Hard/rough Start

[A1218]

I have previously had a rough hard start a few months ago that occurred after driving and then restarting the engine within a half hour to hour. The engine would hard start and rpms rise roughly for a few seconds then stabilize. No drivability issues at all.

I added a can of bg44k and it went away. That was around March.

Now I noticed the same issue arise occasionally again. And now the issue also shows up if you start the vehicle after not being driven a couple hours, shut it off and then restart again within a few minutes.

I don’t have any codes. I’m running another can of bg44k in right now.

I have a feeling the injectors are leaking down. But wanted to get any other ideas and what else I can do. The three outer injectors are easy to replace but the three under the plenum are the issue. Especially to get the egr off to get off the plenum and the bolts on the plenum itself tend to seize.

Should I just try replacing the three outer injectors?

[mdmellott]

Do you still have that Viper remote starter installed which was making your engine shut down?

[A1218]

Yeah I still have it in the vehicle.

The random shut downs happened when I used the key takeover feature.

I had that disabled, so If the vehicle is ever remote started now and I open doors it shuts down and I restart with key. I only use the remote starter in winter time.

Do you think it’s related?

[mdmellott]

Do you think it’s related?

I don't know. Anything that was messing with your ignition to begin with could still be an issue. Before you think anymore about the injectors possibly being the cause, test the fuel pressure to see if it holds as it should when the engine is off so that you are sure about the injectors being an issue or not. This test requires a special pressure gauge. See page EC-25 of the FSM https://www.nicoclub.com/service-manual ... 997/ec.pdf You mentioned that you do not have a DTC being flagged so I assume you figured out and fixed that EVAP system leak that had plagued you for a couple of years.

[A1218]

I was told it could possibly be the ignition switch. Maybe a bad contact inside that could be causing the rough hard start and stalling.

I didn't get around to doing the fuel pressure check yet, but today I drove vehicle and started perfectly in morning. Restarted about an 45 min later and drove again with no problems starting or driving. Went to go out a few hours later and it started, but then immediately cut off as if you took out the key.

Restarted it and it hard started and was rough for a second.

Maybe it is the ignition switch causing this, and the stalling while driving after using the remote start?

[mdmellott]

I have previously had a rough hard start ....
I don’t have any codes.
I’m running another can of bg44k in right now.

What exactly do you mean by "hard start" and "rough start"?
Did you discover the cause and fix the P1441 EVAP system leak trouble code?
The fuel system cleaner you are using could help a dirty fuel system and you mentioned that it did help but then the problems came back. When was the last time you changed the fuel filter?
That Viper remote starter system you have installed is still suspect in my opinion. It does not function as it should so there is an obvious incompatibility with some aspect of your ignition system. Remove it to eliminate this suspect variable to be sure the issue you are having is or is not a self-inflicted problem.
You may have more than one issue going on at the same time. You have already identified an EVAP leak, a dirty fuel system that a cleaner helps temporarily, and ignition problems that your Viper remote system affects.

[A1218]

It cranks a few times more to start. And sometimes when it starts it’s rough for a second or two.

I changed fuel filter last year when I did a big service.

As for the evap leak that was from the small rubber hoses on the bypass cut valve.

I know many Pathfinders with the remote start who didn’t have this issue. So I don’t think it has to do with it not being compatible with Nissan system.

What a few other remote start installers and my Nissan mechanic I go to for major jobs recommended it could be the ignition switch. Because when you do the key takeover and just move the key to the run position it probably doesn’t make proper contact as if you were to crank the engine if it’s off.

I had another switch from some old steering parts I had bought several years ago. I switched it out to see.

They all say and the company also that it is impossible for the viper system to take over and override the key shutting it off.

But who knows. If it happens again I will take it out like you said.

Thanks for the help. I appreciate it

[rgk]

Do you have a scan tool that will show real-time data? I'm curious what the ECU thinks the coolant temp is.

[A1218]

Yeah I do have one

[A1218]

Temp on start up or when warm?

[rgk]

Both, but the idea is that the coolant temp sensor has gone bad and is reading the incorrect temp when warm. The ECU would then send the incorrect volume of fuel to the cylinder. Same goes for idle air temp sensor and MAF sensor. Look up the specs for those sensors in the FSM.

[A1218]

Got it, I’m gonna check that out. That’s the Engine coolant temp sensor correct. Because I know theres two of them there. It’s relatively inexpensive about 29 for the NTK and 40 for dealers.

The MAF sensor was replaced two years ago with Hitachi.

And are you referring to the idle air control valve? Or the air temp sensor. The FSM says the air temp sensor is only used for diagnostics.

The idle air control valve was never replaced. I know when the a/c is turned on the Rpms initially drop slightly then rise to accommodate it. So that seems to be working. What confuses me about it though is that there is a flutter when letting off gas at 50mph with the a/c between 1500 and 1700rpms. If I take the a/c off while it does it, it stops.

[A1218]

So a cold start after several hours not driving the ECT read 124 degrees. After warmed up 191 degrees.

[A1218]

So, the issue with the rough, slow startup happened twice yesterday with the engine failing to start once. Check light came on.

I got the code P0135 O2 Heater Circut Bank 1, Sensor 1.

