When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
I have an 85 C4. Great car. It’s been a pain since day one. Got it from a kid.. he spun a rod. Lots of work later. I’ve rebuilt the original block but it’s now a 383. Slightly bigger injectors.. nice heads. Etc. Car sounds and runs well. Except one thing… code 33.
so. I’ve wired a new plug in. Checked my ground. replaced my burn off module and still.. code 33. MAF seems fine. Could it be my ECU?? Car runs okay till it hits a closed loop and then it’s just awful. Spudders. Runs up in rpm and then drops. Smells rich. Just can’t seem to figure out this code. Any Ideas??
im attaching a photo of my ECU numbers. If I go for a replacement is there a difference between a manual or auto ECU?
I have an 85 C4. Great car. It’s been a pain since day one. Got it from a kid.. he spun a rod. Lots of work later. I’ve rebuilt the original block but it’s now a 383. Slightly bigger injectors.. nice heads. Etc. Car sounds and runs well. Except one thing… code 33.
so. I’ve wired a new plug in. Checked my ground. replaced my burn off module and still.. code 33. MAF seems fine. Could it be my ECU?? Car runs okay till it hits a closed loop and then it’s just awful. Spudders. Runs up in rpm and then drops. Smells rich. Just can’t seem to figure out this code. Any Ideas??
im attaching a photo of my ECU numbers. If I go for a replacement is there a difference between a manual or auto ECU?
I noticed you said it had slightly bigger injectors-what size are they? Was it tuned for them? A scan tool that gives you live data would sure help in figuring it out. Could be a shorted broken wire to the maf also.
I noticed you said it had slightly bigger injectors-what size are they? Was it tuned for them? A scan tool that gives you live data would sure help in figuring it out. Could be a shorted broken wire to the maf also.
26 lb I believe. Holley brand?
ive used my snap on mt2500 and it shows code 33. Most of the trends are okay. The injectors I don’t think would show a code 33? Not sure though. I’m not too familiar with these engines. It just runs really awful when it hits a closed loop. I didn’t see any damaged wiring but I guess I can tear more into it.
26lbs should need to be tuned for. Take a look at your blms-are they maxed at 108? Short term fuel-where's it at? Also watch the maf read out-is the gm/sec consistent? Go up and down appropriately with throttle position? Having the scan tool is half the battle with problems solving on these cars. Also a must have is the fsm-it has a great trouble shooting guide for all the codes.
26lbs should need to be tuned for. Take a look at your blms-are they maxed at 108? Short term fuel-where's it at? Also watch the maf read out-is the gm/sec consistent? Go up and down appropriately with throttle position? Having the scan tool is half the battle with problems solving on these cars. Also a must have is the fsm-it has a great trouble shooting guide for all the codes.
not sure if I can read any of that at the moment due to the code 33. My car is in limp mode and some of those aren’t shown yet. I’ll take a look and see though. I really enjoy my 2500 scanner from Snap-on. It shows all the little things. Saves you a lot of time!! I appreciate your input!! I got an adjustable reg. I need to check all those little things. I’m trying to solve the 33 code first. I know one thing. Once that car is out of limp mode.. holy cow. It should run good.
im assuming I’ll have to go back to stock injectors. I’m thinking of just getting a set and putting them back in as I trace for a broken wire.. I’ve heard these 85 Computers aren’t very fun to tune... but I’m new to these lol.
You should be able to see blms etc. If you happen to be in SoCal I have everything to tune it-not really that hard. Also there are 2 maf relays-I believe you just replaced one?
It sounds like there's a good chance that the MAF isn't getting power to it. Need to test the Purple wire on the MAF plug with Key On to see if you're getting 12v. If not then you can work backwards with key on or at least start from the Fuse box with the "Gauges" Fuse and make sure it's good, then work towards the MAF Burn-Off Module and so on. My understanding is that the ECU defaults to a 5V reading when it sees no signal from the MAF. There's a chance that the MAF is toast, but it seems more likely that the MAF would be putting out weird voltage and you'd see a difference between plugged in and un plugged.
It sounds like there's a good chance that the MAF isn't getting power to it. Need to test the Purple wire on the MAF plug with Key On to see if you're getting 12v. If not then you can work backwards with key on or at least start from the Fuse box with the "Gauges" Fuse and make sure it's good, then work towards the MAF Burn-Off Module and so on. My understanding is that the ECU defaults to a 5V reading when it sees no signal from the MAF. There's a chance that the MAF is toast, but it seems more likely that the MAF would be putting out weird voltage and you'd see a difference between plugged in and un plugged.
before you posed this comment I was reading past threads and decided to do this also. I couldn’t find much for voltage and then I read your comment and someone else’s on the forum. Check the fuses gauge. It looked okay.. so I swapped it out. Code is gone. Car runs 100% different. Finally. I wouldn’t of guessed that fuse being a culprit. I didn’t see it talked about in the old literature. Thanks for the tip! Now I got to get my tach to work. I have my old filter on and hooked up but I think it’s probably bad. One thing at a time haha.
Glad to hear things seem to be working out for you. I have no idea why the fuse is called Gauges, especially when it doesn't seem to actually have anything to do with the dash displays.
ECU question on my 85
