CoOlKidS1979

When I start my car sometimes it will make a coughing sound for a second or two and then turn over, this has been going on since I bought the car, about a year ago. Recently it has backfired a couple of times when starting, but keep in mind that sometimes it starts just fine. The car has a new battery which is connected directly to the alternator, new plugs, air filter, fuel filter, and the alternator has been tested. Also I have tried turning the car to the "on" position and waiting 10 seconds before starting but this doesnt help. Im not sure what to check next?

breaux124

iTrader: (1)

Maybe dirty fuel injectors? Incorrectly gapped plugs?
Or even fuel pump?

Daniel B. Martin

I saw your earlier post on the same subject and didn't respond because I didn't have a good answer. I still don't, so this answer is guesswork.

The cough and backfire suggest that the Engine Control Module is getting wrong signals about when the engine is at Top Dead Center, and as a consequence is firing the spark plugs at the wrong time. This could be the result of trouble with one of the Crankshaft Position Sensors or the Camshaft Position Sensor.

Did the Check Engine Light ever go on? If so, did you do a Diagnostic Trouble Code readout?

Does the engine idle well and run smoothly once it gets started? Does it have normal power?

Please measure the voltage at the battery terminals ...
- before cranking
- while cranking
- with the engine idling
... and post the numbers on this thread.

Sonic

Oh, and to answer the questions before they are asked:

ECU READOUT: http://vbxmaxima.8m.com/ecu.html
And you can get a digital mutlimeter at most auto supply stores, about 30 dollars. Oh, and get a service manual also.

breaux124

iTrader: (1)

There is a service manual on ebay for a 97.
http://cgi.ebay.com/ebaymotors/aw-cg...418144&r=0&t=0

Guessing that it would be very similar for most fourth gens.

CoOlKidS1979

Okay I checked voltage at the battery terminals and were as follows
before cranking - 12.85
while cranking - 11.87
at idle - 14.30

Also the car has always idled smoothly at about 800 rpms, and the check engine light has never came on.

Daniel B. Martin

Those are all good numbers. The problem is not low voltage during cranking which could affect the engine electronics.

If the engine runs well once it gets started, that tends to eliminate the dirty fuel injectors, incorrectly gapped plugs and fuel pump as suggested by Breaux124. If those problems interfered with start-up they would not suddenly vanish after start-up.

You have reported an intermittent problem. These are always difficult to pin down. The best advice I can give, for now, is just keep on driving normally. The problem (or problems) will eventually get worse and produce clearer symptoms such as a Diagnostic Trouble Code.

If you are eager to do something rather than just wait, you could do a fuel pressure test. This is a standard diagnostic test. You will find instructions and a diagram or picture in the Chilton repair manual (page 5-3) and the Haynes repair manual (page 4-3,4).

Bleed the fuel rail pressure by pulling the fuel pump fuse (#32, 15 amps) and making several attempts to start the engine (it won't start). Install a T-fitting with a pressure gauge in the flexible rubber fuel line just downstream of the fuel filter. Install the fuel pump fuse. Start the engine. With the engine idling you should see the pressure maintain a stable 34 psi. Temporarily remove the vacuum signal hose from the fuel pressure regulator. The fuel pressure should increase to 43 psi. Reconnect the vacuum signal hose and operate the throttle to vary the engine speed between idle and 3000 rpm. The fuel pressure should vary between 34 and 43 psi.

Readings less than 34 psi could be caused by an obstructed fuel filter, a weak fuel pump, or a bad fuel pressure regulator. Readings greater than 43 psi could be caused by a bad fuel pressure regulator or an obstructed fuel return line.

After turning the engine off the fuel system should hold pressure for many hours. If the residual pressure bleeds off in only one hour that is a sign of a problem... bad fuel pump check valve, injectors with an internal leak, bad fuel pressure regulator, or an external fuel leak.

breaux124

iTrader: (1)

I was wrong. That's why we leave this stuff up to Daniel Martin. Cause he's the man!

We've learned so much from him....isn't this place amazing?

CoOlKidS1979

I finally got a code, the park/neutral position switch? Does this sound right for the problem I have?

Daniel B. Martin

Please post the numeric Diagnostic Trouble Code.

