nabtastic

Hey,
Been having issues with my fuel mixture. Runs lean 32% fuel trim (hince the p0171), haven't found a vacuum leak, have cleaned throttle body, IAC, new TPS, new MAP, new upstream o2, cleaned IAT, new thermostat
Throttle position idles at 19%
O2 upstream stays at 0.1
O2 downstream stays 0.9
Fuel trim drops to 0 briefly when acceleratING
Vacuum stays around 15hg but has drop to 4hg and up to 22hg

Thoughts?

'90Cherokee

The vacuum goes from 4 to 22 at idle?

nabtastic

Oh, sorry. No. That's the full range during driving. At idle it stays 15-14.
I thought vacuum leak, but I'm considering a restricted cat

'90Cherokee

A cat restricted enough to effect idle would kill power in a huge way. Have you checked the TPS with a meter to be sure it's set right?

CCKen

A clogged Catalytic Converter is on the list of things that can cause running too lean, as well as a bad MAP sensor, O2S faults, vacuum leaks, and clogged or dirty injectors.


For a suspected vacuum leak, note the STFT at idle then increase engine speed to 2500 RPM and hold. If the STFT immediately decreases and moves to acceptable levels and the LTFT slowly starts to come back down, you have a vacuum leak.


A clogged CAT can be found by using a vacuum gauge connected to the intake manifold. Youtube has some vids on vacuum gauge diagnostics. Or google vacuum gauge diagnostics. Look for the procedure for checking for a clogged CAT.

nabtastic

Interestingly, I was moving some wires and apparently killed my upstream O2. Running in open loop now and throttle position idles at like 1%, rear O2 @ 0.1 (upstream is 0 bc it's failed).. only code thrown now is p1135. Searching for a short, or did I kill the O2?

CCKen

Anytime you have O2S issues check the O2S Heaters fuse in the PDC. Not that it's the root cause of your problem, but it should be checked. When in doubt, replace it. See PDC fuses pic.

nabtastic

Thanks, I actually saw a comment from you a while back (I think it was you) and replaced all my fuses and replaced all my relays to no avail..

CCKen

Do you mean P0135? That's O2S heater malfunction.


The O2S heater wires are both White in the O2S pigtail.


The body harness wires are Black, Ground at G101.


Dark Green/White tracer, power from the PDC fuse.


Both up and downstream O2S heater wires the same colors.


Sometimes the upstream O2S wires will chafe on the intake manifold - inspect them.


The downstream wires sometimes chafe or get tangled up in the drive shaft - inspect them.