My pick-ups got the wiggles...

[CN Spots]

I need to pick the brains of the mechanically gifted here. My 92 Chevy 1500 4.3 liter TBI is idling rough. This started after I replaced the EGR valve. the MAP sensor and O2 sensor have also been replaced but made no change. It runs fine at speed and will smooth out for a few seconds at idle but will soon start running rough again. It seems to cycle through these smooth/rough periods. I've sprayed carb cleaner everywhere to try to find a vacuum leak but nothing. <br /><br />I'm outta money and outta ideas and until I get my truck fixed, I'm outta tow vehicle. <br /><br />Yoose guys got any ideas?<br /><br />spots

 

[Laddies]

Re: My pick-ups got the wiggles...

If its rich it could be the temp sender

 

[one more cast]

Re: My pick-ups got the wiggles...

Did you check the egr valve vaccuum line for leaks.

 

[Trent]

Re: My pick-ups got the wiggles...

Did you get a direct factory replacment for the egr? If not did you install the correct washer? Did you clean all the old carbon out of the passageways. Did you replace the PCV valve?

 

[snapperbait]

Re: My pick-ups got the wiggles...

Is the ECM storing any codes?...<br /><br />Disconnect/plug off the vacuum line too the EGR valve... <br /><br />If it idles better after the EGR is disconnected, you may have a faulty EGR vacuum switch...

 

[JasonB]

Re: My pick-ups got the wiggles...

If it were a Ford 3.0 Vulcan V6, I'd tell you to check the idle control solenoid. My Ranger had a similar problem last year. Idled so rough it'd shake the fillings from your teeth, but occasionally, would idle right. Cost was about $75. Don't know if your 4.3 Chebby has a similar solenoid or not, but something to check.

 

[steamboatwilly]

Re: My pick-ups got the wiggles...

check out your fuel pump.They do funny things sometimes.

 

[elmo]

Re: My pick-ups got the wiggles...

i'm a computer/electrical tech, gm background/trained since 1980, can answer your questions with a little more information. first, why was the egr replaced in the first place, why the o2 and map ?? <br /> gm 4.3 -5.0 - 5.7 engines are famous for sucking the tbi mounting gasket inward, especially if the truck is used for towing. but just as often the inside of the distibutor cap fills with gases and creates white powdery substance on the electrodes, thus week spark.<br /> also, guys pinch the injector wires under the air cleaner assy. during filter replacement, partial shorting of the circuits for injection.

 

[elmo]

Re: My pick-ups got the wiggles...

egr valve failure is rare, map is also rare, o2 sensor failure is usually related to the heating element failure (if applicable ) or contamination from oil useage or poor fuel quality.<br /> unless you had trouble codes for these replacements, you aren't there yet.<br /> computer failure was common on the s10 trucks, but not the 1500 thru 3500.<br /> fuel pump and/or fuel filter is a possibility, but again unless mileage is well above 100,000, fuel filter would be most likely. install a fuel pressure gage at the filter to check pressure.<br /> then there was the guy that had 1200 bucks worth of repair shop receipts for futal attempts to correct his problem............ on the 5.7 the computer ground wire is attached to the thermostat housing mounting bolt......... yep, he had changed the thermostat at which time the problems started, replaced the eyelet on the wire and relocated to different bolt, problem solved, time invested - 20 minutes, expense - i didn't have the heart to charge him....... we had coffee and i gained a friend for life.....<br /> i have nearly all information you may want here on my computer ( alldata systems ), give me some more info and maybe we can fix your truck.

 

[CN Spots]

Re: My pick-ups got the wiggles...

The reason for the O2 sensor swap was due to a check engine light and since the old girl has over 140k miles (on the same sensor) I thought that was it. It wasn't. Took it to the Zone where they ran a check on the codes from the flashing "check engine" light which indicated a EGR Valve failure. So I replaced it. (I tried to clean out as much carbon as possible) Then the idle wigged out. So I went back, this time it said the MAP sensor was toast. So I replaced it. No change. Cleaned out the PCV valve and all the vacuum lines. No change. Tomorrow I think I'll pull the EGR valve off again and put the old one back on and see if that fixes the idle. If so, I may have a bad pump. The new one differed from the original and that little washer might have popped out despite punching the edges.<br /><br />Thanks for all the help guys.<br /><br />spots

 

[Colorado04]

Re: My pick-ups got the wiggles...

