# D21 runs poorly once warmed up



## adtsoft (Jun 16, 2009)

I am having a problem with my 94 Nissan D21 Pickup with a VG30E engine. Once it is warmed up to normal operational temperature it hesitates, sputters, backfires and acts like it is going to stall any time I give it gas. The only way to accelerate is to press ever so lightly on the gas. It has no power and it has a hard time getting up to 10mph. I have to pull off the side of the road to allow people to pass. I was actually passed by a bicyclist the other day. While warming up the truck runs perfectly and can easily accelerate up to 60+ without any problems. Also, the problem has gotten progressively worse over the past two weeks. After heated up it sounds / smells like it is running rich. Unless I am doing it wong, I am not getting any codes from the computer. Any ideas on what to check/replace?

So far I have replaced:
Spark Plugs
Spark Wires
Distributer Cap
Rotor
Ignition Coil
Cleaned air filter (K&N)
Cleaned MAF sensor
PCV Valve
Oxygen Sensor
Removed Catalytic converter to test for clogging


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## adtsoft (Jun 16, 2009)

*Coolant temperature sensor*

I also replaced the coolant temperature sensor today and it is behaving the same way. Please help!


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## 4X4D21 (Mar 9, 2009)

maybe when you replaced the distributor and rotor you decreased the timing without knowing it.


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## adtsoft (Jun 16, 2009)

I only went as far as opening up the cover to the crank angle sensor to make sure that it wasn't fouled with oil (it was clean). I only changed the rotor / cap / wires and plugs. I didn't change the entire distributer. I doubt that I rotated the distributer changing the timing. It runs great until it is warm, then nothing for power. Also, I was having this problem before I worked on anything.


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## brookwood61 (Aug 18, 2005)

Could be a dirty gas tank, or the fuel pump going out.If you can, check your pressure, and the fuel flow.
Good Luck


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## zanegrey (Dec 5, 2005)

read the codes...


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## adtsoft (Jun 16, 2009)

The fuel pressure and volume are both good. I checked the timing and found that I am missing sparks erratically. So instead of a steady tick-tick-tick of the timing light I get tick-tick-tick-nothing-tick-tick-nothing, etc. Completely random on the misses. The guys at Checker Auto were nice enough to let me test a new Ignition Control Module on it with the same simptoms. I am thinking it is either the Crank Angle Sensor or the computer itself. I am leaning toward the CAS since it started mild and got increasingly worse and the computer is in the cooler cab. This weekend I am going to pull the CAS and do some electrical tests on it. From my understanding I should be able to supply it 12v and with a volt meter see voltage pulses coming out of it when I turn the slotted plate for both the 120 degree and 360 degree slits. Does anyone know what voltage I should see? It may also be a current issue and not be delivering enough. I am open to any and all ideas.

Thanks


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## zanegrey (Dec 5, 2005)

if those slits are blocked or dirty the opti sensor will not get the signal and not send a spark..


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## adtsoft (Jun 16, 2009)

It was the Crank Angle Sensor. It is now fixed and I didn't have to replace it! :woowoo: :givebeer:

I tested the Crank Angle Sensor on the truck with it running. Here is how I did it. I tested the voltage to check the output and compared it to running good vs running bad. Using a volt meter is crude compared to an ocilliscope, but it worked to isolate the problem. Here is how I did it. The Crank Angle Sensor has four leads. It receives 12v and two 5v signals from the computer that it grounds to indicate each degree and also on a seperate lead to indicate the three 120 degree marks.

GND
12V
5V – 1 degree sensor
5V – 120 degree sensor

Cold (Sparks are consistent even when revving)
Off: Both 5V
Run: 0.4 / 3.6V
Rev: Same

Warm (Exhibiting symptoms)
Off: Both 5V
Run: 0.4 / 4.1V and continuing to climb
Rev: 0.4 / 4.3V 

After Super Chill of CAS (engine still warm only off for 5 min)
I used caned air upside down so that I could get a freezing liquid spray. Probably not an advisable thing to do.
Off: Both 5V
Run: 0.4 / 3.6V
Rev: Same
Symptoms have gone away!

I allowed the sensor to heat back up. Voltages are holding steady and the symptoms are gone. I let it run for an hour and also took a trip to Checker at 50mph. I must have cleaned the optics. It always looked clean with no slits blocked and I previously cleaned it with MAF cleaner. If it acts up again I will look for a more appropriate cleaner. If that doesn't work I will replace it. Thanks, I hope this helps the next person with a similar problem!


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## zanegrey (Dec 5, 2005)

so you fixed all on your own with no help from any one else??

cough cough..


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## adtsoft (Jun 16, 2009)

Well, zanegrey you told me to clean it. Cleaning it was the first thing I tried. I used MAF cleaner but it didn't work. I am suprised that the canned air (as a liquid upside down) cleaned it since it isn't a solvent. Or maybe it is a solvent, the can doesn't say what the chemical is. Do you or anyone know of a cleaner that would be recommended?


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## CMax03 (Jan 17, 2009)

Bad EGR valve! Turns into an air leak...disconnect the vacuum line @ the EGR valve vacuum canister and plug......problem will go away!


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