[mdmellott]

Since your ECU ignores the O2 sensor outputs at start-up, this trouble code is not the problem but it is a symptom. Even if the O2 sensor heater has actually failed, that will not cause an issue with start-up performance. Heavy carbon build-up on the sensor will thermally insulate it and delay the response time expected by the ECU for the O2 sensor to reach operational temperature which will trigger the same trouble code as well. We need more data to begin isolating the root cause of the problem. To begin this diagnosis, fuel trim readings from bank 1 and bank 2 are required. While the engine is running, can your scan tool read the long term fuel trim (LTFT) and short term fuel trim (STFT) on bank 1 and bank 2? Real time data capture functionality of the scan tool will be most useful to fully diagnose the problem. Freeze frame data capture at the time the DTC was triggered will be helpful as well. If your scan tool has both real time data and freeze frame data reading capability, what are the LTFT and STFT readings. If your tool only has freeze frame data that was captured at the time the DTC was triggered, those readings of LTFT and STFT will still be helpful. The readings will be indicated as + and/or - percentages which will give us a starting point to narrow down the possible cause of the problem you are having.

[A1218]

When the vehicle is warmed up, the fuel trims are:

SHRTFT1: -0.8%
LONGFT1: 9.4%
SHRTFT2: -4.7%
LONGFT2: 7.0%

When vehicle was first started, not fully cold but sat for 2 hours

SHRTFT1: -4.7%
LONGFT1: 9.4%
SHRTFT2: -3.9%
LONGFT2: 7.0%

[mdmellott]

When the vehicle is warmed up, the fuel trims are:
SHRTFT1: -0.8%
LONGFT1: 9.4%
SHRTFT2: -4.7%
LONGFT2: 7.0%
When vehicle was first started, not fully cold but sat for 2 hours
SHRTFT1: -4.7%
LONGFT1: 9.4%
SHRTFT2: -3.9%
LONGFT2: 7.0%

Those are actually not terrible numbers. STFT at 0% would be perfect but within 5% is nothing to be concerned with as the STFT is an immediate response to constant variable inputs so this number is always fluctuating. LTFT is a learned response to STFT so it should be more consistent, as it is in your case, and within 10% is typically nothing to be concerned with either as long as both banks are relatively equal, within 5% of each other. In your case, a fairly acceptable lean condition exists so your ECU is adding 7 to 9.4% more fuel to compensate in order to balance the air/fuel mix ratio at 14.7:1. Most vehicles will not trigger any DTC for a lean or a rich condition until the readings are around +or- 20-25%. At this point, I would rule out everything in your fuel system and your air intake and vacuum systems as being the cause of your problem. That brings me back to looking for something wrong with the ignition system. The first and easiest thing I would test is the output voltage of the alternator, which should measure about 14V at the battery while the engine is running. If that's looking good and given there are no other DTCs to make me think about problem coils or other electrical component failures, there may be some issue with your ignition switch as you mentioned or the Viper system install as I was suspecting.

[A1218]

The STFT did eventually get to 0. Thanks for helping me rule out fuel problems.

I changed the ignition switch with an original Nissan one and it didn't help with the hesitation aspect on startup. As for the viper issue where it was shutting down while driving after key takeover, that seemed to have went away so far after changing the switch. Went for several drives to test it out and no shutdown. Ill wait more before I finally put that issue to rest.

The startup issue however is very inconsistent. Ill check out the alternator and see if thats the problem. Yesterday I drove it several times with no problems starting. In the evening after sitting few hours I started and it shut off after hesitating. Restarted it and the idle hesitated again then normal after two seconds.

The distributor is new also, so guess I'll have to do some more investigating.

I ordered an ECT Sensor also to replace.

Appreciate your help!

[mdmellott]

The distributor is new also, so guess I'll have to do some more investigating.

I had forgotten for a moment that you have a '97 Pathfinder. Check the condition of the ignition wires and coil as well to be sure the resistance measurements are within spec even though I assume you may have replaced those too when you replaced the distributor. More importantly, double check the ignition timing to be sure the distributor has not some how been clocked to retard or advance the timing. Remembering now that you have a very different ignition set-up than mine, I can't help but wonder how your timing was set to begin with when your distributor was replaced. The timing should be set at 15deg BTDC but first the engine has to be warmed up to normal operating temperature and then shut off so that the PCM control of the timing can be disabled before the timing can be checked or adjusted. I'm also scratching my head wondering if perhaps the Viper system cuts battery power to the PCM when the engine is turned off because doing that would cause stored operating parameters in the PCM to be lost which in turn would cause the engine to run rough for a period of time while the PCM relearns the information after you start it up again. I'm just wondering but maybe I'm wandering too far away from what's happening.

[A1218]

Yep I did change the leads also. Used NGKs.

If it was resting the PCM though wouldn’t the monitors read incomplete? They’re all ready.

[mdmellott]

If it was resting the PCM though wouldn’t the monitors read incomplete? They’re all ready.

You're probably right. I know it can take up to 24hrs with the battery disconnected to clear those readiness test data. The same is probably true for learned operational data as well, like LTFT. I have no idea how the Viper system is wired up with its complexity of harnesses and added components tapped into the ignition and ECM. I was just wondering if that could be a factor.

[A1218]

Same here, I dont know how they're wired.

Just hope I eventually find the issue, before it turns into something worse.

I appreciate your time and effort into helping out though.