rough idle in cold weather (not a cold engine issue!!)

[Guam180]

Hello NICO,

This is my first post and I know I should post in the newbie thread. But my problem is complex and lengthy, so I decided to make a new post for myself.

I have an automatic 1991 240SX Fastback and according to Carfax I'm like the 5th owner of this car. Engine and transmission might have seen better days, since the last owner told me he has had to get both rebuilt/ repaired. I have yet to see either work orders.

Since I've owned the car, I've gotten a new starter, battery, plugs, wires, distributor cap and rotor, oil change, radiator flush and new freezer plug.

At the time I got the tune-up kit (plugs, wires, and distributor, etc.), car finally ran ok. It would blip on its own (drop rpm by just a 100 rpms) once in awhile. But it never sounded like it was going to stall. Not like before hand.

Now its starting to get cold here in NC. Temps are now regularly dipping into just above freezing. That was just yesterday and thats when it started happenning.

When I first start the car, it idles good. A little high (somewhere between 1500-2000 rpms), but it is a cold start, so nothing to worry about, right?Car runs ok to work (work is about 15 miles away so engine should be nice and warm). But right when I get to the office it jumps around from 300-1200 a few times before finally giving up.

Now on the way to work this morning, I did stop once at a store not even 5 minutes away from my office, and was in there for about that much time. It started just fine then as well. As I said before, as soon as I parked the car AT THE OFFICE, it did that little number. Also, in the first half of my commute, I did notice that it seemed I didn't have a fourth gear. I'll be cruising at 50 mph, and RPMs are at around 3000. Obviously, that's too high for cruising. When letting of the accelerator in this state, RPMS would just fall to just above 2000. It sounds like that's where its suppose to be though.

So oh-wise gurus of NICO, is going on with my engine??

I apoligize for the novel, but I want to be thorough, and show you guys that my problem is unique in reference to all the search results I've been looking at....

[bruinbear714]

Hello NICO,

This is my first post and I know I should post in the newbie thread. But my problem is complex and lengthy, so I decided to make a new post for myself.

I have an automatic 1991 240SX Fastback and according to Carfax I'm like the 5th owner of this car. Engine and transmission might have seen better days, since the last owner told me he has had to get both rebuilt/ repaired. I have yet to see either work orders.

Since I've owned the car, I've gotten a new starter, battery, plugs, wires, distributor cap and rotor, oil change, radiator flush and new freezer plug.

At the time I got the tune-up kit (plugs, wires, and distributor, etc.), car finally ran ok. It would blip on its own (drop rpm by just a 100 rpms) once in awhile. But it never sounded like it was going to stall. Not like before hand.

Now its starting to get cold here in NC. Temps are now regularly dipping into just above freezing. That was just yesterday and thats when it started happenning.

When I first start the car, it idles good. A little high (somewhere between 1500-2000 rpms), but it is a cold start, so nothing to worry about, right?Car runs ok to work (work is about 15 miles away so engine should be nice and warm). But right when I get to the office it jumps around from 300-1200 a few times before finally giving up.

Now on the way to work this morning, I did stop once at a store not even 5 minutes away from my office, and was in there for about that much time. It started just fine then as well. As I said before, as soon as I parked the car AT THE OFFICE, it did that little number. Also, in the first half of my commute, I did notice that it seemed I didn't have a fourth gear. I'll be cruising at 50 mph, and RPMs are at around 3000. Obviously, that's too high for cruising. When letting of the accelerator in this state, RPMS would just fall to just above 2000. It sounds like that's where its suppose to be though.

So oh-wise gurus of NICO, is going on with my engine??

I apoligize for the novel, but I want to be thorough, and show you guys that my problem is unique in reference to all the search results I've been looking at....

I would flush the coolant system and add the proper mixture of anti-freeze/coolant. Also check your coolant temp sensor - the two wire one, not the 1-wire.

Are you getting bad gas mileage?

[Guam180]

Yeah, I'm getting REALLY bad gas mileage. I can go through a tank in a week.

Also, to update my car just won't start this morning. Its not as cold as the past few days. So what gives?

The car turns over, it sounds like its gonna start. But doesn't. I gave it a little gas to see if that helps, but nothing. All my lights remain on after trying to start: "check engine, oil, battery, seat belt"

Do those lights remain on until the car starts? Because I know for sure the battery light stays on until after the car starts.

The mechanic yesterday said it might be a fuel problem. He gave me some fuel system cleaner and anti freeze for the gas. I was gonna do this this morning since I need to fill up anyway, but now I can't.

I gave the mechanic's son ( another mechanic, and owner of the shop) a ride afterwards yesterday, and he's saying it sounds like my exhaust leak might be the problem (and I believe my leak IS really bad. I sometimes feel power loss when it sputters louder than usual).

Now I can't even start it this morning. IDK, this car just seems to have so many problems, with all these different symptoms.

I swear the car was running just fine before I bought it. Maybe I was blinded by the fact it was a 240 to see its list of problems...

[Guam180]

Bump....

Really? Nobody?

Update: Got the car from the mechanic last week friday. Looks like they were cleaning the intake side, particularly the MAF. Gased up the same day as well (from qtr tank to half tank). Ran fine over the weekend. Ran fine on monday. Yesterday took the wife's car to let mine rest. Today I'm at the original problem again. It starts fine. But when warm and in traffic it stalled. It starts back up just fine though, just won't hold an idle. Its at the shop again and now the mechanic is thinking its a fuel problem.

[psmith]

When I first start the car, it idles good. A little high (somewhere between 1500-2000 rpms), but it is a cold start, so nothing to worry about, right?

That seems too high. Even on warm up I think you should be idling around 1200. Have you cleaned you IACV? Seafoam, maybe? (If you can keep it runnning...) I had the stalling problem and cleaning the IAC worked for me.Good luck!

[Bigvinnie]

My recomendations:

Clean your maf / check grounding

Check ignition system, wires and plugs

Clean injectors

Then adjust IACV after doing those procedures

[Rekless KA]

these are the possiblilities...

engine coolant temp sensorintake air temp sensormafpossible injector resistance problemExhaust gas recuirculation leak and/or bad sensor on it, maybe spring actuator on it.

much more but have to get back to work.. sorry

[Guam180]

Thanks for the responses guys. I was beginning to wonder if anyone was gonna help me.

Update: Mechanics seemed to have traced in back to crap in my tank and a bad injector. He said he just stumbled on to the faulty injector by pure luck. Should I be worried about that mechanic??

Anyway, car runs really well now. For the past two days, the only problem I came across, was random sputtering and lack of acceleration from a standstill (I also got a bad exhaust leak from somewhere under the cabin to somewhere in the engine bay). But at times when it doesn't happen, I it seems to have more umph. And it doesn't seem to exhibit the old symptoms (blipping/ rough/ no idle).

So for the time being, I think my problem is solved. Thanks all...