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P0300 & Lean Codes on both banks, Car now stalls out

1K views 6 replies 3 participants last post by  Jeff K 
#1 · (Edited)
tl;dr changed egr vacuum hose and put seafoam in tank, now car idles very rough and stalls out. :unsure:

Alright so I am at a loss right now. Im just going to give the full story in hopes that someone thinks of something obvious.

Recently I noticed that my engine has been pinging (Its been in the triple digits recently and my commute has a lot of uphill driving. hills + ac = high load.) Since the car is about 20 years old I figured it wouldn't hurt to run some seafoam through the gas tank to help clean it out. So i dumped a full can into the fuel tank while it had about 6 gallons in it last night. Then in the morning, drove it 5 minutes to the gas station to fill it up and went to work. When I got in the car to go home and started it up, it pretty much immediately threw a P0171 and P0174, which didn't really surprise me since the car has had a rough idle since I bought it, and because I noticed the other day that one of the egr pressure feedback hoses had a hole in it.

When I got home, I figured I would scan it to see if I could figure out why the code was set, and sure enough my fuel trims were all in the 20%s (so about 40% Short Term + Long Term on both banks) Poked around for awhile and didn't really see anything other than that broken egr hose and decided to replace it.

Went to THE ZONE and got a new hose, replaced the old one and.....

As soon as I started the car it was making a loud hiss and stumbling all over the place, checked the codes and a P0300 had popped up. At this point I took off the new hose and replaced it with the old one but the issue is still there. Then I tried random things like unplugging the IAC and checking the rest of the hoses but nothing seems to change the misfire and stumbling.

Its pouring rain right now so I can't go and check the rest of the stuff I want, like the fuel pressure or the spark plugs, but I am extremely confused as to what happened here. I doubt the seafoam or the vacuum hose have anything to do with this but geez if itsn't a massive coincidence. Almsot forgot, I also added about 5 oz of seafoam to the crankcase as well, but again I doubt that has anything to do with it.

So .... thoughts? :unsure:
 
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#3 ·
^^^^^ Agree 100%
 
#5 ·
Haven't found anything, fuel pressure and spark plugs were good. Car will run when you give it throttle but dies when you let off. I definitely am leaning towards big vacuum leak but just don't see where its from. Maybe I should go buy a vape lol.
 
#6 · (Edited)
Problem Located

Got it sorted out. As I figured it was something dumb I did. B)

I replaced my valve cover gaskets and upper intake manifold gaskets recently and when I did I had to move some vacuum lines so I could torch the egr valve fitting. Well, when I put that hose back on I apparently didn't route it right because it rubbed up against the egr tube and got a hole burned through it. Now I need some help identifying the hose so I can purchase a replacement.

It runs from the back driver side of the upper intake manifold all the way to the firewall on the passenger side of the car. Looks like it connects to the UIM pretty much under the IAC.

Thanks in advance (and retroactively) for help.
 
#7 ·
Get some emission hose of the proper diameter from any parts store and replace it. It is just a hose.
 
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