# Weird idle problem, 95 Nissan truck



## zootal (Sep 27, 2007)

1995 Nissan truck, 4 cyl. I've been fighting a weird idle problem, where the idle is rough and it dies. Slightly off-idle is rough, but any more than that and it runs great. Great power. Great mileage.

After working on it a bit, I realized that this only happens with the air filter in place. If I remove the air filter, it runs fine. The air filter is clean. Brand new. Nothing wrong with the air filter. I can only guess that the slight air flow restriction is enough to trigger some sensor somewhere. And at this point I don't have a clue. Suggestions welcome!


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## rogoman (Dec 16, 2004)

zootal said:


> 1995 Nissan truck, 4 cyl. I've been fighting a weird idle problem, where the idle is rough and it dies. Slightly off-idle is rough, but any more than that and it runs great. Great power. Great mileage.
> 
> After working on it a bit, I realized that this only happens with the air filter in place. If I remove the air filter, it runs fine. The air filter is clean. Brand new. Nothing wrong with the air filter. I can only guess that the slight air flow restriction is enough to trigger some sensor somewhere. And at this point I don't have a clue. Suggestions welcome!


There could be a problem with the MAF; try cleaning it. Use only ELECTRICAL CONTACT CLEANER or a cleaner specifically made for MAF hot wire cleaning. This is the only thing you should use to clean your MAF. No windex, no carb cleaner, no brake cleaner, no rubbing alcohol, and no Q-Tips.


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## jp2code (Jun 2, 2011)

It sounds like someone adjusted the Ignition Timing with the air-filter off the truck.

If you have an Ignition Timing Light, you should check that your timing is at 10°.

If that doesn't work, download the 1990 Service Manual and look through things in Step 5 below, EC-205:

1990 Service Manual:

```
https://www.********.com/service-manual?fsm=Hardbody%2Fd21_truck_1990.pdf
```
NOTE: This site is funny and treats the competition like a reserved word. So, in the link above, replace the asterisks with:

```
n i c o c l u b
```
 (without the spaces).


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## zootal (Sep 27, 2007)

I didn't think you could adjust timing on a 1995 model??? I've owned the truck for 24 years, and the timing has never been touched. I will check it, though...if possible...


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## jp2code (Jun 2, 2011)

You will need a timing light. I got this one a few years ago for mine:



https://www.amazon.com/gp/product/B000EVYH72



There are plenty of others to choose from. You might even find a used one somewhere.

Connect the cables to the battery, clip the induction coil around the #1 Spark Plug Wire, crank the engine, and fire the light at the crankshaft.

If the little blip is not at the 10° mark, you will need to loosen the distributor and twist it one way or the other to get it back to the correct timing.

This is for the V6, but the procedure is the same for the KA24e:


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## zootal (Sep 27, 2007)

Well sadly, my timing light no longer works. Not surprised, I haven't used it in 20 years. I find if I just put two fingers over the air intake, it stalls - not even half covering it - just enough to obstruct the airflow a bit. That should not cause any problems at all. Kinda points to MAF problem, as what is there that would be effected by oh-so-sligh air flow obstruction? I won't deny the timing needs checking, but I'm about 99.5% it isn't a timing problem. I removed the MAF. It looks clean, but I can't really tell just by looking at it. Delicate little thing, isn't it? Is it worth replacing? I seem to recall a lot of complaining about the poor quality of after market MAFs.


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## rogoman (Dec 16, 2004)

zootal said:


> Well sadly, my timing light no longer works. Not surprised, I haven't used it in 20 years. I find if I just put two fingers over the air intake, it stalls - not even half covering it - just enough to obstruct the airflow a bit. That should not cause any problems at all. Kinda points to MAF problem, as what is there that would be effected by oh-so-sligh air flow obstruction? I won't deny the timing needs checking, but I'm about 99.5% it isn't a timing problem. I removed the MAF. It looks clean, but I can't really tell just by looking at it. Delicate little thing, isn't it? Is it worth replacing? I seem to recall a lot of complaining about the poor quality of after market MAFs.





zootal said:


> Well sadly, my timing light no longer works. Not surprised, I haven't used it in 20 years. I find if I just put two fingers over the air intake, it stalls - not even half covering it - just enough to obstruct the airflow a bit. That should not cause any problems at all. Kinda points to MAF problem, as what is there that would be effected by oh-so-sligh air flow obstruction? I won't deny the timing needs checking, but I'm about 99.5% it isn't a timing problem. I removed the MAF. It looks clean, but I can't really tell just by looking at it. Delicate little thing, isn't it? Is it worth replacing? I seem to recall a lot of complaining about the poor quality of after market MAFs.


You can try something real simple. Fully warm up the engine; now let it idle; disconnect the MAF electrical harness connector. Remove the air filter and note the idle conditions. Now install the air filter and note any change in the idle conditions.


