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Engine shake and low power

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engine shake engine trouble low power
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9.9K views 37 replies 17 participants last post by  UR Krew  
#1 ·
Hey I have a 92 240 and my ka has 226k on it. I've owned the car for a little over a year now and my brother owned it for a year before me, but it sat for a year in between us. Ever since I started driving it, the engine has shook and from what my brother says it is way down on power. I've spent most of this last year I've owned it and been tuning it up (all filters, plugs and wires, and distributor cap) and trying to figure out what its problem is, but I just cant seem to figure it out. I've replaced two bad fuel injectors on my car since I've had it so I know how to dianose those and I have regurly ran fuel injector cleaner as well as seafoam through the car so I dont think I still have another bad one.

My mechanic checked the mounts told me he thought it had a bad timing chain, so I replaced the upper one and checked the tensioner and it seemed to be good on the upper and lower chains (the lower chain is a pain in the butt to get to so I wasnt feeling brave enough to try that). Sometimes it runs slightly smoother than other times but never fully smooth and never has very much power. Checked compression on cylinders couple months ago and getting ~165-170 across the board. I've checked the timing and many other things and just cant figure it out.

Any help would be very much appreciated.
 
J
#2 ·
You said your mechanic checked the motor mounts? Engine shaking sounds like a motor mount prob... And as far as the power problem try putting in a nice new fuel pump, with new 300zx fuel filter and maybe some injector cleaner OR could be a vac leak maybe. But my money is on shitty old oem fuel pump... If your compression is good/decent, your either not getting enough gas, spark or air...
 
#3 ·
you checked the chain for tension but what about for timing? and yes mounts on the tranny and motor will make god awful vibrations when going bad and also result in too much engine torque and getting less power to the wheels
 
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#4 ·
Thanks for the help guys, sorry for the very late reply I havent had internet access and it has just been a big mess.

But anyway, Jay420sx my mechanic said he did check the motor mounts (he is very honest, personal friend of my family and I) and he has owned a few 240's himself (SOHC). I've replaced fuel filter, run fuel injector through multiple times, and not getting any trouble codes. Idt I have a vac leak bc I have seafoamed it and there wasnt any smoke under the hood and idt I hear any hissing either. Im just afraid to buy and install a new fuel pump in case thats not it. I did finally clean out my mafs and that helped tremendously on power, but it still shakes, is down on power in upper rpms, and idle sometimes slightly fluctuates 50~100 rpms (idk if thats normal).

Twofizzle I've checked timing with timing light (it was correct) and also tried simply adjusting at distributor but with little to no change. Again Im trust that my mechanic knew what he was doing when he checked the mounts, Im thinking that since the shake varies that that makes mounts less likely but idk much about them.

Im starting to lean back towards the fact that maybe the tensioner in the upper chain is after all bad (when I checked it, there wasnt anything obviously wrong with it). But I didnt want to just change it seeing as how it is 50 to replace. I wish there was a way to test it but from what I read since it works on oil pressure when you take the valve cover off the tension in the timing chain will be different from when the engine is actually running.

Thanks again for all the help and any additional advice or some tests for timing tensioner etc would be very helpful. Im planning on attempting to replace the upper tensioner this winter while I drive my back up car, even if I dont get any replies before then I will try and post the results of changing it
 
#6 ·
I would still lean towards a fuel or spark issue. Is the shake rhythmic, as it is in a miss? If so then pull each plug wire or fuel injector plug and make note of which one did not make a difference in the engine shaking. The one that doesn't make a difference or only makes a small difference is your problem cylinder.
 
#7 ·
Ok what would be the best way to go about checking the motor mounts and vac lines myself?

It's not really a rhythmic shake, sometimes while Im sitting in the car the gear shifter barely moves, but other times it moves a good bit and i can feel my side of the car almost rocking (probably exaggerating a little bit still). I've also pulled the plugs to check all the cylinders and they are all firing, none dead.

