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Severe lack of power like struggles to go over 35 mph. Checked for restricted exhaust 3 psi both banks. Alcohol content reset checked actual fuel around 10%. Fuel pressure 55psi. But what’s weird is map sensor reads 2.5 volts at idle. Goes dead lean. I am replacing front oxygen sensors for heater codes. But still shouldn’t an o2 sensor unplugged still have more power than that. I’m thinking of checking actual vacuum with a gauge and doing a cam crank scope pattern. Does anyone have a known good cam crank relationship. Won’t rev. Customer bought it used at a car lot
The other thing I noticed that’s weird is the mad sensor electrical connector is at the 12 o’clock position. Would you think that would cause an issue?
Cheryl wrote: But still shouldn’t an o2 sensor unplugged still have more power than that.
Agreed. The only way I can think of for an O2 to cause low power is if it's a false rich condition. And you already indicated that the O2's go dead lean.
I’m thinking of checking actual vacuum with a gauge and doing a cam crank scope pattern. Does anyone have a known good cam crank relationship. Won’t rev. Customer bought it used at a car lot
I can get one tomorrow if needed. What's the 8th of the VIN? Or the engine RPO?
I might suggest unplugging the MAF? What does the MAP say KOEO?
The other thing I noticed that’s weird is the mad sensor electrical connector is at the 12 o’clock position. Would you think that would cause an issue?
Can't say I remember. :lol: And I just did an engine oil pressure sensor in one today... Again, I have a couple vehicles to check at work if needed.
I’ll get you the 8th vin tomorrow. But I’ve unplugged the maf sensor still no power. The map sensor reads 2.5 volts at idle thinking it’s low vacuum screwing with the map. This thing will hardly go over a speed bump. It says add oil on dash but oil level is full so it’s probably just a oil level sensor. Weird thing is it’s not misfiring or anything at idle. Also what does your fuel injector balance test start at abs end at on psi readings? Trying to see if it’s restricted injectors. They don’t give specs even though it’s there scantool automatic test
I’ll get a pic for you tomorrow Ben. This thing ain’t definitely spinning no tires. Just trying to see if the timing is off. The highest maf reading I could absolutely get is 169 g/s
Cheryl wrote: IAlso what does your fuel injector balance test start at abs end at on psi readings? Trying to see if it’s restricted injectors. They don’t give specs even though it’s there scantool automatic test
I just ran this test on an '09 Avalanche. I don't recall the exact readings, but I do recall the injectors dropping about 30 PSI each. That's not a hard and fast rule, just what the last set of injectors did. :silly:
Did you drive it with exhaust pressure sensor hooked up? I rigged up a 30psi pressure transducer to 02 bung adapter so I can drive it and see what I can get on. Wide open throttle run . I've wanted to try a pulse sensor in the tailpipe and see how the pulses change (I expect it to not have pulses with plugged cats at high load/pressure) but I havent had any with plugged cats lately..
Cheryl wrote: I’ll get a pic for you tomorrow Ben. This thing ain’t definitely spinning no tires. Just trying to see if the timing is off. The highest maf reading I could absolutely get is 169 g/s
Ok well some pictures graphed will do . I seem to remember the fuel pressure drop test ending around 23 psi on the 5.3 but the amount of pulses may be different between tools ... I haven't tried the pressure drop test on the otc yet but several other functions between the otc evolve and the snapon are way different....
The customer has a snap on tool with bi directional tests. So I’ll just use his since it’s not doing him any good right now. Ill do it on a cold engine
Cheryl wrote: The customer has a snap on tool with bi directional tests. So I’ll just use his since it’s not doing him any good right now. Ill do it on a cold engine
Could get the scan tool set up KOEO then start it and take it for a WOT pull immediately while it's in open loop. That'd should rule out it being the O2 sensors.
