I am based in PHC and i drive a 1998 Infiniti Qx4 SUV.
My troubles started one saturday i returned home after a journey outside the country.
I drove to church the next day with no troubles but alas after service as i made to drive out of church the car jerked and then went off with all the dashboard lights on.
I went home with a cab and later returned later in the evening with my mechanic and the car came on with no problems, i drove it home immediately.
The car was fine for the next 3 days and then on thursday while i was driving home, the car started jerking, the speedometer went down to zero and then the car went off.All efforts to start it again proved abortive.I pushed it to a nearby workshop and went home.
By the next morning, the car started with no problems and i drove it staright to my mechanic.
He then changed the fuel filter, but the problem continued.
he removed the fuel pump and tested it but it was okay.
They checked the plug, distibutor and coil but all were fine.
Now people are suggesting that the brain box may be dead.
Please help me! what do i do now?

please help o!!!!!!!

intermittent issues are not lways easy to trickle until they become prominent but ur issue seem a bit prominent to me. first i idont think this is a mechanical issue. what u have to do is try ascertain the frequency of occurrence and when it occurs. you have to be able to establish a pattern. since u say it starts after a while then i suggest it should be taken away from those mechanics doing trial and error. take it home and try to start it at intervals but dont drive rather let it idle till apoint when it goes off or till it shows some misbehaviours.lest i forget how old is this car? what changes have u made? what model? have u experienced issues with this vehicle before. history of this car will also help to narrow down. we have to establish a behavioural pattern. this is my advice for now atleast in the absence of a scantool else a scan should tell more.

Thanks for your response miccodb.
The car is 1 yr old. I bought it last year in Nov, from a friend at tincan in apapa.It was just brought into d country then.The car has never shown any issues in the past.The is d first time i am experiencing sumtin of this nature.
before i forget in May this year i had a similar issue with jerking and when i replaced the airflow meter it stopped.
But since then it had been a smooth ride all d way.

Oh sorry abt that Siena.
One year old in my hands i meant.
More info coming up,

kkmny81:

Oh sorry abt that Siena.
One year old in my hands i meant.
More info coming up,

Right. So we've established your SUV is at least 13 years old. How long you've owned it is of no importance here. The year starts from when it was first registered in the original country of sale. I've constantly pointed this out to guys on here, the registration in Nigeria has no impact on the vehicle's age, and the sooner this is understood, the more accurate diagnosis can be made.

The engine capacity is 3.3L, horsepower is 168 at 4800rpm, torque (Ib-ft) is 196 at 2800 rpm.It is a V6 engne.
The transmission is 4-speed Auto Overdrive (std).It uses fuel (PMS).It has about a 120,000 miles on it.
If more info is needed, ill gratefuly supply.

NB:We just found that the brainbox is okay.
Please Guys save a soul.

Sounds like a relay issue. Am not sure though, since i dont know how the electricals of the car is. But what I would do is to jumper the fuel pump & ignition coil(s) relays while troubleshooting. If the problem persist, then is not a relay issue. But if the problem stops, then you have found the culprit.


If the car has amplifier module/ignition module, swap it with another and see what happens. When an ignition module starts failing, the engine would stall and wont start untill the module becomes cold again. You can as well pour cold water on a cloth, press the cloth on the module for some minutes when the car refuses to start & remove the cloth when the module is cold enough. Restart the car. If it starts, you have found the cause of the wahala. If it dosent, then its something else. Meanwhile, ignition module should be attached close to ignition coil, if the engine has distributor & not the distributorless engine with coil packs.

These are other  possible causes of stall and no start. Siena will know a lot more.


Ikenna.

I think Ikenna is on the right track, although I would also ask if your MIL is on ?
If on then you may need to run a scan also to know what trouble codes there in your brain box.
Goodluck.

Ikenna351:

Sounds like a relay issue. Am not sure though, since i dont know how the electricals of the car is. But what I would do is to jumper the fuel pump & ignition coil(s) relays while troubleshooting. If the problem persist, then is not a relay issue. But if the problem stops, then you have found the culprit.


