Chevrolet Repair Questions? Ask a Mechanic for Answers ASAP
No oil pressure? Well, that comes first. Is the oil level ok? Any leaks? Is the oil filter tight?
Did all these problems start all at once? Did any of them come first, if so can you list the number they came in and how long between problems untill the next problem occured. have you checked the ignition timing? Checked the air filter? Checked for any engine codes? Is the check engine light on now or have you ever seen it on? Is it an automatic or manual tranny? Is the loud noise a knock, bang, tap, clunk, etc?
To check for codes,
Front seating area, driver side, behind instrument panel, mounted on driver side of steering column .
If a fault occurs intermittently, such as a loose connector pin breaking contact as the vehicle hits a bump, the ECM will note the fault as it occurs and energize the dash warning lamp. If the problem self-corrects, as with the terminal pin again making contact, the dash lamp will extinguish after 10 seconds but a code will remain stored in the computer control module's memory.
When an unexpected code appears during diagnostics, it may have been set during an intermittent failure that self-corrected; the codes are still useful in diagnosis and should not be discounted.
Since the control module is programmed to recognize the presence and value of electrical inputs, it will also note the lack of a signal or a radical change in values. It will, for example, react to the loss of signal from the vehicle speed sensor or note that engine coolant temperature has risen beyond acceptable (programmed) limits. Once a fault is recognized, a numeric code is assigned and held in memory. The dashboard warning lamp: CHECK ENGINE or SERVICE ENGINE SOON (SES), will illuminate to advise the operator that the system has detected a fault. This lamp is also known as the Malfunction Indicator Lamp (MIL).
More than one code may be stored. Keep in mind not every engine uses every code. Additionally, the same code may carry different meanings relative to each engine or engine family.
In the event of an computer control module failure, the system will default to a pre-programmed set of values. These are compromise values which allow the engine to operate, although possibly at reduced efficiency. This is variously known as the default, limp-in or back-up mode. Driveability is almost always affected when the ECM enters this mode.
See Figures 1 and 2
Listings of the trouble for the various engine control system covered here are located in this section. Remember that a code only points to the faulty circuit NOT necessarily to a faulty component. Loose, damaged or corroded connections may contribute to a fault code on a circuit when the sensor or component is operating properly. Be sure that the components are faulty before replacing them, especially the expensive ones.
Fig. Fig. 1: ALDL connector-1988-92 models
The Assembly Line Diagnostic Link (ALDL) connector or Data Link Connector (DLC) may be located under the dash and sometimes covered with a plastic cover labeled DIAGNOSTIC CONNECTOR.
Fig. Fig. 2: ALDL connector-1993-95 models
The order of codes in the memory does not indicate the order of occurrence.
After making repairs, clear the trouble codes and operate the vehicle to see if it will reset, indicating further problems.
Fig. Fig. 1: Carbureted engine trouble codes
If that is fuel injected, those codes are here, too.
You said, When I put the truck in gear to drive there is no movement.
Question: Did the engine rev up at all? Would it rev up in neutral?
As far as the rough idling and cutting out, I would check for vacuum leaks, check the air filter, if the distributor is equipped with a vacuum advance check that and check the ignition timing.
You may also want to do a cylinder balance test to make sure all cylinders are firing.
First of all you will need a 12-volt test light and about 8-12 inches of neoprene vacuum hose. The vacuum hose will conduct electricity cause it is carbon based, use an ohmmeter if you aren't sure and see if the vacuum hose you have will conduct.
Now, cut off the same # XXXXX cylinders you have in small equal lengths of the vacuum hose. 1-2 inches will do fine. The small diameter kind like to carburetors, etc will work as long as they fit over the distributor cap tower connection.
Now, mark all your spark plug wires at the cap and remove them all. Put those short pieces of vacuum hose on the distributor cap connections and shove the other end of the vacuum hose into the spark plus wire boot until it makes a good connection.
Now connect your 12 volt test ground clip to a ground and start the vehicle. With the engine running touch the 12 volt test light to each of the vacuum hoses 1 at a time and listen for the cylinder to short out and die and drop in r.p.m. They should all be about equal. If 1 or a few don't drop or do anything than you have your dead cylinder there.
Vacuum leaks can be checked with a can of starting fluid or either. Spray small amounts around the carb or throttle body base gasket and listen for rpm increase indicating that the starting fluid got sucked into a bad gasket and got burned in the combustion chamber. Also, take both hands and grab the whole carb or throttle body and try to move it forward and backward, right and left and listen for rpm change indicating the bolts may be loose.
