One code may indicate another issue.

[chevyfreakster]

I know this has been discussed here and other sites: The fact that a code for one sensor could mean another is malfunctioning. Here's what happened. For years I'd been cleaning my EGR valve and never replaced the gasket. Six months ago, I finally got a new EGR ...and still used the old gasket. Yesterday, I removed the valve to check it; it was fine. Then reinstalled it with the old gasket again. (I know; don't say it.)

This morning I got code 35 immediately upon driving...IAC valve (OBD1). Also the idle was sporatic and, upon revving, slowly came back to idle rpms (not quickly). Since I've been doing much work on the van lately and knew the IAC was functioning properly, the problem had to be that EGR gasket. I installed a new one, cleared the codes, and all is well again. Neither valve was bad. I swear, vacuum leaks are our worst enemies with these vortecs... at least the old, decrepit ones like mine (255,000 miles). Oh, and always use new gaskets.

[Astrofarian]

OBD 1, 2 or whatever else comes down the pike is only PART of the diagnostic process. Pull off a vacuum hose and read the codes. Replace whatever sensors the codes tell you to as many times as you like and you will NEVER clear the code(s) until you put the vacuum line back on. But is there a CODE to tell you that a particular vacuum hose is off, missing, leaking, or otherwise compromised? No...that's where you have to get busy and go through the basics. No scanner/phaser/transmogrifyer/ or smartphone app is going to do that for you. And it's unlikely that it ever WILL.
Can you imagine how frustrated you'd be right now if you hadn't been an active participant in on-going maintenance and repairs? Glad to hear you're able to step back and ask "WHY?" certain conditions arise or persist.
Hope your '95 starts to respond to all the love you're showing it.....you're definitely putting in the work!
-Mike-

[chevyfreakster]

"OBD 1, 2 or whatever else comes down the pike is only PART of the diagnostic process. Pull off a vacuum hose and read the codes. Replace whatever sensors the codes tell you to as many times as you like and you will NEVER clear the code(s) until you put the vacuum line back on. But is there a CODE to tell you that a particular vacuum hose is off, missing, leaking, or otherwise compromised? "

Yeah, don't I know. It takes deductive reasoning and understanding to diagnose these engines' issues. One out of two, for me, ain't bad. Cuss words can help too; an instant stress-reliever.

[Astrofarian]

LoL yeah, when logic and deductive reasoning fail, there's always profanity. SAE, Metric, or BSW (Whitworth), it fits them all!
-Mike-

[chevymaher]

LoL yeah, when logic and deductive reasoning fail, there's always profanity. SAE, Metric, or BSW (Whitworth), it fits them all!
-Mike-

Whitworth if there ain't no oil under them. There ain't no oil in them.

Towmater

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[Astrofarian]

Towmater

tow.jpg

Randy did WHAT in his cup?!!?
-Mike-

[chevymaher]

Towmater

tow.jpg

Randy did WHAT in his cup?!!?
-Mike-

LOL I got it all memorized. My son watches it on the TV in the van while we drive. I got Spongebob down to.

[Astrofarian]

........if anyone asks, me & you was out smashin' mailboxes, ok?!?!
-Mike-

[chevyfreakster]

Love the humor; don't ever lose that. We need it here.

[mmadden55]

Just out of curiousity, has anyone just blocked off the EGR and what was the result?

[chevymaher]

Mine is blocked a 94 same computer. I get a EGR code.

Your issue is a dicrepancy between the MAF TPS and MAP. Read the % the TPS is showing at idle. I just went through this on a chrysler. If it is to high it throws fits. I actually modified the TPS holes so it was adjustable to get it a lower %.

[WoodButcher]

Yep, vacuum line to my EGR is disconnected and plugged in my '93. I get a code on the highway that resets when I shut the van down. I've read the code with my notebook and confirmed the code 32 as it does not store and flash a code that could be read with a paper clip.