Parameter Description Results
DTC for which Freeze Frame was Stored P0300
Fuel System 1 Status Open Loop
Fuel System 2 Status Open Loop
Calculated LOAD Value 2.35 %
Engine Coolant Temp 161.60 °F
Short Term Fuel Trim - Bank 1 0.00 %
Long Term Fuel Trim - Bank 1 0.00 %
Short Term Fuel Trim - Bank 2 0.00 %
Long Term Fuel Trim - Bank 2 0.00 %
Intake Manifold Absolute Pressure 10.96 inHg
Engine RPM 665.00 rpm
Vehicle Speed Sensor 0.00 mph
Air Flow Rate Mass Air Flow Sensor 0.70 lb/min
Absolute Throttle Position 0.00 %
If you haven’t pulled that upper plenum off to have a look at that spider fuel injection unit, you need to do so. The plenum is not that hard to remove, and there is a very good chance this is what is causing your symptoms and your P0300 code. If memory serves me correctly, you will also not have to buy any gaskets just to have a look since the upper plenum uses an O-ring type gasket set in a groove, which is reusable. The injector unit is now 15 years old, a time point in which they often fail. Look for wear and breaks in the hoses leading to the poppets. They will often wear through on the ones located close to the lower intake manifold, where they rest on the casting.
when i took that hose off the front drivers side where it goes in the intake there was like a goldish white color substance in there, what could that be?
Sounds like condensation, which is normally caused by blowby and/or short hop driving and can be exacerbated by an over-rich mixture. Condensation like this normally only occurs where there is oil circulation and, therefore, the potential for crankcase pressure. Where does the other end of the hose go?
Are you removing the plenum? Please say you are…
Less than 11 inches of Mercury?
yes
when i take the plenum off what do i look for?
The MAP reading should be the “absolute” pressure, so 11inHg should correspond to about 19inHg engine vacuum (about 30inHg or so atmospheric - 11 = 19) which is good.
automechanic1993 - you need to spell out your whole story here. You have X vehicle (make, model, year); it has X number of miles on it; you know X and Y and Z about its basic history; the symptoms you are experiencing are X and Y and Z under whatever conditions; you have tried/checked/fixed…
Another one of your threads got closed down by the site admin. Presumably this was because people started saying things about the nature of your incredibly brief, not-so-informative, difficult to decipher posts. You then responded by being quite rude. I’m going to revisit that theme. You are not going to get good help by posting brief, not-so-informative fragments of your problem across multiple threads with multiple little fragments of information. At this point your P0300 misfire has appeared in at least 3 or 4 posts, and you aren’t telling folks what is going on in any of them.
I’m really not picking on you. I’m just trying to tell you how you can better help people to help you.
the truck has the p0300 code it idles rough i changed the wire plugs cap and rotor pcv vavle maf sensor and it has a slight back fire when u shift from 2 to thrid.
Is this the same truck from your August 19th post? And are we just supposed to review all your multiple threads on the same truck. Or are we just supposed to remember it’s a 1997 GMC Sonoma 4wd 4.3L.
“when i take the plenum off what do i look for?”
Review my first response to this thread. I told you in that one what to look for. To make it short and sweet as you prefer it, you are looking for fuel leaks in the spider assembly, especially in the “legs” of the spider. This is probably what is causing your code, your driveability problems, and is probably contributing to that condensation issue you were asking about a few posts back.
By the way, I am assuming this thread concerns your Sonoma you have mentioned in other threads.
that wasnt the problem
DTC for which Freeze Frame was Stored P0300
Fuel System 1 Status Open Loop
Fuel System 2 Status Open Loop
Calculated LOAD Value 3.53 %
Engine Coolant Temp 91.40 °F
Short Term Fuel Trim - Bank 1 0.00 %
Long Term Fuel Trim - Bank 1 0.00 %
Short Term Fuel Trim - Bank 2 0.00 %
Long Term Fuel Trim - Bank 2 0.00 %
Intake Manifold Absolute Pressure 10.66 inHg
Engine RPM 768.00 rpm
Vehicle Speed Sensor 0.00 mph
Air Flow Rate Mass Air Flow Sensor 0.94 lb/min
Absolute Throttle Position 0.00 %