Q: cracked exhaust manifold pipes/headercar will not go fast revs high but No speed ?Cause?

asked by on December 01, 2016

car will not go past 30 miles an hour engine revs high with no speed increase No power on acceleration while taking off it takes a long time to get up to 20 mph like the engine is struggling. help please 2003 hyundai elantra gls auto 4cl 2.0l

My car has 151000 miles.
My car has an automatic transmission.

In order of priority, if you have a cracked exhaust manifold (leaking carbon monoxide), that actually has to be fixed first or at least coincident with the repair(s) to the engine/transmission. The principal danger from exhaust leaks (carbon monoxide) is NOT death from acute exposure but rather long term tissue damage from chronic low level exposure. Way more people die from chronic, day to day CO exposure than from the kind of acute exposure you read about in the newspaper. So, basically, so as not to damage your health be sure to get the exhaust leak fixed at the same time the acceleration is resolved.

If your vehicle won’t go over 30 miles per hour, it is possible the PCM has forced the transmission to operate in limp mode. Forced limp mode operation can occur if, as an example, there is a fault with the input and output speed sensors on the transmission, or the kickdown switch. There are probably downloadable OBD-II trouble codes that will help the Mechanic hone in on the trouble area. You might try checking the transmission fluid level and condition. If the fluid level is low and/or burnt, that might be related to the problem. To rule limp mode in or out (without a code scanner) sometimes you can disconnect the negative battery cable for a 1 minute to reset the PCM and then see if the transmission shifts normally until it enters limp mode again. There are other possibilities for what you are describing though including faults in the fuel, ignition, air induction systems, and even the possibility of a severely restricted exhaust system. What I would suggest is diagnose the engine/transmission issue first, but again, once that is restored, the car is unsafe (unhealthy) to drive unless and until the exhaust leak is also repaired. Please let us know how we can best assist you.

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