91 ka auto shakey idle in drive

[ma71supraturbo]

I just picked up a '91 240sx today and have some minor bugs to work out. The first item on the list is a rough idle when in drive (automatic). The engine idles fine in neutral or park, and it drives great once I'm moving, but when I come to a stop the rpm drops to ~600 and it vibrates enough to cause the hood to shake. It doesn't really sound like it is missing either.

The car just passed CA smog as well, although the idle Hydrocarbons were on the upper range (86 with an allowable 120). All the other numbers were at or below average.


Distributor cap, rotor, plug wires, and plugs are new. Oil was recently changed. O2 sensor is 2.5 years old (12,000 miles). Maybe bad motor mounts? I'll get a better look tomorrow when its light out...


Also, how often do the timing chains need to be replaced?



Other items on the list:
leaky ps hose at reservoir
Torn steering rack boots
front suspension clunk sometimes when turning
"soggy cardboard" rear spoiler
power antenna tries to retract when I turn off car, but just makes noise
torn front seats (rest of interior is immaculate)
dents on all driver's side panels (previous owner learned about black ice the hard way)
cracked front windshield
paint


Hopefully I can tackle those one at a time over the next year and a half while still in college. Once I'm out (if I still like the car as much as I do now) I will probably swap some CARB legal turbocharged engine/manual transmission in (no SR for me, maybe 3s-gte, 7mgte, or 2jzgte), do coilovers, bushings, and LSD.

Anyway, thanks to anyone who listened to my rambling. I would appreciate any help at all with any of the problems.

[Xandy Boosts]

Last time my car idled hard and shook like that, it was because of a blown headgasket. My car never shook hard for any other reason.

I'm not saying your motor is blown.

[SINxSELEKTAH]

with HIGH Hydrocarbons (HCs), you've probably destroyed your o2 Sensor & Cat. also, high HCs WILL cause CO and NOx to lower. though i'm curious, how were your o2 and CO2 %s on your VIR?

as far as timing chains are concerned, not very often. though timing chain slop will cause power loss and higher emissions

with your idle issue, it might be your IAC or your automatic transmission via torque converter lock-up, slippage, or even a vacuum leak

[ma71supraturbo]

with HIGH Hydrocarbons (HCs), you've probably destroyed your o2 Sensor & Cat. also, high HCs WILL cause CO and NOx to lower. though i'm curious, how were your o2 and CO2 %s on your VIR?

as far as timing chains are concerned, not very often. though timing chain slop will cause power loss and higher emissions

with your idle issue, it might be your IAC or your automatic transmission via torque converter lock-up, slippage, or even a vacuum leak

Cat was apparently replaced withing the last two years (and hasn't been driven much since). Here are the numbers:


Idle: 814 rpm 13.4 co2 2.5 o2 86 Hc 0.02 co
2500: 2306rpm 14.2 co2 1.5 o2 29 hc 0.08 co

[MadMaverick]

I doubt the motor is blown, this is a common idle problem with 240s.

The drop in RPMs when you come to a stop is your IACV (Intake Air Control Valve). It is supposed to open when your off the throttle to allow air past the butterfly so the car doesnt stall out. After a while, the motor gets tired/lazy or it gets gummed up inside. There is a hose that goes from the back of the manifold to your intake piping, its about 3/4" thick. To see if you have the right one, let the car run, pull the hose off the intake piping (the plastic part, not the manifold itself) and plug it with your thumb, the car will stall. Now, get a can of intake/carb cleaner and let the car run with the hose off. Spray a little bit at a time into this hose while holding it upright. The car will try to stall so just give it a little throttle by hand to keep it running. Cleaning out the IACV should help if not cure your problem.

Your power steering hose prolly just needs a new clamp

Your front end clunk is prolly TC rod bushings, get a mechanic to shake down the front end.

Your power antenna has a broken cable inside. I disconnected the motor and pushed the antenna fully down, still gets great reception.

Replace the rack boots when you get new inner/outer tie rods. They are like 15 bucks each.

With emissions numbers like that, I wouldnt say the cat is destroyed. Its still doing its job. A motor that old is gonna have a lot of blow-by, ramping up HC's. If he had a vacuum leak, his HC's would be lower and his NOx would be higher, thought its a good idea to start replacing all those old rubber vac lines.

[ma71supraturbo]

Thanks for the help guys, I'm anxiously awaiting a bit more daylight to get started. Another thing I forgot to mention is the engine doesn't start quite as quickly as I might like (takes 3 or 4 cycles instead of firing after 1 or 2). I suspect this is probably more to do with the age of the engine though.


