When traveling a steady speed, I go to accelerate, nothing happens, I have to lift off and get back in the throttle to get a response. Any suggestions what is wrong? ps Trains rebuilt 10'000 miles ago, and new engine installed. problem stared soon after trans. was rebuilt.

Connecting a pro grade scan tool computer will tell you the DTC Code and that tells you what the problem is and how to fix it. The 'Wrench Light', properly the 'Engine Malfunction Light' is there to tell you that you have a problem and the scan tool tells you what it is?

Surging while steady on the accelerator is a clue as well as taking foot off accelerator and vehicle maintains a speed without cruise control on. Could be that the throttle body itself is dirty. Remove throttle body Use carb cleaner spray liberally. After 10 Minutes reinstall and test. If that fails, replace tps sensor.

It's a gm vehicle, but, I don't know year and model? Any applicable trouble codes.
If fuel trim is negative, low speed and load, look for fuel pressure or injector leak. If problem only on bank 2, then check that bank.
Use a gage and check proper fuel pressure, then with key off, see if fuel pressure holds for a bit. If it drops like a rock, check for fuel leak. How long since a tune-up?

General Motors Driving Cycle

A complete driving cycle should perform diagnostics on all systems. A complete driving cycle can be done in under fifteen minutes.



To perform an OBDII Driving cycle do the following:

1. Cold Start. In order to be classified as a cold start the engine coolant temperature must be below 50°C (122°F) and within 6°C (11°F) of the ambient air temperature at startup. Do not leave the key on prior to the cold start or the heated oxygen sensor diagnostic may not run.
   
   



2. Idle. The engine must be run for two and a half minutes with the air conditioner on and rear defroster on. The more electrical load you can apply the better. This will test the O2 heater, Passive Air, Purge "No Flow", Misfire and if closed loop is achieved, Fuel Trim.
   
   



3. Accelerate. Turn off the air conditioner and all the other loads and apply half throttle until 88km/hr (55mph) is reached. During this time the Misfire, Fuel Trim, and Purge Flow diagnostics will be performed.
   
   



4. Hold Steady Speed. Hold a steady speed of 88km/hr (55mph) for 3 minutes. During this time the O2 response, air Intrusive, EGR, Purge, Misfire, and Fuel Trim diagnostics will be performed.
   
   



5. Decelerate. Let off the accelerator pedal. Do not shift, touch the brake or clutch. It is important to let the vehicle coast along gradually slowing down to 32km/hr (20 mph). During this time the EGR, Purge and Fuel Trim diagnostics will be performed.
   
   



6. Accelerate. Accelerate at 3/4 throttle until 88-96 km/hr (55-60mph). This will perform the same diagnostics as in step 3.
   
   



7. Hold Steady Speed. Hold a steady speed of 88km/hr (55mph) for five minutes. During this time, in addition to the diagnostics performed in step 4, the catalyst monitor diagnostics will be performed. If the catalyst is marginal or the battery has been disconnected, it may take 5 complete driving cycles to determine the state of the catalyst.
   
   



8. Decelerate. This will perform the same diagnostics as in step 5. Again, don\'t press the clutch or brakes or shift gears.

Reprinted on OBDII web site courtesy of General Motors Corporation

© General Motors Corporation

I'd also consider testing throttle position sensor with analog multimeter set on ohms. Remove and clean connection, connect to 2 of the pins at sensor until you see needle sweep as throttle increased,/decreased. Needle on meter should sweep across and back to coincide with throttle. Once you have that, increase throttle slowly and steady all way to floor and back slow and steady and watch needle on meter. If you see meter jump or drop quickly, test again and see if it happens same at same spot roughly. That would indicate a dead/bad spot in throttle position sensor, replace it. Needle should move smooth/steady up and down as long as pedal is doing same. Doesn't cost anything to test it.

Try some tranX. My transmission would drop out from 2nd and 3rd , I put this in and with in 3 days it quit slipping. and shifted normally. It's been over 2 years now without a problem

To perform an OBDII Driving cycle do the following:

1. Cold Start. In order to be classified as a cold start the engine coolant temperature must be below 50°C (122°F) and within 6°C (11°F) of the ambient air temperature at startup. Do not leave the key on prior to the cold start or the heated oxygen sensor diagnostic may not run.
   
2. Idle. The engine must be run for two and a half minutes with the air conditioner on and rear defroster on. The more electrical load you can apply the better. This will test the O2 heater, Passive Air, Purge "No Flow", Misfire and if closed loop is achieved, Fuel Trim.
   