I had simillar sounding problem with my 93' 4.3L vortec in my Blazer. Two things happened. 1. The EGR valve would get stuck open now and again. When I removed it, sure enough a hunk on carbon jamed the valve open. 2. Took forever to find the leaky intake manifold gasket on the front side of the motor. Hardly noticable when looking at it. <br /><br />Hope this helps...

 

[elmo]

Re: My pick-ups got the wiggles...

ok, the map code will set if low vacuum is present, but does not always mean the sensor is bad, usually just saying there is low vacuum in the engine...... as colorado says, carbon stuck inside the egr valve will cause this, creates vacuum leak..... but his s-10 blazer is a linear type egr valve and is prone to do that, yours should be of different type. your comment about the difference in appearance, new part versus old part, makes me wonder..... they should really look identical.... so when you have the new one off, verify the mounting plate and gasket is exactly the same as the old egr valve, if not, you have a vacuum leak created by the incorrect mounting plate..... computer will search for air/fuel ratio to override the leak ( input from the map sensor ), thus erratic idle..... keep posting,

 

[elmo]

Re: My pick-ups got the wiggles...

have one request friend, tell us what the eighth digit of the vehicle vin number is please, count from the left, should be a Z , my 92 g-20 van has the 5.7 vin number is K, 5.0 is H, colorado most likely has a W which has a different fuel system totally, maybe i am on the wrong page with you.....

 

[dolluper]

Re: My pick-ups got the wiggles...

The problem started after the EGR replacement,take a look at your old orginal EGR on the top there is code numbers,one row then a second row,at the end of the second row look for the letter,either a P which is positive back pressure<br />N is negative back pressure<br />and no letter is ported valve<br />Make sure you have the same installed<br />If right start looking for other things such as loose spark plug wires at cap and plugs or the condition leaking at cornors of valve covers,sitting on them [common},heat stove pipe hooked up,terminatic under air breather wires connected tight,also condition of rotor ,cap test pick-up coil look for burn marks on thin green or white wires to module if you note any fillings in this area timer is hitting base means distributor is binding on bushings in housing {won't advance right} or dist shalf bent ,look at coil also ign wire connected tight no corrison inside coil neck,wire connector tight<br />Spark problems show up more at idle they are some times undetected at higher speeds

 

[CN Spots]

Re: My pick-ups got the wiggles...

That digit is indeed a Z. I swapped the old/new valves this morning and it idles smooth as glass now. BUt the check engine light is still coming on. Regarding the design of the original valve and the new one, my original had a collar about the dia of a dime and 3/8in tall around that metal pin, the new one was flush and the new one's pin was about 1/4in shorter. Both Napa and the Zone said this was the only replacement. I now question their logic. <br /><br />I'm gonna hafta buy a part from GM ain't I?<br /><br />ouch<br /><br />spots

 

[elmo]

Re: My pick-ups got the wiggles...

not yet friend, if your idle is back to normal, then let's find what the problem really is. <br /> need ya to do a test, start the motor and while it is idling, stick your fingers under the diaphragm of the egr valve and lift the diaphragm up..... motor should run rough and maybe even stall/die until you let go of it. if it does as i describe, the valve itself is probably not your problem. <br /> if that is successful, let's see if you can talk to the computer and retrieve the trouble codes. you can do this at home, find the connector under the dash ( call the ALDL connector ) where the zone guys plugged in and gave you the code. term numbers a & b are on one corner, turn on the key, don't start motor, take a paper clip - made into a U-shape and stick into both a & b making contact with the metal tangs in those holes. the check engine light will flash now, you read it like s o s coding, flash - pause - flash, egr fault code is 32, so you will see 3 flashes, short pause, 2 flashes, then longer pause, it will give you the codes 3 times, then go on to the next if any other is there.<br /> sounds complicated, but not really if you just relax, we need to know the codes at this point of our diagnosis to get you on the right track......... keep posting

