Ahab,

Thanks for the advise with the OBD Fusion app. I have figured out how to capture and export the logs. Trouble is, I'm not sure which of the many parameters to log - nor what to look for.

From the SAE PIDs I am guessing I want to capture the following

Fuel system 1 status
Fuel system 2 status
Short term fuel % trim - Bank 1
Long term fuel % trim - Bank 1
Short term fuel % trim - Bank 2
Long term fuel % trim - Bank 2
Engine RPM
Vehicle speed
MAF rate
Absolute throttle position
O2 voltage B1, S1
Short term fuel trim B1, S1
O2 voltage B1, S1
Short term fuel trim B1, S1

Any light or advise you can share would be greatly appreciated.

Thanks!

 

Write down LTFT values for each bank. Graph O2 voltages for B1S1 and B2S1. LTFT should be consistent on both banks, near zero stock, maybe offset with the build. Upstream O2 voltages should flip flop between near zero to near 1 volt, with a fairly steady rhythm.

 

Not arguing, discussing so we all can learn. I am not sure what the IRS means in the part description but I do know the D2 uses male plug wire terminals at the coil end as do the LS series engines, however my older Vortec and CJ plug wires are female on both ends. I have not used the universal NAPA style, are they configured such that they will work with the D2?

 

Thanks!

These files are massive. How long and what speed(s) should I be graphing?

From what I can see in the latest file

• The O2 voltages seem consistent and vary fairly evenly - always under 1 volt
• LTFT Bank 2 doesn't seem to vary much at -7.03125
• LTFT Bank 1 varies. Its primarily at -6.25 but will fluctuate to -5.46875 and -4.8675. It was only even with bank 2 (-7.03125) momentarily when RPMs and throttle kicked up

Struggling on how to convert to a graph that make sense...

 

OK - making progress...

O2 sensors. Bank 1 and 2 sensor 1.

 

Long Term Fuel % Trim.

 

So, good news. Those trends look good. ECM is controlling fueling between rich and lean using O2 sensor feedback. Both banks are very similar, with similar time responses. ECM looks for voltages crossing around 0.45 volts (stoichiometric), then adjusts duty time of the injectors (each bank independently).

Long term fuel trim values are similar for both banks. Pulling fuel back -6 or -7%, so no vacuum leak. Vacuum leaks usually cause fuel to be added. Not pegged near maximum limits +/-25%. New stock engines LTFT should be between -3 to +3% if all is well, but yours is not stock anymore, even -6 or -7 is not bad, nothing to worry about. Maybe caused by higher fuel pressure or higher flowing injectors? Doubtful leaky injectors, since that is very rare, especially since both sides are nearly equal.

Bad news is this data indicates a normal running engine, so does not help find the misfiring. Did you consider raising idle speed as a test? Will require more diag to get to the bottom of it. In the mean time, enjoy the ride!

 

Thanks for the quick response!

Standard fuel pump and injectors.

I hate throwing parts at it without knowing what is wrong - but maybe upping the idle may do the trick. Only problem is, I don't know how. I may need to take it to a local indy LR shop - unless it's something simple. The only parts not changed recently are the injectors (installed rebuilt ones 2 years ago), coil packs and crank position sensor - both also 2 years old and Bosh or genuine LR.

 

Not quite sure how to raise idle speed on a D2, but maybe another Forum member knows an easy way. A simple way to try is to tighten the throttle cable adjustment until the throttle plate opens slightly. Be advised, this might cause other issues (e.g. on D1 causes really high idle 1500 - 2000 when started) or throw a different code if the Adaptive Values (i.e. TPS initial value) are not reset. The ECM will attempt to adjust the IACV to a pre-set RPM, so any adjustment of the cable will need to overcome the IACV limit.

Pay attention to the pre-test position of the throttle cable so you can restore it later. Usual setting is to back off until the cable just goes slack, plus a little. Now that I write this down, it seems a bit complicated to me for little gain. Successful result of the test would be smoother idle RPMs (no more lope) so no more misfire codes. Then just put everything back to the starting point with no resolution of the problem. Maybe not worth the effort to gain a little knowledge.

Maybe just clear the codes then put a brick on the gas pedal (850 - 950 rpm), to see if the misfires do not re-appear during a long warm up and idle. Just rambling now.... Keep calm and Rover on!

 

The idle can be adjusted on the linkage. The two cables are the throttle and cruise control. It's a tedious process getting wrenches in. I had to up the idle when I had fuel injector seal leak. Then had to lower it after replacing the seals. The linkage had never been adjusted so 20+yrs of rust and gunk made it slow going. Currently, after warm-up I idle about 680rpm. If you suspect your injectors are a problem I had success using www.mrinjector.us. If you have the old/originals they will clean, rebuild and test. They also send a before/after performance flow chart.