Help me fix my broken car...

[PMan_S13]

I posted this in the main forum, but I'll try here where people actually have some background knowledge on what they are doing...

The car is a '91 nissan 240sx. Rebuilt by me with lower compression pistons, t3/t4 turbo, larger 370cc injectors, MAF installed in blow through position, blow off valve, front mount intercooler, new timing chains, blah blah.. all the stuff to make it go fast and then everything else was replaced.

Well the other day I was coming home. It was raining and I was really low on fuel. Pulled away from a stop light and the car just dies. First thought is I am out of fuel. Fuel light wasn't on. Second thought, the chain snapped and I broke the motor. So I sat there freaked out for a minute and then tried starting it again. It starts. So I start to drive again, this time while I'm in third I feel it start to loose power, so I give it more gas to keep it alive. It was so bad I am using like 50% throttle just to cruise in 2nd a 1/4 mile down the road to my house. The thing just was making no power what-so-ever. Limp it to a parking spot and shut it down. Now I have checked everything I can think of and I can not get it to run right at all.

-It fires on all cylinders. (Spark/Fuel is getting to each)

-It simply has no power and takes forever to rev up even in nuetral.

-If you floor it in nuetral it will rev up to ~4k and either it is bogging out or cutting out. While if you let it rev up at partial throttle you can rev it higher than this. I didn't try higher than ~5.5k

-Car idles fine.

Here is all the stuff I have checked.

-Timing. Both ignition and valve timing is spot on perfect. I tore the thing down and reassembled like 3 times, so I know it has to be correct.

-MAFS, checked with two others and one from a very well running 240. They all run about the same to me.

-replaced fuel filter. Runs better, but still has no power. Pump seems to be working still.

-Vacuum is good, shouldn't be any leaks. I do notice the motor sucks in a lot more air now, I can actually hear it sucking in the air through the filter. I'm sure this is because it takes so much throttle to get it to go.

-looked around for loose wires and whatnot. Only thing worth mentioning is that it seems to run the same with the TPS unplugged. It stumbles for just a second when removed, but after that it seems the same to me. I reset it to .45v and tried it again, but it still runs and idles the same whether plugged in or not. This is my only red flag at the moment.

-the exhaust smells like exhaust to me, might be a little bit cooler than I would guess it should be. Although I truthfully never felt it before to see what temp it was at. no smoke or wreek of fuel.

I'm pretty confused. I could use some good advice right about now. Thanks

[180fan]

even though the mechanical timing may be correct, your timing can and probably is still off. Use a timing light to verify that you're at the proper timing setting.

[navysnail]

also, make sure that the intercool piping is still attached, a common overlooked problem

[s13sr20chris]

poss vac leak at intake manifold. maf issues. maybe watch your maf voltage while its messing up.

[vacnsewmedic]

hey i was given a 1991 240sx. that i have always wanted and the timing chain is broken,,,please help, im pretty good with mechanical aspects and need some help, im in hampton Virginia

[vacnsewmedic]

hey chris,

I was just given a 91 240 sx by my older bro, i really love this car, but the timing chain is broken, where do i go from here, it is in great shape, im from hampton, virginia

[DAEDALUS]

I posted this in the main forum, but I'll try here where people actually have some background knowledge on what they are doing...

The car is a '91 nissan 240sx. Rebuilt by me with lower compression pistons, t3/t4 turbo, larger 370cc injectors, MAF installed in blow through position, blow off valve, front mount intercooler, new timing chains, blah blah.. all the stuff to make it go fast and then everything else was replaced.

Well the other day I was coming home. It was raining and I was really low on fuel. Pulled away from a stop light and the car just dies. First thought is I am out of fuel. Fuel light wasn't on. Second thought, the chain snapped and I broke the motor. So I sat there freaked out for a minute and then tried starting it again. It starts. So I start to drive again, this time while I'm in third I feel it start to loose power, so I give it more gas to keep it alive. It was so bad I am using like 50% throttle just to cruise in 2nd a 1/4 mile down the road to my house. The thing just was making no power what-so-ever. Limp it to a parking spot and shut it down. Now I have checked everything I can think of and I can not get it to run right at all.