If it will help I will try to post a video of everything.

Thanks everyone
 
#8 ·
sounds like u do need new motor mounts but its more than likely something else "causing" the shaking. it probably just made the motor mount situation more apparent.

to check the mounts there are a few ways but i would just pop the hood and crank the car up and watch to see how much the engine shakes. also rev it a few times. if it rocks side to side more than a few inches then its time for new ones/filling old ones.
 
#9 ·
i know these are two completley different engines but my Brotheres 91 300zx did about the same thing and we found out that he had spun crank bearings. cam bearings will do the same
 
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#10 ·
Welp I've done a few more tests

I changed out the upper timing chain tensioner, re-tested compression on all cylinders, seafoamed every part of the car lol, checked resistance on all of the injectors, and vacuumed tested it.

The old tensioner had a lot of wear on it, but switching out with new one doesnt seem to have done anything.

Image


The compression on cylinders 1 through 3 read 175 with cylinder 4 reading 165.

Seafoaming the intake showed a small leak near the exhaust manifold, around a pipe fitting that I think is the egr pipe (it goes behind the engine to the intake).

The vacuum test seemed to rule out a vacuum leak, but I'm not really sure if I read the readings right. Here's the link to a video of it.


I took a snapshot of one point of the test after I had just blipped the throttle where it reads 1.5 psi, the tester reads 1.5 vacuum when its not hooked up to anything so i assume this just means 0

Image


Still totally lost on why it runs so rough, any more help or advice would really be nice.
 
#12 ·
Thanks for the quick reply, ya sometimes I can feel the whole car shaking when idling and the gear shifter and actual engine visibly shake always but to different extents. It feels like it has good power between 2k and 3k, but below or above that it just doesnt have any power. Its hard to know if its still shaking when Im actually driving along so idk if it only does it when Im parked somewhere.

Here's another video, I think you can see where if I hit the gas when its idling it bogs and shakes real bad before reving up, I rested my hands on the steering wheel at the start to show better where the car rocks real bad.

 
#16 ·
Ya I've went through all the diagnostic modes on the ECU and as far as I know the alternator is good I've never had my battery die on me and the headlights dont dim or brighten with change in engine speed, my battery is almost brand new. Im going to try and do a fuel pressure test tomorrow, does it matter if I have fuel injectors from a SOHC in my DOHC? All of my injectors work but I was wondering if they were any different
 
#21 ·
Well found out my guage only goes up to 10 psi so I'll have to buy a different one to check fuel pressure but I checked the tps sensor and it was getting like 1.3 with throttle closed and like 9 with it opened Im gonna try and adjust it this weekend. When I tried to adjust the idle tho, I disconnected the tps sensor and started the car and the idle went up to 1000 and was surging after warming up instead of 900 with tps plugged in. When I tried to adjust the idle screw, it was already in almost all the way. Putting it in further did not affect the idle but after I took it out a good ways it started to raise the idle.

So why would disconnecting the tps sensor raise the idle, I thought it was supposed to lower it. Also, why wont my idle go below 1000? and should it be surging with the plug disconnected?
 
#25 ·
Ok back to working on it...

Took it to a shop and had them check the motor mounts, they said they looked good and that they thought it was a miss in the engine related to spark somehow.

Invested in a Nissan Consult, MAFS, TPS, O2 Sensor all within proper voltages and still no fault codes. However, my injectors pulse during idle is like 3.4 msec and the FSM says it should be 2.3-3.0 msec. At 2k rpms it should be 2.1-2.8 msec but mine raises past the idle until I let off the throttle. What does this mean? Am I running rich and what can I do if I am?

Also, when I turn on the base timing mode I am able to set timing to 650, but when I go back to normal mode it raises to ~875. Is this because its running rich or something?

Lastly, anything else I should be looking with when using the consult? I still need to get a fuel pressure gauge...
 
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