Occasional surges, and a code 51

[Speedwagon]

87 Brat with SPFI. I get occasional surging when I'm driving the car, but only briefly and sporadically. Maybe for a second tops when it does it. It will do it randomly.

 

I also have a code 51 that comes on sometimes, but not all the time. Are these things linked? Or just coincidence?

[stratman977]

Code 51 is the neutral safety switch.

 

I was getting code 51 intermitantly after an auto to manual swap because it was always in neutral. I wired in a switching relay to switch the computer from drive to neutral when the starter is engaged and this fixed that code.

 

I would start with the temp sensor for the computer. This one always seems to cause erratic computer behavior.

Edited December 11, 2014 by stratman977

[DaveT]

Sounds like the beginning of my story in the intermittent idle thread a few more down from this one.

[Speedwagon]

This morning I noticed the following:

 

Cold start, driving in 1st gear to get out of the subdivision and warm things up. The ECS light would come on, and then turn off. At the same time the light went off, the car surged forward. Then the light came back on, and the car slowed down. Did this a few times, while I didn't move the throttle. When I got out on the highway, the light didn't come back on, and the car seemed to be normal again. Eventually the code 51 came back on. I suspect I'm getting a different code when it is surging, but I can't see the light while I'm driving to confirm this.

[DaveT]

I would sometimes get a CEL flash with mine. The problem is that the sensor isn't necessarily going out of a valid range, it's just lying.

[Crazyeights]

I had no end of trouble fighting cold hesitation, flat spots in the throttle, etc for a while now on 2 different fresh SPFI EA series engines. All the other simple had causes had been ruled out. It ended up being a bad spot in the TPS right off idle (where most gas pedal usage is done). It was worn enough to cause a drivability problem but NOT enough to set a code. If you are all out of other options, ready to give up and frustrated then I suggest trying a TPS that doesn't already have 250k+ on it and see if the problem gets better.

 

My EA82 Wagon runs like the NEW engine that it is for the first time after sorting this out. Also, make sure ALL of the code related issues are fixed as the engine cannot seem to run properly and idle down all the way if it is in the 'fault code' mode of operation. In other words you should actually fix that long ignored purge or egr code or whatever.

 

Check this, on BOTH of my EA82 wagons the service engine lights were already pulled out by previous owners long ago. Try a simple bulb check too. Is your SES light MIA?  More often than you would think.  It's a dirty trick to sell a car with nagging sensor problems - "that light will NEVER come back on now!"

Edited December 13, 2014 by Crazyeights

[Speedwagon]

TPS would make sense. I've suspected it might be a problem for a bit. Every so often the engine 'hiccups' while driving. Just a sudden bump like I let off the pedal quickly, and back on again. I'll replace it and see what I get, along with the neutral switch.

Edited December 14, 2014 by Speedwagon

[Speedwagon]

Which one is the neutral switch? I believed it to be the aft sensor on the drivers side. Changed that one out, still getting a 51. Is this the wrong sensor, or do I have a wiring issue?

[Speedwagon]

Found my code 51 problem. The black/red wire came off and want connected anymore.