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Discussion Starter · #1 ·
I've got a 1998 5-speed manual 4-cylinder Frontier. It has started throttle surging pretty badly. It runs smoothly at idle, but once I push on the throttle the engine starts surging, even in neutral. It's not subtle - the surging is bad enough to make the vehicle undriveable with how badly it bucks. No check engine light. Disconnecting the throttle position sensor makes the problem go away (although the CEL does come on then, of course, and it makes the idle high and the gas mileage poor). I've replaced both the TPS and the MAF with no change. I'm driving it with the TPS unplugged for now, but what should I troubleshoot next?
 

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X2 2004 2.4L frontier’s💸😵‍💫
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My question is what brand tps and maf you’re running? I’ve had bad luck where I bought aftermarket, non OEM parts and it was causing all kinds of issues. Once I bought oem Nissan parts installed them, the same issues you have went away.
 

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MCV...have you downloaded a copy of the Nissan Factory Service Manual for your model year Frontier?? See attached link...

You might want to check the Fast Idle Circuit on your throttle body.....use the procedures listed in the Factory Service Manual. Also check to see if there is a thermostatic fast idle solenoid on your model year throttle body....see attached Youtube video....

Hope this helps...Good Luck!!!
 

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2001 Nissan Frontier XE King Cab 3in BLift Ka24de Lift Single Owner Nov 2000
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This happened to me, changed out my tps No Go
Checked my F Idle S
Changed my air control valve , bingo for me!

Hope what the guy above and what I said at least helps direct you in a path where you get this figured out. Good luck.
 

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Discussion Starter · #5 ·
Thanks for the input - I tried another throttle position sensor today in case I got a bad part, and no change in symptoms. I also did a voltage / continuity check on the TPS connectors (both sides), and all seems well there.

With respect to the fast idle circuit / idle air control valve - the truck runs fine at idle, and also runs fine (but at high idle) with the ECM side of the TPS disconnected. Before I go throwing money at more parts, does it make sense that the idle air control valve and/or fast idle solenoid would be an issue when the idle itself seems fine? The throttle surging only happens with the accelerator pressed part way. The idle speed otherwise seems normal and consistent.
 

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Just out of curiousity, how well maintained is your truck? Changed the fuel filter lately? Checked the vacuum line going to the fuel pressure regulator, (FPR)? How's the vacuum on the FPR at idle & at full throttle? How's your spark plugs, timing and idle?? Swapped your distributor cap & rotor lately?? Checked your Spark Plug wires with a digital voltmeter for continuity? No vacuum leaks? No leaks around the fuel injector o-rings?? What motor are you running? the KA24DE or the VG33DE??
 
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