Hello! Which engine is installed in the vehicle; 5.0, 5.7, 6.5 (Diesel) or 7.4?Guru...Saailer
I’m happy to help further over the phone at https://www.6ya.com/expert/david_6df67de3b14de867
Testimonial: "Saailor is an excellent troubleshooter. He figured out a wiring problem that has plagued me for months. I highly recommend this gentleman."
Hello! Thanks...Are there any trouble codes? On a flat road, with a steady pedal does the engine run normal? Will the engine idle smoothly? If you could answer these questions I can establish a base line for troubleshooting the fault...Also, do you have a multimeter and a wee bit of experience using it? Send a comment.....Guru....saailer
Hello! Engines use quit a bit of +5 volt circuity...These sensors require solid resistance free grounding...Lets eliminate any chassis grounding issues right up front...Set your meter on the X10 ohm scale...If you do not have X10 go higher...Place one meter probe on the CENTER of the (-) battery post and the other on bare metal of the body (fender bolt or firewall bolt) Just make sure it's bare metal...Record reading...Must be close to zero...Move the probe from the body to bare metal on the engine block...Again, record reading....Send results...saailer
Hello! Yes we are still working on the problem...I apologize for the delay....My keyboard went down...I am back...8 ohms is a good reading...I don't know what time zone your in...I'm on the East coast and it is now 8:50...I'm going to send you a couple of test procedures in 10 minute...I sign off at 10 Pm...But because of the keyboard (not your fault) I'll stay on longer...Test procedure in 10 mins...saailer
Hello! Whether you changed the Manifold Absolute Pressure (MAP) sensor not the issues could be in the connector....The MAP is bolted to the throttle body...It has a 3 wire connector with wire colors...Gray...Light Green...And Black...Using two safety pins push the point of one into the rear of the in-place connector into the Black wire...The other into the Gray wire...Set the meter to read 5 volts...Clip the (+) meter probe to the Gray pin and the (-) probe to the Black pin...Start the engine...At idle must read 5 volts...Raise RPM's to 2000...Meter should read 2 volts...send results...Saailer
Hello! Use the same method on the TPS (I know you replaced it )...Three wire connector ...Bolted to the throttle body...wire colors are...Black...Gray...And Dark Blue...Push one safety pin into the rear of the in-place connector on the Black wire and the other pin into the Dark Blue...Meter still set for 5 volts...(+) probe to the Dark Blue and (-) probe to the Black...Start the engine...Should read less than 1 volt at idle (.85)...As you increase the throttle to full the voltage must rise to 4 volts...Rise must be smooth and not **** or jump around....Send results...Saailer
Hello! I'll meet you back online at 8am EDT...sleep well...Saailer
Good morning! I am here.................Saailer
Just came back in. The TPS checks out. The MAP sensor, I can't locate. If you tell me where it is....... Also what is the unit bolted to the Throttle body right next to the TPS?
Hello! Follow the wire colors for the MAP...I'll send you a location diagram in a few minutes...Saailer
Hello! See diagram of MAP location...Wire colors Gray...Light Green...And Black...I think this is the culprit...saailer
MAP LOCATION
Hello! This is the TPS location and the MAP is next to it...Saailer
TPS LOCATION
Hello! Photo, part # and price for a MAP...Saailer
ACDELCO Part # 213796.....Cost $50
OK. Thanks. I will get the readings off the MAP and send them. But I need to take off and take care of some business. I will be back mid-afternoon. I will let you know when I ready to start on this beast again.
Hello! For the Map test..... Typical Readings: Output voltages between 0.5 and 1.5 volts indicate a high vacuum (low pressure) situation, such as idle or deceleration... Output voltages between Output voltages between Any reading of 0 volts or over 4.5 volts indicates a problem......Saailer
Sensor output voltage range is 0.5 to 4.5 volts...
1.5 and 3.0 volts indicate a medium level of vacuum (pressure) such as a
cruise or slight acceleration condition...
3.0 and 4.5 volts indicate a low vacuum (high pressure) situation such
as hard acceleration or a mechanical failure...
Indeterminate readings on the MAP, so I just replaced it. Made no difference. Problem unchanged.
Sorry about yesterday. It turned into a larger problem than it needed to be. I didn't get home until late and figured it was to late to continue.
Hello! indeterminate readings on the MAP could very well be the problem; Looking back into the connector....Tell me what you read with the ignition on/engine off...Then at idle ...Then at 2500 RPM...Knowing those readings will lead to the solution....Saailer
You mean hook the multimeter back up to the MAP the same configuration as before?
Yes...follow test procedure...MAP is called the "fuel boss" and is probably bad, in that the wiring that carries its signal is open or grounded...Does not have to be the component...That's why it is measured with the connector in place...Send the readings...I am here!..saailer
OK 1.0 key on not running 5.01 at idle 5,01 at 2500rpm
Last message was in error. 5V across the board. All three positions.
