99 Tahoe 5.7 vortex P0300 code HELP
- Thread starter Mackb23
- Start date
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It's running lean based on your short-term fuel trims (fuel is being added -- a lot!). One possibility is a vacuum leak, or something else could be causing that. Check the intake from the MAF to the throttle body to be sure there aren't any leaks in that plumbing. It could be a hose left unplugged, or damaged.
I’ll definitely take a look at that in the morning! I appreciate it.
Hoesgottaeat2
Full Access Member
Did the new motor come with new ignition components?
My '99 Hoe had a P0300 and it wound up being a bad distributor cap, that was replaced just months before the issue arose.
The new cap resolved the issue immediately.
My '99 Hoe had a P0300 and it wound up being a bad distributor cap, that was replaced just months before the issue arose.
The new cap resolved the issue immediately.
It did not come with anything but I did replace the distributor cap and rotor, along with new plug wires and plugs
I’m also having multiple misfires on 1 and 5
Multiple parts on this series of trucks-most aftermarket parts don't work or not very long.
The first on my list- Dist cap/rotor. Use only Delco, Delphi, or United DCR820x only. Packard Wires a help also.
Gmt 400 trucks do not like certain aftermarket parts.
First on my list is Dist cap/Rotor- Use only Delco/Delphi, or United DCR820x. Packard wires a help too.
Looking at fuel trims- 1st do an idle leak check using carb cleaner around intake. 2nd- fuel pressure check, Best is a 6 foot fuel hose and stick Gauge under wiper. Report findings here. We're here to help.
Looks like a vacuum line, but I wouldn't mind seeing a pic of where it is on the engine.
So, a quick update, replaced the pcv valve along with the hose connections, and it’s not bogging down when I take it out of park, still throwing the code and running a little rough, gonna dig some more into it this weekend, would any one suggest getting new grommets for the intake?
Might be helpful to post new short- and long-term fuel trims after your initial repair.
Unfortunately I don’t have the OBD scanner anymore so now I’m at a loss
Will be here Monday, thank you!!
east302
Full Access Member
They can seep oil over time, wouldn’t hurt to swap them if they’re original. They’re the same part for both valve covers.
As others mentioned, aftermarket distributor caps are a weak point.
Follow the hard vacuum line from the PCV fitting over to the solenoid on the passenger firewall. Make sure it isn’t broken somewhere. From the solenoid is another vacuum line to the heater valve.
Okay yeah they’re original. Came with the new motor, I’ll get some, I also just changed the MAP sensor, what’s the best way to check the hose from the solenoid to the heater core ?
east302
Full Access Member
It’s just a rubber hose from the solenoid to the valve (#14 in diagram) so it can crack over time. The only way it could cause a vacuum leak is if the solenoid is energized - when the a/c temp dial is in the Max detent.
#20 is the hard line to the PCV fitting.
#20 is the hard line to the PCV fitting.