Today's order of business:

Clean K&N filter (looking through service records, a shop recommended it 10,000 miles ago -- but I doubt it is related to this issue)
Replace spark plugs (they are new, but are bosch crapnums & I am partial to NGK copper)
Spray starting fluid around intake manifold looking for leaks
Clean IACV
Replace fuel filter (its cheap, and I don't see a record of it)


The car has been sitting for 7 months, so I do have a wee bit of hope that after running the new gas through for a while it will get better.

[Phlip]

I doubt the motor is blown, this is a common idle problem with 240s.

The drop in RPMs when you come to a stop is your IACV (Intake Air Control Valve). It is supposed to open when your off the throttle to allow air past the butterfly so the car doesnt stall out. After a while, the motor gets tired/lazy or it gets gummed up inside. There is a hose that goes from the back of the manifold to your intake piping, its about 3/4" thick. To see if you have the right one, let the car run, pull the hose off the intake piping (the plastic part, not the manifold itself) and plug it with your thumb, the car will stall. Now, get a can of intake/carb cleaner and let the car run with the hose off. Spray a little bit at a time into this hose while holding it upright. The car will try to stall so just give it a little throttle by hand to keep it running. Cleaning out the IACV should help if not cure your problem.

Your power steering hose prolly just needs a new clamp

Your front end clunk is prolly TC rod bushings, get a mechanic to shake down the front end.

Your power antenna has a broken cable inside. I disconnected the motor and pushed the antenna fully down, still gets great reception.

Replace the rack boots when you get new inner/outer tie rods. They are like 15 bucks each.

With emissions numbers like that, I wouldnt say the cat is destroyed. Its still doing its job. A motor that old is gonna have a lot of blow-by, ramping up HC's. If he had a vacuum leak, his HC's would be lower and his NOx would be higher, thought its a good idea to start replacing all those old rubber vac lines.
This is support that ones' post count does not drive their intelligence level.
Listen to this man, as the IACV is what is more than likely what is causing your funny idle, it is what caused mine and a couple other people, all of whom were "cured" when we cleaned/replaced it. +rep for you, my friend.

[ma71supraturbo]

Update:

Before doing anything else, I used an AFM & throttle body cleaner to clean the IACV. Interestingly, the car would die if the 3/4" hose was plugged or left open (it would die immediately if plugged, and slowly die if left open). So I had to leave the hose horizontal and use my left hand to hold the throttle...

I sprayed probably 5 or 6 times -- each time a ~1 second blast that made the car nearly die, followed by me waiting until the engine recovered and ran normally before spraying again... Then I reinstalled the hose and tested it out:

At first, the car was awesome -- perfect idle both in park and in drive. I took it for a test drive, going ~ 2 miles to the freeway and having it run perfectly at stoplights. I then went another ~5 miles on the freeway before turning around. When stopped on one side of the overpass, the car idled well. When stopped at the other end of the overpass, it slowly began to idle worse (not quite as bad as before). After accelerating back on to the freeway (about 3/4 throttle) the check engine light came on. I babied it back home, although from this point on it drove exactly like it did before the cleaning -- running well once underway or in neutral, but idling like crap when in drive.


So now I need to read the engine code. How do I do this on an OBD1 nissan? I searched google and came up with this: http://www.240sx.org/faq/articles/ecm_codes_doch.htm but that seems ridiculously complicated compared to OBD1 Toyota. Is there another way, or do you have to access the ECU each time you want to check codes?

I also went to clean the supposed K&N filter, only to find that instead of cleaning it 10,000 miles ago, the previous owner threw a paper filter in... It is still fairly clean though. I'll do the fuel filter for now, then do some more searching on the check engine light.

Thanks again for all your guys' help. I really appreciate it

[ma71supraturbo]

Pulled codes per those instructions. Kind of a bitch, but it worked. Codes:


32 - EGR malfunction (California models)
34 - Detonation (Knock) Sensor

[V1A]

I'd say the fuel filter is your culprit. A piss poor idle under load can usually be attributed to a faulty fuel system... since filters are about $15 you should start there. If that helps your idle, I’m pretty sure those engine codes, which are also fuel related, will also be fixed.

[Rayne]

Pulling the check engine codes can be easier if you have the tool to pull the codes. If I recall correctly the 91-94 s13 240sx is obd1 and the computer connection is near the fuse box underneath the driver's side kick panel.

[ma71supraturbo]

Update:

Reset codes & ordered Knock sensor (looking through receipt history, 15,000 miles ago the previous owner had a shop clear a code 34). Replaced the fuel filter and nearly emptied the rest of the TB cleaner in the IACV hose using the same procedure I listed above.

The results were pretty much the same -- drove like a dream for a few miles, then slowly started idling lower and lower (~550rpm in drive, ~600rpm in Park/neutral). Still drives great once underway... Does this sound like I just need to get a new IACV?

