dr_bowtie

So my trucks stuttering issue is getting worse and it has rained the last two days and with it being very damp the truck has gotten very bad.

it runs excellent when warming up and doesnt skip a beat but fully warm you cannot give it more than 1/2 throttle and and a little longer and its down to 1/4 throttle...it stutters very badly and and the warmer it gets the worse it is...it gets to a point it does it just barely touching the gas and it wont hardly accelerate.

I am convinced this is a grounding issue. The reason I say this is my 88 GM truck did the exact same thing and it is fuel injected speed density with a throttle body... I mean the exact same thing...when there is a load on the engine requiring more load on the ignition it just cuts out and you get massive spark scatter and timing fluctuation all over the place...it cause from the ignition trying to pull amps that it cannot so it freaks out and quits...

It isnt the Module nor the distributor nor the coil or MSD box...so dont go there...its simply a ground. I need to know where all the ECM grounding points are for my truck...so it anyone has the wiring schematic please post up...

I have cleaned several ground but there has gotta be a main ECM ground or grounds that are losing connection...

today I let the truck run long enough for the needle to just barely move and drove the truck and it purred like a kitten and ran fine up to 4500rpm never missing a beat...warmer it got the more it started missing until it started stuttering very badly...

transmaster

Have you checked the temperature sensor the ECM uses to help calculate the fuel air mixer. If it has failed it will fool the ECM into thinking the truck engine is still cold. I am assuming you have pulled the codes off the diagnostic system.

Just call me Sean

iTrader: (1)

There are so many things I could tell you to check, except I would assume you checked them all...

I don't know where your grounds are.

dr_bowtie

Yes I have done all that and all the sensors are within range....NO codes.

It doesnt spit codes even stuttering this is how I know its a ground causing loss of power to the circuit...its not failing and throwing a code like normal



yea but you know me....


I have checked, checked and rechecked the sensors...

originally the front pump would just cause a bucking once in a while but switching to the rear tank fixed that...then the bucking turned into a stutter and both tanks do it and fuel pressure doesnt drop below 58psi...

Its definitely in the ignition circuit...I checked the module and distributor and all the sensors...and have been cleaning grounds and lubing them as i find them...

Anything you think I forgot????

Runs killer cold...terrible when warm..

like its got moisture in the distributor cap...but it doesnt

Nitehawkjr

Dr what size motor do you have? The reason I asked 58psi on the fuel would be ok for a stock 4.9 but the V8's usually run in the 35-45psi range.

dr_bowtie

its the 4.9L...and yep thats why its 58psi....

dr_bowtie

anyone?

farmer12

The only ECM ground I know of is on the drivers side up above where your 60 pin comes out of the firewall. Up by the hood hinge. When I worked at ford one of the diagnostic guys told me that. One black wire with another bare wire with it. I'm guessing you cleaned it but that's the only one I know of.

ymeski56

What do you think about a failing PCM Diode?

dr_bowtie

hard to believe there is only 1 ground for the ECM...I am going to look harder and look on the engine. The ground on the fender above the ECM harness is a tiny black wire and its right above the Module mount for the Dizzy...cant imagine that would be enough of a ground for the ECM? GM uses a 10ga wire for a ground...

As for the DIODE...WTH is the purpose of that? and what if it does fail? never noticed it....???

Whatever it is Damp weather and heat really aggravate the issue its gotten colder/freezing and its not been that bad..but we're supposed to get warmer and rainier so we'll see if it is truly aggravated by those combination...