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The first step would be to find out if you have an issue with the engine or the transmission because at this point it could be either. If you have any check engine lights start with that and see what you come up with. Also not a bad ide to check for sticking brakes by jacking up the wheels and see if they spin by hand, if you can’t spin them the truck might not be able to either.
To check the trans you might try starting out in 1 or L instead of D to see if it moves forward then, if it does then you might have a transmission problem. Also check the fluid level and condition.
Good luck.
Hi grizlybear,
In addition to what ETCG stated, check the vacuum of the engine while running. A plugged exhaust or plugged catalytic converter will severely compromise the engine’s ability to breathe, and thus move the vehicle. The vacuum at idle should be at least 18″ Hg. You can open up the throttle and watch the vacuum. The vacuum should initially drop, but recover back to its original starting point. A plugged exhaust will create back pressure, and this would be evident by watching the vacuum pressure continue to drop as the throttle is opened up and left open.
Any other conditions to report? I am curious to know if this symptom just started, or has the vehicle gradually lost power over time. Keep us posted.
Another option (if it’s an automatic) would be to do a stall test. With the vehicle in drive and yer foot mashed on the brake pedal, stomp the gas (no more than 15 seconds if i remember right). You would have to look up the specs on where the RPM’s should be. If they are lower than the spec, look at yer engine. Higher than the spec, look at yer trans. Make sure you have a clear path in front of you, obviously.
Everyone made some great points listed above.
If you suspect a restricted exhaust system, you could remove either o2 sensors to see if you have a better throttle response seeing as there would be an abittional hole for the exhaust gasses to flow out of.
If your using a vaccum gauge, as mentioned above anything from 18 to 22″ is good at idle. The needle has to be steady when you take your idle readings. Also, with an engine being basically an air pump, as you ‘goose’ the throttle, the vacuum should drop to near zero, then back upto its orginal reading. However, a restricted exhaust will cause the engine not to ‘breath’ and the vaccum gauge reading will be low and start to drop.
Some places also sell exhaust back pressure gauges that use the same hole as the o2 sensors. I would have to refer to my tech book but, i believe a reading over 1.7 psi is a sign of a restricted exhaust. (If anyone would like to correct me here, then please do S:)).
More food for thought is if an o2 sensor is stuck lean (refer to your fuel trims if you have a scan tool or even graphic of the o2 sensor voltage), if will cause very poor throttle response, rough idle and a shear strain with a load on the engine climbing a steeper gradient in the road.
But alas, first thing is first with the retrieval of any diagnostic trouble codes!
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