Replace ECU Next? (1 Viewer)

[bicycleagent003]

So, I am trying to diagnose and resolve a persistent and intermittent shudder and I'm thinking about replacing the ECU as my next step. Please give me your opinion about whether our not that is a good next step and if not what you would suggest instead.

Thus far I have replaced the fuel pump and sock, plugs, wires, dizzy cap and rotor. All OEM.

I also tested the O2 sensors per the FSM and they're fine, the intake rubber from filter to TB is not cracked, I just cleaned and checked thr MAF, and cleaned out an already pretty clean TB and put in a new OEM TB gasket.

I called the local dealership and talked to a service rep who did not give me any confidence they could figure it out unless it happens on a test drive.

The truck is not throwing any codes and the CEL works. Interestingly, the PWR switch does not work although I have confirmed that the switch is fine and there is continuity from the switch you the ECU. I mention that because it makes me suspicious of the ECU and one way to describe the problem I'm experiencing is that the truck doesn't seem to know what gear to be in momentarily. I'm not sure that's it, but I'm not feeling sure of much at this point.

Sorry for the long post. Thanks in advance for your suggestions.

-Russell

 

[ChiTown]

A few questions.

How old is your throttle position sensor? When was the last time it was calibrated?

What is the history of the transmission? Services/mileage/fluid condition/cable adjustment?

This is going to sound silly but have you checked the ecu for codes with a scanner or did you figure there were none because the check engine light wasn't on? If you haven't please do and report back.

 

[elhombre]

You may have 2 problems. First, I would check the cable that goes from the Throttle body to the transmission for slack/or adjustment. You may have not got it right where it needs to be when you cleaned the TB.

2nd, I would try a Fuel Pump relay. If the points are getting bad, the power to the fuel pump maybe causing a momentary interruption when it switches from High voltage to low voltage. Not knowing what exactly you are calling a "shudder"...........

I would also check the wire harness at the EGR. Move it around with your hand and see if you can recreate the problem. These are two common problem areas that may can cause an intermittent problem without throwing codes.

 

[bdruff]

I would bet we have a very similar problem. I described it as a rough idle but it's not as though it is about to stall. It is more like a shutter as you described. Very curious if the ecu fixes it or if you find a solution. Mine was intermittent but now is constant. Also read about a replaced temp sensor fixing a rough idle and also a replaced maf sensor curing it. Good luck to you.

 

[bicycleagent003]

I just realized something. The first time my shudder occurred was the moment I plugged in an OBD2 reader in as I was driving on the freeway. That may be a really stupid thing to do, I didn't think it could damage anything. I wanted to get a water temp number on a long hill I was going up. Instantly, the truck chugged/hesitated, then recovered. The problem never occurred before I did that.

 

[bicycleagent003]

I have checked for stored codes, inspected the wire harness at the EGR, the trans cable looked tight when I did the TB cleaning.
I think I may have damaged the ECU when I plugged in the reader on the freeway as I described above. Does that seem possible?
Thanks.

 

[customcruiser]

I had a similar issue... replaced the EFI relay and all is good....
I also have a 97 ECU if interested... PM me if so

 

[Surfdc]

My scangauge caused the same symptoms. How did you end up fixing yours? I am very curious!

Customcruiser, do you still have your ecu?