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87chevys5.7

87 Chevy 5.7 will not run while in gear

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Posted (edited)

Hello, I am new here and have a head scratcher.

 

I have an 87 Chevy Silverado with the 5.7 and it does not stay idling when placed it gear.  I have checked the torque converter actuator is working properly, iac is new and still working properly with the correct signals, tps is at .5 volts at idle, idle baseline has been set to 700 rpm, injectors have been replaced, timing set to 0 tdc while est circuit 423 is bypassed (tan/blk wire), circuits 423 and 424 are acting accordingly, pcm was replaced, wires replaced, ignition coil and module replaced and plugs are new and gapped to .06 inches.

 

I am getting a flash code 42 and have run that diagnostic sheet from the service manual from top to bottom where it says replace pcm, that is why I have a new one.

 

I recently installed electric fans and a high output alternator to increase fuel economy.  My ground from battery to frame is new and 1/0 again, the alternator to battery is 1/0 awg.  My ground to block is 4 awg, ground to body is g awg.  I found out that the engine is a 97 block with vortec heads and a GM aluminum performance intake (not stock i know).  I also added some new headlights that have a halo ring on them so that is a new circuit along with my fan circuit.

 

I am thinking it is a bad ground, but do not know where it could be.  Any help would be much appreciated.  Thank you.

Edited by 87chevys5.7

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Vacuum leak?it is struggling,so any load is stalling it?

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I have gone through every inch of vacuum hose and replaced anything that looked like it might be leaking.  She sounds fantastic in park or neutral.  I can driver her if I toss her in neutral right before i come to a complete stop.  

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Does this motor have a aftermarket cam?and has this been a problem from day 1?,I would think,too much air,or not enough fuel,how's the spray pattern from injectors? you could try unplugging the cts,richen it up,see if you are lean

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I would assume that it is the same can on the 97 Chevy 5.7.  The truck has never had this problem before.  

 

Originally, I took the truck down to do the fan, alternator and oil pump replacement.  The injector pattern is great.  I will try the temp sensor idea and see how it goes.  I am willing to do anything at this point.

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After cts test,try unplugging vac line from map,plug line with something

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There is the possibility that the new module is defective,have you tried advancing the timing?

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We have advanced it with no luck, I will try the CTS either tomorrow or the next day along with that map sensor idea.  I removed the eprom and calpack chips and check them for any visible defects with no luck either.

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Ok, so the cts and map sensor idea is not the culprit.  She will not even run with the cts disconnected and the map sensor floods it too much for it to idle properly.  The truck will keep running if I place it in neutral before I come to a complete stop.  I am going to take it to the parts house and use their data logging tool and see what I get.

 

Thanks for your help this far @riverbanks

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So, I hooked up the scan tool to do data stream and the truck started acting crazy.  It would idle real high then the engine would start to flood out.  But, these are the readings I got, not sure if they are all that reliable since connecting the scanner caused more issues than it solved.

20190610_180510.jpg

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Blm is close,128 is optimal,try unplugging 02,let it rely on tps and map,and reading back, you said,plug gap at .060,a bit much?.045 comes to mind

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.045 is for the 87, because it has a 97 engine, I put it to the 97 spec of .060 and used the 97 plugs.

 

I will try the O2 later today or tomorrow.  However, the loop was open during the whole test.  Which I thought means it was not even looking at the o2 sensor.

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Ok , Never mind 02,open loop,damn,is code 42 still present?and I would go .045 to match the coil from 87,and who's plugs?

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Yes 42 is still present, ac delco plugs, msd wires.  I will adjust the plug gap, but not confident that will solve the issue.

 

There could be interference from the wires (I think) since they may not be resistor wires.  The are 500ohm per foot.

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I don't think it will solve it either,but your working that coil hard,so with 42,sorry misread that,is screw contacts clean for module on distributor?

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