-It fires on all cylinders. (Spark/Fuel is getting to each)

-It simply has no power and takes forever to rev up even in nuetral.

-If you floor it in nuetral it will rev up to ~4k and either it is bogging out or cutting out. While if you let it rev up at partial throttle you can rev it higher than this. I didn't try higher than ~5.5k

-Car idles fine.

Here is all the stuff I have checked.

-Timing. Both ignition and valve timing is spot on perfect. I tore the thing down and reassembled like 3 times, so I know it has to be correct.

-MAFS, checked with two others and one from a very well running 240. They all run about the same to me.

-replaced fuel filter. Runs better, but still has no power. Pump seems to be working still.

-Vacuum is good, shouldn't be any leaks. I do notice the motor sucks in a lot more air now, I can actually hear it sucking in the air through the filter. I'm sure this is because it takes so much throttle to get it to go.

-looked around for loose wires and whatnot. Only thing worth mentioning is that it seems to run the same with the TPS unplugged. It stumbles for just a second when removed, but after that it seems the same to me. I reset it to .45v and tried it again, but it still runs and idles the same whether plugged in or not. This is my only red flag at the moment.

-the exhaust smells like exhaust to me, might be a little bit cooler than I would guess it should be. Although I truthfully never felt it before to see what temp it was at. no smoke or wreek of fuel.

I'm pretty confused. I could use some good advice right about now. Thanks

Good man, even checked the vacuum on it. I assume it was up around 18" Hg? That is probably the most extensive first-time trouble-shooting I have ever read on NICO. To me the most likely candidate is fuel. Pumps often don't fail at once. Tee in a pressure gauge and tape it to your windshield. Make sure you're getting the min at all times.

[PMan_S13]

The timing is perfect. Yes I have a timing light and yes I used it. 20 btdc

Intercooler pipes are still attached. You are not understanding the problem. It has no power even off boost. Something is just really messed up here. Feels like bogging and cutting out, but not so general.

I did check Maf voltage, seems to be fine to me. Might be reading a little low, but that's probably because the motor isn't making the power, therefore the vacuum, it normally would. But it is pulling evenly, plus I tested out 3 other mafs.

Can't be vacuum, I am still reading vacuum on my guages and the car will still build boost (eventually)

If your timing chain is broke, the car might be toast. If it broke while driving then you have either some smashed up pistons and/or valves. Best bet is to go buy a chiltons or the like. They will lead you by the nose on what to do.

The fuel pump is a new walbro 255 that I got last year when i turboed the motor. Has less than 10k miles on it. I can still hear it turning on, but I need to go and buy a fuel pressure gauge to make sure. I doubt the pump is the problem, it's either on or off, and it sounds the same as always.

Any thoughts about possibly dirty injectors or something stuck in the fuel rail/line? I always use 93/94 octane and the car has plenty of wot runs daily, so this seems obsurd to me. Just wondering. What about a problem with my FPR? might not be functioning right anymore? Checking fuel pressure will let me know

Tested removing the TPS on my brothers bone stock 92 240sx. It runs pretty bad when removed. Mine doesn't even make a difference in performance. This is my only real lead. We are going to try swapping throttle bodies and see how that does. I don't think there is a way to get the TPS out of the TB, so I figure just swap the whole thing.

I'll let you guys know

[vacnsewmedic]

so if your timing chain breaks, its a good possibility the valves or pistons are smashed or is there a good chance they might be not be harmed

[DAEDALUS]

Vacnsewmedic, please start a new thread for your car. Thanks.

[PMan_S13]

Well it's not the TPS, I switched it with a known good working one and it still runs the same.

Something interesting I discovered though. If I disconnect the line that goes to the FPR and block the vacuum leak with my finger, the car seems to run the same. Does this sound like the FPR is not working?

I really need to find a fuel pressure tester, but no one carries anything but domestic style checkers around here. If I could see what the fuel pressure is, I feel I would be greatly enlightened.

