Help!

[Steve Taylor]

Hi all, I am new here and am having some serious trouble with my 95 Maxima. It had been starting rough for about two weeks (i.e having to give it gas to get it to start) and then one day I had real hard time starting and my check engine light came on. I followed the procedure to pull the code out of the PCM and actually got two codes 1. Knock sensor and 2. Crankshaft sensor (REF). I was intending to check out both sensors but before I got a chance two mornings ago I went out and started her up and it immediately stalled after starting. After that it would not do anything...not even crank. I checked to see if I now had anymore codes but did not. I checked both sensors and it appears the knock sensor is bad but the crank sensor is not. Could the knock sensor being bad cause my PCM to disallow ignition? I'm just not sure which direction to go from here and would appreciate any help that any of you folks might be able to offer. Thanks in advance, Steve.

[maxhopper]

Welcome to NICO.

The knock sensor will not prevent the engine from running, but a bad crank sensor will.

[Steve Taylor]

Thanks for the welcome. The problem I have is that when I check my crank sensor, it checks out good ( about 450 ohms) so that leads me to believe I may have an actual problem that was causing that sensor to go off. I will probably check out the starter solenoid and motor today and see what I find.

[loystock]

Per FSM, the spec for the Crankshaft sensor (CKPS) resistance is 520+/-50 ohms. So 450 ohms is below the lower limit of 470 ohms. Also check the sensor harness/connector to the ECM is good.

Ensure the battery connection is clean and tight and that the battery voltage with engine off is 12.5VDC or higher. Another cause of starting problem is the main engine harness ground points (top of engine, besides intake plenum, near cylinder #2). Make sure they are clean.

Also check if during starting, you are getting the start signal to the starter solenoid thru the single-wire connector of the starter. Another possibility is problem with fuel delivery. But right now, it seems that the CKPS is bad.

A bad KS will set a fault code but will not turn on the CEL. Also, engine run will be rough in the lower range but it should not prevent engine starting. Replacing the KS may be difficult, depending of tools available to you. Refer to the FAQ 'sticky' in this forum. Also. you can view the YouTube video (2 parts) courtesy of "boredmder."

http://www.youtube.com/watch?v=R2ntaxi7bXk

http://www.youtube.com/watch?v=fPIMOIwLISc

[Steve Taylor]

Per FSM, the spec for the Crankshaft sensor (CKPS) resistance is 520+/-50 ohms. So 450 ohms is below the lower limit of 470 ohms. Also check the sensor harness/connector to the ECM is good.

It also states that the temperature is a fctor saying that it should be 68deg. It was definitely colder in my garage when I was doing the check and I'm not sure if this would make the resistance lower or higher.

Ensure the battery connection is clean and tight and that the battery voltage with engine off is 12.5VDC or higher. Another cause of starting problem is the main engine harness ground points (top of engine, besides intake plenum, near cylinder #2). Make sure they are clean.

I did check, clean and tighten the battery connections, as well as checked the voltage so that's all good. I have not checked the main engine harness and will definitely do that.

Also check if during starting, you are getting the start signal to the starter solenoid thru the single-wire connector of the starter. Another possibility is problem with fuel delivery. But right now, it seems that the CKPS is bad.

I am going to check the starter solenoid today. I hope it is only the CKPS, that would at least be something I could fix myself.

A bad KS will set a fault code but will not turn on the CEL. Also, engine run will be rough in the lower range but it should not prevent engine starting. Replacing the KS may be difficult, depending of tools available to you. Refer to the FAQ 'sticky' in this forum. Also. you can view the YouTube video (2 parts) courtesy of "boredmder."

The book I am referencing says to pull the upper and lower intake manifold (ugh!) , but it looks like with the proper extention I should be able to reach it......it's wrth a try I suppose. Thanks for the advice, I really appreciate it, Steve.

[loystock]

The CKPS has copper wire wound around a magnet to pick up crankshaft position. Copper has PTC ( Positive Temperature Coefficient) of resistance so actual value may drop at lower temp, but not much.

Several members in this forum have already replaced the KS without taking out the manifold. A small hand (have children?) may be of help during installation. Buy OEM KS or something that's reliable. There are some replacement KS available from eBay but avoid the cheap ones.

[Steve Taylor]

The CKPS has copper wire wound around a magnet to pick up crankshaft position. Copper has PTC ( Positive Temperature Coefficient) of resistance so actual value may drop at lower temp, but not much.

Ok that makes sense, I just got back in from checking it again and it is at 496 ohms so I am not sure it is bad. I also looked at the wiring harness and didn't see anything obvious...I'm assuming it goes directly back to the "brain" right? Maybe I actually have something wrong the sensor is picking up?! Several members in this forum have already replaced the KS without taking out the manifold. A small hand (have children?) may be of help during installation. Buy OEM KS or something that's reliable. There are some replacement KS available from eBay but avoid the cheap ones.

Yeah I've got some kiddos that could probably help me with that....my primary objective right now is to get the thing running though. Quick question; what kind of signal should I see at the single wire on my starter solenoid when I turn the key? I'm assuming it will be some sort of low DC voltage signal I.E 5 volts or something. Anyway just came in to grab one of the kids so they could turn the key for me when I check voltages. Thanks for the help, Steve.

