Surging problem and cause

[kevinde1]

Can somebody look at this wiring diagram? Where do the injectors get there ground from if Lt Green and Blue are supposed to have 12 to 14v and the Red and White wire is going to the positive on the ICM and Ignition Coil? I seem to remember having a ground at the red and white wires when I was checking, is that correct? What is the other box in the diagram a relay? If so where is it located?

 

[kevinde1]

This is the chart I was using

 

[kevinde1]

This is a little of topic but can somebody tell me what the pink/white stripe wire is at the bulkhead of the fuse box? It would be the 3rd wire down on the right side, my guess was the fuel sending unit but this wire has fluctuating voltage. I don't recall fuel sending unit wire having voltage, am I wrong?

 

[crpntr78]

Does your truck have the dual tanks? I think it may have something to do with that.

 

[kevinde1]

yes it does have dual tanks. 87 r10 5.7L

 

[kevinde1]

Here's an update on the situation. Pulled the timing cover to check the timing chain and gears I wanted to know if I had the plastic gears and see what kind of condition they were in and they looked fine I went ahead and replaced them with a double roller chain. Pulled the oil pan and changed the oil pan gasket cause it was leaking some. I bought a new distributor from NAPA, installed that and swapped the coil with a known good one. Previous coil tested fine but figured it was worth a try. So far, still no luck with this truck, still surges. But I have not yet give up and I'm determined to find out what is causing this.

 

[kevinde1]

I have a couple questions that I'm having trouble finding any information about.

1. Where should the throttle plates be set on the throttle body? I would assume that the IAC would make the adjustment for idle but my throttle plates are set at opened as far as they can be set open. Doesn't seem right to me.

2. Can the TCC cause the engine to surge? Or can the speed sensor cause it to surge?

The weird thing about this truck is it surges from nearly stalling to about 1300 RPM. But when you put it in gear the surging stops but it is idling way to high. If you let off the brake it will take off and go to point of shifting gears when it should be at an idle roll.

 

[Georgeb]

The way I understood the trottle plate setting was to read tps volts and set the throttle plates accordingly. You will want to be reading 4.5 volts with the plates closed. Adjust that with the engine not running. Open and let the throttle snap closed a few time rechecking the voltage each time. Then do an IAC relearn. I also noted my TBI 350 liked a little more timing advance. Try somthing like 8-10 deg adv.

 

[kevinde1]

Thank you for all the replies. I started this thread in Feb and it is now Dec. I had to walk away from it for awhile because of the frustration and stressing myself out. But I've picked it back up for a couple of weeks now. I have spent countless hours reading forums on this subject (surging idle, stalls) and many these threads are 87 R10 seems to be a common problem with this year of truck maybe more so than the others. Either I or the previous owner have replaced computer, prom, all the sensors, egr valve, TCC solenoid, timing chain, distributor, ignition module, fuel pump, filter, regulator, rebuilt throttle body, injectors, plugs, wires, cleaned grounds, set timing base 0 and at 8 to 10 degrees, reset IAC. replaced intake manifold gasket and throttle body gasket to ensure that there are no vacuum leaks. There are no codes. Bought the ALDL connector for my laptop and couldn't get the truck to communicate with the 2 programs I was trying to use, pro tuner was one of them. What were my results you ask? Lol! It still surges and stalls, runs lean when warm with a dead spot in the throttle, runs rich when cold with no dead spot, when you put it gear if you feather the gas a lil bit to keep it running hold foot on the brake you can get it to quit surging most of the time but not always. Put it back in park will straighten up for about 5 to 10 seconds then back to surging. I have been collecting the parts I need to do a carb swap. I'm going to pull the ecm harness first if I don't see any obvious signs of a bad wire or wires melted or its getting a carb this weekend. Thanks again, and good luck to the rest of you.