Car is an automatic. When it is in overdrive(4th, whatever)....it feels like its hitting a wall around 50 mph when I give it ANY gas. If I downshift to 3rd manually, it will accelerate ok...but still stumbles throughout all the RPM band.

Its the worse in 4th at around 50ish.

Also, it runs rough at idle while cold or hot. When the car gets hot, the RPMS will drop and I have a few Scanmaster readings if anyone can look them over please.

When engine is COLD:
IAC reading normal..stays above 20 at idle
RP and LP(Pulse) are normal and stay linear(together)
Lin and Rin(injectors) are normal as well
RBL and LBL are similar around 128, but quickly one of them quickly moves up(LBL I think goes up to 160...I can confirm this tomorrow)

When engine is HOT:
IAC drops to below 04(very low)
LP is usually half of what the RP is
Lin is about half of what the Rin is
already said the LBL goes up to around 160


The car will throw a Left O2 sensor running lean. From these numbers people have told me it might be a vacuum leak. I adjusted all of the rocker arms hoping some of them were too tight causing a vacuum leak, but this did nothing. I also replaced the IAC but it didnt help. Plugs are new and gapped at .035...Coil is good. Opti was replaced with no improvement.

Would you guys recommend chaning wires AGAIN? They probably only have like 500 miles on them, if that. Maybe they are bad?

Also, would a vacuum leak cause all of the readings on one side of the engine(the injector readings) to be half the numbers as the other side..I guess thats my biggest question, if that sounds related to vacuum or ignition.

Thanks for any help. I can clearify anything if u need...please I need to fix this thing.

 

Really need help...One other thing I was thinking that might be a big clue...

When the Service Engine light comes on, doesnt the car go into closed loop(like when you're WOT)? Well after I drive the car for a while, and its shaking like crap, as SOON as the SES light goes on, all the sudden the idle smooths out and it runs much better. This would suggest its not a bad injector atleast right?

BTW The code it throws is Left o2 running lean..but I replaced both o2's and it runs the same.

 

I'm having a similar issue with my idle counts.. i have a very very low IAC too, replaced the IAC motor with no help. I'm starting to thing that i might have an intake leak... but have not been able to find it

 

To me it seems like you may have a bad injector on the left bank. My logic may sound strange but just bear with me. On a carburetor you have whats called an accelerator pump. The purpose of this part is so that when you initially give the car some gas, the carb will shoot a little extra fuel in that the car won't run lean. Seeing as though our cars are fuel injected we don't have carbs which also means we don't have accelerator pumps. To the best of my knowledge the TPS data is fed when you give the car some gas, and this injector is supposed to provide for this extra fuel you need. Seeing as though you mentioned the car smoothes out when the SES light is on, it could very well be the TPS( it could also be that when the SES light is on the car runs rich which may mask the injector that is causing you to run lean). There are ways to test that sensor. Were it me, I'd get a chiltons manual if you don't have one already and run through testing all of the sensors and those left injectors. Odds are one is f--ked up or you could have a bad injector. Usually a parts store will let you rent out the meter needed for testing the sensors. It would just seem strange if you had a bad sensor that it would onlt effect the left bank though...With that being said IMO I'd test the injectors first.

Also, a quick way to tell if one cylinder is running leaner than the rest in to compare the spark plugs. Usually a well tuned engine will have light tan/gray plugs, a rich running engine will have darker/black plugs and a lean engine will have like a white color (I believe).