engine misses and surges, wont go over 25 mph, and over 2500 rpm,s after warmup

[johnboyhick1]

engine starts up fine and runs ok up to 3 to 5 miles down the road or 3 to 5 miles, then it starts surging 500 rpm,s to 1200 rpm,s without touching the gas, sometimes cuts off, then restart and push on the gas anything above 1/4 throttle it surges at a higher rpm 2500 to 3500 ,nothing higher no matter how far you push the gas , even to the floor, ive replaced coil , module beside the coil, cap. rotor, wires, plugs,ECU( three times ) checked all electrical conections , replaced throttle body assy with known good one, nothing has changed , even a little, this truck has 250000 miles and it dont , tick, knock, smoke, all this started when the first ecu went bad, and hasnt run right since. im stuck, any help thanks johnny

[Bretticus]

Holy crap, my truck started this same behavior Sunday morning 3/2. I've replaced the cap, wires, rotor, and fuel filter. The plugs are fairly new and Now, (after replacing the wires) I'm confident by the manner it's missing at different cylinders that it's not a spark issue. I think it's the MAF unit. The truck runs strong and works fine cold, then as soon as it warms up, Bam! It behaves as you've described, almost exactly. The MAF is $350 from some spots online with 2 day delivery, but shoot, i don't want to cough that up and it not fix the problem. I'm wondering if anyone knows if there is a diode / gate to check if it's shorted. That's easy if I know the test points. Not sure how the thing works but any info on trouble shooting the MAF unit would be SUPER helpful...

[Desert Rat]

Is the check engine light on in the Xterra? If so, get your codes pulled...that'll tell you what part is malfunctioning.

On the HB, this sounds like a huge vacuum leak to me. Get a can of carb cleaner and, with the truck idling, start spraying around all vacuum fittings and the throttle body and listen for changes in the idle speed.

[Bretticus]

Dude, no check engine light. Got a code reader and the best it says is the knock deal (O325) yeah, it's gonna say when the engine jerks... THe Piezo will squirt some voltage and trigger the ecu. The engine is jerking subsuquent to what ever is making it mess up. Now, tonight with the code reader after allowing the car sit all day I started it. Checked codes. Only code of value, it seemed, was the P1320 (ignition issues with the ECU). Again, the ecu will have a hard time if either there is no air at the right time or no fuel to burn. we show a P0300 "random MisFire"; No kidding, I heard it randomly misfire . Likely due to the real problem. The cool thing is no MAF or Temp sensor codes... Bad side is that it seems like the darn fuel pump may be going bad. You know, the first thing i did sunday when it first messed up was... fill it with a full tank of premium Exxon... No better! time for the fuel pump to show it's colors... Anyway.. We (the wife and I) shut down, cleared codes and restarted it. All we got was the O325 code, but if the engine shakes, the Piezo element should squeeze voltage and flip a code accordingly.. right? So, we let it idle for 20 minutes until it starts missing real good sitting in the driveway. Now, the engine is good and hot. We clear codes and go to ON and see whats up. NOTHING. Yep, no codes. So we disconnect the reader, turn the key to off and try to restart the car. guess what... it wont start now. it just turns over..... like my bronco when the fuel pump kicked the bucket. Now we're letting it cool. IF this b starts cold, i'm going to bet a salary pay check it's the fuel pump... I did fill the tank full with premium Exxon Sunday... Murphy just may have me by the nads what do you think bud?