ecu code 51 = injector opencircuit or short

[ponzy]

i got JAMIE's consult and was able to pull a code from that (worked for me for a couple min, got to try it again some time) there were ECU code 35 egr temp sensor and code 51. i was able to reset the ecu and code 35 disappeared but code 51 retained.

i did the plenum job (changed most of the underplenum hoses, bypass hoses, booster line and a lot more; DEATSCH-flushed rails and 6 injectors; 2 new injector from joe; changed knock sensors and harness; changed fuel lines from the filter-to-rail-fuel regulator; changed fuel pump and filter; cleaned the plenum, egr, TB, IAC, 2 months ago and was't that succesful cause i still have the "vibration" and additional symptoms: high idle rpm at start up (1250) then fluctuates at 450-750 constant at normal temperature 174 (ideal is 167.x i guess)

some of the tip-plastic cap of injector was chipped but was replaced with new ones from DEATSCH before replacing unto the rails. From these info, what do you think could go wrong? i did not changed the injector harness but they are all ok. it seems to be i need to send this car to a reputable shop and spend more dollars or just let it die out (i spent almost 3 g's already --- including some suspension parts which hasn't yet been installed like jeff's FSTB; tokiko sets; eibachs; FSB/RSB -- complete bushings; spl subframe collars and planning to buy SPL FUCA, RUCA, tension rods; jamie's usb-consult)Now, i am not sure yet if this' worth another dollars and just stop and cut my losses. i know this car was taken care of the previous owner and as the new owner for almost 10 months now, i've used the car no more than 4,000 mi and taken care of her a lot. but the maintenance thing is driving me crazy. the other side of me wants to go on and have this car fixed and the other is telling me to stop. PLEASE help me figure this out........i can get the money to fix this but i just want to be smart enough when to stop.......

thanks a lot.
Modified by ponzy at 10:42 AM 6/20/2007

[goody90q45]

I think code 51 (leaky injectors/injector analysis) is what comes up when O2 sensors need replacing. Didn't see that on the list of things that you had repaired. I believe this is the same code I had on my 90Q when I bought it. What is your consult showing on the O2 dial?

You've got to wonder why neither of the O2 sensor codes don't come up when they go bad. One of the shortcomings of OBD1.

Don't give up on your Q, you're almost there. Good luck.

[ponzy]

i have to check it again.......but i think it registered 2.x at idle and 40 when cold start up as per O2 (both O2 and O2 right)..not sure with the values i have to try it again when time permits......

will the vibration be caused by a fouled O2 sensor?

thanks mike.......i need that encouragement.......

[Q45tech]

The only way for an ecu to guess that an injector is leaking is some abnormality in O2 switching rate.................at cruise the ecu goes rich and expexts a rich response, lean and a lean response................this how it zeros in on a 14.7 after a number of tries..................the ecu has a preprogrammed injector open time in millisecs [say 1.2] and it tries 1.3 and 1.1 then 1.25 and 1.15 then 1.22 and 1.17 then 1.21 and 1.19 looking for 1.20....................now due to age and changes 1.2 may nolonger be optimum so the adaptive learn shows a percentage deviation from preprogrammed value [100% 105% 110%] a number for each cylinder bank to tell you how far the system now says is required.

[elwesso]

remember the difference between code 51 and 45 (circuit vs LEAK)... The injector circuit code is most likely not related to o2 sensors like code 45 is.

Normal temp shoudl be above 176F but below 195. if you never see 176 then that could be part of the problem

I would start by ohming the injectors at the harness and see if you get any that come back open circuit.

Dont give up on this car, dont let something simple bring you down! Once you get evreything sorted, its an incredibly easy car to own.

[ponzy]

i found an exact procedure with regards to ecu code 51 on the FSM. It is on EC - 120 (diagnostic procedure 16). But before code 51 appeared on the self-diagnostic, code 35 - egr tem sensor appeared first. code 35 is a diagnostic procedure 12 (EC - 109) on the FSM. i just reset the codes without correcting it, prolly i'll check on code 35 first then on code 51. Now, with it's unstable idle there's a procedure also in the FSM, it's in the EC - 178 (diagnostic procedure 35) which accounts for checking BPT; injector / harness; spark plugs; coil packs/harness; power transistor; fuel pressure; heated oxygen sensor; mixture-ratio; vaccum leak; iacc-aac/tb/pcv clogging; engine compression; ECM harness instabilities.......

a whole lot of procedure. 2 questions, esp for those 'expert' on laptop powered-consult: 1.) which software is readily available now that can do the "POWER BALANCE TEST" and " MIXTURE RATIO TEST" -- (running rich>>>>lean>>>rich>>>lean>>>>rich )?2.) What do you mean by "check egr valve for sticking" ?

thanks again.......

[elwesso]

Power balance isnt going to tell you much in this setup besides which injector is cuasing the problem. If its truely in the electricals, ohming the injectors at the harness will give you the same results.

Mixture test you can do on the ECU and again thats not gonna tell you a whole lot.

[ponzy]

Update is on this thread:

zerothread/256573

injectors/harness ok (by mechanic)

ruled out pinched intake rubber gaskets

#3 cylinder not firing -- changed coil pack

now, left bank is not firing (passenger side=left ? Or driver side?), have to change the ignitor chips (chips will be donated by jamesmost, thanks man)

...still waiting. what else could you suggest. Pls reply. Thanks a lot in advance.