[DAEDALUS]

Well it's not the TPS, I switched it with a known good working one and it still runs the same.

Something interesting I discovered though. If I disconnect the line that goes to the FPR and block the vacuum leak with my finger, the car seems to run the same. Does this sound like the FPR is not working?

I really need to find a fuel pressure tester, but no one carries anything but domestic style checkers around here. If I could see what the fuel pressure is, I feel I would be greatly enlightened.

It may not be detectable at idle anyway, but...FPRs rarely fail. But if the fuel pressure is low, it won't be doing anything to the pressure regardless of whether it's hooked up. Air, fuel and spark--which one hasn't been eliminated? A FI gauge can be bought for about $30.

[PMan_S13]

well what I meant is that I can rev it up and it still runs the same, not just idles the same. Seems to me the fuel pressure is the culprit.

I still can't find a freakin pressure tester that can just slip in line. All the ones I find go to domestics. I may just go to Jegs and buy a fuel pressure gauge. What's one more gauge in my cockpit?

[s13sr20chris]

some ideas...take a fuel sample. i have seen a few with deisel or water in the fuel. water will seperate out quickly when sampled. check that pressure but also check the flow(good time to do that sample). a good pump will fill up a 1 liter coke bottle real quick. i have seen pumps that worked really well but had a lot of sand in the "sock". that is tough to diag. i am not leaning towards the injectors being clogged as that tends to be cyl specific. it would be rare for all the injectors to clog up without shutting down.try looking at the plugs. give them a good sniff. smell fuel?

[PMan_S13]

Oh yeah something else I forgot to mention.

My ecu is not throwing any codes. I pulled the ecu out so I could see the light on back. I wasn't sure if the check engine light bulb was not working correctly or what. (It does show up with key on) The thing I thought was weird is that if I unplug the maf or TPS or some other essential electronic, it will not throw a code of any type. Yeah the motor will start to buck and fight, but no check engine light. It's always been like this, I'm just wondering if that is how it is designed to work.

I also tried putting it into self test mode, but I got nothing but blank readings. Not sure if I did it right or not. Even the factory service manual is a little less than vague on how to do it. I'm going to leave the battery unplugged for a few hours and see if the stored values were just jacked up.

This is getting really old. I don't know if you guys realize the day and night difference the car has now. This is not a small problem, it makes the car very very difficult to drive. Right now I think the car is probably making maybe 50hp tops. Horrible.

How hard would it be to screw up a distributor? Anyway the crank angle sensor or even the cap itself got shifted when the timing gear was free floating? I might try switching that with my brother's too and see how it does.

At this point I'll try anything...

[PMan_S13]

well I took the pump out when I first had this problem, I figured the little sock filter was clogged up. But once I saw what was in the tank I changed my mind. It was sooo clean in there, no deposits or anything. I checked the sock too, but, of course, found nothing.

As far as fuel pressure goes. You know the small filter on each end of the injectors? The ones that filter just before the pressurized fuel gets out? I wonder if something got caught in the #1 injector filter. That would cut flow to the remaining injectors and make the pressure build up from the FPR and the pump useless.

I looked at the plugs too when this first happened. Looked a little lean if anything, but certainly not rich. I'll have to pull them out again now with a few more days running on them and see what I have.

I would like the think that the ecu was throwing it into a fail safe and just running a base map. But every other time it has done that it will run so rich it billows out black smoke from the larger injectors the ecu doesn't know about. But I've checked every sensor I can think of and gotten nothing, plus no smoke. If anything it almost sounds like I'm getting some slight detonation at WOT.

Fuel starve?

[PMan_S13]

real quick..

checked the plugs 1, 3, and 4. (Hard to get to #3 with strut tower bar on)

They have some black carbon deposits on them (nothing horrible, just enough to make them black, not clumps or anything) except near the tip and stem, where it is a little white. Also they look like they have small white flecks on them. All three looked identical so it can not be cylinder dependant, whatever is wrong is general to the system.

All it has done for the last few days is idle and get revved up a little. I think the last time it ran it sat idling for a sec before shut down.

