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I recently had my timing belt and water pump changed on my '91 Surf. Since getting it back, I have noticed a peculiar problem. The engine will have an intermittant "surge" even while at idle. However on my commute back in from work tonight, the check engine light would go on and conversely the turbo indicator light would go off. I have not been driving the truck very much, as I usually take our other vehicle in to work, so I am not totally sure that this problem was there right after getting the truck back from the shop. My wife had mentioned to me that this light has been coming on/off for a while now.
I was halfways expecting that the surge/power loss was perhaps the A/C compressor cycling on and off, as I that is kind of what it feels light while driving. The A/C is not in use however, and I changed the setting on the heater control to anything other than the defroster, as I have heard that the defroster will engage the compressor. But tonight, on the drive home I noticed that my boost pressures were fluctuating very slightly between 7 or 8 lbs of boost to as low as 5 lbs even though the throttle was kept at an even pressure as well as my speed.
I am at a loss of what may be causing this...and was hoping one of the many genius' out there might be able to point me in the right direction...troubleshooting wise. Could they have messed something up during the timing belt changeout? I would think that if the belt was off by even one tooth, that the truck would run horribly if at all. The following is what I have done since posting everything written above...as I have copied this post from another site.
Well started raining yesterday (I am garageless), but before it did, I checked my vacuum lines and did not find any leaks. I ran a code check and got a code "4", which indicates "coolant temperature sensor". I disconnected the batteries to clear the codes and took it for a test drive. The check engine light again came on with the turbo indicator light going out. This is accompanied by a noticeable power loss.
As far as the engine speed fluctuating at idle, it is indeed vaccuum related. There was a little arm that looks like it has an adjustment screw on it attached to a vacuum just above the intake. Vacuum advance? This arm when it goes to about a 45 degree angle (normally sitting at 90 degrees with vehicle running), increases the engine idle speed momentarily. Before I had the timing belt/water pump changed out, neither of these instances were occuring. I changed out the fuel filter only 2000km's prior to this work being done.
I was halfways expecting that the surge/power loss was perhaps the A/C compressor cycling on and off, as I that is kind of what it feels light while driving. The A/C is not in use however, and I changed the setting on the heater control to anything other than the defroster, as I have heard that the defroster will engage the compressor. But tonight, on the drive home I noticed that my boost pressures were fluctuating very slightly between 7 or 8 lbs of boost to as low as 5 lbs even though the throttle was kept at an even pressure as well as my speed.
I am at a loss of what may be causing this...and was hoping one of the many genius' out there might be able to point me in the right direction...troubleshooting wise. Could they have messed something up during the timing belt changeout? I would think that if the belt was off by even one tooth, that the truck would run horribly if at all. The following is what I have done since posting everything written above...as I have copied this post from another site.
Well started raining yesterday (I am garageless), but before it did, I checked my vacuum lines and did not find any leaks. I ran a code check and got a code "4", which indicates "coolant temperature sensor". I disconnected the batteries to clear the codes and took it for a test drive. The check engine light again came on with the turbo indicator light going out. This is accompanied by a noticeable power loss.
As far as the engine speed fluctuating at idle, it is indeed vaccuum related. There was a little arm that looks like it has an adjustment screw on it attached to a vacuum just above the intake. Vacuum advance? This arm when it goes to about a 45 degree angle (normally sitting at 90 degrees with vehicle running), increases the engine idle speed momentarily. Before I had the timing belt/water pump changed out, neither of these instances were occuring. I changed out the fuel filter only 2000km's prior to this work being done.
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