EGR problems only in drive/reverse
Thread Starter
Supreme Member
Joined: Feb 2005
Posts: 1,054
Likes: 1
From: Ajax, ON
Car: 85Z28 87GTA 91GTA 98SS
Engine: SBC, LS-x
Transmission: T-5, 700-R4, T-56
EGR problems only in drive/reverse
This is a 95 350 that I want to transplant into a 91 Camaro but want to get the bugs out of it pre transplant so there will be less issues to deal with later on. Since I have the chance to try it in the donor vehicle ( a 1 tonne van) I figure why not.
The EGR functions fine in park and neutral. It opens further and further the higher the engine revs. If it's in drive then the egr valve doesn't move no matter what RPM. This is causing spark knock which I can eliminate by manually opening the EGR with my fingers by pressing on the diaphragm or by applying ground to the grey wire on the EGR solenoid valve which would sort of simulate what the PCM would do.
There are some other underlying issues which may be related. The spedo randomly works. I have replaced the VSS in the tranny with a brand new one and it does the same thing. I am thinking the VSS is working up to the PCM since the tranny does shift beyond 2nd gear. I don't know how the entire curcut works and if someone would care to explain where the signal comes from to drive the spedo, I am all ears.
One other issue is that the reverse lights do not come on when it's in reverse. They do blink for a bit before reverse is selected which is suggesting that the park/netural safety switch may be shot or need adjustment.
My guess is that my EGR woes are related to either the VSS/Spedo issue and/or the park/netural safety switch. Can somebody explain how they both relate to EGR operation? I don't have a bunch of cash to throw at this thing so I'm trying to save a few bucks while learning at the same time.
The EGR functions fine in park and neutral. It opens further and further the higher the engine revs. If it's in drive then the egr valve doesn't move no matter what RPM. This is causing spark knock which I can eliminate by manually opening the EGR with my fingers by pressing on the diaphragm or by applying ground to the grey wire on the EGR solenoid valve which would sort of simulate what the PCM would do.
There are some other underlying issues which may be related. The spedo randomly works. I have replaced the VSS in the tranny with a brand new one and it does the same thing. I am thinking the VSS is working up to the PCM since the tranny does shift beyond 2nd gear. I don't know how the entire curcut works and if someone would care to explain where the signal comes from to drive the spedo, I am all ears.
One other issue is that the reverse lights do not come on when it's in reverse. They do blink for a bit before reverse is selected which is suggesting that the park/netural safety switch may be shot or need adjustment.
My guess is that my EGR woes are related to either the VSS/Spedo issue and/or the park/netural safety switch. Can somebody explain how they both relate to EGR operation? I don't have a bunch of cash to throw at this thing so I'm trying to save a few bucks while learning at the same time.
Thread Starter
Supreme Member
Joined: Feb 2005
Posts: 1,054
Likes: 1
From: Ajax, ON
Car: 85Z28 87GTA 91GTA 98SS
Engine: SBC, LS-x
Transmission: T-5, 700-R4, T-56
Re: EGR problems only in drive/reverse
I cleaned up a bunch of the body/engine grounds today and the egr is actually working now in drive. So are the reverse lights when they should be. I adjusted nothing. I'm going to go thru the whole thing over the next week. Bought a timing light today cause I have no idea where the timing is right now and I'm going to build an ODB1 cable to have a better look at what is or isn't going on.
The spedo is still intermittant but not as often as it was. There is a harness that goes thru the firewall, it was a touch loose but also contaminated with some kind of tar like substance inside. I cleaned most of it out with carb cleaner then a final cleaning with electronic contact cleaner. Carb cleaner was the only thing I had that would dissolve it. What a mess!
The spedo is still intermittant but not as often as it was. There is a harness that goes thru the firewall, it was a touch loose but also contaminated with some kind of tar like substance inside. I cleaned most of it out with carb cleaner then a final cleaning with electronic contact cleaner. Carb cleaner was the only thing I had that would dissolve it. What a mess!
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