1992 Chevy Truck 1500 running BAD!
arkansas girl
16 years ago
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timwilliamsbiz
8 years agojohnandapril6969
8 years agoRelated Discussions
dodge or chevy 2500 ?
Comments (10)"The 5.7 L in the 1500 should be perfectly adequate and get better mileage.." That is a inaccurate guess many consumers make. Just because it is a smaller engine they think that it gets better milage. Truth is, in the real world they dont. The smaller engine has to work twice as hard to get the same job done as a 2500 with a 6 litre engine. I am talking if you take a 1500 and a 2500 hook up a trailor to each of them that weights the same. With the same amount of fuel in the tanks. I will bet anything that the 1500 will have to stop for fuel way before the 2500 with the 6 litre engine will. "The 2500 rides like a dump truck.." If you are talking about a Chevorlet, You could not proove that by me. The Dodge 2500 and Ford F250 and F350's I have had did not give a comfortable ride at all. They were rough riders. DuraMax, Cummins, Power Stroke diesel's? Sure they are strong powerful engines. Cant afford to use them. 8 to 10 miles per gallon. Maybe 12 if you drive down hill a lot. Insurance nearly twice the cost of a gasoline in the same class. Parts..lol.. Take one $850 dollar fuel pump for a Power Stroke diesel, add a $250.00 cam sensor (wont run without one). I will stick with my Chevy 2500HD's....See More1992 Chevy 1500 no injector pulse
Comments (3)When a shop posts a help request similar to what is above, the normal reply is to tell them to substitute a known good technician. VBG... Test this and change that is not how to diagnose and repair a problem like this, well, by now you probably realize that because it simply doesn't work. Now sure there are times that this method does work, and occasionally you don't even spend a fortune doing it. But as a pro, you'd fail so often you would not last as a technician. A "noid" light is not an accurate test of the systems ability to turn the injectors on. The injectors initially start to draw current at such a level that if they were allowed to stay turned on long enough they would each draw twenty amps+ of current. To prevent overheating the injectors the computer uses what is called a peak and hold system. How it works is one transistor (also referred to as a "driver") turns on and starts to open the injector. Once a sufficient current flow is reached, a second transistor turns on that has a resistor in series with it, the first transistor turns off and that limits the current flow to around 1.8 amps. The "peak" part of the voltage waveform causes the injector to open, and the hold portion allows the injector to remain open long enough to dispense the right amount of fuel. A noid light will flash with as little as 1ma, or .001 amps. This type of testing has tricked just about everyone who relies on it at least once. The right way is to measure the current flow with a low amps probe an an oscilloscope. You can also use the scope to monitor the ground side of the injector to watch for both drivers signatures, and their inductive kick on turn off which is an indicator of the strength of the magnetic field that was created when the computer turned the injector on. Now just because current is flowing that does not mean that the injectors physically opened, nor does having fuel pressure guarantee there is fuel at the injectors under sufficient pressure to be injected into the engine. There are screens on the injectors themselves that serve as a last defense filters, as well as there is usually an inlet screen to the throttle body just inside of the fuel inlet nut. Once you prove that electrically the injectors should be opening, by measuring the current flow with them connected, and/or measuring their inductive kick. Plus you re-confirm that there is fuel pressure, AND volume. Then you have proven that problem is inside the throttle body, and you will need to take it apart to find out what is going on....See MoreCombustion problems with a 1986 Chevy 350/5.7 engine
Comments (2)A bad MAP sensor can cause the symptoms you describe. Also, check all vacuum lines for breaks/leaks. Insure that all are properly conected. Some of the vaccuum connectors may be ported (Have internal restrictors). If any of these have been replaced with regular connectors, system upsets can occur. A very good repair manual is required to identify which connectors, if any, are ported. Back in 1986, the ignition system may have used a conventional distributor enhanced with some electronics. (Be gentle with me here. I'm flying blind relying on memory alone.) The ignition advance was still by governor springs and weights plus a vaccuum advance unit. Engine power can be reduced at part throttle if the vaccuum advance is missing - also the vaccuum will be down because the throttle is opened more that normal. Abnormally low vaccuum will cause the enrichment needle to rise in the carbureator and excessively enrichen the fuel mixture....See More4.3 Ltr Runs Great when cold
Comments (5)The O2 sensor was a PITA? You should try doing diagnostics and repairs on a vehicle that has already had a grocery basket load of parts thrown at it without any attempt at real diagnostics being performed. The computer uses inputs from the MAP sensor, and engine speed to calculate the initial fuel injector pulse width. From there it uses the coolant and intake air temperature sensor inputs, battery (system voltage if running) as well as the movement of the TPS to modify the base pulse width calculation. Then the computer looks into its learned memory, and applies the long term fuel trim, known as block learn on your truck. Finally when in closed loop the computer then uses the O2 sensor(s) and modifies the fuel pulse (integrator) to achieve good fuel trim. That being said the computer does not know what the actual fuel pressure is, and it does not know if something is making the engine not breathe correctly, such as a clogged catalyst. Those are things the technician diagnosing the vehicle must test and be sure about. The computer does not know the actual flow rate of the injector, if that flow rate has changed from its initial design. Lastly, while most vacuum leaks on these engines simply result in a faster idle, a specific leak that drops the vacuum signal to the MAP sensor would simply look like a partial engine load to the computer and the computer would start with a larger base pulse width than the engine really needed, and you would see fuel trim once in closed loop having to try and take that fuel back away. Fuel trim is monitored in scan data, and again on your truck its block learn for the long term trim and integrator for the short term trim. The ideal numbers, no correction from the initial modified pulse width is 128 on both of them. When the computer subtracts fuel from the pulse width, that is reported as a number lower than 128. When the computer adds fuel to the base pulse width, that is displayed as numbers above 128. There was one more thing that would occasionally occur with these systems. Noisy distributor grounds can cause the PCM to think the engine is running faster than it really is. That causes additional fuel pulses to be delivered. So whether the fuel pressure is incorrect, (restriction inside the throttle body or return line) the injectors sloppy, the MAP inaccurate, a vacuum leak for the MAP signal (the throttle body base gasket is a common cause for that), the distributor ground is noisy, the exhaust is clogged, corrosion in the ECT harness altering that signal causing the engine to look too cold, or something spiking the TPS signal, or the pcm is detecting low system voltage, or the pcm itself is faulty this should be an easy diagnosis for an experienced technician. Provided you haven't added any problems as you swapped parts....See MoreBarry Nelson
8 years agoBarry Nelson
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