WE HAVE LOCTED THE FAULT!!! The wiring to the MAP connector is at fault...Pull the MAP plug and give it the bright light inspection...It would appear that the signal lead (Gray wire) is shorted to the +5 volt reference voltage on the Light green wire...With plug pulled...Clip the (+) probe to the Light Green wire and the (-) probe to the Black...With the key on ....And you read +5 volts we got it ...Just received your last...We have it isolated....If the Black wire (with the plug off) reads +5 t5o chassis ground that's the no-no...because the black lead IS chassis ground...Tell me if there is 5 volts on the light green wire with the plug off.
We don't got it. reads 0.0 black to light green. 5.0 black to gray. 5.0 gray to light green.
You ready to call it a night? I am. Let me know when we can get after this thing again. Thanks for all the help.
Yes We do have it....When you read +5 volts from Gray to Light green that means The Light green lead is at ground...Gray is the +5 volt output from the PCM...and Light Green is the input from the MAP... With the plug off the light green lead should not be at ground...You can stop whenever you like...When ready, Measure the light green lead to ground with the power off using an ohm meter set to the X1 or X10 scale...record reading...saailer
Good morning.
I am getting 0 readings on lt green to ground. I checked continuity on gray and lt green and bother set the beeper off. I believe that is a positive reading.
The Gray lead is +5 colts from VCM (computor)...The Light Green is the signal input...The Light Green is the bad guy...It is shorted to +5 volts (Gray wire)...Probably in the harness...THIS IS THE FAULT...Use ohm meter set onX1 or X10 and with key off and connector for MAP pulled off read between the Gray and the Light Green... I believe you will find continuity between the two leads...Remove C-2 from the Vehicle Control Module (VCM)...Pin # 21 on that connector is the Light Green MAP input...Read between the Gray and Light Green (ohm) at the MAP connector ...If they read together (Wrong) You can cut the Light green Out from both ends and run a wire spliced into either end and I bet the "K" runs perfect....Saailer
You are very very good. Thank you for all of the hard work. I would recommend you to anyone having automotive problems. The truck runs like a ***** rabbit.
Saailor, don't I owe you some money? I don't see any way to pay you. Let me know ASAP please. I don't like owing money to someone who has definitely earned it.
Hello! Go to the link below and file the original trouble report under GM Cars &Trucks...
God bless.....Saailer
http://beta.fixya.com/users/saailer
Maybe I am getting to old or my eyes aren't working right. When I check the GM Cars and Trucks box it takes me to the credit card page. I filled out the form. Did you get payed? If not what else should I do.
Hello! All is well and correctly processed... I thank you for your tenacity as we searched for a nasty one...If you or any friends or relatives have a vehicle problem don't hesitate to contact....Saailer
Hello! Go back to the link;http://beta.fixya.com/users/saailer
And rate the solution there...Switched to new system and rating did not follow...God Bless...saailer
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SOURCE: 96 Chevy K2500. Approx 170,000 miles Auto trans
Backfires are usually out the tail pipe on deceleration and can
be caused by several things. First is the most common and that is an exhaust
leak close to the front of the exhaust system. Other causes are ignition timing
off. ------------ The backfire,bucking,sputtering,misfiring etc etc is most likely due to the gas still pumping into vehicle cylinder when the engine cuts out, then is overloaded with gas when the engine kicks back in. It happens due to a rich mixture of fuel and it's bad for your plugs (ie it fouls them) and catalytic converters over time. That unburnt fuel ignites in your exhaust and you hear the backfire, sputtering. So get the compression test done, get the fuel pressure tested and this will point towards the problem. --------- Thanks.Helpmech.
An oil leak at a breather pipe will not cause a backfire although an engine
problem can cause a backfire inside the engine that can blow breather pipes off
which then can be an oil leak. To be safe, you should have a compression test
run on the engine to eliminate that one as a cause.
You can also experience a popping sound due to gas flow through an exhaust. As you change gears fast gas flow is mixed with slow gas flow and a pop occurs due to the reverberations.---------
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Usually answered in minutes!
MAP LOCATION
Sorry 5.7
No trouble codes. It does not run normal on flat roads, it stutters, bucks and backfires any time it is not under a load. It seems to idle smoothly. It starts a little harder than it did before the problem manifested itself. I have a multimeter, and just a little experience. I have a history is the auto trade. I retired as a heavy body repairman. If that helps.
I got a reading of .8 ohm from the body and the engine.
Are we still working on this?
We seem to be at a standstill here.
I am in northern Michigan. It is dark here now so I think I will stop for tonight if that is OK with you. I have lights but it has been a long day. We old retirees need our beauty rest. I am an early riser so I will do this procedure first thing in the morning. What time should I expect you to respond?
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