1999 Idle Probs

[Pathfinder]

My Tahoe is idling rough...Hooked it to the comp..threw 22 troubles. All 4 O2 sensors and mass air flow sensor. Would replacing the mass air flow eliminate most of these troubles?

 

[lesterl]

What were the CODES?

 

[Pathfinder]

It was showing P0300

 

[lesterl]

Thats not a bad O2 sensor code.....

 

[lesterl]

How many miles on your hoe? Last tune up? This is a random missfire code (p0300)

 

[Pathfinder]

There were several...he didn't give me a complete printout. It says random cylinder misfire on the one little slip he gave me. He read em out to to me as the O2 sensors. And the mass air flow.?

 

[Pathfinder]

I just bought this from a buddy...I'm sure he didn't have much done to it... Engine was rebuilt 60g ago and the tranny 70g ago... Plugs look rather rough on it from that I can see if the outside of em. Haven't taken on out yet.

 

[lesterl]

Well check the plugs, cap, rotor.

Codes are just a guide and not a "you need to replace this" usually.

The codes should still be stored unless they were cleared. If cleared get them scanned at the local autoparts and see what has come back, if not, see what is stored, clear them and run around a bit....

 

[Pathfinder]

Im gonna replace the plugs and wires first and see how that does.

 

[Pathfinder]

Ok heres the codes I got:

P0300 Random Misfire
P0138 O2 High Voltage
P0140 O2 Circuit No activity
P0141 O2 Heater Circuit
P0151 O2 Circuit Low Voltage
P0161 O2 Heater Circuit Bank2 Sensor 2
P0174 System too lean Bank 2
P0420 Catalyst System Efficiency Below Threshhold Bank 1
P0151 Circuit Low Voltage Bank 2 Sensor 1

I cleaned the Mass Air Flow sensor circuit and still no luck...Stumped here.

 

[lesterl]

What code has to do with the MAF sensor?

I would check running temps of the 2 cats, I suspect maybe the bank 1 cat has taken a dump on you.

P0300 Random Missfire
P0138 O2 High voltage (rich on bank 1 drivers side pre cat)
P0140 O2 circuit no activity (bank 1 sensor 2 -after cat if cat is plugged no activity)
P0141 O2 Heater circuit (bank 1 sensor 2 - possible bad heater they go bad)
P0420 Catalyst Efficency belwo Threshold Bank 1 (drivers side cat is probably plugged due to rich condition on bank 1)
Now possibly you have a leaking FPR or something that may have taken out that cat so dont just swap it out, but a backpressure test would be in order.

P0151 O2 Circuit Low Voltage (bank 2 sensor 1 - Lean on passenger side)
P0174 System too lean bank 2 (passenger side)
O2 low voltage could be a real lean condition, check fuel pressure....