3. Accelerate. Turn off the air conditioner and all the other loads and apply half throttle until 88km/hr (55mph) is reached. During this time the Misfire, Fuel Trim, and Purge Flow diagnostics will be performed.
   
4. Hold Steady Speed. Hold a steady speed of 88km/hr (55mph) for 3 minutes. During this time the O2 response, air Intrusive, EGR, Purge, Misfire, and Fuel Trim diagnostics will be performed.
   
5. Decelerate. Let off the accelerator pedal. Do not shift, touch the brake or clutch. It is important to let the vehicle coast along gradually slowing down to 32km/hr (20 mph). During this time the EGR, Purge and Fuel Trim diagnostics will be performed.
   
6. Accelerate. Accelerate at 3/4 throttle until 88-96 km/hr (55-60mph). This will perform the same diagnostics as in step 3.
   
7. Hold Steady Speed. Hold a steady speed of 88km/hr (55mph) for five minutes. During this time, in addition to the diagnostics performed in step 4, the catalyst monitor diagnostics will be performed. If the catalyst is marginal or the battery has been disconnected, it may take 5 complete driving cycles to determine the state of the catalyst.
   
8. Decelerate. This will perform the same diagnostics as in step 5. Again, don't press the clutch or brakes or shift gears.

maybe the cam timing is off. If the engine was torn down and reassembled wrong, that would do it. Connect a vacuum gauge to the intake manifold and see what you get for vacuum readings.
It should be about 17 inches at idle. And, it should be steady.

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

1. 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.
   

1. 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.
   

1. 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).
   

1. 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.
   

1. 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.
   

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

1. 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.
   

1. 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.
   

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

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

1. INSUFFICIENT SPARK PLUG GAP: When spark plugs (12405) are gapped too close, a regular, small pulsation of the needle can occur.
   

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

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

1. RESTRICTED EXHAUST SYSTEM: When the engine is first started and is idled, the reading may be normal but as the engine rpm is increased, the back pressure caused by a clogged muffler, kinked tailpipe or other concerns, will cause the needle to slowly drop to 0 kPa (0 in-Hg). 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, search out 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 an accessory unit such as the power brake booster (2005), the unit will not function correctly. ALWAYS FIX VACUUM LEAKS.
   

Performing a GM OBDII Driving cycle:

1. Cold Start. In order to be classified as a cold start the engine coolant temperature must be below 122°F (50°C) and within 11°F (6°C) of the ambient air temperature at startup.
   Do not leave the key in prior to the cold start or the heated oxygen sensor diagnostic may not run.
   
2. Idle. The engine must be run for two and a half minutes with the air conditioner on and rear defroster on. The more electrical load you can apply the better. This will test the O2 heater, Passive Air, Purge "No Flow", Misfire, and - if closed loop is achieved- Fuel Trim.
   
3. Accelerate. Turn off the air conditioner and all the other loads and apply half throttle until 55mph (88km/hr) is reached. During this time the Misfire, Fuel Trim, and Purge Flow diagnostics will be performed.
   
4. Hold Steady Speed. Hold a steady speed of 55mph (88km/hr) for 3 minutes. During this time the O2 response, air Intrusive, EGR, Purge, Misfire, and Fuel Trim diagnostics will be performed.
   
5. Decelerate. Let off the accelerator pedal. Do not shift, touch the brake or clutch. It is important to let the vehicle coast along gradually slowing down to 20 mph (32km/hr). During this time the EGR, Purge and Fuel Trim diagnostics will be performed.
   
6. Accelerate. Accelerate at 3/4 throttle until 55-60mph (88-96 km/hr). This will perform the same diagnostics as in step 3.
   
7. Hold Steady Speed. Hold a steady speed of 55mph (88km/hr) for five minutes. During this time, in addition to the diagnostics performed in step 4, the catalyst monitor diagnostics will be performed. If the catalyst is marginal or the battery has been disconnected, it may take 5 complete driving cycles to determine the state of the catalyst.
   
8. Decelerate. This will perform the same diagnostics as in step 5. Again, don't press the clutch or brakes or shift gears.

You will need to have a test run of the electronic engine controls, if nothing shows test the Throttle Position sensor, closed throttle voltage should be around 1-1.25 volts, while the meter is hooked up and the key on tap on the sensor the volt reading should remain steady, open and close the throttle repeated times, it still should return to 1-1.25 volts closed throttle blade.