CoOlKidS1979

It was 10 long flashes, 3 short flashes

Daniel B. Martin

Please refer to the Sticky Thread Important: ECU Diagnostic Trouble Codes. It contains some information about DTC 1003 including a Park/Neutral Position switch test procedure. If the switch is bad, replacement is something which can be done by the home mechanic.

I don't see a connection between a malfunction of this switch and the coughing sound described in your previous post, but it is the best clue we have at this time.

laserloser2

i have a 95 max that use to do that everynow and then when it was cold... I took it to the dealer 3x and they finally replaced my IACV (idle air control valve) and I havent had the problem since....

Daniel B. Martin

A problem with the Idle Air Control Valve - Auxiliary Air Control valve might cause that "cough" symptom.

Here's the factory service manual component inspection procedure for the IACV-AAC.

1) Make this test with the ignition key OFF. Disconnect the IACV-AAC valve harness connector.

2) Looking into the valve connector with the latch at the top, you will see two rows with three terminal positions in each. They are numbered 1-3 (top row, right to left) and 4-6 (bottom row, right to left). Check resistance between the following terminals.
2 and 1.
2 and 3.
5 and 4.
5 and 6.
At a temperature of 68 F, the reading for all measurements should be approximately 30 ohms.

3) Reconnect the IACV-AAC valve harness connector.

4) Remove the idle air adjusting unit assembly (IACV-AAC valve is built-in) from engine. The IACV-AAC valve harness connector should remain connected.

5) Turn ignition switch ON and OFF, and verify that the IACV-AAC valve shaft smoothly moves forward and backward. If NG, replace the IACV-AAC valve.

CoOlKidS1979

I found out that the Park/Neurtal position switch light came on because somehow the connector came undone, so the problem was not related to that. Next I checked the crankshaft position switchs according to the Haynes manual. I tested the REF and got a reading of 580 ohms which is pretty close to the Haynes specs, then for the POS I got a readout of 5volts from the electrical connector, and then I watched the voltmeter as I plugged in the switch, which was removed from the car, and the reading went from 5 to like over 200 the second the switch was plugged in, then when I touched the tip of the sensor with a screwdriver the reading dropped to low 100's. Definately not what I was expecting. What do you make of this? Could I have performed the test wrong?

CoOlKidS1979

Well I bought a new crankshaft position switch and installed, it then tested it following the factory sevice manual and I got perfect results, I then trested the old switch and could'nt get anything close to what I was looking for. I did this a couple times going back and forth between the 2 switches just to be positive of the results. Finally I go and start the car and the problem WAS NOT solved. I have no idea where to go next, but the problem is getting worse. Also I noticed on the old switch that on the little magnetic tip that there was shaving of metal on it, which cant be good. Finally on the old switch the little peice of metal is about 1/4 inch of exposed metal, while the new switch is a 1/4 inch of plastic with just a small slit of metal exposed at the top of the plastic.

emax02

iTrader: (1)

I think I may have a simalar problem to you. I also replaced my cranshaft position sensor{and starter}, to no avail the problem persists. Wel anyways today I got a MIL code from god, my ecm detected a bad camshaft position sensor! I really hope this fixes the problem, I will let you know if it fixes the car or not in a few days.

emax02

iTrader: (1)

I just swapped my camshaft sensor with my I30's one and the car still starts like crap. What a freakin suprise! WTF!

vmok

Since you have a donor vehicle to play with, maybe you can try swapping the MAF and TPS/TB as well... do you smell unburnt gas in the exhaust stream right after the car coughs and finally starts?

-V

CoOlKidS1979

I definatly smell unburnt gas when it finally starts, sometimes it even backfires.

vmok

You need 3 things for a car to start. Air, fuel, and spark. Along with that, the spark needs to know when to fire and there needs to be compression for the mixture to be able to ignite. Assuming that you're comporession is fine (which also assumes that your battery is strong enough to turn the engine at a decent speed during starting), it leaves us with spark as we assume that there is air in the system.

So the car either doesn't know when to fire the spark, and/or the doesn't know how much air is in the car. We're also going to assume that the ignition system that provides spark is ok since there is an individual coil on top of each plug and it's unlikely that they would all go bad at the same time.

