scan reading ....HELP ..!

[smokingjoe]

can someone help me to read a scan test done with autoxray 6000 : my problem is the IDLE :when starting at cold it's ok , but after 2 or 3 minutes become very rough , as engine become engine hot , from 768 to 672 rpm , like one , or 2 , 3 cylinders missing ...? (sparks plugs , wires , etc NEW !!)i've check all spark plugs : OK ! injectors ok ...! O2 sensors OK !
could it be a problem with injectors 1 or 5 : not driven by PCM ..? ICM ? or cam/crankshaft sensors ?
The problem is : fuel adapt readings : 40.8 % on bank 1 , - 9.5 % on bank 2 !!!!
my snake is a 94R/T , with a 96 GTS engine , STOCK PCM ( 94 R/T )
ANY HELP WELCOME ..!!!!!!!!
Oh , yes : I've no cats !
can mail you the scan readings ...IF you !!?
Thanks , JO.

 

[smokingjoe]

Anybody .....?

 

[Ulysses]

There should be Bank 1 Sensors 1 and 2, Bank 2 sensors 1 and 2. I believe, but I don't have the shop manual in front of me, Bank 1 is the upstream pair and Bank 2 is the down stream sensors. At any rate, one is reading Rich and the other is reading slightly Lean. I'm pretty sure the 94's did not have rear O2's so the Bank 2 reading may not mean anything at all.

Did you just put this engine in? PCM might be in the learning mode.

 

[smokingjoe]

i dont have rear O2's , front o2's are new ! may be i've to drive the snake a bit more ,i've only 40 miles since engine change ..!?
i think the main problem is the adapt fuel factor ....: what's that ?

 

[Ulysses]

Long Term and Short Term Fuel trims. Accounts for degradation in O2 sensors over time. Until the PCM learns, the car will run rich. Rough idle is normal during this process, however, idling like it's missing a few cylinders is a bit extreme.

 

[smokingjoe]

How many miles , for pcm to relearn ...?

 

[Ulysses]

I'm just pulling a number out of my you know what, but I think it's around 50 miles or so. Some Vipers are touchy. You can speed up the process by running with the AC on.

From the Viper Wizard:
"Since I disconnect at least two a week, every time I do the first time start-up: As soon as you see your oil pressure gauge comming up, hold 1800/2000 RPM for 20/30 seconds and then slowly let up on the throttle back to idle. This makes the PCM learn it's parameters faster. 99% of the time this works."

 

[smokingjoe]

Thanks , will try this to-morrow morning !

 

[Dave R]

Your idle problem may not be related to the 'adaptive fuel' readings your getting from your AutoXray (Bank 1 short term % running rich).

I also have a 94RT and use an AutoXray scanner. My car idles and runs perfectly, but I have always had the same 'strange' Bank1 adaptive fuel reading using the AutoXray. (Bank1 short term adaptive = +40% to +47%, Bank2 = -2% to +3% which is normal. Bank1 and Bank2 long term adaptives fluctuate between +16 to -32 microseconds.)

In theory, if the Bank1 short term % is greater than +-10%, the long term adaptive should increase/decrease to a point where the short term adaptive drops below +-10%. But this never happens!!!!! The short term stays in the +40's and the long term doesn't increase.

Coincidentally, I have been working to solve this problem for the past week. I have a VEC2 and have been altering the base fuel by as much as 50%, from 2.5 ms to 3.5 ms and the short term adaptive still reads in the 40% range??

I am still working on this anomaly, but am beginning to suspect a software/hardware problem with the AutoXray or the OBD1 output stream of the PCM. The fact that you are also getting the same readings just strengthens my suspicion.