Sluggish below 3,000 rpm (4.4 V8)
Thread Starter
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Mudding
Joined: Dec 2007
Posts: 174
Likes: 2
From: Shreveport, La
So, just to recap the OP's concern, there are two issues...
1. The engine falls on its face when pushed from a lower RPM.
2. There is a delay in down shifting.
Did both of these occur around the same time?
Is the lack of power at all speeds, or only when in a higher gear?
If you put it in manual 1, and give it say 50% throttle from a rolling start, does it take off, or would this cause it to 'studder' as well?
When it is 'shuddering', does the engine speed increase, as if the trans (torque converter) is slipping?
If engine speed does not raise, and it only gets up and goes once at a higher RPM, regardless of selected gear, I would be looking at either a large vacuum leak, or a bad MAFS(cleaning may not be enough, as the only part that gets 'dirty' is the IAT sensor bulb, which I don't see causing this dramatic of an issue. Both of these should be setting the MIL on, and throwing codes. If nothing else, try another scanner.
Other possible cause for the above scenario would be a (or multiple) misfires, again, should have codes, and a misfire like this is not that common on this engine.
You're at the point of throwing a part at it, or having it diagnosed, I would choose the latter.
1. The engine falls on its face when pushed from a lower RPM.
2. There is a delay in down shifting.
Did both of these occur around the same time?
Is the lack of power at all speeds, or only when in a higher gear?
If you put it in manual 1, and give it say 50% throttle from a rolling start, does it take off, or would this cause it to 'studder' as well?
When it is 'shuddering', does the engine speed increase, as if the trans (torque converter) is slipping?
If engine speed does not raise, and it only gets up and goes once at a higher RPM, regardless of selected gear, I would be looking at either a large vacuum leak, or a bad MAFS(cleaning may not be enough, as the only part that gets 'dirty' is the IAT sensor bulb, which I don't see causing this dramatic of an issue. Both of these should be setting the MIL on, and throwing codes. If nothing else, try another scanner.
Other possible cause for the above scenario would be a (or multiple) misfires, again, should have codes, and a misfire like this is not that common on this engine.
You're at the point of throwing a part at it, or having it diagnosed, I would choose the latter.
Pro Wrench
Joined: Apr 2008
Posts: 1,475
Likes: 37
Change the MAFS or take it in to get it diagnosed. Both will be around the same amount of money, one is a guess(educated, but still a guess) the other will need a repair after the diag.
It's a gamble, how lucky do you feel?
It's a gamble, how lucky do you feel?
Thread Starter
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Mudding
Joined: Dec 2007
Posts: 174
Likes: 2
From: Shreveport, La
Cleaned the MAF (noticed some buildup when doing so), replaced the air filter and disconnected the battery to reset it and it runs much much better. I used the CRC MAF cleaner. Next is a fuel injection service. Thanks for all the replies everyone. Transmission seems to be more responsive as well. Maybe the misfiring and sluggishness mad it feel unresponsive.
Thread Starter
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Mudding
Joined: Dec 2007
Posts: 174
Likes: 2
From: Shreveport, La
For anyone else who wants to do this just attach the straw and spray close to the sensor but do NOT touch it with anything. The stream of cleaner coming out of the straw is more than enough to clean it just follow the instructions. I will post fuel economy gains when I get back into town and drive it enough to document it.
Super Moderator
Joined: Jan 2011
Posts: 16,322
Likes: 88
From: Savannah Georgia
It is also very important to do this when engine is cold, and you have not turned on the ignition key (like to move truck into garage, or listen to radio, etc.) Turning on the key warms up the sensor inside at a tiny spot to like 350F. Hot and cold don't like each other.
Thread Starter
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Mudding
Joined: Dec 2007
Posts: 174
Likes: 2
From: Shreveport, La
It is also very important to do this when engine is cold, and you have not turned on the ignition key (like to move truck into garage, or listen to radio, etc.) Turning on the key warms up the sensor inside at a tiny spot to like 350F. Hot and cold don't like each other.