Tomorrow I'll go through the EGR diagnosis per this FAQ: http://www.240sx.org/faq/ Which reminds me -- since there is a separate code 35 for egr temp sensor, do I need to check it since it isn't throwing that code?

Thanks again to everyone for their help. I'm kind of glad this car is an automatic, because it's so much fun to drive -- I'd be tempted to mod it if it were 5spd...


Also: I installed new hatch lifts ($19/each) and gussied up the interior. I tried out a Pepboy's seat cover, but it fits like ass so I'll have to take it back. Has anyone found seat covers that fit semi-decently on a S13?

[ma71supraturbo]

The knock sensor came in, so today I installed that. The car fought me every step of the way:

I'd changed the oil a few days ago since it was pretty black, and had planned on doing another change shortly afterwards so I just installed a fram filter. I installed that filter by hand with greasy fingers, but that fucker wouldn't budge (I'm always able to take my oil filters off by hand). So I got a cheap channellock-style oil filter wrench and gave it a go. Wouldn't you know it -- the filter wrench punctured the filter before getting it to budge. I tried a few different locations, and just ended up with a crinkled, leaking oil filter. Went back to the parts store and got the strap-style filter wrench, but it either slipped or just further crinkled the filter. Gave up and resorted to the shade-tree style hammered-in screwdriver and finally got that filter off.

The intake manifold bracket was easy, but then the fuel line bracket wouldn't get enough out of the way so I had to remove the fuel lines. They were stuck on the nipples so I tried twisting them with a pair of pliers. By the time I was done, the hoses were chewed-up enough I had to replace them...

From there on, it was pretty straight forward. The old knock sensor was badly cracked, which was a bit of a relief since I wasn't looking forward to doing any rewiring. I was able to leave the subharness plugged in and feed the sensor/harness through so I didn't need to use the wire hanger method per the FAQ. (Just for fun, I bablefished the japanese writing on the knock sensor. The translation? "stupidfatfingeredamericanshouldhaveboughtacamaro")

As I was draining the oil, I decided I might as well clean the throttle body. Of course the numb-nutted fool who last worked on the car left every hose clamp oriented in bizarre directions, so I had to remove the upper radiator hose as well. And of course I loosened the JDM hose clamps too much, so the little washer at the end of the bolt fell out rendering the hose clamp worthless. Once I got the little accordian hose off the TB, I discovered that there was a hose that goes down next to the radiator and plugs in to the plastic air tube -- and this hose was not connected. Does anyone know where this hose goes (or what it does)? It was getting dark so I didn't have much time to investigate. Anyway, buttoned everything back up, and decided to clean the big ground wire on the intake manifold & the two ground wires at the back of the head on the exhaust side for good measure.

The result? The car idles slightly better, but it now doesn't seem as responsive to small throttle adjustments (I'm guessing that hose has something to do with it). I still need to check all the EGR stuff, but with fuel-irritated hands and bloody knuckles, I was ready to call it a day.


PS, how much oil does the KA24de take? My owners manual says "about 4 with oil filter," but I added 3.5 qts before double checking the level and it shows being just slightly overfull (yes I started the engine first to pump oil through the filter, then turned it off and waited a few minutes before checking).

[idlafie]

Oil with filter usually runs about 3 1/4 to 3 1/2 quarts, (depending on where you want the level at on your dipstick). With the engine cold, check to see where it is at. You don't want it going over the Full mark. If it is, then you've got too much oil in the pan. As the crankshaft rotates it will churn the oil, causing aeration and eventually sustained foam may form. This can lead to overheated motor oil, oxidation and a loss of oil pressure. Spongy aerated oil is hard to pump. It starves the engine and critical lubricated surfaces and could lead to a blown motor, hence the reason not to overfill your oil.

As for your idle, you may have it set too low. Normally KA idles are set at 700-750 rpm. You'll need a Nissan Factory Service Manual, (use the SEARCH feature here on Zilvia.net to download one). Disconnect your throttle body subharness & reset your idle to 700-750 rpm. Hopefully, that will solve your low idle problems.

Anyhow, hope this helps.
ID

[Dan14911]

this is all too crazy my car ('92 coupe auto aswell) has been doing the same exact shit and we have been troubleshooting the same i too am about to just reset the idle and see where that gets me.....GL and keep me posted if i figure anythingout that works well ill be sure to let you know aswell

[cycloneskate]

I have a 92 that was doing the same thing- the brake booster vacuum line was cracked and the engine almost died at idle. It was better sometimes because the hose moved a certain way and closed the hole but once I found the problem a new hose fixed it perfectly. Try setting your e-brake hard so the car doesn't move, and put it in drive with the hood open. Listen for any hissing noises as that may be your problem. good luck!