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Discussion Starter · #1 ·
So I had this issue right before I blew my head gasket fixed that issue replace plugs and wires, head gasket sealed back up. Well now it has come back. When the car sits overnight and the temps get down into 30s or below it has rough idle, almost stalls, maybe toss in a back fire. After it gets through that idles fine and runs/drives like nothing ever happened. I currently do not have a CEL. Any ideas of what IAT should be compared to ambient air also MAF numbers should be during idle.?

Here is a video of what happens.

 

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For what it's worth, the intake air temperature sensor is integrated into the mass airflow sensor. Are you able to access a diagnostic tool with the ability to read pending codes and/or live data?
 

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Discussion Starter · #3 ·
Yes I borrowed a scanner from work to view live data. I’ll be interested to see what the numbers are after sitting all night.
 

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Discussion Starter · #4 ·
The pictures with the spikes for the IAT the car was still cold/idling, the picture without was when the temp was warmer and the vehicle had been driving for 15+ minutes to work. Are those spikes normal.? I would think not even though they are small and not out range. I did notice on the startup the MAF portion was not high enough for the initial startup. I turned the key heard it struggling turned it off than immediately turned the key again and the graph showed a higher input the second around like almost double. I’ll attach the screenshot that will be the 4th picture.
 

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For some reason, can't see the images too well. Be that as it may, were the intake air temperature sensor's readings realistic? Generally speaking, they should read around +/- ten degrees of the vehicle's ambient temperature. Located this thread, Rough Idle on COLD start. By the way, what brand and model of scanner were you using?
 

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Discussion Starter · #6 ·
Scanner is Snap-On. I’ll through that post you mentioned. Here is a snap shot from this am. Air temp is within a degree what it was today. It did the same thing chug-a-lug shut it off restart right away no issue. I do keep having a B101D code come up. Battery charge is reading 79% started at 50’s. Oreilly claimed it was good according to their tester. I’m scratching my head at this point. Got about 1 more cold night than it’s on the back burner until fall...ha
 

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Snap-On makes good tools and recently paid over $150 to replace a broken while borrowed 1/2" drive breaker bar. Am thinking the B101D has something to do with the restraint sensing and diagnostic module. Are there any other "electrical" issues? May or may not be worth a look (underside), Battery ground bolt. Probably neither here nor there, but what band of battery are you using?
 

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Discussion Starter · #8 ·
I was just considering that ground bolt. A couple years ago I had starter issues, it was sounding like it was bad, it would just click & not engage. Ended up being the ground bolt rusted up the threads causing a bad connection. I’ll take a look at my repair & probably further repair, meaning replace my both I repair & spray some paint coating over it.
I’ve had some other wonky codes but nothing stuck so I didn’t think much of it, which they were all electrical related also.
 

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Would check the battery connections as well. Speaking of O'Reily's, are you using a Super Start battery?
 

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Could it be that 1 or more fuel injectors have developed a leak down condition ? Since it seems to only happen on your first start attempt after a long shutdown period, maybe 1 or more cylinders are somewhat flooded. Maybe you could try the "clear flood" engine procedure in the morning. Throttle pedal to the floor an hold. Rotate key to start position an hold for about 5 seconds worth of cranking. Rotate the key to the off position, then release the throttle pedal. If any flooding had occurred, maybe this action would clear the cylinders and you could then see if a normal "cold start" event now happens.
 

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Just wondering if you have cleaned the MAF.
 

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Discussion Starter · #12 · (Edited)
Ponyman: As a matter of fact it is an Oreilly super start gel battery. You have ini peaked my curiosity.

Gopherit: I will be trying this at some point.
I mean full throttle first thing in morning my neighbors would love me.

Hot Rod : I replaced it thinking it would be the end all, which wasn’t the case. It did help with throttle response & transmission shifts atleast that’s what I think.
 

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May sound stupid but, I went to all fuse and relay locations and pulled them all in an out several times to make sure that after sitting for 10 years they still have a good connection.
 
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I'm trusting that the GM info is correct (with the throttle pedal pressed to the WOT position) while the engine is cranking. The injectors are suppose to be commanded to shutoff the fuel to them when doing this. That would then give you max air into the cylinders with no fuel added.to clear out its cylinders, so the engine should not start. But if the info has a flaw in its wording (an the engine tries to run an go to max RPM), turn the ignition key to off.
 

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As far as I know, the intake air temperature should be within +/- 10 degrees of the "under-hood" temperature, factoring in both the outside and engine temperature. By the way, what brand is the mass airflow sensor replacement? Have never purchased a Super Start battery, but have a neighbor whose battery went out in less than a year*. Be that as it may, batteries are notorious for coming in bad "batches". Typically purchase Interstate for due to availability and warranty.
 

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After resting for say 8 to 10 hrs, the resistance of the IAT an ECT sensors should have about the same resistance value That value equals X amount of degrees.. From that point on the resistance values of the 2 sensors will separate. It looks like the IAT temp reading would tend to stay about 10 to 20 deg above the ambient. That value would most likely increase once your trapped in stop an go type traffic (maybe to a value of 40 deg above ambient as an example) The ECT will ramp up to its set temp of about 186 deg.

I'm thinking, if you have a good size spread (resistance wise) between the IAT an the ECT first thing in the morning, either higher or lower than the service manuals RES equals TEMP chart says it should be, it might influence how the engine reacts at various times from cold to normal running temp.
 

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Discussion Starter · #18 ·
I picked up a carquest MAF from advance.

I tried the “clear flood” procedure this AM & the car started just fine. Which I will say works the engine will crank but will NOT fire. The temps were a little warmer being 43*. There are a couple colder days this week, to compare to today, but than after that this might be a project to finish when fall comes, unless of course it happens during the warmer spring/summer months.

I’m going to try to get the scanner from work for later in week to see those startups with IAT, fuel pressure, etc etc.

I’m hoping it might just be a sticky injector & not the pressure regulator.

thanks for help so far.
 

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As you're probably aware, the fuel pressure regulator is housed in the fuel pump assembly so replacing it would require dropping the tank. The other option would be to cut a hole for fuel pump access.
 
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Discussion Starter · #20 ·
Yes I’m not really looking forward to replacing that...just hoping that’s not the issue...
 
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