Also spray starting fluid around the intake manifold gasket and all vacuum hose connections while wiggling them and listen for rpm increase.
If the distributor has a vacuum advance you can either reach down there and move the advance arm by hand and listen for rpm to change as you move timing, or pull hose off and on while reving engine a little or if the diaphram is actually busted you can blow smoke into the hose disconnected from the vacuum advance at the carb end and smoke with come out of and all around distributor cap.
You may want to take off the distributor cap and inspect that for worn terminals, cracks and inspect the rotor for wear or a burnt button,etc.
If your check engine code shows any codes then you will have to inspect that circuit or part.
Also, if equipped with an EGR, reach down while the engine is idling and push in on the diaphram and plunger on the inside of that EGR, the engine should die or almost die. If not and there is vacuum to that EGR either it is bad or the gasket is bad. Rev engine a little and pull off and push on EGR vacuum hose and watch to see if the plunger moves.
Another cause of engine running rough and cutting out may be too lean or too rich of a fuel mixture.
One good way to check for a too lean fuel mixture is to take a shop rag and completely cover the air horn of the carb or throttle body completely cutting off all air going into it. The engine should die. If not it is getting air from somewhere else such as a vacuum leak.
To check for too rich a mixture look down the air horn with a mirror while engine is idling and look to see if any gas is dripping on the throttle valves. Or in the case of fuel injectors they are dripping.
You may also want to go around to the rear while engine is idling and smell the exhaust. too rich and it will smell like gas and maybe burn black smoke. Too lean and it may burn you eyes and have a strong smell. Also, feel the exhaust with your hand, it should be hot, not warm and should have constant puffs not one small or big puff every once in a while.
Is the fuel filter the inline kind under the frame drivers side looks about the same size of a soda can?
You will need line wrenches for that.
As far as the screeching and loud bang goes, you are going to have to determine where that is coming from.
A good way to determine if it is the engine or not is once you get that vehicle running is get it up to speed to where the noise occurs and shift into neutral and turn key back 1 click to run as to not lock steering and shut off engine for a few seconds. If an automatic just make sure the engine did infact die and then just turn key to start while in neutral, if a clutch then shift into a medium gear and pop clutch with key in run. If the noise goes away with engine killed then it was most likely the engine, engine accessories or exhaust or front half of tranny making noise. If not, the second half of tranny, the rear, wheels, brakes, etc.
Air Injector Reactor (AIR) System
The A.I.R. system is not completely silent under normal conditions. Noises will rise in pitch as engine speed increases. If the noise is excessive, eliminate the air pump itself by disconnecting the drive belt. If the noise disappears, the air pump is not at fault.
To test the check valve, disconnect the hose at the diverter valve. Place your hand over the check valve and check for exhaust pulses. If exhaust pulses are present, the check valve must be replaced.
Pull off the vacuum line to the top of the valve with the engine running. There should be vacuum in the line, if not replace the line. No air should be escaping with the engine running at a steady idle. Open and quickly close the throttle. A blast of air should come out of the valve muffler for at least one second.
Disconnect the hose from the diverter valve. Start the engine and accelerate it to about 1500 rpm. The air flow should increase as the engine is accelerated. If no air flow is noted or it remains constant, check the following:
Exhaust Gas Recirculation (EGR)
See Figures 3, 4, 5, 6, 7 and 8
Refer to the appropriate chart for diagnosis the EGR system. On linear EGR systems, an OBD-II compliant scan tool will be needed.
Fig. Fig. 3: Ported EGR system wiring diagram
Fig. Fig. 4: Ported EGR system check
Fig. Fig. 5: Negative backpressure EGR system test
Fig. Fig. 6: Negative EGR system wiring diagram
Fig. Fig. 7: Linear EGR system test
Fig. Fig. 8: Linear EGR system test (continued
Manifold Absolute Pressure (MAP) Sensor
See Figure 4
Fig. Fig. 4: Manifold Absolute Pressure (MAP) Sensor wiring diagram
Fig. Fig. 1: Inspect the oxygen sensor tip for abnormal deposits
Remove the sensor from the exhaust. If the sensor tip has a black/sooty deposit, this may indicate a rich fuel mixture. If the sensor tip has a white gritty deposit, this may indicate an internal anti-freeze leak. If the sensor tip has a brown deposit, this could indicate oil consumption.
All these contaminates can destroy the sensor, if the problem is not repaired the new sensor will also be damaged.
Fig. Fig. 2: Oxygen sensor (02S) wiring diagram
Throttle Position Sensor (TPS)
See Figure 1
Fig. Fig. 1: Throttle Position Sensor (TPS) sensor wiring diagram