My 4.0 misfires when cruising.

[big5dogg]

My 99 sport 4.0 ohv engine recently started to misfire when I would start it in the morning but would only do it for like 10 seconds then it would go away, now it starts to misfire, sputter when I am giving it gas around 30mph even if the engine is warm.
I've replaced lower and upper intake manifolds, new plugs, wires, Iac valve, new coil. Would a MAF sensor cause my engine to misfire when cruising?
any help appreciated thanks!!
p.s. no check engine light or codes present.

 

[4.0blue98]

My 99 sport 4.0 ohv engine recently started to misfire when I would start it in the morning but would only do it for like 10 seconds then it would go away, now it starts to misfire, sputter when I am giving it gas around 30mph even if the engine is warm.
I've replaced lower and upper intake manifolds, new plugs, wires, Iac valve, new coil. Would a MAF sensor cause my engine to misfire when cruising?
any help appreciated thanks!!
p.s. no check engine light or codes present.

How many miles? Wouldn't hurt to clean the MAF. It could cause sputtering and sluggishness but not really a true misfire. How's your fuel filter? Is it carbon knock or detonation?

 

[big5dogg]

How many miles? Wouldn't hurt to clean the MAF. It could cause sputtering and sluggishness but not really a true misfire. How's your fuel filter? Is it carbon knock or detonation?

It's got 137k miles. I had recently replaced to fuel filter not too long ago and had also cleaned out the MAF sensor.
More like a detonation when rpms are around 2k...

 

[Flash]

Crankshaft sensor and throttle position sensor.

Then a Seafoam cleanout.

 

[4.0blue98]

I'd say carbon knock! Mine does it periodically and then I use PM-3 and follow the TSB. I only use one can at a time. Maybe if I did the three repetitions it would last longer. I do this about once a year. Great product and cheap at the dealer. Check this out:

http://www.explorerforum.com/forums/showthread.php?t=57953

 

[Rickademus]

If you suspect the MAF meter you could try to see if the problem goes away when you disconect the plug . The ecu should default to a basic setting in the ecu memory...

 

[big5dogg]

I'd say carbon knock! Mine does it periodically and then I use PM-3 and follow the TSB. I only use one can at a time. Maybe if I did the three repetitions it would last longer. I do this about once a year. Great product and cheap at the dealer. Check this out:

http://www.explorerforum.com/forums/showthread.php?t=57953

Yeah it's the only thing I could think of now that it could be carbon knock since now I have replaced the TPS sensor and Crankshaft sensor.

 

[big5dogg]

Now since I replaced the TPS sensor check engine light came on p1121.
Maybe MAF gone bad?

 

[4.0blue98]

Now since I replaced the TPS sensor check engine light came on p1121.
Maybe MAF gone bad?

Could be. Or the new TPS is defective. I've seen that before. Did you use MAF cleaner when you cleaned the MAF? Really the only thing you should use. Those things are touchy. MAF replacement is easy but get a good one. I try to get Motorcraft as much as possible. Always great quality but expensive.

I'd try what Rickademus suggested first.