Egr problems
 

Hello to all. Having some egr problems. Stammers and studders . Only code I ever get is 32, and only after I press brake wile in cruise control. I think it is my exhaust which is free flowing and therefore not producing much back pressure. Only thing left to do is change ecm and prom. I am thinking of putting a new prom chip in, stage 2 180 tstat. Wondering if anyone has had problems or success. I have chased down a lot of gremlins. New map, egr, egr selonoid, temp sensor, o2 sensor, intake manifold, distributor, plugs, wires, coil. Rebuilt the tbi. The only other thing I think it could be is the Computer.

Hi,
There are a lot of differences in models/engines over the years. You need to provide a more info to get help and responses. Stuff like the year, engine, model. Whether it’s stock or has had mods, etc. Also, a bit more on symptoms. Does it idle ok? Hot and cold?, etc.
That said, generally I would think the computer is way down list for a culprit causing stammer and studder.
Check basics first - fuel pressure and base timing. Those two things can cause a whole host of problems if wrong or marginal, in case of the fuel pressure.
Double check vacuum lines and make sure grounds are ok - the are a bunch of them and if marginal can cause problems with ECM getting input from sensors. It’s a good idea to remove and clean them.
With everything you’ve replaced, if I was entering an office pool - I’d bet on marginal fuel pressure.

More info
 

The vehicle I am working on is a 91 Chevrolet Silverado
C-1500, it’s got the 5.7,350, and I believe the 700r4 transmission. My mods at this point are a cherry bomb replacing the old clogged muffler, and a air intake.
I Replaced the cat, it was empty, hence the clogged muffler.
It stammers when cold but is worse after it’s warm. I did the timing at a friends house, tdc 0degrees with computer unhooked. I changed fuel pump, but need a pressure gauge. It is in idle or neutral, but I can rev it in neutral or park and it seems barley notable. It’s really bad in the lower rpms, if I get on it it’s way better, usually. Also on the freeway and to a lesser extent surface streets it will get hot. I thought head gasket, but I did a compression check and things look good. No coolant in oil, no oil in coolant. No white smoke except on start up. It will not suck back from coolant tank, but I am not confident in the currant radiator. I will try and get to a friends house to check fuel pressure and timing and repost. Thanks for help. I need to check all grounds too, got a gas gauge that never reads right.

Sounds like you've been pretty thorough, definitely frustrating chasing stuff like this.
It looks like the code 32 is a map/egr circuit thing - so since you replaced those this is where cleaning up grounds might help. Bad grounds can cause noise, poor feedback from sensors, etc messing up ECM. If you have a code intermittently and have replaced the stuff it points to - then check the circuit/wires/grounds related to that. On mine, from memory - there is one on t-stat housing, one on back of engine somewhere, one on firewall - maybe more, I can't remember.

on the fuel pump - a couple questions.
-Did you replace fuel filter at same time? if no - definitely do that when you check fuel pressure. I think easiest place to check it is downstream of fuel filter. At least on my 93 it's easier to get some space on fuel lines at that location vs at engine. on mine its in frame rail by driver's door.
-what fuel pump did you use? I replaced a fuel pump a few years ago with a Autozone brand. Recently I had stall/sputter problems on accel. Turns out my fuel pressure was about 10-11 and would drop when I punched it. I read in forums that some pumps can't deliver pressure well and replaced with an ACDelco - it provided 13psi solid all the time and my problems went away.

two other curiosities - not saying they are concerns or problems
- when you rebuilt the TBI - did you replace the fuel regulator spring? I don't think it comes in some rebuild kits.
- I didn't see a knock sensor in your list above. If it was obviously bad/open circuit it should throw a code. If there were a bunch of erroneous knock counts generated it could cause ECM to retard the timing -but I wouldn't think it'd be all the time, don't know. Regardless, again, if that was the case I'd check grounds again before replacing the knock sensor.

Good luck!

Weekend of work
 

Thanks Sabino , I will be checking all the gounds this weekend. Might try and invest in a pressure gauge. It was Spectra pump. I try and stay away from autozone, but I had the egr and it’s sensor from there. I was looking at knock sensor, but I might invest in a multi meter, even if just from harbor freight. Btw I did replace the spring in the tbi. It looked different but it was an ac delco part.

when you say this did you replace them due to the shuddering issue or was it because of something else?​​​​​​​
https://cimg5.ibsrv.net/gimg/chevrol...fba80e411f.png
https://cimg8.ibsrv.net/gimg/chevrol...4269f9bb50.png

Cheers
 

Wow, nice diagrams, thanks. The reason for some parts was due to their demise, distributor and fuel pump, some of this was just maintenance, some one gave me the truck two years ago and it was not well maintained the last couple years. But the map sensor and egr selonoid was trying to chase down code. The temp sensor connector broke when putting the intake back on. Rebuilding the tbi just seems to make sense once I pulled the intake manifold. I might have focused to much on egr because someone swore it was that. Good friends don’t make great mechanics. I feel like I am
at a point where I could just chase parts, but that would be dumb. And truth be told I’m broke. Lol.

so have you replaced anything recently? and how old is the gas? did you fix the temp sensor right or just rig it up? that can cause all sorts of problems but i would imagine you would see that at idle
if you need to test the sensors you can use a basic multimeter that can read ohms and using
Troubleshooting sensors and how to test. these computer aided engine need good grounds, so check them and clean them so you get metal to metal contact and apply some sort of moisture displacement gel (like the stuff used for battery terminals)

Daily
 

It’s my daily driver so fuel is clean, looked at tank when down, looks good, I replaced the temp sensor outright, only like $10 on Rock auto. I am going to do grounds and verify fuel pressure this weekend, need to buy a gauge along with a multi meter. Only sensor left is knock sensor lol. Maybe my luck. Lol. Thanks for help.

It’s good to make sure basics are good before troubleshooting and throwing more parts at it. That’s why the recs for making sure fuel pressure is good and you have good grounds. You said you already checked the timing. You didn’t say if you replaced fuel filter when you did the fuel pump?

after this, chase down whatever codes you have - it may not solve everything but if you have a code something is not right and it could be a part of the problem. After no codes & basics confirmed, then it’s easier to troubleshoot drivability problems.

On the code 32 - you say check engine light only comes on when you hit brake after cruising in cruise control. It doesn’t do it if you are “manually” driving at same speed and take foot off pedal and hit brakes?