1995 Chevy 350 tbi surging

drake.whitehead

Original poster
Member
Apr 14, 2021
6
Indianapolis
Alrighty, so I have a 1995 k2500 Silverado with 350 tbi. this thing is surging and its always a 50/50 chance of it stalling out when ever I come to a stop or get into reverse, it has just under 238k on the engine and its only does this at idle when i have my foot on the gas pedal it doesn't surge at all but once it idles or its just sitting still it surges. I've replaced a lot on this engine to get it to stop so far. the list of what I've replaced is :Tps, Map sensor, engine coolant temp valve, IAC, vacuum lines, spark plugs, distributor cap and rotor, intake manifold gasket, and throttle body gasket. Another thing is I've checked the fuel pressure its reading at 12 and I did a combustion pressure test too its reading fine as well. The only things I have left that I can think off is the wires which I will be doing tomorrow and also the o2 sensor. I did look at the injectors and they don't appear to be spraying weird or dripping, and i know the system is running rich since I can smell gas from the exhaust and I've asked a few buddies to what my exhaust when i rev it up and it doesn't shoot out any black or white smoke so ii have no idea what the problem could be. if anyone has anything to say it would be greatly appreciated since I'm loosing my mind over this probably super quick and easy fix that doesn't want to show its self through a scan tool either.
 

Reprise

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Jul 22, 2015
2,724
Might be a little deeper down in the distributor; to wit, the reluctor wheel / sensor. The reluctor wheel has 8 cogs / spikes / teeth on it; if it and the sensor get too corroded, the signal that's sent to the ECU (and then to the injectors) gets out of whack. Worse, it won't generate any codes.

For more info, check this out: https://www.cargurus.com/Cars/Discussion-t66634_ds929017
Scroll down to the answer by 'EmeraldPawn', about halfway down the page.

I'd guess you might have 3 options, depending on your mechanical aptitude / budget:
Clean / replace the individual part(s), as needed;
Rebuild the distributor with a kit (it has to be removed to fix this issue, anyway),
Or, replace it outright (either with an OEM, or an upgraded aftermarket unit, depending on your long-term plans for this engine / truck.)
 

Mooseman

Moderator
Dec 4, 2011
25,257
Ottawa, ON
Didn't they also have an EGR valve? Check that it's sealing and working right. I would imagine you also checked for vacuum leaks?

I don't know what the specs are but I would think 12 psi for any fuel injected system is too low. And they had return systems then so give the pressure regulator a check.
 

drake.whitehead

Original poster
Member
Apr 14, 2021
6
Indianapolis
I'm hoping that its not the distributor but at this point it very well could be, and yes there is a EGR valve but I cleaned it out I'm going to get new one soon if this o2 sensor doesn't work. at the moment I cant get it off I should have a new one on soon depending on who I can get to give me a ride to the part store. But for A chevy obs or any obs chevy truck 12 psi for the fuel line is actually spec. that's why I know it isn't a fuel pump and I forgot to add in the first post I did replace the fuel filter as well. as you can see the list of things I've done is long. The plan right now is to do this o2 sensor, then get a new EGR valve since even though I cleaned it I'm not too sure anymore with the current one and then after that its replace the whole distributor and rebuild the throttle body. Unless the previous things end up working.
 

northcreek

Member
Jan 15, 2012
3,310
WNY
It could very well be the 02 sensor if it's that rich and maybe your cat is damaged now because of the rich condition. As long as your replacing the sensor it would be a good time to check the pressure at the bung. With 238k has there been a cam replacement in there at sometime ?
 
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