chain since that photo, which it appears you have, then your timing is now off. You need to rip the front cover off and re-time the whole valvetrain from step one. Good thing you have that tutorial.^

Also it seems you're getting valve timing and spark timing mixed up, they have NOTHING to do with each other. Valve timing is mechanically set with the chains and gears in the valvetrain, spark timing is set by the position of the distributor but is also variable (within the certain window allowed by the physical rotation of the distributor) controlled by the ecu. Now there are a few different parameters that control spark timing, coolant temp is a major one. So say your CTS took a s*** and the ecu got an "off the scale hot" signal, it would pull all your timing, and you would have no power. Just one possibility, there are others. All I'm trying to tell you is that the engine is (was) mechanically sound and that the valve timing wasn't your issue. It is an issue now however... My hypothesis would be that you have a sensor issue somewhere that's causing your ecu to retard your spark timing and make it run like a dog.

Wow, you really need to calm down. I'm not sure why you think attempting to insult me is helpful, but I assure you it's not. I read every bit of your previous post, including all the attitude, as well as every bit of this one. I have no need to argue with you at all. Timing chains have skipped on this and other cars in the past. They are not bulletproof; it happens. Whether or not that is 100% what happened to me remains to be seen.

Either way though, my goal here is to fix the car, not to prove anything to you. I appreciate your opinion on the issue and what you think has occurred, you very well may be right. I'll find out when I can find some more time to work on it again. I'll update the thread once I get more information. Thanks.

EDIT: Let me throw this out there too, you said "Valve timing is mechanically set with the chains and gears in the valvetrain, spark timing is set by the position of the distributor but is also variable (within the certain window allowed by the physical rotation of the distributor) controlled by the ecu."

The original reason I posted this thread was because I honestly don't think what I did had any effect at all. I followed the guide but basically all I did was remove the cam sprockets and the re-install the chain so the links matched. The cams were not rotated, and the sprockets/motor were in the same exact position. I reinstalled the cam chains with the links matching the marks on the sprockets.

The only other change I made was to loosen the lower chain, support it so it didn't fall, and then remove the idler sprocket and move it over two teeth. Again, I don't see how this could have done anything, either positive or negative, in respect to my timing. I was moving two gears that basically weren't attached to anything. From what I could tell that is exactly what the guide I posted said to do, it didn't add up though which is why I posted this thread.

In essence, it really just sounds like I moved the idler sprocket over 2 notches while it wasn't bolted on or had any tension on it. Then I re-installed the cam chain so the links lined up, again not moving anything. Maybe I'm missing something here.. Also, if for some reason this did do something couldn't I just rotate that idler sprocket back 2 teeth using the same procedure? Thanks.

[SX APPEAL]

Like I said in my last post, I'm not trying to be an ***hole or insult your intelligence. My post was a bit sarcastic because you've asked a couple of questions on this board, and people (not just myself) have given you good, educated answers and so far as I can tell you haven't really listened to any of them. We're here to help, but you gotta let us. And don't worry about me, I'm not sitting red-faced at my computer stabbing feverishly away at the keyboard with veins popping out of my head, I just used a bit of all caps to try to make a point. Don't read into that too much, it was meant to come off more lighthearted than it did. In the end though I am trying to help you because I have experience with the problem you are having.

You are correct, all you did was move the chain in relation to the sprockets, as long as none of the sprockets moved in relation you each other, your timing should be fine. I was under the impression you have moved the cams in relation to the crank in order to make the marks line up, which you didn't, this is good. There are a multitude of things that can cause a sudden drop in power like the one you experienced. You've eliminated your valve timing as one of them, that's good. Remember Occam's Razor, the vast majority of the time its the simplest possible explanation. Now you said when you got home you found that your timing was extremely retarded. (past any visible marks) I assumed you were checking your spark timing with a timing light, am I right? If this is the case then your issue is definitely electronic, not mechanical. Like I mentioned previously, there are a number of inputs that effect the ECU's timing control; coolant temp (CTS) engine load (MAFS) driver load (TPS) knock sensor (KS) intake air temp (IAT) fuel mixture (O2S) and so forth. A failure of any one of these could cause the problems you are experiencing, and is a whole lot more likely than a timing chain "jumping."

The reason I'm being so unequivocal on the timing chain thing is because it is misinformation that is spread around the net which causes people who read it to to make wrong diagnoses and spend more money and time than they need to trying to fix their cars. The next thing you know you've got people spending $500 on new ECU's when in fact their problem was just a bad fuel injector, or ripping apart their motors when their problem was just low coolant. There's a lot of this type of misinformation being passed around by these internet forum know-it-all's who just regurgitate what they heard someone else read about this one build that a guy in CA paid a shop to do for him 5 years ago and sound like experts, when in fact they have no firsthand experience with the material their talking about. This annoys the hell out of me, as I'm sure it does many others, and its no good for the community. [/endrant]

[compactfean]

Consider this a godsent that you're timing chain didn't break! I have FIRST HAND dealt with this problem as well. If guides are broken, and stuff has jumped teeth there is no doubt that there is a unrevealed issue. To ignore these facts would be irresponsible (and that's being polite) does a tsb say anything about skipping teeth and breaking a ”useless” guide? Not that I've seen. Anything less than all new timing components would be a patch job imo.

[liquid_cool]

Please listen to what i have to say...its sound advise from someone who has been working and modding cars from the 80's till today.....start from scratch..you DONOT need to remove the lower timing cover..just the upper one and the valve cover..now follow my directions on my first post and it will solve this issue...i do believe it is possible to skip a few teeth..i have donw it ..but only when the coller on the cam that holds the cam sprocket center broke on me..you might want to check that..and thats the only time...so good luck..take the sound advise or leave it ..your choice.