Hope you gurus can decipher than. I'll be back on Thursday, got to go work two 12 hour midnight shifts...

[s13sr20chris]

little white flecks are prob your pistons due to the slight detonation your are experiencing. i agree that this is wierd in that if the ecm is worried it goes way rich. especially if you have big injectors. are you running a cat? may want to check for a restriction in the exhaust. can you tell i am running out of stuff? you can also pull the fuel rail and have someone crank the motor to check the atomisation and such. i would say valve timing off but that would throw off ign timing and that was good. do you still have egr? if so the valve may be sticking open or coming open under any small amount of load. you can pull it off and stuff a rag or something in the holes to see if that was the issue. how about pulsed air injection? same deal.

ah hah! i was just going through the service manual and realized something. i always thought the dohc motor did not have any swirl control valves(little butterflies in the runners). the early dohc motors did. this is a perfect example of how a stuck shut swirl control valve acts. i have seen them on a sohc motor once but never on a dohc. check to see if its moving and if not try moving it by hand. on the sohc motor i was able to jam a screwdriver in the actuator and free rev it. it was instantly obvious that she was better.

[PMan_S13]

The flecks were just white spots, not actual metal fragments or anything. Looked more like it made some of the carbon fleck off, leaving the clean underneeth to show through.

Here's the deal. I drove the car to work tonight. I haven't had enough wheel time behind it to really know how it feels so I decided to try it out. Besides the complete lack of power the motor runs fine. And actually my A/F gauge reads fine too. This leads me to believe that the motor is getting the correct air fuel or at least close to it. If the ecu as going rich it would be 27% rich, that's something like 9-10:1 A/F and that would be horribly rich at low rpms.

I am really wondering if my distributor is broken or messed up. It might be reading that I am making 20 btdc but if it is broken then it could be making anything. I'll have my brother bring up his distributor and we'll try it out this weekend.

Also to back up this point, the motor sounds really different. The exhaust note is almost hollow somehow. I think points to the combustion happening at the wrong time in the cycle.

I have no cat, egr, aiv, bpt, carbon canister, and pcv is vented. No emissions in Columbus, Ohio. =). I did check the swirl control valve for operation when this ordeal started. The little valve opens as soon as it comes off idle. I doubt it could cause that much trouble anyway. It seriously has so much trouble making power it is pathetic. I think the turbo is the only think supplying enough air to make it drivable on the street at the moment.

And to top if all off the freakin lower timing cover must not have set in right cause it is leaking oil pretty badly. Yippy.

[PMan_S13]

Well this is interesting...

Just happened to test vacuum on the highway by letting my foot off the gas while in gear. This normally pulls about 25 vacuum, but I was reading 15. I'm too tired from working all night to think what this means, but I hope that is some substancial news to someone with more zest than I =)..

I'm going to bed... good night.

[vacnsewmedic]

HEY DAEDALUS,

WHAT DO MEAN BY STARTING A NEW THREAD FOR MY CAR????

[DAEDALUS]

New thread man! All the posts in this thread should be for PMan's car cause he started it. If you have a similar problem, then fine, but otherwise go back to the Nissan Mechanic forum and click the "New Topic" button for your timing chain situation. If everyone started to put random non-related things together in the same thread things get pretty messy real quick. It's called "thread-jacking" and isn't very appreciated. Thanks!

[s13sr20chris]

now please humor me. i think the valve is normally open. i think that the valve should snap shut at idle and then open back up as it revs. does it open back up? you said it would open, your sure that was not it closing?

[PMan_S13]

Whoops, I meant I can see it open as it comes off idle. I know how it is supposed to work, but I really can't prove it is opening or closing without the manifold off.

All I know is that it is at one state at idle and switches to another state when it comes off idle. I think the thing is working alright.

Does anyone else think it is significant that I am only making 15 hg of vacuum while decelling in gear as compared to the 25 I usually get?

[PMan_S13]

What a wasted day...

Me and my bro have been trying out everything we can think of and have come to the conclusion that my car sucks.

We tried switching parts over from his car back and forth and haven't really found anything to be helpful.

