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1987 Fleetwood Brougham
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239 Posts
Discussion Starter #1
Well, since I put the new fuel pump on my car, it has a problem with running rich. The engine is throwing a code 12, normal, a code 34, MAP voltage, and 45, rich exhaust. I didn't think this car had a map sensor since it was carbureted. The guy at the carb shop says my fuel pump is putting out 11 PSI of pressure, but if that were the case, I should be rich all the time. It's random and usually accompanied by an SES light. Anybody have any ideas?
 

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94 Fleetwood Brougham
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7,534 Posts
11 psi is waaaay too much for a Q-Jet. 7 psi is max, and that is for racing. 3-4 is best for fuel economy. How did he measure it? Sounds fishy.

Yes, you have a MAP sensor. It is used for engine load determination by the ECM.

Check the map sensor hose. It is a black hardline vacuum line from the carb to the pass side fender (well, is on my Cutlass!) and ensure you are getting manifold vacuum. It should come from the vacuum tee on the top front pass side of the carb, which is a manifold vacuum port (aka, below throttle blade port). Verify lines are ok, replace/repair as needed. Carefully bend the rubber connectors that the hard rubber lines go into. They get old and crack or break.
 

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1989 Fleetwood Brougham d'Elegance|2018 Chevy Colorado Z71
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6,421 Posts
I had a rich code problem when I had my new carb put on. Turned out it was the purge valve. Cheap fix. Have that looked at. Mine was full of fuel. Every time my car would run at a steady speed the CE light would come on for a few seconds/minutes and then go out.
 

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1987 Fleetwood Brougham
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239 Posts
Discussion Starter #4
So I just inspected the Caddy, and the vacuum line that's to the driver's side of the fuel inlet, at the bottom of the carb, was just laying on the manifold. I guess I bumped it off while I was in there. Needless to say, I plugged it back in, and my god does the car run good! It ran a little choppy and rough at idle, but once it warmed up and hit closed loop, the car ran better than it ever has before.

The 307 has the power I'd expect it to now, which is enough to get the car up to 55mph in a reasonable time frame without people honking at you. Now if I could only find someone to tune this Q-Jet properly, I bet this car would run absolutely perfect.

The car also doesn't stink. I think the majority of the stink coming into the cab was due to the fuel pump hanging halfway off the block. I bet I was smelling oil vapor and not exhaust through the air vents. It still sounds nice now that I replaced all the exhaust gaskets and that one rusted out pipe though. That 307 is so quiet and smooth when running properly that I keep thinking I stalled it out while sitting at a stop light.

Oh, and for those of you experiencing knock, relpace your O2 sensor. My knock is virtually gone now.
 
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