It would appear with the smell of fuel and back fires that there is plenty of fuel and when it finally starts, that spark is fine. So it would appear that it is a sensor or ECU issue. If someone had a FSM or service manual, I would check to see what kind of sensors could possibly effect a no start condition. Too much fuel can flood the engine and cause a no start condition as well. So we've eliminated the fuel system, air, and ignition system components, but not the components that tell the ignition system when to fire.

Right off the bat, I'd think some sort of temperature sensor, maybe the throttle position, maybe the mass air flow. You say that you've replaced the crank angle already and that once the car starts, it runs fine, so it appears that sound mechanical items are fine. Since this occurs before the car has been started, I'd also assume that vacuum hoses and such are not the culprit as the engine hasn't built vacuum yet as the car starts. I'll think about this more and let you know if I can think of anything else...

-V

CoOlKidS1979

Thanks for taking the time to help out, just a little more info,the air mass snsor can be eliminated, as Ive swapped tha out for my friends and it had no effect on th problem, the plugs are new, and Ive tested most of the sensors. I was thinking that next I was gonna check the injectors and the fuel pump. Do you think that either of those 2 could cause the problem? One other thing I find odd is that when I took out my starter and cleaned and regreased the internals the car started fine for about week?

hockeyghst

ok no ofense DBM but i thought u were leaving for personal reasons....i mean its great that ur back.......just curiuos on whats going on???

CoOlKidS1979

I started this thread several months ago.........

hockeyghst

my fault then.......

gabuchu

I am pretty sure that the ecm looks at the cps ref when the car is starting. If it doesn't see the signal, then it doesn't give ignition and car doesn't start. Once it sees the signal and tries to start the car, your engine it flooded with gas so it coughs and backfires.

skip

I am getting this exact code: 1003 and need to know how to locate and check the Park/Neutral Position switch.

Thanks,
Skip

pocketrocket

iTrader: (1)

Urrgghhh .... post back from the grave. Urrghhhhh .... scary ...

sean05

iTrader: (13)

I just got this code today too. I would like to know what it does and why it came on. Does it have a significant meaning?

Thanks

Sean

THT

iTrader: (8)

Wow...talk about thread resurrection part two...

~THT

nitromax

I wanna know if anything was ever solved and how?!

96MaximaLex

Hi,
I have just bought a 96 maxima and i have been having a little problems out of this one. i have had this thing scanned like 10 times now and i have only got one code left. 1003 haha. i have bought the part and i am going to install it because i know it is bad. My reverse lights dont work. so i have the same problem. my engine wont start good and it spits and sputters when i hammer down on it. i have replace the plugs, ari intake system, o2 sensors (all 3), knock sensor, fuel filter, radiator (needed it was rotted), and i am still haveing this problem. if anyone has fixed this problem with there car. please please help me i am running out of money. and i really dont want this car to be a lemmon. email me at ryanwentworth@gmail.com Thank you 96MaximaLex

NmexMAX

iTrader: (22)

I propose a new rule .... And I think most know what it will be ..

Nissan 6

Are you stupid? your hijacking a four year old thread

rguida

iTrader: (1)

not only has be hijacked a 4 year old thread, but this thread wasn't really originally about the 1003 problem, it was about a rough start....

saylee

iTrader: (2)

i guess im going resurrect a thread thats has been passes for almost a decade. 1003, that is the code that my scanner is finding. Car still runs good and everything still functions fine, i just dont know how i can really go about this problem

Kevlo911

iTrader: (36)

wow you couldn't just start your own thread or find a more recent one? Did you look to see what 1003 is?

NmexMAX

iTrader: (22)

Blackwind

iTrader: (9)

WTCRUNCHYF!! IS GOING ON HERE?!!

saylee

iTrader: (2)

sorry, i figured that i'd pick it up from where it left off because people who will experience it, could look at the thread that hasn't been solved. 1003 is the NEUTRAL POSITION SENSOR, whats weird is that it never popped up until my reverse lights wouldnt respond when shifted into reverse. Thinking it was a bulb and i should change it but the bulbs weren't blown, nissan tech found that i had a shortage and my sensor was okay. weird??