MAP issue?
Thread Starter
Burning Brakes
Joined: Oct 2001
Posts: 1,205
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From: Dallas City IL
MAP issue?
Posted this in tech, but thought I should have put it here afterwards
Guys,
Coming home from a car show last week, the car started to stumble and run rough. A week earlier, I had melted a plug wire on my B&B short tube headers, and thought I had fried another. I replaced all wires, as I was having a hard time finding the one. Well, that wasn't it, next I replaced the sparks that only had 2k miles on them, which were very black, meaning rich. But instead of just one of them, they all were. After replacing them, this issue still exists. My wideband is now showing a rich condition, (11:0 to 1 at idle) and the car smells as such. It stumbles and doesn't want to idle. This is a SD tune, the MAF is out of the loop. It is running a COS3 from EFI Live that I have tuned. Looking at passed logs, I noticed my MAP reading avg is higher at idle than before. Map readings used to be in the mid 40's, now the mid 60's, which is why it's adding too much fuel. At key on, engine off, my reading is 99, which is correct. Also, my IAT sensor seems to be correct. I don't know if this means my MAP is still good, and I have a vac leak somewhere?
The car has a mild h/c with about 50k miles. Where should I look for vac leaks? I checked the PCV, seems to be ok. What should I check or log before I pull the intake? This is a LS1 with an LS6 intake and SVO 30#'s that was added back in 02'.
Guys,
Coming home from a car show last week, the car started to stumble and run rough. A week earlier, I had melted a plug wire on my B&B short tube headers, and thought I had fried another. I replaced all wires, as I was having a hard time finding the one. Well, that wasn't it, next I replaced the sparks that only had 2k miles on them, which were very black, meaning rich. But instead of just one of them, they all were. After replacing them, this issue still exists. My wideband is now showing a rich condition, (11:0 to 1 at idle) and the car smells as such. It stumbles and doesn't want to idle. This is a SD tune, the MAF is out of the loop. It is running a COS3 from EFI Live that I have tuned. Looking at passed logs, I noticed my MAP reading avg is higher at idle than before. Map readings used to be in the mid 40's, now the mid 60's, which is why it's adding too much fuel. At key on, engine off, my reading is 99, which is correct. Also, my IAT sensor seems to be correct. I don't know if this means my MAP is still good, and I have a vac leak somewhere?
The car has a mild h/c with about 50k miles. Where should I look for vac leaks? I checked the PCV, seems to be ok. What should I check or log before I pull the intake? This is a LS1 with an LS6 intake and SVO 30#'s that was added back in 02'.
Last edited by M396 #00-011; Jun 17, 2011 at 11:02 AM.
Tech Contributor
Joined: Apr 2007
Posts: 10,924
Likes: 78
From: Forney Texas
You have a vacuum leak. No other explanation. You mentioned an EGR, so I'm assuming this isn't on a Vette. Otherwise, you're checking something else. I've seen Fast intakes crack across the bottom. I've seen loose intake bolts, loose PCV hoses etc. Many shops keep a smoke machine for finding vacuum leaks. You can waive a propane torch with the flame off around the intake with the car running. You can also shoot butane on it, carb cleaner etc. and listen for an idle change. The only thing that affected the idle on the cracked bottom side on the Fast intake was butane.
