Your ’80s to early ’90s General Motors (GM) OBD-1 engine doesn’t run right and you can’t find anyone to work on it. What do you need to diagnose and repair your engine when it won’t run properly? I will explain the basic concepts using my 305 Tuned Port Injection (TPI) 3rd Gen Camaro IROC-Z. I will go though the tools and service information required to diagnose your engine, how to use that service information, and then provide some demonstrations. I discuss OBD1 scan tools, digital voltmeters (DVM), and test lights. These basic techniques apply to Chevrolet, Buick, Cadillac, Oldsmobile and Pontiac cars with 4 cylinder, 6 cylinder or V8 engines. I discuss the computer controlled carburetors with a mixture solenoid and throttle body injection (TBI), in addition to port fuel injection . I explain how the computer controlled (CCC) closed loop system uses an oxygen sensor to fine tune the fuel mixture. Each GM model will have its own specific details because they all have slightly different sensors and actuators, but the basic principles of closed loop computer controlled engines and 3 way catalytic converters are the same.
DISCLAIMER: In my videos, I provide demonstrations, suggestions, and opinions on techniques, methods, and materials for various projects. While I try to be sure that what I share is accurate, there are no guarantees, expressed or implied, that my information is correct and will work for you. If you wish to use any of this information, you must check and verify that it is appropriate for your use – use it at your risk. Do-it-yourself projects are variable and there are risks in conducting them.
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Do you have an email I can contact you at. Wondering if you could give me any tips on a 1986 Cutlass AIR/Smog issue I’m having.
I’d love to see a comprehensive diagnostic on cruise control on these cars.
What model of Actron scanner are you using? Very good info. Thanks!
You should go help him and record it for you channel.
Can you post your friends car manual website?
Could the Icm inside the distributor of my 305 tpi motor be going bad making it run one day and not the next day?
Just ordered the service-manual and electrical diagnostics-supplement from your buddy at Books4Cars as well as an obd1 to Usb-connector so that I can record and datalog what's going on with my 87 iroc. Perhaps this is what I need to fix my random missing and sputtering at idle and around 1800-2000 rpm at part-throttle cruising. Runs like a champ when "beans are given".
Looking forward to not just rely on Youtube and old forum-posts haha.
Awesome video, best in-depth description I've seen. Thank you so much, looking forward to future videos man!
Nice to see another video,sadly no time to watch whole thing this morning, will finish it tonight. Have an update Im downloading on this winters work on our Formula, I do a little each year. Once I get this back together I have a question about plug gapping. I changed them during summer and gapped to manufaturer specs, cant rmember what it was, the plugs I took out burned lean. Recently saw someone mention gap should be .45 with the hypertech chip setup, mine has had this chip previously installed. Car runs and idles great except the sticking idle we discussed before and I believe I nipped that in the bud, total cleanup of throttle body. It of course needs valve guides so she does a little puffing on startup but doesnt seem to be running to rich or lean other then plugs. If you dont miind will share a link later to where I am on rig.
Great information. Wish I was your neighbor a few years back. I do have the GM manual and it is definitely a must as you mentioned. My only problem is it has a problem passing California smog do to high NOx. The parameters [ goal posts] seem to be pushed back every year and the car was not designed for the limits now enforced. I've done all the system checks that have to do with high NOx and all is functioning. Extreamly aggravating. I even played with the timing all the way to zero and still no luck.
Thanks for this video – I have my GM shop manual – it has bern great. Fixed a spun crank bearing with it!
Ah, Dan, now you've touched on something I've had to work the most on – with my 3rd gen camaro. The ECM and the PROM chip. When I bought my car, the guy I bought it from had run a wire from the cooling fan into the dashboard with a switch so he could manually switch on and off the cooling fan (due to overheating when stationary). I quickly took to youtube to find if others were having similar issues. Turns out, the cooling fan not coming on often enough in these older 3rd gens is a common problem – since the cars were meant to run at 240 degrees instead of 180 anyway. When these ecm's age, my guess is that the ecm board and capacitors and resistors don't resist and capacitate and amp as they used to — causing the fan to turn on way later than it did when the car was new. (Yes, before this Hypothesis, I DID change every temp sensor in the car with NOS ACDelco replacement sensors – first!) Well to most of us, we want to cars running in the 180 – 200 range instead of the high 240 anyway, so with the help of this site: https://www.thirdgen.org/technical-articles, I was able to learn how the factory proms are programmable once you find the right decoder to decode the particular chip you have and interpret it with a some free or cheap downloadable support sites. To make a long story short, it was awesome, I was able to copy my original prom with a usb chip burner (generic one off of ebay not a gm thing) and I can take a copy of my original chip program, modify the copy, change the "Fan ON" temp and "Fan OFF" temp, and as of last summer I did all that and used the original chip reprogrammed to turn the fan on and off inline with keeping the car at 190 degrees to 200, instead of the factory wild high 240. It was an engineering technology major's dream! I loved it. My car runs just fine at 180 – 200 instead of the ridiculous factory 240, and its all done the right way, instead of a wire hanging from the dash!
Great video! For my ‘82 Corvette I use a free tool called WinALDL, runs on my laptop. Needs a cable that if you’re handy you can make one but I just bought one from OBD Diagnostics for about $60. Allows me to see in real time what the ECM is seeing. Was key to helping me find a bad IAC. Thanks for sharing your experience and knowledge.