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The Intake Air Temperature is available to Torque Pro. Be sure to add the additional GM PIDs. Go to settings, choose Manage extra PIDs/Sensors, choose MORE at upper right corner, choose Add Predefined Set then choose Pontiac/GM/Opel/Vauxhall.

That will add a whole bunch of PIDs available when you select which PIDs to monitor in realtime or Graphing.

Ted
 

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Discussion Starter · #42 ·
on older GM V8 engines 2 sensors used one for dash other for computer. the NBS and newer only one . GM did this to save a few cents.

my 96 LT1 has 2 sensors. 2000 5.3L only one. temp sensor is on the driver side full fwd on the head .

the MAF does have a temp sensor the IAT. this sensor will effect the fuel trims. so if it is damaged and indicates -40F then that could do it.

using carb cleaner or other non approved solvents will damage the MAF electronics.
Yes I checked the iat as well and it was reading sort of what my outside temperature but more, like 90f. My maf reading was .7 lb/min and map 10 inhg. This is in closed loop when my engine was doing ok in regards to fuel pressure. My fuel trims became negative 13 on bank 2 and like negative 9 on bank 1.
 

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‘01 Silverado 2500HD 8.1/Allison 5sp xcab long bed
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Thanks for the education about the CTS.

Love sites like this. Learning every day.
 

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Yes I checked the iat as well and it was reading sort of what my outside temperature but more, like 90f. My maf reading was .7 lb/min and map 10 inhg. This is in closed loop when my engine was doing ok in regards to fuel pressure. My fuel trims became negative 13 on bank 2 and like negative 9 on bank 1.
with the data you have an intake leak . neg LTFT is lean, also engine vac @ idle should be 18-21 inches.
 

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Discussion Starter · #47 ·
with the data you have an intake leak . neg LTFT is lean, also engine vac @ idle should be 18-21 inches.
On the 18 to 21 inches are you referring to the maf reading at idle should be?
I'm going to do a smoke test on that brake vacuum line hopefully tomorrow. Intake manifold right not exhaust? The intake manifold leak would cause fuel pressure to go up and computer to not close the loop? Thanks for helping
 

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On the 18 to 21 inches are you referring to the maf reading at idle should be?
I'm going to do a smoke test on that brake vacuum line hopefully tomorrow. Intake manifold right not exhaust? The intake manifold leak would cause fuel pressure to go up and computer to not close the loop? Thanks for helping
the maf reading should be 4-5 grams per sec.. the MAP 18-21 inches of vacuum or 10 inches HG ... 30 inches HG is 0 inches of vacuum .. the MAF does fail intermittently as the signal output of 2500HZ does drop out then the PCM creates improper fuel injector controls and perhaps the fuel pressure varying with your vehicles fuel pressure control system..

the fuel trims indicate a sensor is messed up since its intermittent . but if the fuel pressure is wrong and the PCM being programmed for the fuel to be expected at the correct pressure would cause erratic control on the fuel ratios.
 

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Discussion Starter · #49 ·
Update

So I finally hooked up my torque connector with live data app and I finally found misfire data. I attached a screenshot. Code is still only p0300 and I have installed all new upstream and downstream oxygen sensors. I have misfire counts on 6, 7, and 8. Brand new plug and coil wire. I also switched the 8th ignition coil to 4th cylinder and no misfire at 4 so ignition coil also good. So should fuel injector be my next thing or compression? Also would these cylinders misfiring make my fuel pressure read high then misfire?
 

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You can swap injectors like you did with the coil. I would write down where they were swapped from and to so you don't get confused.

A compression test is always helpful. If you get a low value for 6, 7 or 8 squirt some light lubricant through the sparkplug hole and retest. That will seal the rings if they're worn. If it's still low that says valves. Put 50 psi or so shop air through the sparkplug hole with a rubber nozzle and listen in the throttle body with the butterfly open. If you can hear the leak that says intake valve. Sort of a poor man's quick and dirty leak-down test.

I don't think misfires cause high fuel pressure.

Ted
 

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Discussion Starter · #51 ·
You can swap injectors like you did with the coil. I would write down where they were swapped from and to so you don't get confused.

A compression test is always helpful. If you get a low value for 6, 7 or 8 squirt some light lubricant through the sparkplug hole and retest. That will seal the rings if they're worn. If it's still low that says valves. Put 50 psi or so shop air through the sparkplug hole with a rubber nozzle and listen in the throttle body with the butterfly open. If you can hear the leak that says intake valve. Sort of a poor man's quick and dirty leak-down test.

I don't think misfires cause high fuel pressure.

Ted
Ok update.

I swapped fuel injector 8 to cylinder 2 which had 0 misfires and the misfire counts were still high on 8 and rate of misfire on 8 were still extremely fast. Also ohms on the injector was good and no misfire on 2 at all. So I'm ruling out injectors and fuel injector wiring on 8 as well since it passed the noid light.
So I went ahead and did compression test on all cylinders. Cylinders 1 through 5 had 150psi.
Cylinder 6 had 135 cylinder 7 had 120 and cylinder 8 had 127.

Will this really cause such a bad misfire on cylinder 8 and 7 which are my 2 most misfiring cylinders? My book says 100psi on this vehicle is ok. I'm almost lost totally.
Also I'm now getting codes u0100 u0109 and u0073. All this after cleaning my fuel control module and ecm connectors. Also lost my fuel pressure reading on my scanner for some reason it reads 0 but same high readings manually.
 

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Discussion Starter · #52 ·
So I have lower compression on cylinders 6 7 and 8 than 1 through 5 but I don't know if that would make my truck misfire since those cylinders are still above 100. Any thoughts?
 

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this is one of the longest posting of the 300 code . I still believe its the fuel pressure control system.

at idle fuel pressure is low not at the max ...
 

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Discussion Starter · #54 ·
I agree and apologize for this 6 page topic but this p0300 is taking me in every direction. The compression test has me confused as I do not know if my cylinders are bad and also do not know if my cylinders or fuel system control module computer is also bad and which one is giving me this p0300.

I'm about to just bite the bullet and pay 250 for the fscm programmed from this website I found on YouTube. Also don't know if my ecm could be to blame. So far codes are p0300, p0109, and p0100
 

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the codes 109 indicates a MAP issue . check for volts DC at the MAP output . eng off key on volts should be 4.5 ...
eng on the volts should be 1.2-1.7 v... engine vacuum should be 18-21 inches .

code 100 is most times a bad wiring to the MAF but also can be the MAF itself has been damaged due to using the wrong solvents to clean it or damage to the MAF from improper handling.. make sure the wiring and connector is in perfect condition and that the wiring is not stressed out .

these two sensors will cause the PCM to act improperly and cause all sorts of engine operation issues this is how it determines the fuel ratios ..with your system sure could cause high fuel pressures at idle by receiving bad sensor data.
 

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Discussion Starter · #58 ·
I went through that procedure and everything checks out fine.

I will be getting an fscm from gm flash I'm thinking and hoping it works. The u0100 has me thinking should I also get an ecm they are 150 programmed but would the computer also being bad give me a host of other problems?
 
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