Intermittent misfire

[God]

My 97 yukon runs well sometimes and other times runs terribly.

The misfire I am getting is most apparent when I am in Drive but not accelerating- the RPMS will bounce 600 to 400 back and fourth continuously and the truck will feel like it wants to stall. If I accelerate it will run fine. Sometimes when I am slowing to a stop the RPMs drop off and I come to a complete stall and have to restart truck then it will run good. This is an intermittent issue. I havnt attempted a diagnosis or scanned it for codes yet, but the SES light is also intermittent, sometimes on, sometimes off. Figured I'd write my symptoms here just in case anyone has had this exact issue and can say "it's probably this" . Thanks!

 

[SunlitComet]

pull the misfire history to see what cylinder are dropping off then inspect in detail the cap, wire and plugs as your first steps.

 

[God]

Scanned for codes earlier and got p0121 (tps circuit A)

So should I just replace the throttle position sensor? No misfire codes

 

[SunlitComet]

the misfire is different then misfire codes it actually keeps a running total of misfires in individual cylinders. you would need a scanner that can read proprietary gm data to see it. Regardless the tps is a primary sensor that greatly effects the engine fuel control so replace it as the pcm is telling you that the tps is not outputting expected data based on other data from other sensors. Replace it with this. http://www.amazon.com/ACDelco-213-912-Original-Equipment-Throttle/dp/B000C9JSBG/

 

[God]

I was just reading about the p0121 code and apparently it could be one of two sensors - either the tps, or the pps(pedal position sensor).

Also sounds like it could be a dirty throttle body tripping the code.

Where should I go from here?

I'm inclined to throw parts at it, tps on eBay are pretty cheap, is it ok to go with the cheap part here or should I go name brand?

---------- Post added at 01:31 AM ---------- Previous post was at 01:24 AM ----------

the misfire is different then misfire codes it actually keeps a running total of misfires in individual cylinders. you would need a scanner that can read proprietary gm data to see it. Regardless the tps is a primary sensor that greatly effects the engine fuel control so replace it as the pcm is telling you that the tps is not outputting expected data based on other data from other sensors. Replace it with this. http://www.amazon.com/ACDelco-213-912-Original-Equipment-Throttle/dp/B000C9JSBG/

There's a 6 dollar one on eBay with a lifetime warranty and free shipping though:/

---------- Post added at 01:37 AM ---------- Previous post was at 01:31 AM ----------

Also, the code says:

Throttle/ Pedal position sensor
Circuit A
Range/Performance

How can I know if it's tps or pps?

 

[ccapehartusarmyINF.(ret)]

yes you should definatly replace the throttle position sensor the Onboard diagnostics isnt trying to trick you lol plus yer descibing the exact symptoms of a faulty TPS
its sending incorrect throttle position to the PCM causing either rough idle.high idle. low idle,hesitation,rough shifting,stalling, and not to mention a check engine light
pedal position sensor throttle position sensor are the same thing
that thing on the floor next to the brake the technical term for that is the throttle

 

[SunlitComet]

as capehart has said replace the tps. do not replace it with anything but the part number i provided. no equivalents or nothing. definitely not a $6 unit from ebay. you are reading to far into the code as there is no "a" circuit as it applies the the obs models. that is for nbs models.

---------- Post added at 03:01 AM ---------- Previous post was at 02:58 AM ----------

pedal position sensor throttle position sensor are the same thing
that thing on the floor next to the brake the technical term for that is the throttle

going to have to argue that one with you. on units with throttle by wire setups those are actually two separate sensors mounted in two separate places monitoring two separate mechanical inputs. one has 2 monitor circuits the other has three.

 

[ccapehartusarmyINF.(ret)]

LOL i didnt know that hey i learn something new everyday
and you dont have argue with me your one of the few on this forum whos automotive knowledge and expertise ive come to respect

 

[God]

So I bought the $6 sensor off eBay! Wish me luck! Hey they're probably all made in the same factory and then rebranded anyways right? Might as well get generic!

If it doesn't work I'll buy the ac delco lol.

Thanks guys!

 

[SunlitComet]

there is a difference trust me.