If the car has amplifier module/ignition module, swap it with another and see what happens. When an ignition module starts failing, the engine would stall and wont start untill the module becomes cold again. You can as well pour cold water on a cloth, press the cloth on the module for some minutes when the car refuses to start & remove the cloth when the module is cold enough. Restart the car. If it starts, you have found the cause of the wahala. If it dosent, then its something else. Meanwhile, ignition module should be attached close to ignition coil, if the engine has distributor & not the distributorless engine with coil packs.

These are other  possible causes of stall and no start. Siena will know a lot more.


Ikenna.

This is most llikely your problem.[size=13pt] If not this[/size], then check your car battery and alternator.

Informed guess,
If it's not your distributor, it's your crankshaft sensor.
Stop messing with other things till you check those.

If you have any problem, scan the car first before you do anything. Let the car tell you what the problem is other wise its a guess.

If you scan and nothing shows up but you still have same problem the culprit might be the crankshaft position sensor CPK

http://www.ehow.com/list_6006744_crank-position-sensor-symptoms.html or

http://www.ehow.com/about_5903731_camshaft-position-sensor-failure-symptoms.html

One other thing you need to know is if someone messed with your truck while you were way

.

Thank u very much guys.
Someone was actually telling me that it has to do with the relays and advised me to get the car scanned first.
car diagnostic machines are very rare in this town but i am searching for one now.
Ill print all this page b4 the car technician comes because i am sure ill forget most of them when i stand up from here.

NB:Please whats MIL?

it think you guys are taking the search too wide for a start. since this problem is intermittent then im very sure its electronic. basic queries have to be run here. confirm the ignotion coil, supplies voltage form both the ignition end and spark plug end. if it does then that exonerates the brainbox too. one thing you must test too is voltage supply to the nossles for each cylinder and finally this very stubborn man that is usually the case with most strating issues(mr MAF)
had a similar issue wif a car that would start then when you engage power dops and the car goes off. also it would start and wen the engine heats it would stall and die out. i had to cool down to check almost everything and low and behold mr MAF agai.() airflow meter. this goes to most guys that believe the only symptom to bad MAF is black smoke from tail.

miccodb:

it think you guys are taking the search too wide for a start. since this problem is intermittent then im very sure its electronic. basic queries have to be run here. confirm the ignotion coil, supplies voltage form both the ignition end and spark plug end. if it does then that exonerates the brainbox too. one thing you must test too is voltage supply to the nossles for each cylinder and finally this very stubborn man that is usually the case with most strating issues(mr MAF)
had a similar issue wif a car that would start then when you engage power dops and the car goes off. also it would start and wen the engine heats it would stall and die out. i had to cool down to check almost everything and low and behold mr MAF agai.() airflow meter. this goes to most guys that believe the only symptom to bad MAF is black smoke from tail.

So it is possible that the airflow meter could also be a problem.I changed it last year.Is it possible that it could have gone faulty again?

from my years of study in electronic and computer engineering its a fact that any thing electronic isnt failsafe at all. your airflow meter can fail as many times as it likes cos it contains ICs, transducers and other semiconductor components which operate at set condition so if your vehicle violates any of these then we have an issue. if u knew how to use a multi meter or osciloscope then u can test it but ind absence of dat na plug and play testing you go do o!

lest i forget dont forget to update us when u get this issue resolved as this served as a learning point for all of us ere.

I have come to realise that not so many of us here understand how EFI engines work.  A symptom a car is having must not be faulty of a particular component. How do i mean? A car that emits black smoke from exhaust pipe tail can be caused by components other than MAF/AFM. An engine that rough idles & misfires cant be attributed to spark plugs or plug leads failure, other faulty sensors can be the cause.

