I have a 95 6.5td with 188,000 on it. I've put about 4 thousand miles on it since i bought it. The truck as far as I know is stock except I put a 4in exhaust on it. My truck recently in the last couple days has been starting harder, my fuel economy dropped, it will blow black alot easier, and it seems to be alot doggier lately. Any ideas as to what this would be and what it would take to fix it?

 

do have check engine light on ? if so do know what the codes are

hard start could have some thing do with glow plug system

For the black smoke check for vacuum leaks make sure the waste gate working this could be why you have loss of power and poor fuel economy

 

No i dont have any check engine lights. I figured it was the injectors or the wastegate.
So if it was the vacuum on the waste gate, how do i go about pin pointing the problem?

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found my problem,
it ended up being a hole in the vacuum line

 

EFI Turbocharger Wastegate control is part of a true Digital Vacuum Regulator, managed by PCM.

The turbocharger is an exhaust-gas driven turbine motor that powers a centrifugal fan which compresses intake air, making Boost pressure - a Wastegate in the turbine housing is used to bypass exhaust gas in order to regulate that pressure for safe engine operation

The Turbine Wastegate is controlled by a DIGITALLY REGULATED vacuum system consisting of the Manifold Air Pressure sensor (Boost sensor), the Vacuum Pump, the pulse-width modulated Wastegate Solenoid Valve, and the Vacuum-operated Wastegate servo-actuator, that round cannister on the side of the turbocharger.

PCM controls vacuum to Wastegate via pulses to the Wastegate Solenoid coil, by varying the width of the pulses, termed Duty Cycle - wide pulses open valve against spring pressure, narrow pulses allows spring to close valve.

Wastegate Solenoid consists of a three-port spring-loaded armature-driven valve, with a port to Wastegate Vacuum Servo cannister, a port to the Vacuum Source and a vent-port to Atmosphere.

When valve is closed, solenoid off, vacuum source is blocked off, and Wastegate port is vented to atmosphere - permits some actuating vacuum in Wastegate Vacuum Servo cannister to bleed off, allowing Exhaust Pressure to pass thru Wastegate into the exhaust elbow, bypassing the Turbine Blades.

Valve open ports vacuum to Wastegate Servo, restricting vent, but not closing it - this allows REGULATION of vacuum applied to Servo.

Wide pulses keep Solenoid valve open to vacuum source, narrow pulses allow spring to close valve.

Vacuum applied to Wastegate Servo forces Wastegate closed against Exhaust Pressure on Wastegate flapper valve.

Exhaust Pressure increases with RPM and heat, created as result of Fuel Combustion - as Exhaust Pressure increases servo vacuum must be regulated to maintain factory determined Boost levels, usually 7-8psi max without cooling and exhaust modifications, and without reduction of Charge-air temperatures via some form of heat exchange.

With 67% Duty Cycle to WG Solenoid at idle, any rising exhaust pressure immediately 'spools up' - increases rpm - the turbine blades, shaft, and compressor fan, creating instant Boost, which rises further as exhaust energy - pressure, volume, and velocity - increases.

As PCM senses rising Boost pressure via MAP sensor in intake plenum, Wastegate Duty Cycle is reduced as required to vent vacuum and maintain correct Boost levels.

MAP sensor signal - on pin B - to PCM varies from 0 volts at 0 psiA to ~2.4 volts at 15psiA, to ~5 volts at full Boost.

Note the unusual pressure figures in that statement - they are in Pounds Per Square Inch ACTUAL, which is based from ZERO Atmospheric Pressure = 0hg on the Barometer Column scale.

Since Vacuum is terminology for measurement of pressure less than Atmospheric, where ZERO Vacuum would be 15psia or 30"hg, Zero Baro would be (-)30" on the Vacuum scale

PCM calculations are based on 0 psia - MAP sensor is calibrated to 0 psia, such that it's output is actual Atmospheric pressure at ~15psia.

Boost Pressure is based from 15psia Atmospheric - 30" Barometric - where 15psig Boost would be 30psiA.

As PCM sees increasing voltage from MAP pin B, indicating increasing pressure,Wastegate Duty Cycle is reduced accordingly, reducing Vacuum to Servo, venting Exhaust Pressure around Turbine Blades, regulating Boost.

As PCM sees decreasing voltage from MAP pin B, indicating decreasing pressure, Wastegate Duty Cycle is increased - a true DIGITAL VACUUM REGULATOR .

Because Vacuum on the Wastegate Servo is infinitely variable, Wastegate does not simply 'blow open' to dump Boost, but is 'metered' to allow just enough exhaust gas to bypass turbine such that Boost level is maintained without wild swings, or reduced when necessary.

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This is easily observable when a Boost Gage is installed - PCM may allow stock Boost to spike on sudden accel, but recovery is even and smooth, down to 7-8psia factory limit.

Digital Vacuum Regulation is used in EGR system, where equipped, also.

Voltage readings for testing -

PCM bases all pressure readings on actual pressure of 0 pounds per square inch, or psia, tho some call this pounds per square inch atmospheric

Since the Manifold Air Pressure sensor is calibrated for 0volts, repesenting Zero Pressure, to 5volts, representing some higher pressure, it's output is approx 2.4volts at Atmospheric pressure, or ~15psia Barometric pressure.

2.4volts is approx half of 5volts, so we would assume the max MAP output, at 5volts, would be a little above 30psia: 15psia Baro + 15psi Boost = 30psia.

PCM uses these voltages at the pressure input to control vacuum on the wastegate, regulating Boost pressure

The "S" engine, with EGR, uses a MAP sensor for Boost, with a separate pressure sensor on the firewall to measure Barometeric pressure and vacuum for EGR operation - the "F" engine has only the MAP sensor, using it to measure Baro pressure during Wait to Start, then measuring Boost when the engine is running - identical in appearance, their calibrated outputs are different and specific to the separate purposes, so cannot be interchanged for testing