I just tried the hose from the brake booster and still the engine revs/surges.

The car does as follows, you start the car and it runs normal for a minute then the car`s rpm increases to 2000 then drops down to 600, increases to 4000 then drop downs and continues to do so. It is a constant increase/decrease in RPM.

We have changed the following on the car. Some may not apply to this case.

A new opti spark accell
A new ICM module
A new Maf sensor
A new IAC valve
A new PCV valve
New O2 sensors

We had the computer programed by Mad tuner.

The car was running good and one day this started. We have taken off the vaccum hoses from various places and plugged then and no change. The only thing that was not re-checked was the transmission, it was rebuilt one year ago. Some things may not apply just wanted to give everyone the whole picture. The EGR has been removed from the system re programing the computer. The vaccum hose from the internal heater and other devices in the car, when that hose was removed and plugged the car did not rev up immediately. It took a minute or so more then it did exactly the same thing as stated above.

Could it be my fuel injectors, would it cause such a surge in RPM if they were clogged etc ?

PLease help if you have any ideas.


nash

 

HI:

I mad a discovery to my problem, increase rpm/surging rpm. If I unplug the Brake power booster hose from the power booster ( yes I did test the hose, it is fine)the rpm does not surge. Once the power booster is plugged back in, the rpm surges from 800 to 2500.

So I unplugged the hose from the booster, plugged it, the idles goes up to 1100 and stays there. No surging. If I put the car in gear( reverse) the rpm jumps too 2500-3000 and stays there. So is the problem the Brake Power Booster?


nash

 

I finally got a code, code 41 where should I look?

 

You gave a lot of info but did not say what engine or year.
Assuming you have an OBDI V8 then:
DTC 41, Computer seeswrong voltage coming from the ignition module. The DTC is set during cranking, so it may not be the problem. Anyways,
Possible problems causing DTC 41 to be set:
Open circuit between PCM and ignition module
Bad connection between PCM & ignition module
Bad ignition module
Bad connection between ignition Mod & coil
Bad PCM

There is a possibility that the PCM lost its mind, you may want to swap in another one temporararily to see if the surging stops.

 

Ok, we fixed the surging problem to some extent, no code anymore. The engime is a 5.7 LT1 engine. The car now only surges to 2000 rpm and stays there. No more increase/decrease in the rpm. what would cause this?