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EGR troubles..
4x4 Chevy/GMC Trucks 4x4 Chevy/GMC Trucks Discussions (alt.autos.4x4.chevy-trucks)
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#11
 
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Re: EGR troubles.. -
10-14-2004
, 08:32 PM
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:| :|"Rolf" <nozel99 (AT) hotmail (DOT) com> wrote in message :|news:aKmbd.19154$qU.6758 (AT) clgrps13 (DOT) .. :|> Bret :|> A simple way to test egr open or closed at idle: :|> disconnect vacume line between egr controlling solenoid and egr :|> valve(assuming your ride is so equiped) , then run the engine. :| :|> If idle has smoothed out, the controlling solenoid would appear faulty.You :|> could prove this out by sticking vacume gage on the downstream side of the :|> solenoid.Should be no vacume. Then, with engine still running, connect a :|> vacume source directly to egr valve, if idle becomes lumpy with vacume :|> applied and smooths out when released, it would prove egr valve is :|> serviceable. :| :|> Further, I have proven that the egr is controlled open under most part :|> throttle settings and will close at WOT by connecting (tee in) vac gage :|> between control solenoid and egr valve. If I'm not mistaken, at WOT, ecu :|> control goes open loop therefore closing egr. :| :|> If you leave the vac line between the solenoid off , go for a drive, :|> chances :|> are the ecu will set the egr code because map sensor has not sent the :|> correct value signal back to the ecu. :|> Ecu is looking for set values based on CTS, TPS, MAP, Knock and VSS(again :|> assuming all sensors are working properly). :| :|> Doc feel free to correct me... :| :|Dunno if that was sarcasm or not, but I agree with everything you said. If :|it's loping w/ EGR attached and removing the vacuum source from EGR stops :|the loping, the problem is either the EGR solenoid OR the signal being sent :|to the solenoid. Even if the solenoid is ok, it's still going to open when :|it shouldn't if the ECM tells it to. :| :|I'd hook up a vacuum gauge directly to the EGR solenoid when it's being :|symptomatic and see what the hell it's doing at idle. If there is vacuum to :|the EGR line at idle, I'd then check to see if the ECM was telling it to do :|so by backprobing the signal wire and checking the voltage. :| :|Doc :| :| :| :|> Respectfully submitted :|> Rolf :| :| :| |
did you guys miss my OP? back probing the metripak gives intermittant
voltage spikes when the engine is revved. that's what's opening up
the solenoid and causing the lope.
-Bret
#12
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did you guys miss my OP? back probing the metripak gives intermittant voltage spikes when the engine is revved. that's what's opening up the solenoid and causing the lope. -Bret |
it <should> close as soon as the voltage is no longer present.
Does driving the truck with the solenoid electrical connector unplugged make
the problem go away?
Doc
Quote:
#13
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:| :|"Bret Chase" <nunya (AT) business (DOT) net> wrote in message :|news:ag6um0tmhvc6l9lhnl7gfh8dr7asc7vnrl (AT) 4ax (DOT) com... :| :|> did you guys miss my OP? back probing the metripak gives intermittant :|> voltage spikes when the engine is revved. that's what's opening up :|> the solenoid and causing the lope. :| :|> -Bret :| :|No I read it. What is the voltage at idle? Even if it spikes when revved, :|it <should> close as soon as the voltage is no longer present. :| :|Does driving the truck with the solenoid electrical connector unplugged make :|the problem go away? :| :|Doc :| |
a semi-repeatable voltage spike between 6 and 14V. I've not caught it
w/ the VOM while the idle is messed up (it usually clears itself
before I can get out, get the hood open, unplug the connector and
measure it.)
it's acts up the worst when the cruising with a very light foot at low
rpms (<1krpms) w/ the connector plugged in)
yes, unplugging the connector makes the problem go away.
the original solenoid leaked about 10 in/mg all the time.. new one
doesn't leak. warm idle was 21 in/mg when I last checked it (same
time I checked out the old solenoid)
I'd go check it out now, but I've spent enough time out in the rain
today.
-Bret
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