omg help this car is killing my brain x.x

[Sirspeedy77]

Ok, so after reading threads for over a week hoping to come across one that solves my problem, i'm ready to add mine to the list.

2001 Nissan Sentra GXE 1.8 164k miles....

Hard to start in the mornings, the colder it gets the harder it is.. breaking point seems to be around 28 degrees F. I can crank and crank and it wont fire up. Gets spark, after a few minutes i can smell fuel flooding the cylinders. After about 20 minutes of cranking it may or may not actually ignite and run. No check engine lights on. When car does start it runs rougher than a corn cob for about 10-15 seconds, low power, almost like its choking out. Usually feathering the throttle clears this up in around 5 seconds.

The check engine light was on when i bought the vehicle about 4 months ago. I had it checked at autozone, threw codes for MAF and O2 sensor bank 1 sensor 2. priced parts, made a plan to replace MAF first. About a week later i was driving home in the rain and the C.E.L went off, and has not been on since. Since the sensors would total me out around 500. i decided if the light isnt on they are working and dont need replaced.

When the vehicle does start it is usually through a combination of holding the accelerator to the floor and occasionally letting it back up then pushing back to the floor. I dont know why, and i know that it really doesn't do anything other than open the throttle body.

The car seems to run a little poor. Occasionally i can accelerate with supreme power, mostly its just a lugging slowly up to speed. Not enough to warrant any safe mode operation suggestions, just not up to par.

Lately i have been chasing down a cold heater problem, it is intermittent. At Idle it will blow cooler air through the heat setting. As i have just replaced both the thermostat and the water pump i am assuming this is residual air trapped in the heater core or somewhere else in the lines. No overheating issues.

And lastly, i have noticed that while sitting in my car at lunch, idling, i press the accelerator to bring RPM's up to around 1800 for some scalding heat, and the engine will knock the RPMS back down around 1500, then jump between 1800-1500 in a cycle if i keep my foot locked where 1800 was. If i attempt a steady no load idle of 2000, it will knock it down to 1500, jumping from 1800- 1500.

Are these problems related? Is there a sensor going out? MAF? IAC?

I have replaced plugs, oil change, air filter. Have cleaned throttle body, and IACV. Both of which had a layer of black soot on them. Car is driving me absolutly nuts. Anyone out there with the cure all answer? lol

I've seen so many threads relating to this problem i'm flooded with ideas on what to replace, where to start etc. If some people with experience could give me a place to start it would be greatly appreciated

[djtorello]

Ok, so after reading threads for over a week hoping to come across one that solves my problem, i'm ready to add mine to the list.

2001 Nissan Sentra GXE 1.8 164k miles....

Hard to start in the mornings, the colder it gets the harder it is.. breaking point seems to be around 28 degrees F. I can crank and crank and it wont fire up. Gets spark, after a few minutes i can smell fuel flooding the cylinders. After about 20 minutes of cranking it may or may not actually ignite and run. No check engine lights on. When car does start it runs rougher than a corn cob for about 10-15 seconds, low power, almost like its choking out. Usually feathering the throttle clears this up in around 5 seconds.

The check engine light was on when i bought the vehicle about 4 months ago. I had it checked at autozone, threw codes for MAF and O2 sensor bank 1 sensor 2. priced parts, made a plan to replace MAF first. About a week later i was driving home in the rain and the C.E.L went off, and has not been on since. Since the sensors would total me out around 500. i decided if the light isnt on they are working and dont need replaced.

When the vehicle does start it is usually through a combination of holding the accelerator to the floor and occasionally letting it back up then pushing back to the floor. I dont know why, and i know that it really doesn't do anything other than open the throttle body.

The car seems to run a little poor. Occasionally i can accelerate with supreme power, mostly its just a lugging slowly up to speed. Not enough to warrant any safe mode operation suggestions, just not up to par.

Lately i have been chasing down a cold heater problem, it is intermittent. At Idle it will blow cooler air through the heat setting. As i have just replaced both the thermostat and the water pump i am assuming this is residual air trapped in the heater core or somewhere else in the lines. No overheating issues.

And lastly, i have noticed that while sitting in my car at lunch, idling, i press the accelerator to bring RPM's up to around 1800 for some scalding heat, and the engine will knock the RPMS back down around 1500, then jump between 1800-1500 in a cycle if i keep my foot locked where 1800 was. If i attempt a steady no load idle of 2000, it will knock it down to 1500, jumping from 1800- 1500.

Are these problems related? Is there a sensor going out? MAF? IAC?

I have replaced plugs, oil change, air filter. Have cleaned throttle body, and IACV. Both of which had a layer of black soot on them. Car is driving me absolutly nuts. Anyone out there with the cure all answer? lol

I've seen so many threads relating to this problem i'm flooded with ideas on what to replace, where to start etc. If some people with experience could give me a place to start it would be greatly appreciated

Well, your issues can be numerious. A vacuum leak can do most of your issues, as well as the bad IACV, fuel pump may be going, bad A/F o2 sensor, Bad timing, water in the fuel, etc.....

Do you get dimming lights when you drive the car?

[ABNRML4U]

What kind of gas do you put in your car? I stay away from Walmart and 7-11 gas and citco gas. Im thinking maybe bad gas. I just don't think your B-15 does not like the cold weather. +1 on A vacuum leak.

[Sirspeedy77]

Well, your issues can be numerious. A vacuum leak can do most of your issues, as well as the bad IACV, fuel pump may be going, bad A/F o2 sensor, Bad timing, water in the fuel, etc.....

Do you get dimming lights when you drive the car?

Thank you for the fast reply, i appreciate it

No dimming lights, have switched to midgrade and have not noticed a difference.. I did notice a mild hiss from the engine compartment when i pulled up in the garage today. I will investigate for vacumn leaks further tonight.

Should the IACV make a clicking noise when i turn the ignition on? or is it supposed to be silent.. It makes some odd noises.. Not sure if its normal or not though. I did an Idle relearn last night without consult. I could hear the idle resetting itself.

However it has not solved the random RPM jumping when i try to hold a high RPM with no load. Its almost as if the fuel is cut for a split second. Damnest thing is it is a rythmic rpm jump. almost like a idle pulse. And will drop to 1500 - 1750 loop even if i try to hold an idle of 2000+

Did some researching through the factory service manual and thought maybe the ecm could be operating the car in safe mode for MAF failure? says it will not let the rpm past 2400, however i can rev up to 8k if i want. I did notice some "slack" in the tach when i'm driving down the road, its like the transmission is running @ 2100, but the car will idle down to ~1500, when i accelerate it will catch back up to the transmission and move right along.

I've tried stress testing the transmission to evaluate for slippage, have not noticed any slipping or fouled transmission fluid. So i can eliminate the transmission as the culprit. Seems as if something electronical is failing o.0

[nametakennow]

TPS is also a possibility.

As for the start, it could also be the fuel pump.

Start with the TPS. Jumpy idle could be MAF as well, but, again, TPS works there too.