Engine Performance problem
1996 Chevy Truck V8 Front Wheel Drive Automatic 175000 miles

When driveing on the highway if I shift into 3rd gear as if pulling my boat the truck starts lungeing and service engine light blinks then stays on. It will also do this if put in first and and drive at 3000 to 5000 rpm. The code is a rondom misfire code

Hello –

First, please give me the specific model of your truck as there are about 20 different ones. Is it a 1500 -2500 etc pick up, a Tahoe, Suburban etc. Then I need the specific engine in liter and the 8th digit of your VIN. Is this a 2WD or 4WD. Then is it an automatic or manual….the confusion there is the post states automatic and then you discuss shifting into 3rd.

I want to make sure we are talking about the same item to better assist you.

First I know you told me what the code was, but I need the specific code number to better assist you. So please go to Auto Zone or O’Reilly’s and for FREE they can pull the codes to the car. Most important: Once they check your codes, if they find something and you don’t get it fixed and need to get back with us, please make sure you tell us exactly what the code was, number and all. Example, if the code was E0568 O2 Sensor bad. Then make sure you give us all of that. While there for FREE also they can bring their tester out and check your battery, alternator and starter.

When was the last time you did a tune up….plugs, wires, fuel filter?

We don’t need to do a fuel pressure check yet based off of your code, but we may need to later.

Please do the above and provide the information requested and we can take it from there.

Thanks for the donation

Please let us know if what the final fix was for your car so we can better assist others. Thanks!

Find a car repair manual for your car repair questions.

The truck is a 1996 chevy 1/2 ton 4x4 w/5.7 auto trans the eighth is an R
I have changed plugs,wires,cap and rotor ,O2 sensors trying to correct this.
The shifting to third that I spoke of is putting trans in third (out of overdrive)that is done when pulling trailers.
I have taken to auto zone do not have the exact code

Seems to have a slight surge in OD leading me to think TPS. maybe?

Hello –

Thanks for the update….

Without the exact code I would be searching thousands of codes…..that is how they are listed. So unless I am able to get that we will have to kind of search around.

The TPS is a possibility --- so is the MAP….I have attached info for both for your review.

I might also suggest talking to a transmission shop – sometimes it is a small fee for a diagnostic check. The transmission will also throw codes.

Thanks for the donation

Please let us know if what the final fix was for your car so we can better assist others. Thanks!

Find a car repair manual for your car repair questions.



MANIFOLD ABSOLUTE PRESSURE (MAP) SENSOR. This sensor is mounted on or connected to the intake manifold to monitor intake vacuum. It changes voltage or frequency as manifold pressure changes. The computer uses this information to measure engine load so ignition timing can be advanced and retarded as needed. It performs essentially the same job as the vacuum advance diaphragm on an old fashioned mechanical distributor.

On engines with a "speed density" type of fuel injection, the MAP sensor also helps the PCM estimate airflow. Problems here may cause an intermittent check engine light (light comes on when accelerating or when the engine is under load), hesitation when accelerating, elevated emissions and poor engine performance. The engine will run with a bad MAP sensor, but it will run poorly. Some PCMs can substitute "estimated data" for a missing or out of range MAP signal, but engine performance will be drastically reduced.

MAP Sensor Strategies: Some MAP sensor problems are not the fault of the sensor itself. If the vacuum hose that connects the MAP sensor to the intake manifold is loose, leaking or plugged, the sensor can’t produce an accurate signal. Also, if there is a problem within the engine itself that causes intake vacuum to be lower than normal (such as a vacuum leak, EGR valve that’s stuck open or leaky PCV hose), the MAP sensor’s readings may be lower than normal.

THROTTLE POSITION SENSOR. Mounted on the throttle shaft of the carburetor or throttle body, the throttle position sensor (TPS) changes resistance as the throttle opens and closes. The computer uses this information to monitor engine load, acceleration, deceleration and when the engine is at idle or wide open throttle. The sensor’s signal is used by the PCM to enrich the fuel mixture during acceleration, and to retard and advance ignition timing.

Throttle Position Sensor Strategies: Many TPS sensors require an initial voltage adjustment when installed. This adjustment is critical for accurate operation. On some engines, a separate idle switch and/or wide open throttle (WOT) switch may also be used. Driveability symptoms due to a bad TPS can be similar to those caused by a bad MAP sensor: The engine will run without this input, but it will run poorly.

I will get the exact code and get back to you.