Yeah I thought about this too, I'll test this

 

Another no start day. Its about 33 degrees here. Motor cranks easy, have TAC bounce, starter turned over decently. Heard a few pops from the motor but no start. Almost like a few cylinders fired but not all of them. I jumped the fuel pump and verified fuel at the rail, I'm temped to do a complete tune up but past experience tells me this is wasting money. Out of ideas....

 

Is the starter motor cranking the motor too slowly for the motor to start?

Or is the starter motor cranking the motor fast enough, but the motor just isn't starting?

 

When my car was in Virginia sitting in my wife's driveway, the oil made a significant difference. With 20W-50 synthetic the car turned over slowly and the oil pressure alarm light stayed on for 5 seconds. The weather was about 25 degrees and the car still started. I switched to 5W-30 synthetic and it turned over much more freely and the alarm light only blinks when starting.

The car is back in Seattle now with fresh 5W-30 synthetic. It does not get cold or hot in Seattle and I am using the car temporarily as a daily driver until my other car arrives from overseas. In 40 degree weather, the car seems to like 5W-30. I am not pushing the car very hard and the temperature never goes above the quarter mark.

 

Its a little of both. I get a strong pumping action and every few pumps it seem to slow or struggle, Like a hesitation. It seems like it cranked fast enough for ignition though, I think its when a cylinder fires but the next one in line misses and causes it to miss a beat. What's strange is as soon as it gets into the 40s there's no issue.

 

Check the connection to the DME temperature sensor, namely the plug and wires to the sensor. Check for continuity. I had corrosion on my plug contacts and it did the same thing when car was cold. All I had to do was to wiggle the connector/wires and the car would fire right up.

 

+1 I'd check the sensor itself too. See clarks for values and procedure.

If the car starts to crank and then feel like it's kicking back, then I'd look at your speed and ref sensor wiring too. They updated the mount for those sensors to reduce electrical interference. Do you know if you have the updated mount with built-in shield? The theory goes that electrical interference can cause phantom ref sensor tirggers and throw the DME out of whack. Sloppy wiring, with alternator and battery cables too close to the speed and ref sensor wires can also cause this.

 

Do recognize if the engine is cranking too slow, when the cylinder fires, you may get push back. There has to be enough rotational inertia (speed) to carry the combustion stroke forward.

All the comments are valid places to look. And weak cranking; battery or starter will look like other issues.

Go for the oil change.

And you may want to pull one spark plug and see if you have gas fouling (soot) from these start issues.

 

Ive checked the speed and ref sensors, gap is good, super clean with completely refurbished bell housing a few months ago. TAC bounce is normal while cranking. The DME temp sensor was changed and I'm confident in its operation. An oil change is probably going to be next. 10-30 or 10-40? Let me know what you guys prefer in the winter. I smell fuel from over cranking and I purposely ran the fuel pump for a minute to build pressure ( just in case it had a leak down issue) no luck. Probably wouldn't hurt to do a spark test just to be sure its sparking each plug and checking gaps. Though fairly new: cap, rotor, ignition wires, injectors, all intake seals and vac lines, anything with a seal got changed. The coil is the ms blaster 2 (direct replacement one). All grounds cleaned, new Nissan alt and harness. This has just been annoying because the issue doesn't exist in 40 and above temps. Never has an issue on a warm start regardless of outside temps or cold start on a warm day. Sometimes its normal even on a cold day. But its a coin toss.

 

you can get 5-50 synthetic.

 

Switched to 10-40 so well see.

 

When I stopped to get my 10-40 oil I saw an oil that was designed for German car, Porsche, Audi, vw, BMW, etc. It was 0w-40. Anyone have experience with that grade oil? The cold grade seem appealing for cold starts.

http://mobile.walmart.com/ip/Mobil-1...5-qt./23636902

 

I used Mobil 1 0W-40 for years in my 924S with exceptional results. If it got colder or hotter in Seattle, I would consider it for my 951.

 

Your valve train is not going to like that oil ....

It sounds like you have no spark, weak battery or both

Your Msd coil might be the culprit

 

But that doesn't explain why its perfect in 40 and above temps, and is off and on at lower temps, also when its perfect on a warm start on any temp day. It makes sense for it not to fire due to slow rotation, and the culprit of that is probably a combination of things. Looking at the owners book there is a wide range of accepted oils. It comes down to outside temps and ultimately what the motor is doing. Hard racing would boil lighter oil. But a winter trip to shop n save is fine even with moderate boost. I also have a Lindsey 3x oil cooler helping oil temps stay lower. With a space heater parked in front of it overnight seems to fix the issue too.

So far with 10-40 oil I haven't had an issue but I can't say its a full solution until I get through a few morning start ups.