Camus

So I bought a '93 this Saturday w/ 230,xxx and a five month old rebuild. Runs fine, everything has been fine. Been driving everywhere last few days. Today I replaced the worn 30" tires w/ 31"s. Driving back on the freeway I was in 4th gear for maybe 2-3 min going about 60 miles per hour. When I got to the top of the hill, I went to shift to 5th and saw the check engine light turn on. Got home, quick check, all fluids seemed ok, no new sounds, runs the same. Nothing dripping or making funny noises. I added a little oil since it was low-normal. Let it sit and restart. Same deal. Light still on.

Any clue at all? Haven't done anything to it except new battery and tires. I can probably call up the shop (who did the rebuild) and hassle them tomorrow since it's a one year warranty, but they're a good 30mi from my house and there doesn't seem to be anything wrong.

I don't want to ignore this though, given I know very little about this truck as of yet.

EDIT: Diagnostic code "71"

EWAYota

Couldn't even began to guess without you having the codes pulled. Get a paperclip, jump the terminals and pull the code then go from there. You can get the detailed instructions of how to do that on 4crawler.com

Camus

Will do

Camus

Well, I'm new to this reading the blinks, but pretty sure it is code "71"

Which, according to the link from your link means

Hmmm. . . .

Camus

Checked vacuum hoses and connections, everything seems connected and not leaking.

Jay351

Screw the egr. Block it off and throw a 10k resister on the sensor, that will take care of the code.

js9924

I agree im not sure about the resistor value but ill take his word for it sounds about right. unless you have to pass emissions then it may become an issue

Jay351

The resister is a tried and true method of blocking the code 71 from comming up Im lucky enough to not have said sensor on my truck so a simple tug of a vacuum line and the egr no longer functions

Camus

I need to take it for smog tomorrow. . .

Better find somewhere with a free retest

notanymore

hes in CA so thats not a very good idea

Jay351

Why? When its time to go get tested, remove the resister, connect the vacuum hose and its back to stock. Up here in southern bc we have sniffers similar to the ones in cali. When its time to go I just have to connect a hose..

BUT to fix your problem, you might want to check that its opening and closing properly. Might want to clean it out if you can..

Camus

Gonna try that tomorrow morning and see how it pans out.

notanymore

im not opposed to disabling the egr, but if its not working hes going to have to fix it for emissions, which he said he has comming up soon. once you pass emissions you can do whatever you want, but your egr does lower your emissions.

Georgiadave

Jay DON'T advise someone to break the law. That in itself is a crime. Camus, don't listen to that guy.

All you have to do is trouble shoot the EGR. Attach a vaccum to the EGR valve, and if it is good, the engine will stop or run rough. You can use engine vaccum as a source. On the sticky, you will find the FSM that spells out in detail how to diagnose and fix this problem.

4Crawler

iTrader: (3)

Likely the EGR valve is partly clogged. The temp sender registers the high temps of the exhaust gas flow in the valve and if the ECU does not see a high enough temp after a certain period of time after it sent the command to open the EGR, it assumes that there is no EGR flow and trips the CEL. Happened to my buddy's '94 pickup. He put a new EGR in and fixed the problem. But troubleshoot it as noted above and you can also try cleaning the valve out. I used a gun cleaning kit to clean mine. The gun cleaning solvent solvent works well at dissolving the carbon deposits and the small round brushes get into the passages for cleaning.

Jay351

Yes sir!!

Camus

Thanks for the all the advice guys, going through the posts and service manual now.

But how would I remove the EGR valve to clean it? It's pretty cramped back there and I can't get to what's holding it down on the bottom.

Camus

Nvm, just looks like it would be a pain to remove, hopefully won't come to that.

To test the egr, I can use engine vacuum, but what hose should I use, I don't think anything reaches, I don't have cruise control to leach off of.

Georgiadave

Use the vaccum hose to the power steering as a source. Look at the FSM to see where it connects for a test. You may have to buy a length of hose, which could then be used to replace any old vaccum hose you have on the truck.

Camus

EGR was completely clogged, little tube on the side completely blocked and the valve seized. Cleaned it out with gun solvent and dremeled out the rest of the junk until it was functioning. Re-installed and everything is running fine, but check engine light is still present. Am I supposed to reset it myself or should it detect the fix and fix itself? I ran it till it was warm and at fairly high RPM. If this isn't the fix I suppose I could buy a vacuum gauge and check the vacuum lines, but I was pretty sure I'd found the problem given how disgusting the valve itself was.