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Engine shuddering at under 2000 rpm

2006 for f150 with 107k miles…suddenly started shuddering whenever I give it anymore than a feather of gas, and it’s under 200 rpm…after 2000 if seems to break out of the shutter and run fine. Exact same thing happenes to my 89 accura with 230k

Check engine light on?

Umm…meant FORD, and under 2000 RPM, not 200

It came on for about 30 seconds while it was shuddering(one of the times), but went out after hitting 2000 rpm and the shuddering stopped. for now I’m only giving a feathering of gas to keep it from starting up.

First step is to scan for codes. These may exist even when the CEL is not illuminated.
AutoZone, Checkers, and most big box parts stores will do this for you free.
Apparently the states of California and Hawaii have taken exception to this and will not allow it.

A wild guess might be an air leak between the throttle plate and MAF sensor.

If it did come on at all there should be history codes in there. Not all scanners will pull history codes, but a lot of auto parts stores will pull error codes for free. I’ve actually noticed some variation in the quality/capabilities of the scanners they use. If you call around and ask you might find a parts store that can pull history codes - and at free the price is always right. If the light ends up on steady then any parts store can just pull the codes.

Alternatively you could pay whatever diagnostic fee to a shop - most will be able to pull history codes but ask first if you go that route. If you do manage to get some codes, write down the exact code - its looks like “P1234.” These codes basically give you a starting point so that you don’t have to just guess.

(None of that applies to the Acura. It is on the OBD 1 system and the parts stores won’t be able to pull those codes. There is often a “key dance” procedure you can use - I’d just search the web for how to pull codes from an '89 Acura).

That said, how well have you done in terms of keeping up with maintenance? At 107K I hope that you don’t have the original plugs & wires in there. Same goes for the air AND fuel filters. If any maintenance is not up to date do that first. Often little issues like this are as simple as bad plugs/wires or restricted fuel filter or something.

My guess is faulty wires…change the sparkplugs and wires…cap and rotors too if you have them… Sounds like typical signs of needing a tuneup. YOu seem to be describing a misfire…it seems to go away with additional RPM because at that time you cant feel it anymore. You have a misfire is my guess… Educated guess…

A compression test wouldn’t be a bad idea.

How long since the 89 Acura had its valves adjusted?