I used the search, didnt really see anything that was EXACTLY like this...

Bought a 1992 240sx Coupe, automatic, as a project car/daily driver for my girl. It was running great up until yesterday. She called me saying the car was "shaking" on her way to class.

Here's what I did so far...

After reading some posts, with similar problems on a couple message boards (TR, zilvia, 240sx.org) I still can't seem to figure it out. It hesitates to start sometimes (seems like starter is going out) but cranks once it gets spark fine. Once running, the idle fluctuates and the engine shakes periodically. Giving it gas doesnt help the fluctuations, it's pretty much just doing it on it's own no matter what RPM. Right after startup, it kinda sounds like it's knocking, but not 100% sure.

I know it's hard to diagnose problems over the internet, but before I tow it to a shop for work, just want to know some opinions on what could be wrong...

Thanks in advance for replies.

 

could be fuel related.

mine idles shaky everytime i start it it and sometimes i cant start it at all

 

I was thinking that after reading some other posts here, but the fuel pump sounds fine, and I'm replacing the fuel filter today to see if that helps...

 

Give it a complete tune-up, hopefully that will help hesitation

"Kinda sounds like knocking" - thats never good, but its too difficult to diagnose over internet.

 

might seem silly but check your plug wires. I have had wires with bad connections vibrate loose/together depending on forces...sometimes it would arc, othertimes it wouldnt. They were in the thick rubber area too, so they didnt visually look broken.

S13's are also notorious for timing chain rattle, it could be what is "knocking" but that is why its called rattle, a knock would be much more obvious...and its silly to say that rod knock is not a common occurance

Nissan MAF's go bad pretty often aswell. The whole intake system can cause some idle headaches....

Cleaning your MAF sensor with some electrical parts cleaner can help you a bit, and checking your intake system for air leaks is a good idea. A leak in your intake will cause a rough idle, and RPM's to drop when coming off of idle.

 

OK.

Replaced the fuel filter and pump today, and nothing changed, except:

1. The idle fluctuations are lower... as in the RPM's that it ranges from is slightly lower.
2. Now the car is smoking from the exhaust... which is wasn't before. It's a white/black tinted once released smoke... hard to describe actual color.

Now what? I'm doing plugs, wires, and MAFS in a bit... but any other suggestions???

 

After everything was replaced, I just did diagnostics, and got code 34 - Knock Sensor...


NOW WHAT!?!?!?!

Do I have to replace that? Need help...

 

I got that same knock on start up.

My car died today, rodnock like crazy.

 

Crazy, somehow when I started the car up today, the fluctuations went away, and the car runs perfect... but... I reset the ECU, and I'm still getting the Code 34 - Knock Sensor... What now?

 

You will get that code until you replace the sensor. Problem is, it's pretty f'ing expensive. You can live without it. If the engine is still smoking or begins "acting up", again.... Try adjusting the IAC by small increments (no more than a quarter turn at a time). Shut off the engine after each adjustment, then restart it to see if you have fixed the problem , but try to mark or remember the original placement. If that has no positive effect, move on to the TPS. Hope I've been some help.

BTW-- The knoc sensor is a pretty common problem and if 9/10ths of 240 owners ran diag's on their cars, would get the same code.