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maxima dies at startup then runs fine
11-20-2017, 07:30 AM
Post: #11
RE: maxima dies at startup then runs fine
I scanned it last time and no codes, I've never tried starting live data before turning the key the first time. I have a bosch 1300, so I do have live capability.

Did it yesterday leaving for church, no time to investigate further and I Just tried it now as I'm leaving in my truck for work. Both mornings are coldest mornings of year, well below average. Runs fine if you give it throttle while turning key and idles fine after.
I'm thinking of going ahead and picking up iacv today and putting it in, leaning heavily on that, don't believe fuel pump is issue.
Yeah, its time to let it go, wife hasn't found another vehicle yet that she likes yet though.
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11-20-2017, 10:04 AM
Post: #12
RE: maxima dies at startup then runs fine
So, before you drop in the IAC tonight maybe you can get a quick reading of the intake air temp and engine temp to confirm the sensors are where they should be, just for peace of mind. You could also take a reading in the morning when you double check the cold start after the repair. It would be a good way to gain experience. Keep us posted on your progress.
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11-20-2017, 01:16 PM
Post: #13
RE: maxima dies at startup then runs fine
So at start up with cold engine the iat should match ambient temperature and then rise as the air coming off engine warms when the engine gets to operating temp...is that correct? Thanks
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11-20-2017, 11:58 PM
Post: #14
RE: maxima dies at startup then runs fine
In general, at start up IAT should be close to ambient but a variation of 10 degrees is not uncommon. (shade, sun, wind, etc) Since the intake air moves rather fast it typically wont show much of an increase as the engine warms up, although 30 - 40 degrees higher is likely. As an example, in my shop (heated to around 65) I see mid 90s IAT on a fully warm engine. Remember, some of this depends on the intake routing. In my case that's off to the side of the radiator with the snorkel facing down. Some vehicles may have a pipe through the radiator support for full fresh air and others will have a blend via another pipe to the side of the exhaust manifold. IOW, it will vary so use your best judgement on where it should fall. The idea is you WANT to see that variation to be sure things are working properly and not stuck in one place.

BTW, since your issue seems to be in the first few seconds that will be well before temps have a chance to change. This is more to see how the system is responding as a whole, starting from square one. (cold)
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11-21-2017, 12:40 AM (This post was last modified: 11-21-2017 12:55 AM by salamander.)
Post: #15
RE: maxima dies at startup then runs fine
so I did some more investigating tonight. Picked up new iacv, but have not installed it yet. Hooked up my scanner and the vehicle has no active codes and none in memory.

Ran two live data streams when the vehicle was still somewhat warm...Engine coolant temp was 120. The iat started off about 10 degrees warmer than ambient and then dropped about 5, and then rose about 10 degrees as the engine warmed to normal temp...close to 200.

Next I let the engine cool completely for 3 hours during which the ambient temperature dropped 15-20 degrees. When I started the engine this time it almost stalled and then picked itself back up. I let it run for about 45 seconds and shut it off, when I tried to start it back it did the whole stalling out thing again. Had to rev the engine slightly a couple times before it would idle on its own..about 3-4 seconds elapsed time.

When I graphed the recording of the iat these two times it showed the same basic picture as before...started off a bit above ambient, dropped close to ambient temp within ten seconds or so and the climbed some as engine warmed. I never got the extreme readings one way or another that I've heard indicate a bad sensor. It seemed to me like it acted within parameters of what it should.

My wife did say that it has happened 4 or 5 times in the last month that I was not aware of...all since it has been cooling off drastically at night. Also engine coolant temp sensor seems to be working good. Other items on live data all seemed pretty normal to me, or at least consistant...fuel trim, air flow, manifold pressure, etc....as far as I can tell.