The clostest we got was by trying to recreate the problem on his 240. I thought we struck gold when I retarded his timing down to nothing. It takes forever to rev out and sucks in a lot of air, just like mine is doing. Plus it does the same cutting/ boggin out mine does when you floor it. It acts EXACTLY the same. But when we tried solving this on my motor (advancing timing) it does not help. It gets somewhat better at maybe 25-30 btdc, but after that it just bogs and jerks really badly. This would make me think that if it isn't ignition timing, then maybe it's valve timing. Which I have already checked and redone like 4 times now.

This sucks so bad...

We're taking a roadtrip down to my grandpa's to get my compression tester I left down there. Not that I think the cylinders are blown. Number one, they couldn't all blow at once like that at low throttle. And number two, if they did there would be some oil or other nastiness on the plugs, which there isn't. But maybe if it shows low compression that might prove to me that the valve timing is off somewhat.

Anyone know what the proper compression pressure for 8.5:1 pistons on a ka24de would be? I'd guess 150-170 would be close.

[InsanityInc]

9.5:1 stock pistons are 179, so probably closer to 150.

[PMan_S13]

Well the results are kinda interesting...

Number 1- 160Number 2- 180Number 3- 180Number 4- 160

I didn't round, they all came out exactly as they read above. All plugs pulled at the same time. I thought it was fine at 160, but when I read 180 on the 2nd I got confused. Not really sure how 2 and 3 can have higher compression like that, especially with lower compression pistons on a motor with only 4900 miles on it. Maybe the log mani I'm using helped those cylinders breek in with less distance out the turbo. Or maybe my valves are starting to go.

I'm giving up for the night. I'll be back tomorrow..

thanks for the help guys

[s13sr20chris]

Does anyone else think it is significant that I am only making 15 hg of vacuum while decelling in gear as compared to the 25 I usually get?

yes i find that a significant factor. i just dont know what to do with it. poss1)motor not sucking2)lack of restriction3)prob at vac porti cant say which of those seems better(or worse)

[DAEDALUS]

What is it at idle?

[PMan_S13]

A few things really confuse me...

-The motor runs smooth. Weak, but very smooth. This makes me think it is something general to the fuel or air systems. Not a cylinder specific problem. All cylinders are firing at equal strength. Spark must be good.

-The plugs look fine to me. Maybe just a hair rich, but certainly not fouled. This leads me to think that the motor is getting the correct fuel/air mixture.

-Timing *should* be correct. I know that ignition timing at the least has to be correct. There is no way the crank pulley can be off and no way the timing gun would tell me wrong. Just not possible.

-The ecu is not throwing any codes in self-diag. That makes me think that the electric components are not shorting out with the key on. Now if they read correct when the motor runs is of course a different matter.

-This problem started while I was driving in the rain and at low throttle. Low throttle really doesn't put much strain on the motor. I can't see something breaking from slow acceleration. And even if something broke, I think I would have found it by now. So that means something was affected by the water? that sounds like an electrical problem.. but I have looked at every electrical system already.

So what have I concluded from this?

-Has to be something general to the system. Air/Fuel ratio then?-Doesn't affect air/fuel at all, or much. Must be timing then?-Timing is correct. Must be compression then?-Compression is weird, but should be making power.

So if it has good A/F and still has compression and still runs, what else would effect power? Timing. But timing has been checked so many times now. Ignition timing is not even an issue anymore. So what, does this mean I get to tear down and look at valve timing again? BUT WAIT!!! This all started while I was driving. How the freakin heck could the timing chain jump while I was driving without something exploding under my timing covers? The lower timing chain could never jump unless it destroyed the bottom stoppers somehow.

Sorry for the ranting. I just wanted to share my frustration...

Since this oil leak is so bad I may devote tomorrow to tearing it down... again... fixing the leak, and since it's all apart just check to see how timing compares to this image of the cams at TDC (http://jimwolftechnology.com/wolfpdf/CA ... KA24DE.PDF)

there's no way I screwed it up 4 time in a row, but there is nothing left. N o t h i n g.