I have been chasing a stumbling to the point of staling on deceleration problem on a car for 6 months have replaced all ignition components, Timing is a little advanced but it is a chevy and seems to like it there, I cant find a vacum leak, have changed fuel injectors and pressure regulator. The stupid thing has no simptoms pops no lights and is a general pain in my ass. Any thing I have missed It s a 95 1/2 ton Suburban Sorry for the run on and on and on sentance and poor spelling but i just got up.
O2 sensor or throttle body seal (gasket) most likely. Do you have anyone who can scan it and look for any diagnostic codes for you?
With GM's that still have Distributors, I've seen similar conditions where the distributor shaft would wear out, and would result in too much play on the shaft & cause the reluctor pickups inside to not jive quite right. Just a thought... BYC
I dont what kind of injection they put on that truck but if it's throttle body injection there's an idle air-bypass that can get clogged up and not let the idle air in when in needs it. It's on the passenger side rear of the one on my Astro Van V6. that could be it. Or if it only does it after it warms up it but idles ok cold it could be the temp sender by the thermostat housing, yea, the $28 sender... The computer takes care of timing advance, you should set it to spec.
I have replaced the O2 Sensor and replaced all the top end gaskets(ie manifold thottle body internal and base gaskets. And would there be any tell tale signs the ditributer has too much end play (unnatural timing, like advace doesn't curve correctly hard to time) The problem is intermittent G/D Wish I could get rid of all this expensive electronic crap and just put a carb and basic ignition on this thing
If it were the distributor thing that I described above it would be more of a side-to-side type of play, like if the center shaft or bushings were worn out. You could see if this is happening by pulling the distributor cap & wiggling the rotor. Basically youre looking to see if there are any damaged or bent reluctor pickups. BYC
It's been a long time since I wrenched for a living.. I retired and gave all my shop tools to my son a few years ago.. Before I gave it up and went home, I did a lot of driveability work... My dollar's on the EGR valve... Probably sticking, but could be receiving the wrong signal due to bad logics in the computer..
Wouldn't EGR pop a light on the dash? When EGR went bad on my blazer It would (pop a Code.) There is no code staying lit. so it is not a hard code as it is called . so it is not a problem with smog or it would give me a code. Right?
Did you "Slap" your computer? Really-at Idle with computer dropped down where its accessible- flat hand"slap" it a good one and see if it[engine] stumbles....if it does -it has a cracked circuit board and needs replaced[kinda rare]NO -IM NOT JERKIN YOUR LEG....
"pop a lite"?? True, under most circumstances, and so would an O2 sensor problem.. But maybe not if the problem is with the computer itself.. That's what I meant when I said "bad logics".. The computer is "divided" in to two areas.. Logics - reads the sensor information (O2, temp, RPM, Speed, manifold vacuum, etc), does the computing and thinking.. Commands - sends the signals to the various control devices (timing, EGR, IAC, etc) . In other words, the computer could be sending the wrong commands to the control devices.. Hook up a scanner and monitor the data stream.. This will tell you about what is taking place.. The hardest fuel injection "engine dying" problem I ever worked on ate my lunch for a month.. Got to the point where we just threw parts at it and hoped.. Turned out to be low oil level.. Oil would slosh away from the pickup during decelleration.. The drop in oil pressure would shut down the fuel pump. Oil pressure lite never came on.. This happened to me when fuel injection was in it's infancy.. Some times it's the simplest of things.. Don't bypass looking at the basics.. I could be all wet on this.. Like I said -- It's been a long time since I did any work on a "pro" level.. The 95 models were just a gleam in the designer's eyes when I took that last trip home..
IS it an auto or manuel??If its an auto, try to un-plug the lock up converter, Ive seen em get stuck locked and falls on its face when you drop rpms down to idle..Worth a try..Either that or it sounds like the IAC.. Matt
96 and up would trip a light for egr or o2. get a scan tool and look at the tcc (torque coverter lock-up sol.).
check the throttle shaft bushings on the throttle body for air leaks. check the idle control motor to make sure it's working properly (it works when the a/c or defrost is on). make sure your throttle cable and/or pedal isn't sticking. if the lights not on there shouldn't be a code.
Thank you all for your help I would pee in the tank right about now if you told me to. Well back into the garage gotta get her running.
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