Now, the best way to diagnose a car, to me, is to start with harmless & cost free diagnosis. Fisrt, when you identify the symptom, then you list components that can cause such symptom, if failed. You start with the ones that wont cost a dime to check. It will be so painfull and wasteful to spend huge money to scan your car, when it wouldnt start. Only for the scan result to point at broken/failed fuse in the fuse box, as the culprit. So if the car stops him on highway, where no life exists, he must get his car scanned before he figures out what is wrong with it?

I would start with eliminations (manual diagnosis) before scanning comes in, if necessary.

CKP, MAF/AFM, CTS,etc.


1. CKP (Crankshaft Position Sensor): Yes. CKP can cause similar symptom: Stall when engine temperature rises to normal operating temperature & and the engine wont start untill it cools. But it will also be having another pronounced symptom. @ poster, if the ckp in that car is failing, the engine and the entire body will be vibrating, i mean, terrible one. If it fails, the distributor wont be getting high volts current from the ignition coil. The sensor, ckp, monitors the position of crankshaft, via holes on frywheel or other sources, and signal to Calculator/Ignition ecu or ecu. The ecu will now use Amplifier module/ignition module to break  the current that comes from coil and the distributor will via rotor distribute the high current to all the spark plugs. CKP is an ignition component/sensor.

2. MAF/AFM (Mass Air Flow sensor/Air Flow meter): The only way MAF will stop a car from starting is if its unplugged or burnt internally. What normally spoils MAF is terrible wrong connection. The Bosch MAF, that I know of, is a Die-cast sensor. A dirty MAF will tell on the fuel economy which you would have noticed. It can easily be cleaned and put back. A failing MAF will always show itself by rough idling the engine & also hinder the fuel economy. You should know if the car is showing such symptoms as well.

3. CTS (Coolant Temperature Sensor): If it starts failing, the engine will hard start when cold or hard start when hot. It can also stall the car and no start when the car is in motion. But it will also tell on the fuel economy; black smoke from exhaust tail will be obvious. My car recently, when engine cold, was having a cold engine hard start & would stall when in motion and wont start after  several attempt. I discussed it with Siena. He suggested that i check the cts. I did this morning. Guess what! He was right. The cts was the culprit. Before, i use to think that cts was just to determine quantity of fuel that goes into the combustion chambers when engine  cold or hot (open & closed loop of the ecu). I never knew it could stop a car from starting or stall when in motion. If not for Siena!

So Poster, the ball is on your court. How you want to play it, is upto you. For me, I would rather ask those that know better than me, diagnose it myself and learn it. Worst case scenario, i purchase the scanning tool and be scanning the car myself than visiting scanning centres every now & then.

Siena, how are my doing?

Ikenna.

The MAF measures airflow volume, and airflow temperature (unless the intake has a separate IAT (Intake Air Temperature) sensor. A dead MAF will not kill an engine, it will overfuel like mad, but it will still run. On turbocharged engines, if there is a boost leak (split intercooler or pipework) the car will not idle. The only way to get home in such cases is to unplug the MAF connector. That way it doesn't detect an air leak.

Components that will prevent non-starting:

01) Faulty Crankshaft Position Sensor (CKP).
02) Faulty Camshaft position sensor (CPS).
03) Faulty Ignition Power Output Stage (POS). Also referred to as Ignition Amplifier.
04) Faulty Ignition Coil (for single coil systems).
05) Faulty Hall Sender in Distributor System.
06) Faulty Coolant temperature Sensor (CTS).

I would rule out injector and ignition coil feed. We're talking component PARTIAL failure, with heat making that failure ABSOLUTE. Most likely culprits are CKP, POS or CPS. These components are all solid state, with no moving parts. They are all made of semi-conductor material, with a tightly-wound inner copper coil. A tiny crack is all it takes, either the outer core, or the copper coil. When it gets hot, it expands, and contact is lost. This is the period of ABSOLUTE failure. This is also one of the reasons it will start when cooled, either naturally or artificially.