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## zootal (Sep 27, 2007)

rogoman said:


> You can try something real simple. Fully warm up the engine; now let it idle; disconnect the MAF electrical harness connector. Remove the air filter and note the idle conditions. Now install the air filter and note any change in the idle conditions.


I didn't think it would run without the MAF? I'm in the process of getting some MAf cleaner (over priced electrical contact cleaner). I'll clean it and put it back in and do what you suggest. If the problem does not occur with the MAF dissconnected, would that indicate the MAF is defective? 

More specifically, if cleaning the MAF doesn't help and the problem does not occur with the MAF disconnected, is that enough to replace the MAF and see if fixes the problem?


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## jp2code (Jun 2, 2011)

zootal said:


> I didn't think it would run without the MAF? I'm in the process of getting some MAf cleaner (over priced electrical contact cleaner). I'll clean it and put it back in and do what you suggest. If the problem does not occur with the MAF dissconnected, would that indicate the MAF is defective?
> 
> More specifically, if cleaning the MAF doesn't help and the problem does not occur with the MAF disconnected, is that enough to replace the MAF and see if fixes the problem?


It should idle OK with the MAF disconnected, but the ECU will go into Fail-Safe Mode (limp mode) at 2500 RPM with it disconnected.

If you disconnect the MAF at idle and the engine runs better, you know the MAF is bad. Weird way to look at it, but it works.


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## zootal (Sep 27, 2007)

Disconnect MAF. It idles great. I can plug 80% of the air intake, and nothiing changes. I got some MAF cleaner and cleaned it thoroughly. Plug in MAF. Start engine. Back to the same problem - if I just put two fingers over the air intake, restricting the airflow every so slightly, the engine stalls. So I guess now I go find a MAF.... is it worth buying it from Nissan assuming they still have them? Or are the $50 units on Amazon good enough?


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## rogoman (Dec 16, 2004)

zootal said:


> Disconnect MAF. It idles great. I can plug 80% of the air intake, and nothiing changes. I got some MAF cleaner and cleaned it thoroughly. Plug in MAF. Start engine. Back to the same problem - if I just put two fingers over the air intake, restricting the airflow every so slightly, the engine stalls. So I guess now I go find a MAF.... is it worth buying it from Nissan assuming they still have them? Or are the $50 units on Amazon good enough?


I don't believe Nissan dealers stock them any more but you can ask them if they have re-man MAFs. Some of the ones on Amazon are OK. You don't need to replace the entire MAF; just the sensor only that bolts on; you can get them at RockAuto.com:






1995 NISSAN PICKUP 2.4L L4 Mass Air Flow (MAF) Sensor | RockAuto


RockAuto ships auto parts and body parts from over 300 manufacturers to customers' doors worldwide, all at warehouse prices. Easy to use parts catalog.



www.rockauto.com


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## jp2code (Jun 2, 2011)

You could also have corroded connections for the MAF or a wire that has finally broken into. Check the continuity for all connections to the sensor as well as checking the sensor.

Usually the only way that the sensor goes bad is if the wire breaks. That won't happen unless you break it yourself.


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## zanegrey (Dec 5, 2005)

make sure bat is charged and alt is working correctly 
clean and service fusible links.

but mostly to me it sounds like the pcv is not working correctly...


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## zootal (Sep 27, 2007)

zanegrey said:


> make sure bat is charged and alt is working correctly
> clean and service fusible links.
> 
> but mostly to me it sounds like the pcv is not working correctly...


I replaced the PVC valve. Sadly, it made no difference. I can't believe where they put the pcv valve on these things! Battery is new, alt works. This is definitely related to MAF/air flow. If I put just two fingers over the intake at idle, it dies. If I unplug the MAF, I can obstruct half of the intake at idle, and it makes no change. The MAF is sensing the subtle change of airflow, and that somehow causes it to die. I have a new MAF on order, should get it in a few days. I hope that is the problem cause I'm going to be stumped if it doesn't fix it.


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## zanegrey (Dec 5, 2005)

ok..well if you have trouble finding one . i should still have mafs for that truck.


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## zootal (Sep 27, 2007)

So many hours later and much $$, I think it is time to retire this truck. I've traced wiring all over, checked grounds, replaced the maf twice. At this point everything points to the control unit under the seat as being bad, but I've been down that rabbit hole with a different car and I'm not doing it again. I have found reports of others with the exact same symptoms, and they were not able to fix it either. Thanks everyone for your help.


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## Greenbeanhardbody (4 mo ago)

Did you ever figure this out? Mine is doing the same thing.


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## domnickjerron (6 mo ago)

the ECU will go into Fail-Safe Mode (limp mode) at 2500 RPM with it disconnected.
Speed Test​


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