OK, I drove around some today with my scanner hooked up. The EGR valve looks good as I could see the duty cycle changing when it should. It almost appears this MAT sensor reading is redunant, since the coolant temp is feeding same info to ECM? Just a thought. I'll get back on this issue later. Thanks for all replies.

Joel

Hey John, whatever you're doing,keep on doing it, That was a lucky drive. I agree with the red statement!

Joel

Yes I have followed the FSM on both High temp and even Low temp Problem trees. Do agree with you, it seems there should be a "short/ground" issue. I put it back together yesterday afternoon, really just got fed up with for now. I'm going to drive it soon today with scanner hooked up and monitor some functions. Really more concerned with proper EGR function. Will post results later if you're interested. Thanks for your reply. I guess my posts are just too long and dull.

Joel

I usually spend a couple hrs total on forums. Latley more on this site but also CF and a W-body GM site.I spend most of my time here reading and searching, usually mosy posts are answered by folks smarter than me!

Joel

I'll get back with on that! What is your procedure to verify a shorted/open circuit. I know I need a new DVM before I probe on the ECM. Thanks


Joel

Well another afternoon working on this MAT problem and no luck. Does anybody know which bulkhead the MAT wires run to? I see one behind the battery and one behind the right side valve cover. Thought I would disconnect bulkhead and try to isolate the tan wire as my next step.

Joel

How much for a round trip ticket?

Joel

That is what I thought could be the problem, but if shorted why would there still be the 5 volts on the power wire? Thanks .

Joel

Sorry to hear about your car. Ya know, that has just got to one of the disgusting feelings when then IS nothing that can be done(legally) to some A--hole like that. I agree with TommyT-Bone about the jail. Hope you can get it repaired correctly. I've been there, I know the pain.

Joel

Hey guys, need a little help on this one. 1989 auto. with L98. I've had car for 10 years. I use a Actron scanner, older model but seems to work fine on all my cars. Car runs very well with no problems. Only thing is when I scan it the MAT always reads 392 degrees. Same reading cold or hot. Today I finally decided to start trying to find out why. Replaced MAT sensor in plenum, no change. Disconnected harness from sensor, no change. Discinnected extension (FSM calls this a jumper) from main harness, no change. Checked voltage on tan wire CKT 472 for the 5 volts as per FSM and OK there. If I read the diagram correctly this sensor CKT 452 black wire at ECM shares the ground with CTS and TPS. No problem with these sensors, so I assume the ground is good at ECM. Also no codes at all, I would think a 25 should have been set(high temp). Car is bone stock. Only other thing is that car does have a replacement ECM. Label says :Remn. by GM Service Part# 16198445. Prom says APKC 1304. All this should be the correct ECM and PROM unless I'm wrong. Any thoughts?

Here and ready

There is no way I would weld that close to a fresh paint job. At the very least you should "layer" several sheets of tin foil over roof and the side of car. But I do agree with the earlier reply of hanging a tarp or some type of containment. Flying sparks can do a lot of damage, and they usually travel further than you want. Look for more splatter without gas.

Joel

These lights can be usefull under certain conditions. No, they are not bright enough to really do any engine work. But they do help replacing a belt or just checking oil, trans fluid,etc. And also they look good with the glass lens.

Hello Pete, I have not had any trans. questions for you but I do enjoy reading ANYTHING you post on. Hope you can find a happy medium between job (paying the bills) and your passion for hands on working. Don't stop with all this good advice, as I am sure my day is coming.

Joel

First let me say it is not a trophy winner at all. Actually I have a 1989 Coupe L98 auto. with 90,000 miles. I got the car 10 years ago and enjoyed every day after. I also have have a 1968 conv. I have owned for 25 years. This one needs a fair amount of work but it all there and runs good. But the true love of any Corvette I have owned is the C4. I do try to keep my cars as original as possible. I have replaced exhaust with as near original equipment as I could find last year. Also just the usuall IAC,TPS, head light motor rebuilds, flex plate, starter,etc. Not what you expected, hope I did't mislead ya.

Joel

I'm new to this forum, but I do like what I see so far. This idea is great. This is the area where I get the most enjoyment from. Hope this stays around, will try and help out all I can.

Joel

Just joined today and want to say hello. Hope I can add to the quality and info of this forum. I have a 1989 coupe L98 auto. with 90,000 miles and a 1968 small block and 4/speed vert. I've been turning wrenches under a shade tree for a lot of years and still enjoy it as long I can look at the bow tie emblem while I work.