It's also worth noting a faulty fuel pump can cause similar issues. The pump is a roller-cell type. The motor seldom fails, but the roller-cells do. They rely on providing pressure by the cells being as close to the housing as possible, without making contact. When this wears, the gap between the roller=cells and the housing gets larger, resulting in pressure drop. This gap increases with heat (expansion). A cold engine has different fuel requirements from a hot one.

Unfortunately a faulty fuel pump will not come up on a scan, a faulty fuel pump trigger however will.

kkmny81:

he removed the fuel pump and tested it but it was okay.

A fuel pump should never be run without being immersed in the tank with fuel, or fitted in-line with its fuel supply. I'm willing to bet your mechanic ran the pump dry with a 12V supply, heard it run, and decided all was okay. Not the right way.

He needs to test the pump for flow, AND pressure. He needs to know how many CC's your pump would return to the tank in 30 seconds, and how much pressure your fuel rail and pressure regulator see with the engine running. The flow test requires the return line (fuel pressure regulator end) is disconnected, and placed in a calliberated jar, with the engine running too. He'll need to know the values for your Infinity, down to the correct year and engine type, as well as the tolerances. Otherwise, he's wasting his time, and yours. I don't need to stress the precautions your mechanic needs to take, when doing the flow test. Fuel vapours are highly explosive.

But of course, a scan is recommended first. He shouldn't clear any fault codes without writing them down first!

@ Siena

Siena, this morning, i checked the continuity of the two cts wires to the Ignition and Injection ECUs, and they where both ok. Then i now pulled out the cts plug, to see if the car would still hard start without the cts plugged. Before i could turn the ignition switch to the last turn, the engine was already running. This was a car that would take more than 15 mins of engine clanking to start. It feels so good when you diagnose and fix your car. It's a pleasant experience.    At least, its now obvious that the cts harness isnt the culprit, but the cts. But when i plugged the cts back and drove off, the car stalled in motion. The injection ecu supplies ground to Injectors and fuel pump relay. So the wrong signal or feedback the injection ecu was getting from the cts made the ecu to cut off the ground it was supplying the FP & Injectors relay.  I bypassed the ground supply wire fron inj ecu & drew ground from negative battery terminal, the car started again and never stalled or went off until i reached my destination. But the engine was still giving sign that the cts was faulty: sluggish movement when slow & the obvious sign - black smoke.

I will have to wait till Saturday, when i will have enough time from work, to go to APO village and look for the cts and replace.

Sorry poster for derailing. But people can still learn from my own situation, since its a similar issue with yours.

Ikenna.

Thanks Miccodb, ikenna and siena.
I will have them check the CPS,CKP and POS manually first b4 they run a scan.
Hopefully i will detect the problem and update u guys accordingly.

But Ikenna could it be the CKP since my car does not vibrate at all.

Who said vibration is as a result of a dead CKP?
[quote][/quote]

Me

Anyway, there was a time the bolt holding the ckp on the bell housing in my car was loosed. So the ckp was dangling as the engine was idling and when the car was in motion, and would stall sometimes. The engine was terribly vibrating, which was also vibrating the entire car. When i was checking all the sensors, i now saw the culprit (loosed ckp on bell housing). In fact, it would have fallen off if i had continued using the car, without checking.

It could be that symptoms differ from vehicles or because mine was only dangling but not failed. My mistake!

Ikenna.

thanks for clarifying.

The guy with the scanner will be here in an hour.
Siena, Do u mean that he should only scan the car when the problem has ocurred.that is when the car fails to start?

kkmny81:

thanks for clarifying.

The guy with the scanner will be here in an hour.
Siena, Do u mean that he should only scan the car when the problem has ocurred.that is when the car fails to start?

Apart from whatever the scanner man will tell you endeavour to post the trouble codes here if any.

hello All,
I did the scan on saturday and the codes were:
P1320- ignition signal primary
P0141-02 sensor heater circuit malfunction.
The car guy said the P1320 was the major trouble code. He is suggesting that the distributor is faulty.
what do u guys think.