Engine stumbling above 4k RPM

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Zach Hampton

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My 98 runs great from idle to 4k but once it hits 4,000 rpm it's like half of my engine stops working. It stumbles and pops in the exhaust and has a very large loss of power. Anyone had this problem before? I just did an oil change, cleaned the air filter and MAF sensor and throttle body.

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df2x4

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Is it throwing a check engine light? Any trouble codes?
 

michael hurd

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Popping in the exhaust sounds like ignition problems at WOT. Clean engine grounds and the positive cable ends as well to start.

Once satisfied you have a good connection, take it out for a spin, to see if the problems still occur. Distributor cap and rotor would be my next stop, if age is unknown.
 

Zach Hampton

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No CEL and the grounds are clean and the power is good. It also hesitates for the first 10 seconds or so if you start it after its been warmed up. If you let it sit for 10-15 seconds it's fine but if you immediately drive it feels like you're trying to drag a house behind it.

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Biggershaft96

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No CEL and the grounds are clean and the power is good. It also hesitates for the first 10 seconds or so if you start it after its been warmed up. If you let it sit for 10-15 seconds it's fine but if you immediately drive it feels like you're trying to drag a house behind it.

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Sounds like a fuel problem, check fuel psi. Anything below 50? Is bad i belive
 

michael hurd

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No CEL and the grounds are clean and the power is good. It also hesitates for the first 10 seconds or so if you start it after its been warmed up. If you let it sit for 10-15 seconds it's fine but if you immediately drive it feels like you're trying to drag a house behind it.

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Symptoms sound like leaking injectors. Does it start right up fine cold?
 

98sierraslt4x4

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Mine did the same thing. If i tried to go as soon as it started it would chocke up. Also if i pressed the accelerator above 2500 rpms it would just drag like it was towing something. It did this for a couple of days before it gave me a P0101 code-
Code P0101 is set when the signal from the mass air flow sensor is out of expected range.

In my case, I was told my popping was due to it being too lean of a fuel mixture b/c of Maf

I pulled the throttle body and mass air flow cleaned them both really well and made sure all my clamps were tight and sensors were in snug, no cracks, and it luckily fixed my problem. Been a month and still hasn't came back on.
 
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