maf readings
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Mountain Pass
Joined: Jul 2019
Posts: 139
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maf readings
Shop said " MAF sensor is reading to high, truck also idles to high at times." Do you guys agree? What I found online was normal should be at 4.5 to 6 grams per sec at idle, and 11.5 to 17 grams per sec. at 2500 rpm.Can you circle what is bad, so i have something to give to my shop? See attachment...
Fleet Mechanic
Joined: Jun 2023
Posts: 1,357
Likes: 377
From: WA
You should ask your shop to show you or tell you what they are seeing. "Too high" doesn't tell you much. If they've already decided to sell you a MAF sensor showing them a Chat GPT thing probably won't help.
And, why is it in the shop? Is there a code? Are you still working on the P0174 code? MAF sensor is often suggested as a cause for that. But on the 4.2 it's usually the intake manifold gasket leaking because of bad isolator bolt bushings or the IMRC bushings.
And, why is it in the shop? Is there a code? Are you still working on the P0174 code? MAF sensor is often suggested as a cause for that. But on the 4.2 it's usually the intake manifold gasket leaking because of bad isolator bolt bushings or the IMRC bushings.
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Mountain Pass
Joined: Jul 2019
Posts: 139
Likes: 2
No more lean codes after auto shop replaced my MAF, it seems to run well. I went back to my transmission shop for trans. warranty work, a little bit of a noise downshifting from 2nt to 1st. Trans. shop said to get the MAF repaired first, this can cause some minor shifting problems.They gave me the MAF print out to show the shop that just replaced the MAF. He said "the print out can easily be read, it shows the MAF is running to high" Does the sensor test result show that?
Fleet Mechanic
Joined: Jun 2023
Posts: 1,357
Likes: 377
From: WA
I see. I spent some time figuring out the graphs. It looks like you had a MAF sensor reading of 6.6 at 894 RPM at one point, assuming the end of the time plot. That is high. Not sure it would cause a transmission problem but probably worth showing to the shop that did the MAF sensor work.
But, and I'm not sure why, I looked at some of my old scans of my engine and find that a few RPM can make a big difference at idle. At 820 RPM I had 4.4 g/s, at 836 I had a 5.4 and 6.2. I also had a more recent reading of 4.4 at 818 RPM.
There's no engine temperature on the graphs. Can't tell if your engine is fully warmed up. A cold engine will idle higher and have a higher MAF sensor reading.
In short, it doesn't like you have a significant MAF sensor problem. And it's not clear why you have a high idle RPM. The idle RPM might be the real problem.
But, and I'm not sure why, I looked at some of my old scans of my engine and find that a few RPM can make a big difference at idle. At 820 RPM I had 4.4 g/s, at 836 I had a 5.4 and 6.2. I also had a more recent reading of 4.4 at 818 RPM.
There's no engine temperature on the graphs. Can't tell if your engine is fully warmed up. A cold engine will idle higher and have a higher MAF sensor reading.
In short, it doesn't like you have a significant MAF sensor problem. And it's not clear why you have a high idle RPM. The idle RPM might be the real problem.
Hotshot
Joined: Jul 2020
Posts: 10,354
Likes: 2,592
From: Near Salt Lake City
You can get a reference table of pids from AllData for your 4.2
That way you can compare all the pids with the reference table
Some MAF tables are in pounds per hour, so you have some math to do sometimes
That way you can compare all the pids with the reference table
Some MAF tables are in pounds per hour, so you have some math to do sometimes
Thread Starter
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Mountain Pass
Joined: Jul 2019
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Likes: 2
I see. I spent some time figuring out the graphs. It looks like you had a MAF sensor reading of 6.6 at 894 RPM at one point, assuming the end of the time plot. That is high. Not sure it would cause a transmission problem but probably worth showing to the shop that did the MAF sensor work.
But, and I'm not sure why, I looked at some of my old scans of my engine and find that a few RPM can make a big difference at idle. At 820 RPM I had 4.4 g/s, at 836 I had a 5.4 and 6.2. I also had a more recent reading of 4.4 at 818 RPM.
There's no engine temperature on the graphs. Can't tell if your engine is fully warmed up. A cold engine will idle higher and have a higher MAF sensor reading.
In short, it doesn't like you have a significant MAF sensor problem. And it's not clear why you have a high idle RPM. The idle RPM might be the real problem.
But, and I'm not sure why, I looked at some of my old scans of my engine and find that a few RPM can make a big difference at idle. At 820 RPM I had 4.4 g/s, at 836 I had a 5.4 and 6.2. I also had a more recent reading of 4.4 at 818 RPM.
There's no engine temperature on the graphs. Can't tell if your engine is fully warmed up. A cold engine will idle higher and have a higher MAF sensor reading.
In short, it doesn't like you have a significant MAF sensor problem. And it's not clear why you have a high idle RPM. The idle RPM might be the real problem.
. If it helps my temp was at 190 and he ( trans shop) sat in the truck and read the codes. I never seen it "some times idles high" seems to idle fine at about 900. My impression at the trans. shop was they didn't really want to repair the trans under warranty, they said it can shift a little hard because of the new shift kit.
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Mountain Pass
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Fleet Mechanic
Joined: Jun 2023
Posts: 1,357
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From: WA
Is it shifting hard from Park to Drive or is it shifting hard between gears while rolling? One might be a high idle problem, the other something else. I don't think a high MAF sensor reading is going to affect shifting behavior.
Just curious, but did you have the transmission rebuilt or did you have a special shift kit installed? Usually "shift kit" means a change in shifting behavior. Snappier, harder. A "rebuild kit" would restore factory performance.
Whatever it is, good luck with it.
Just curious, but did you have the transmission rebuilt or did you have a special shift kit installed? Usually "shift kit" means a change in shifting behavior. Snappier, harder. A "rebuild kit" would restore factory performance.
Whatever it is, good luck with it.
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Mountain Pass
Joined: Jul 2019
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shifting issue
Is it shifting hard from Park to Drive or is it shifting hard between gears while rolling? One might be a high idle problem, the other something else. I don't think a high MAF sensor reading is going to affect shifting behavior.
Just curious, but did you have the transmission rebuilt or did you have a special shift kit installed? Usually "shift kit" means a change in shifting behavior. Snappier, harder. A "rebuild kit" would restore factory performance.
Whatever it is, good luck with it.
Just curious, but did you have the transmission rebuilt or did you have a special shift kit installed? Usually "shift kit" means a change in shifting behavior. Snappier, harder. A "rebuild kit" would restore factory performance.
Whatever it is, good luck with it.
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