F105d

I have a 1994 LT1 Automatic with 89,357 miles. Recently I have noticed that when I am at a stoplight and my fans become operational at about 225 or 228 degrees, my engine will begin to surge to 3,000 RPM and then slowly returns to the normal idle position. There is nothing erratic about this RPM surge and it ends when the fans turn off. My concern is when I experience this situation while in idle at a traffic light, I feel pressure on my brakes to move forward, so as a precautionary measure I place my car in neutral. The RPM surging still continues, but I do not have the fear of hitting the car in front of me. I would appreciate any suggestions to correct this situation.

don hall

Some suggestions...... may, or may not help:

http://www.autoserviceprofessional.c...d-engine-surge

F105d

Thank you for the website information, I will check it out. Just seems strange that the RPM will surge only when the fans become operational, then become normal when the temperature drops.

Nowhere Man

does your check engine light come on? do you have access to a fuel pressure gauge. a scan tool with a read out off all the sensors can help too. it could be a number of things. there is no need to throw parts at it

F105d

When the RPM surging begins no check engine lights come on, so I am not sure if using a scan tool would tell me anything. Since the engine returns to normal operation when the fans stop running, would a fuel pressure gauge check only be required if there was a constant RPM problem? I should also add that the air conditioner was not turned on when the RPMs began to rise and fall.

Nowhere Man

A good scan tool will give you a read out off ALL sensors. Then you can see if all of them are in the correct parameters Some can be out and still not turn the light on.

Dougs63

For the past several weeks, I've noticed on my '94 that the fans came on and ran continuously while driving. Just last week, I noticed the car surging on acceleration and I finally got a "Service Engine" light.

I checked my codes (using the paper-clip method). The car was showing a H44 - Lean L.H. Oxygen sensor.

My car has about 114K miles and was pretty sure the O2 Sensors had never been changed - or at least not changed in a very long time.

So - I swapped out the AC/Delco O2 sensors (which if not original, were at least OEM) for a new set of Bosch sensors.

Amazing difference in the car now - no surging, no cooling fan coming on, no codes - seems like I added 30 HP to it.



So - I would certainly check for codes - even if the Service Light is not coming on.

F105d

I researched a previous thread on using the paper-clip method and downloaded the module codes, so I plan on performing the check soon and will let you know the results. Looks like on the 94 I will have to short pin "12" to pin "4". Thanks again.