5.7 TBI barely idles, stalls in gear, runs and starts ok at part/full throttle - Chevy Impala SS Forum
 
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post #1 of 7 (permalink) Old 03-13-2011, 01:52 AM Thread Starter
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Question 5.7 TBI barely idles, stalls in gear, runs and starts ok at part/full throttle

Hi everyone.

I'm helping a friend get his 92 Buick Roadmaster wagon ready to sell. It has a 5.7 Tbi with 190k on the clock. We were cleaning out the car as his daughter was not very tidy and the interior was a complete mess. We were also fixing some minor odd and ends, fixing the hood release, re-gluing some carpet, ect. I couldn't believe how big the back is with the seats folded down! Well Friday it started up with no problem, idled at about 1000 rpm when it first started then evened out about 800 rpm. So Friday the engine is good and sounds real nice.

Well I came over today to take some pictures and it ran like crap. It wouldn't start at all unless you held down the gas then the second you let off it stalled. I thought maybe it was low on gas (1/8 of a tank) so I add some gas from a gas can. It didn't help. I managed to get the engine idling if came of the gas very slowly but it idled unsteadily at about 400-600 rpm. The exhaust smelled very rich. When I put it into gear it dies. If I let off the gas quickly it dies. The odd thing is if I give it just a little gas maybe a little as 5% the "idle" stabilizes and if give it part/full throttle the engine runs fine. I checked under the hood no vacuum lines or plugs were disconnected but the snorkel to air box is missing. I didn't hear a hiss of a disconnected vacuum line at idle. I checked the air filter and ran it briefly w/o the air filter no change. There is no check engine light.

I'm guessing a vacuum leak but I'm not sure. The only other variable I can think of is it was about 10 degrees cooler today 39F. So what do you guys think? How should I start pinpointing the problem. Also keep in mind the budget for repairs will be limited.

1996 Impala SS
1966 Ford Mustang Coupe - Project Car WIP
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post #2 of 7 (permalink) Old 03-13-2011, 04:02 AM
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Quote:
Originally Posted by SaveOldSchoolMuscle View Post
Hi everyone.

I'm helping a friend get his 92 Buick Roadmaster wagon ready to sell. It has a 5.7 Tbi with 190k on the clock. We were cleaning out the car as his daughter was not very tidy and the interior was a complete mess. We were also fixing some minor odd and ends, fixing the hood release, re-gluing some carpet, ect. I couldn't believe how big the back is with the seats folded down! Well Friday it started up with no problem, idled at about 1000 rpm when it first started then evened out about 800 rpm. So Friday the engine is good and sounds real nice.

Well I came over today to take some pictures and it ran like crap. It wouldn't start at all unless you held down the gas then the second you let off it stalled. I thought maybe it was low on gas (1/8 of a tank) so I add some gas from a gas can. It didn't help. I managed to get the engine idling if came of the gas very slowly but it idled unsteadily at about 400-600 rpm. The exhaust smelled very rich. When I put it into gear it dies. If I let off the gas quickly it dies. The odd thing is if I give it just a little gas maybe a little as 5% the "idle" stabilizes and if give it part/full throttle the engine runs fine. I checked under the hood no vacuum lines or plugs were disconnected but the snorkel to air box is missing. I didn't hear a hiss of a disconnected vacuum line at idle. I checked the air filter and ran it briefly w/o the air filter no change. There is no check engine light.

I'm guessing a vacuum leak but I'm not sure. The only other variable I can think of is it was about 10 degrees cooler today 39F. So what do you guys think? How should I start pinpointing the problem. Also keep in mind the budget for repairs will be limited.
Maybe TPS or fuel pump going out. JUst off the top of my head.

1995 B4U-running motor delete
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post #3 of 7 (permalink) Old 03-13-2011, 09:45 AM
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Fuel pump.

Old cars, just like classic rock... 60s, 70s, 80s, and 90s!
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post #4 of 7 (permalink) Old 03-13-2011, 10:57 PM Thread Starter
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If the fuel pump has gone bad how come the engine runs ok at part/full throttle but not at idle. In a low fuel pressure condition wouldn't the idle be ok and the engine stall and lack power at part/full throttle?

So I need to test fuel pressure to confirm the fuel pump providing the correct fuel pressure and that fuel filter is not clogged. I'm told I need to be about 11-14 psi correct? I have inline fuel filter with a 15 PSI pressure gauge attached I was planning to test with. So could I hook that up with some rubber fuel line and hose clamps at stock fuel filter location? From what I can tell from pictures of replacement fuel filters it looks like it uses some sort of special quick connect. I also need to know the location of and what fuse to pull to disable the fuel pump and so I can relieve line pressure.

1996 Impala SS
1966 Ford Mustang Coupe - Project Car WIP
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post #5 of 7 (permalink) Old 03-15-2011, 02:13 AM Thread Starter
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Well the engine is running again at idle. Good news is I don't have to replace the fuel pump. The problem was the idle control valve. It was stuck fully closed and the engine wasn't getting enough air at idle. On a hunch removed ICV and cleaned the tip of the valve and its mounting location in the throttle body with carb cleaner. I then cleaned the electrical connecters, replaced the gasket, and reinstalled the ICV. I still don't get why the computer didn't throw a code. Anyway cool no-cost fix.

So one last thing to get this wagon road worthy and sellable, brakes. I know it's not the right area in the forum but thought I would share. I hate deferred maintenance. See for yourselves:



This was the better of the 2 driver side pads!





Luckily somebody replaced the passenger side rotor not so long ago so can get away with pads on that side. I honestly don't know how anybody with a sense of self preservation could let the brakes get this bad and then continue driving the car.

1996 Impala SS
1966 Ford Mustang Coupe - Project Car WIP

Last edited by SaveOldSchoolMuscle; 03-15-2011 at 02:20 AM.
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post #6 of 7 (permalink) Old 03-15-2011, 10:47 AM
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Aren't you being a bit harsh?

If you look closely at both the left and right sides of that rotor, there's still plenty of wear area left...

Take a close look...

-KP

Last edited by kpeters59; 03-15-2011 at 02:55 PM.
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post #7 of 7 (permalink) Old 03-15-2011, 02:36 PM
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"Lady driven."

Run away. Run far and run fast.

'93 Roadmaster wagon, 3.23 and posi. All stock except for Monroe SS shocks, WS6 front sway bar and Crown Vic bolt-on rear bar. AC Delco O2 sensor and spark plugs - MANDATORY! And now new GM rear LCAs and steering shaft. Air Lift 1000s installed. Also new center link and idler arm for MUCH less wander. Tie rods. Steering box adjusted for bearing preload and sector shaft interference.

** For sale in exchange, power vent windows and motors for wagon.
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