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Discussion Starter #1
I have had trouble with my car running lean for a while now, and I can't figure it out. I have been talking to Alberto, and he says that my engine vacuum of 18 inHg is too low. I need some people to measure their vacuum and tell me what it is so I can get a reference.


I have a 1997 with the Vulcan. I specifivally need Vulcans, and a 1997 would be preferred. The more people that post, the better my reference point will be.


Thanks everyone.



Daniel J
 

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Well I could help but where is it located since I have a Vulcan too.

Frank
 

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Discussion Starter #3
You need a vacuum gauge. You can rent one from Autozone, I think. That's where I bought mine.


Oh, and so others know, I am getting about 18.5 inHg at idle.
 

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I'll buy one tomorrow and tell you what mine is.

Frank
 

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Here's some info from Furd....


Intake Manifold Vacuum Test

Bring the engine to normal operating temperature. Connect Rotunda Vacuum/Pressure Tester 164-R0253 or equivalent to the intake manifold (9424). Run the engine at the specified idle speed.

The vacuum gauge should read between 51-74 kPa (15-22 in-Hg) depending upon the engine condition and the altitude at which the test is performed. SUBTRACT 4.0193 kPa (1 in-Hg) FROM THE SPECIFIED READING FOR EVERY 304.8 m (1,000 FEET) OF ELEVATION ABOVE SEA LEVEL.

The reading should be quite steady. If necessary, adjust the gauge damper control (where used) if the needle is fluttering rapidly. Adjust damper until needle moves easily without excessive flutter.


Vacuum Gauge Readings--Interpretation

A careful study of the vacuum gauge reading while the engine is idling will help pinpoint trouble areas. Always conduct other appropriate tests before arriving at a final diagnostic decision. Vacuum gauge readings, although helpful, must be interpreted carefully.

Most vacuum gauges have a NORMAL band indicated on the gauge face.



Following are potential gauge readings. Some are normal; others should be investigated further.



1. NORMAL READING: Needle between 51-74 kPa (15-22 in-Hg) and holding steady.

2. NORMAL READING DURING RAPID ACCELERATION AND DECELERATION: When engine is rapidly accelerated (dotted needle), needle will drop to a low (not to zero) reading. When throttle is suddenly released, the needle will snap back up to a higher than normal figure.

3. NORMAL FOR HIGH-LIFT CAMSHAFT WITH LARGE OVERLAP: Needle will register as low as 51 kPa (15 in-Hg) but will be relatively steady. Some oscillation is normal.

4. WORN RINGS OR DILUTED OIL: When engine is accelerated (dotted needle), needle drops to 0 kPa (0 in-Hg). Upon deceleration, needle runs slightly above 74 kPa (22 in-Hg).

5. STICKING VALVES: When the needle (dotted) remains steady at a normal vacuum but occasionally flicks (sharp, fast movement) down and back about 13 kPa (4 in-Hg), one or more valves may be sticking.

6. BURNED OR WARPED VALVES: A regular, evenly-spaced, downscale flicking of the needle indicates one or more burned or warped valves. Insufficient hydraulic valve tappet clearance will also cause this reaction.

7. POOR VALVE SEATING: A small but regular downscale flicking can mean one or more valves are not seating.

8. WORN VALVE GUIDES: When the needle oscillates (swings back and forth), over about a 13 kPa (4 in-Hg) range at idle speed, the valve guides could be worn. As engine speed increases, needle will become steady if guides are responsible.

9. WEAK VALVE SPRINGS: When the needle oscillation becomes more violent as engine rpm is increased, weak valve springs (6513) are indicated. The reading at idle could be relatively steady.

10. LATE VALVE TIMING: A steady but low reading could be caused by late valve timing.

11. IGNITION TIMING RETARDING: Retarded ignition timing will produce a steady but somewhat low reading.

12. INSUFFICIENT SPARK PLUG GAP: When plugs are gapped too close, a regular, small pulsation of the needle can occur.

13. INTAKE LEAK: A low, steady reading which can be caused by an intake manifold or throttle body mounting flange gasket leak.

14. BLOWN HEAD GASKET: A regular drop of fair magnitude can be caused by a blown head gasket (6051) or warped head-to-block surface.

15. RESTRICTED EXHAUST SYSTEM: When the engine is first started and is idling, the reading may be normal but as the engine rpm is increased, the back pressure caused by a clogged muffler (5230), kinked tail pipe or other concerns, will cause the needle to slowly drop to zero. The needle then may slowly rise. Excessive exhaust clogging will cause the needle to drop to a low point even if the engine is only idling.

When vacuum leaks are indicated, pinpoint and correct the cause. Excess air leaking into the system will upset the fuel mixture and cause concerns such as rough idle, missing on acceleration or burned valves. If the leak exists in the power brake, the system will not function correctly. ALWAYS FIX VACUUM LEAKS.

 

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Discussion Starter #6
I know all that stuff, but thanks anyway for helping.


My enginge vacuum is fluctuating like it should, it's just low. Alberto says that it should be right at 20 inHg. I never tested it before I put in the chip and new injectors (when the problem atarted), so I don't have a baseline to judge against.
 

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try doing what is called a decarb on the engine should help with the vacume problem
 

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Discussion Starter #9
BUMP.


I REALLY need your help guys/gals. It's been almost seven months now and I still can't figure out this thing. I can't afford to pay for a mechanic to look my car over. Please help.
 

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I'm searching through my Ford shop manual and can't find this...Tell me where I might look for engine vacuum specs, and I'll look it up for you...
 

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o2 sensor's?
 

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incidentally, how do you know your car is running lean? from a code? if so, what's the code and I can try and post the diagnostic tree for that code to pinpoint the problem...
 

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Discussion Starter #13
You haven't been around for the whole porblem, but let me assure you it's a vacuum leak.

I know it's running lean because 1. I get codes PO172 and PO174 (lean banks 1 & 2). Also, I have an A/F ratio gauge that shows me it's lean.

The ford maual states that vacuum at idle should be between 17-22 inHg. I want to know what actual Vulcan engines are getting. The range they give is farily wide, and therefore I don't trust it.

It's not the HO2S sensors - they were replaced 8K ago. Besides, the chances of BOTH going out at the same time are slim-to-none.
 

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With the engine hot and idling spray some carb cleaner all over the intake surfaces that could be causing a leak. EGR, Intake Manifold, any vacuum hose.
 
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