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Originally Posted by jharri7140
Running into an issue recently of my 4runner misfiring at idle. A couple months ago it developed an issue where on cold starts after a night of sitting it would fire up and run rough for about ten seconds then it would go away and be ok. Then recently it is still doing it on cold start, but now when it gets to running temp and I come to a complete stop and idle it runs super rough, and even threw a misfire code. Also a couple months ago I had a misfire while driving on the highway so I replaced plugs, wires, and coils. Then in an effort to make sure fueling was good I rebuilt the fuel injectors last weekend. So now I know I have solid spark and fueling, so now I am thinking some sort of a vacuum leak or intake valve. Does anyone know what this issue is, or have any advice what to check or clean?
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What do you mean you rebuilt the fuel injectors?
Also when you have this issue on cold-start have you noticed more smoke/vapor from the tailpipe? Have you done a compression test and/or leak down test on the vehicle while you were changing plugs and such? What was the misfire code(s)?
Quote:
Originally Posted by jharri7140
Thanks for the information on checking the coils, I gave a new IAC a try and now the problem is still there but not as noticeable as the thing is idling at 1500 rpm. And while I was in there I cleaned the MAF sensor and checked vacuum lines and the throttle body fly, everything looks to be ok. I will check out the coil resistances to ensure they are good, it would just surprise me the misfire would only be happening at idle.
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Something I ran into with an older Tacoma that had the cable driven throttle body was that the center shaft for the throttle body had actually worn out enough to "stick" around the idle position. It would act like the dash pot was holding it open (you could physically press the linkage fully closed and it would idle fine) but if you revved the vehicle it would stick and idle high at about 1500+RPM. The fix was a new throttle body unfortunately. I didn't end up keeping that part because when I inspected it after replacing I could see where the throttle plate was catching on the bore and how much play was in the shaft, so I didn't think it would be worth rebuilding
IF it was even possible to do so.
Quote:
Originally Posted by Bad Luck
What are your long term fuel trims at idle once the engine is warm?
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This is also something worth looking at, this will give us a better idea of how the engine is running from a fueling/efficiency standpoint and help narrow down possible culprits.