Hesitation at temp
#1
08-14-2006, 02:58 PM
Hesitation at temp
Hello. I have a '95 Z28. I had some issues with the DexCool last year and ended up replacing my radiator and heater core after both failed.
Last July (before the replacements), I began noticing a hesitation in acceleration. It was rather dramatic last summer. After replacing the radiator and heater core, the problem diminished.
I have now noticed the hesitation begins occurring when the engine temp gets to the thermostat temperature (I'm still on stock 185° units). Before the engine heats up, acceleration is great, powerful, and smooth through all gears and RPMs. Once i get to the thermostat temp, when I accelerate at lower RPMs (especially on the freeway when accelerating in fifth and/or sixth gears below 2000 RPM), I have a very noticeable hesitation and shake in the car. Power is pretty low as well.
I had replaced my thermostat a couple of times earlier, and, thinking perhaps that was the cause, I switched back to the original thermostat. The problem further minimized for the first trip in the car, but came back to former noticeable levels later in the afternoon. (I live in Albuquerque, NM - the desert SW).
Also, if I drive in city traffic without the A/C on, the engine temp pushes over the mid mark (210°) and doesn't cool. Before last summer, I never had troubles with the engine temp going past the thermostat temp (185°). Now, when I get home from work after a 20-minute drive, my temp gauge usually reads about 210°. Five minutes after shutting off the engine, the DexCool is boiling out of the overfill reservoir.
Could this problem be caused by the water pump? I don't know how engine output and operation is affected by temperature in this case. As I said, when the motor is cold, it runs brilliantly, but once the temp climbs, it falters.
Does anybody have any advice?
Thanks in advance.
Last July (before the replacements), I began noticing a hesitation in acceleration. It was rather dramatic last summer. After replacing the radiator and heater core, the problem diminished.
I have now noticed the hesitation begins occurring when the engine temp gets to the thermostat temperature (I'm still on stock 185° units). Before the engine heats up, acceleration is great, powerful, and smooth through all gears and RPMs. Once i get to the thermostat temp, when I accelerate at lower RPMs (especially on the freeway when accelerating in fifth and/or sixth gears below 2000 RPM), I have a very noticeable hesitation and shake in the car. Power is pretty low as well.
I had replaced my thermostat a couple of times earlier, and, thinking perhaps that was the cause, I switched back to the original thermostat. The problem further minimized for the first trip in the car, but came back to former noticeable levels later in the afternoon. (I live in Albuquerque, NM - the desert SW).
Also, if I drive in city traffic without the A/C on, the engine temp pushes over the mid mark (210°) and doesn't cool. Before last summer, I never had troubles with the engine temp going past the thermostat temp (185°). Now, when I get home from work after a 20-minute drive, my temp gauge usually reads about 210°. Five minutes after shutting off the engine, the DexCool is boiling out of the overfill reservoir.
Could this problem be caused by the water pump? I don't know how engine output and operation is affected by temperature in this case. As I said, when the motor is cold, it runs brilliantly, but once the temp climbs, it falters.
Does anybody have any advice?
Thanks in advance.
#2
10-03-2006, 04:41 PM
RE: Hesitation at temp
That could be a fuel pressure problem. Don't try to accelerate in 5th or 6th gear, it's just not made for that, not enough gearing for acceleration.
#3
10-03-2006, 06:34 PM
RE: Hesitation at temp
Using a scanner (not a code reader) check the ETC & IAT sensors & verify they are giving sensible inputs to the PCM. They could be giving wrong temp indications to the PCM, which could make the cooling fans come on late and provide the wrong A/F ratio. Also, while you have the scanner hooked up, take a good look at O2 sensors & verify they are working and not falling asleep. Clean the crud from the EGR valve and exhaust gas passage, & clean out the throttle body just for the hell of it.
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