 

[elmo]

Re: My pick-ups got the wiggles...

dollup has a point about the numbers on the top of the diaphragm, gm did alot of messing around with the type of operation of the valve. but it sounds like the new valve is not the correct application for your engine, the parts guys can only read the box numbers and not at fault, it happens.<br /> i've seen too many parts replaced without a thorough diagnosis, i never had that kind of money myself, time is always cheaper......

 

[dolluper]

Re: My pick-ups got the wiggles...

As elmondo says get the codes now the idle is back, under your steering wheel there is the dianostic connector ALDL[usually plastic cap on it],there are 2 rows of connection slots,on the top row FAR RIGHT as you can go is term A and to it's right is B jump these two with paper clip or wire,turn key on but not as far to start,now watch the check engine light, first code will be code 12 "flash pause flash flash ",it will pause and 12 will come two more times,it cycles three times [code 12 shows system is working] then other stored codes will come out and also three times[like government in triplkit} after the last code it will go back to code 12 turn key off then pull jumper out Let us know what codes you get<br />List of codes<br />Diagnostic Trouble Codes - 1992<br />GMC<br /> 13 Open Oxygen Sensor Circuit <br /> 14 Coolant Sensor Circuit Shorted <br /> 15 Coolant Sensor Circuit Open <br /> 21 Throttle Position Sensor (Signal Voltage High) <br /> 22 Throttle Position Sensor (Signal Voltage Low) <br /> 24 Vehicle Speed Sensor (VSS) Circuit <br /> 25 Manifold Air Temperature Sensor (MAT) Shorted <br /> 28 Pressure Switch Manifold (PSM) Fault <br /> 32 Exhaust Gas Recirculation System <br /> 33 Manifold Absolute Pressure Sensor (MAP) Voltage High) <br /> 34 Manifold Absolute Pressure Sensor (MAP) Voltage Low) <br /> 35 Idle Air Control (IAC) System <br /> 39 Torque Converter Clutch (TCC) Stuck "Off" <br /> 43 Electronic Spark Control (ESC) Circuit <br /> 44 Oxygen Sensor Circuit Lean Exhaust Indicated <br /> 45 Oxygen Sensor Circuit Rich Exhaust Indicated <br /> 51 Faulty Mem-Cal or PROM Problem <br /> 52 Fuel CALPAK Missing <br /> 53 Over Voltage Error <br /> 54 Fuel Pump Circuit (Low Voltage) <br /> 58 Transmission Temperature Sensor Circuit (High Temp) <br /> 59 Transmission Temperature Sensor Circuit (Low Temp) <br /> 68 Overdrive Ratio Error <br /> 73 Force Motor Current Error <br /> 75 System Voltage Low <br /> 81 Shift Solenoid "B" Circuit Fault <br /> 82 Shift Solenoid "A" Circuit Fault <br /> 83 TCC Solenoid Circuit Fault <br /> 85 Undefined Ratio <br /> 86 Low Ratio <br /> 87 High Ratio

 

[elmo]

Re: My pick-ups got the wiggles...

dolluper, care to make a guess on this one, you sound quite educated, i'm 55 and not alot of guys out there wanting to take the diagnostic time these days. mine ? tbi mounting gasket is damaged, with possible egr control solenoid incomplete function due to the lose of vacuum internal to the tbi unit. yours ??

 

[CN Spots]

Re: My pick-ups got the wiggles...

The codes read 32 and 33. The engine DID begin to stall when I pressed in the diaphram.<br /><br />Basically, I'm back to where I started 'cept I now have a shiny new MAP sensor and a thorough understanding of how to remove/install an EGR valve. (I drop the nut on the passenger side EVERY time)<br /><br />spots