[Steve Taylor]

Ok,I just got back in and here's what I found:

I have voltage on the B connection coming straight off the batt. (roughly 12.5 volts), when my daughter turns the ignition on I can here an audible sound coming from the starter assembly and I have about 11 VDC on the single signal wire and about 11.5 VDC on the S connection of the solenoid. So......it appears the solenoid is getting a signal and closing but my starter motor is not rotating........bad starter motor? Local parts store says they have it in stock for 119 bucks or I could go rip one out at the junkyard for quite a bit cheaper I would imagine. Sound like I am on the right track?

[loystock]

It's not difficult to remove the starter - just 2 bolts and of course the electrical connectors. If you are mechanically inclined, you can dis-assemble the starter. You may have a 'sticky' or gummed up starter. Just put alignment markings so it will be a lot easier to put them back.The front end is the mechanical side - clean them thoroughly and then apply a liberal amount of white lithium grease. The rear end is the rotor and stator assembly. This section may be gummed up. Clean them Contact Cleaner. Check the condition of the brush and the operation of the starter solenoid (Positive (+) on the single-wire connector and Negative (-) on the starter frame). Gear should extend when power is applied.

With the starter removed, you can check it yourself or go to AutoZone for a free testing. If confirmed bad, you call whether to get replacement from junk yard or buy new/refurbished one.

[Steve Taylor]

It's not difficult to remove the starter - just 2 bolts and of course the electrical connectors. If you are mechanically inclined, you can dis-assemble the starter. You may have a 'sticky' or gummed up starter. Just put alignment markings so it will be a lot easier to put them back.The front end is the mechanical side - clean them thoroughly and then apply a liberal amount of white lithium grease. The rear end is the rotor and stator assembly. This section may be gummed up. Clean them Contact Cleaner. Check the condition of the brush and the operation of the starter solenoid (Positive (+) on the single-wire connector and Negative (-) on the starter frame). Gear should extend when power is applied.

So you think it's the starter? Does the signal voltage sound right? It would be nice if I could get away with just cleaning it as opposed to having to but one.

With the starter removed, you can check it yourself or go to AutoZone for a free testing. If confirmed bad, you call whether to get replacement from junk yard or buy new/refurbished one.

I'll probably have them test it. I'm not sure I would trust one out of a junkyard, I would probably spend the money to get one I know was good. Thanks for all the help, Steve.

[loystock]

The fact that you are getting close to Battery voltage on the test points and that the starter solenoid is energizing means the starter motor-side is not working.

[maxhopper]

You could always try smacking the starter with a hammer, then see if it works. You can usually get 1 or 2 starts out of it that way.

[Steve Taylor]

Well, I took my starter down to the parts store to have it bench checked and it checked out good!?!? I guess that is good news to some extent but it also means that I am back to square one I did have a friend at work who owns a 98 Maxima and had the same problem as I'm having. He took his starter to the store to have it checked and they told him it was good....well after two days of further troubleshooting he bought a new starter anyway and put it in......and low and behold it worked. He seems to think that because the tester didn't really put a load on the starter the folks at the parts store thought it was good but in fact it wasn't. I really don't relish the thought of buying a starter only to find out that isn't the problem but I'm not sure what else to do at this point. I appreciate any input anybody might have, thanks, Steve.

[Steve Taylor]

Ok, quick update: I put the car back together and low and behold.......it starts! I think the starter might have been gummed up and putting it on the test bench and spinning it at the auto parts store freed it up. I'm pretty sure I still need a new starter though because it makes a gruinding noise every time I start it. At least now I can be sure what the problem was though. Thanks again for all the input, Steve.

[loystock]

In both I30s that I have, I was able to 'recycle' both starters by cleaning them up, both mechanical and electrical side. A 'sticky' start may not engage properly or remains engaged briefly after the engine has started.

[Steve Taylor]

Whay exactly did you use to clean it up? This would be alot better option than buying a new one. Thanks, Steve.

[loystock]

Before starter dis-assembly, put alignment marks so re-assembly will be easier. For the front end, mechanical portion (pinion gear and planetary gears), use carb cleaner for cleaning, let it dry and then apply a liberal amount of White Lithium Grease. For the rear end, rotor and stator, use contact cleaner to remove dirt and gunk and just let it dry. After re-assembly, check the starter extension (use the starter frame as ground) and then the actual starter operation.

[Steve Taylor]

Thanks loystock, I cleaned it up and it seems to be working real well.......that's the good news........now for the bad news.........I am still getting an engine light for the knock sensor and the crankshaft pos sensor (REF) Also I stopped at the store on the way home tonight and when I came back out and started the car up I noticed it was running a little rough. When I got home I pulled my codes again and I had yet another one ( Intake Air Temp sensor ) which since it helps the PCM to fine tune the fuel metering, I'm assuming this could be the culprit as far as the engine running rough is concerned.....does that sound right? Anyway I checked the incoming voltage and I have about 4.75 VDC which I think is about right. I also checked the resistance but as it varies with differing temp I guess I better put a thermometer near the sensor when I do it to be sure. Anyway this car is really begining to discourage me Thanks for all of the help thus far, I really appreciate it, Steve.

[loystock]

I think your problem is still with the Knock Sensor and Crankshaft Position Sensor. The Air Intake Temperature Sensor is primarily used for diagnostic and is not used by ECM for engine control.

For the age of you car, a failing KS is not unusual. To confirm it, you can install a 550K ohm resistor (The Shack?) in place of the KS. If the KS code goes away, then you are positive that the KS is bad. A failing Crankshaft sensor may be problematic and may even prevent you from starting the car. Once those problems are fixed, they you can look into the Air Intake Temp Sensor problem.