As much as I hate to say it, since its $150, I'm still leaning toward iacv. I think it would probably pass a resistance check, but I can see the plunger briefly sticking when the temperature drops drastically. So I guess tomorrow I may go ahead and install it...Sorry for the rambling post, Do you have any other thoughts on something I might look at? I realize its hard to diagnose something you cant see or feel, LOL, I do appreciate your input though!
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11-21-2017, 01:03 AM
Post: #16
RE: maxima dies at startup then runs fine
Ok, you show 200 degrees IAT so the engine must be drawing air from a heated source, which would be about right... BUT... having not worked on that vintage Maxima I'm not sure where they draw the line, temp wise. In an ideal world the intake air should only be warm for the first few minutes, then various controls (that I have lost track of) should cool it off once the engine has reached operating temp, which helps with fuel economy. Maybe you can prove that one out once the repairs are done? It will be a learning experience for all of us.
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11-21-2017, 07:25 AM
Post: #17
RE: maxima dies at startup then runs fine
I wondered if I should have re worded that...the 200 degrees I referenced was what the engine coolant was measured at. At that point the iat was up around 68, have risen from a low of 62. Ambient air was around 50.

The intake comes off the wheel well on 4th generation so I'd expect it to never read significantly over ambient air.

I need to periodically run the live data on our vehicles when everything working good and print it off for a reference point. That way I'd have a standard to compare against when stuff like this comes up.
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11-21-2017, 11:34 AM
Post: #18
RE: maxima dies at startup then runs fine
Excellent point! Your last statement is something I feel we are ALL guilty of not doing, which puts us in a pinch when the chips are down. If you have the ability to print other screen tests that may come in handy too. I know around here we do emissions testing based on a scan so knowing which car has which functions (both completed or NA) is the one they look at BEFORE you can pass inspection. This tells them if you have cleared the codes recently to fudge things, or perhaps the battery was disconnected for repairs.

You brought up another good point, where in your case the scan showed % opening of the IAC, which would be nice to know in the future. Not every car has that reading available.... and it will change with AC or PS load, so something to know if it's not within the normal range.
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11-24-2017, 09:49 PM
Post: #19
RE: maxima dies at startup then runs fine
The original iacv from Nissan comes with a brass colored deflector shield that mounts on back of iacv with 3 self threading screws. It covers the plunger hole and I assume its there to keep gunk from inside the throttle body from getting on the plunger. There are 2 cutouts on the side of the shield for air flow.

The new iacv I purchased is a Borg Warner. It does not come with the shield or screws, but it is made exactly to match the original, with a place for this shield to go. so I took the one off my original, but when I placed it on the new unit I found that it is not drilled and tapped for the mounting screws. The new unit has dimples on the back surface where the screws would go but the are not actually drilled.

Thought maybe it was bad from factory, but every borg warner iac for this car is the same...distinct place for shield to mount but not drilled. Went to another store and the Duralast brand is the same situation.

The hole in the back of the unit where the plunger goes in and out is designed a bit different on these after market valves so I thought maybe in the last 20 years its been re designed and I don't need the shield any longer. But if that is the case, why is there still an obvious place for the shield to fit with dimples in metal where screws would go? Tech service at Duralast is closed for 4 days and good luck getting anyone at Borg warner.

I hate to not mount my old shield on the new unit, not knowing for sure that it is not needed anymore. I have the capability to drill out for the mounting screws myself, But I hate to have to start fabricating on a $150 part. I don't recall ever putting on any kind of new part on any vehicle that I personally had to drill and tap. What do you think about this?
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11-25-2017, 09:22 AM
Post: #20
RE: maxima dies at startup then runs fine
If I was doing the job I would mount it as it came. If you start drilling holes in it you will void any warranty that may be on it. Sometimes aftermarket parts use the original molds and dies to make their parts. Even if it is redesigned not to need the shield, the mold or die still has the locations in it. The company just doesn't drill and tap it because it is no longer necessary. It is also possible that the original was designed to last a hundred thousand miles and the aftermarket is far cheaper and only designed to last fifty thousand?

So unless you are going to wait till you get an answer from the company, I would just install it and see how everything works. Please let us know too!

Thanks for using the forum,
Garner

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