rough idle, big headach

[180sxpanda]

ok i so need help. I've searched this entire forum and cant seem to find exactly the ansewer. I have a 1992 240sx

Ok, when i'm at idle after the car is warmed up, my idle is rough and car is shaking. When i press on the brakes it gets worse, when i turn on the headlights its even worse, and the strange part is when i turn my steering wheel it gets really bad, almost drops the rpm 400.

I've changed my plugs, plug wires, distrib. cap and rotor, removed the AIV, replaced o2 sensor, replaced gas filter, cleaned the egr, replaced all 4 injectors with new 0-rings.

I've been thinking its my alternator going bad, but my lights never dim.

Any info you could give would be great.

Thank.

[hugotv]

I'm experiencing the exact same problem with 91 240sx. Same thing with turnin lights and wheel, which lowers the rpm substantially to a point where the engine just stalls. Now I have to brake and slightly keep the tip of the foot on the gas to rev the engine so that it doesnt stall on the road, or worse, when going off the curb on the highway. I think by this time I've mastered the heel and toe braking technique you'd see racers do when engine braking ;-) It sux and it seems to get worse when you increase the fan to the highest setting, and see that rpm drop to 400 rpm. When I pop the hood, the engine seems to give a hissing noise as if strugling, the sound seem to be coming out of where the block is and somewhere maybe from the injector area. Would be great if I had a hidden turbo there somewhere It gives that hissing noise only when rpm lowers. Could be injectors? Maybe. Howver I've just done an ECU check, and it seems that I have a foul O2 sensor, since when I run the engine in Mode2, the red LED doesn't blink for more than 5 times during 10 seconds as described in FAQ section, rather the red LED is completely red for about 20 seconds, then it is off for no more than 5 seconds, and it goes completely red again for 20 seconds. I suppose that is the exhaust gas sensor problem, as described in the FAQ section, because for the self diagnositc mode it gives a 55 code, which means no other potential problems present. Did u perform ur ECU check, 180sxpanda?

[180sxpanda]

yes, i'm only getting one code, and thats the speed sensor. everything else is good on the ecu codes. I was talking to one of my friends who is a mechanic, he was saying that the place that serviced my transmission might have put in the wrong oil, might be too thick. wondering if that could be the problem?

[hugotv]

Could be the oil but it still doesn't make much sense. Of course, I assume he didn't fill the transmission with some heavy duty glue. How do you feel the engine when revving? If it revs normally, then the oil isn't a big issue here. If it's sluggish rev, maybe the oil is the problem. In my situation, the rev is normal under load or without load, but when you brake, the engine rev will drop suddenly, which signifies that the engine is probably missing the timing. I should try checking my belts too if 02 won't work as it hasn't in your case

[180sxpanda]

well today i advanced the timing a bit, helped out, but still have rough idle problem. After the advance the car seems to have more power threwout the whole powerband now. Seems to be reving with no troubles.

I was also wondering if a bad fuel pump might be to blame? But wouldn't the pump be faulty at higer rpm's not just at idle.

OH, also i have noticed that it bogs a bit when the engine isn't warmed up.And when the engine cranks over on startup i feel a jerk in the clutch pedal, just right when the engine fires up.

What a freekn' headache.
Modified by 180sxpanda at 12:59 AM 3/14/2005

[180sxpanda]

Got underneith my car today to change the speed sensor since i am getting a number 14 code on my ecu. After the change it didn't resolve it right away, but i just drove it tonight and the rough idle has seemed to lessen. BUT, bad stuff i noticed when i was under my car, the rear transmission seal is leaking really really bad, its like an oil works under there. Also i noticed a big pudel of powersteering fluid on the ground. Also noticed that there was a ground wire which goes from the under of the body to the exhaust which broke loose not conected.

Could this rear transmission seal and leaking powersteering unit cause this rough idle as well?

Or would you say it was this ground wire?

[hugotv]

Looks like we have the same problem. I got a crappy transmission too and it is covered up with lotsa crap, to say the least. My steering seems to be making the screeching noise when you turn it sometimes. Though I didn't notice anythin leakin on my drvieway. Now, you're saying that your wire is disconnected. COuld it be running to speed sensor or maybe 02 sensor? Find out where it's connected to. And also, did u check your ECU for 02 sensor problems specifically, not just stored diagnostics? All I can say is that I will have to replace my 02 for sure. Then we'll see what happens from there. Oh, and I noticed that the engine is idling really bad when you run it in the cold weather. Another indication that it may be 02 sensor for me.

[180sxpanda]

well talking to the parts guys at my local nissan dealer, they said an 02 sensor last about 30,000 miles, i was way over due. I say it cant hurt to change it anyway.

Today i changed that broken ground wire. It was conected from the exhaust right behind the cat to the bottom of the car body. Didn't seem to solve too much, but my car is for sure running better. Lots of power again, i can finally feel what this new engines got.

Tomorrow i am asking my neighbor to use his air tools so i can get to the rear transmission seal. That should fix the rest of my vibrations. I would recomend doing a rear transmission seal change if your saying your transmission is as bad, seal cost 12 bucks. I'll let you know how it goes and post any hangups or trouble spots.

[Smooth240]

The hissing you mentioned you hear may be a vacuum leak which would cause an idle issue. I did have a vacuum leak in a line, a bad ground, and a bad O2 sensor. Replaced them all at the same time and the idle really settled out.

[hugotv]

Thanks Smooth240, that really explains a lot. Any suggestions on how I can inspect vacuum lines and fix if there are any cracks? Of course, I will try to dig up some more info from my manual, but any suggestion would help. Thanks.

[corn322]

I read someone said to spray carb cleaner around the vac lines with the engine running. if the rpms go up, there's a leak. I don't know how well that will work.

[Gyllom]

I have a '90 240sx with ka24e and have the same rough idling problem. As soon as I start the car the engine shakes real bad then when the RPMs raise it seems to run fine. I bought the car like this so I don't know what could have caused this.I have a power steering leak but I don't see why it would cause bad idling.I have to change my alternator because it doesn't charge enough then I will look for the rough idling.

If you guys can resolve it I would like to know what you did.

Thanks.

[180sxpanda]

Ok, well think i've figured out whats wrong with this car. Took the driveshaft off to get to the rear transmission seal and noticed that my Yolk was loose and not rotating corectly, took it into a transmission shop and showed me it was bent a bit which is the cause of all the vibration.

Called local parts stores and non of them sold either part,(Yolk and bell housing bushing). My local Nissan dealer can get them but not by themselfs, for the yolk i have to get an entirely new driveshaft, and for the bushing i have to get the entire bell housing. Now this is what the part guy was saying at nissan.

If anyone knows or has any of these parts for sell PLEASE let me know. Thanks.

[Gyllom]

This would make the car vibrate even in neutral position (driveshaft not spinning) ?

[180sxpanda]

yeah it vibrates the worst at idle. Driveshaft seems to spin fine, and is still in great shape. Just the yoke and bushing need fixing.

Pick-A-Part had a huge 1/2 off everything sell today and so i picked up my yoke and a much needed ebrake cable for under 15 bucks, cant beat that.

Install is going to happen on monday, let you know if this finally solves my rough idle problem.