Rich Silvestris

My 87 started radically hunting for idle RPM the other day. I had just washed it, no engine cleaning, and when I went to put it away; big trouble!

The engine RPM cycled up and down and the car stalled very easily when I tried to take off gently. I had to goose it a couple of times just to get it in the garage.

Last night I started it again and the same thing happened. Hello Mr. paperclip. Code 33 -- one of the MAF sensor codes.

I've got the Manual, the V-O-M and the test light and all, but I am kinda slow with this kind of work. Is there a very common cause for this code? (There are no mods on the car to speak of, and the wiring seems to be in good shape.)

Also, if I have to start probing the harness; what's the right way to do that if the weather-pak connectors have to stay connected?

Pete K

For me, it seems to be the relay most of the time.

rick lambert

Probably time to replace the MAF sensor, but you might want to check the connections first.

Rich Silvestris

Thanks, guys. I waited to see if there would be a tie breaker here, but no luck. The relays are dirt cheap, so I will probably replace them for starters. If the problem persists, I'll do the real work. I sure hope it's not the MAF $en$or!

vader86

Always always always replace relays and check connections first, they are the usual cause.

Then its the MAF.

kopbet89c4

Code 33 = High gms of air/Sec, or >45 gms/sec. Either MAF is bad or the MAF power relay and/or MAF burn off relays are bad. A burn off signal while the car is running can also result in a code 33, but that is intermittant, meaning the SES light will go out after 20 seconds. Good luck, and time to spend $$$ if indeed your MAF sensor is bad.

CFI-EFI

Cheap or not, why throw miney at the problem, blindly. CHECK the relays before youpay to replace possibly good parts. Things would go more smoothly if you followed the trouble shooting charts in your factory service manual. The manual isn't cheap, but once it is among your other "TOOLS" it will continue to advise on subsequent projects. The money spent to replace a good relay is gone.

RACE ON!!!

Rich Silvestris

I have the Helms manual, and I have used it to troubleshoot some other electrical stuff. I have precious little time, though. So I am treating this like I would have to pay for the diagnosis, and make a second appointment to install the parts. I picked up the relays today, and I will put them in first. $30 down the drain and 15 minutes wasted if it doesn't work; $0 wasted, and about 3 hours saved if it does. With my schedule, I'm lucky if I can spend an hour with the car in an evening. Then there's the fact that if the diagnosis points to a relay, I'd have to get it the next day anyway; so it would be longer before I could get to drive the car again.

I wanna minimize my down time, so I can ........RACE ON!

CFI-EFI

But that isn't all... based on what you went on to say.

So, if it isn't the relay, it isn't just $30.00 and 15 minutes. NOW you have to figure out another cause. Still without trouble shooting? Isn't there any time involved there? What about the part for the new theory? The relay wasn't on hand. Will the next guess be on your shelf? It will take time to remove the wrong guess and more time to return it. You might win a couple with the "stab in the dark" method, but one loss could eat up all the gains over just doing it right, in the first place. "There is never time to do it right, but there is ALWAYS time to do it over." Suit yourself.

RACE ON!!!

bogus

My biggest concern with the mid-80s C4s is that the wiring SUCKS.

You see, in 1990/1, SAE mandated a change in the composition of the wire. This improved the insulation a ton. If you look closely and many of the weatherpacks on a higher mileage C4, the wire will start to pull back, the insulation gets hard and brittle, it can and will crack, and is prone to abrasive failures - it chaffes.

Check the harness ends, check where the relays mount. You name it.

Something else I have observed... if the relays fail, they can damage the MAF. It's not likely, but it can happen.

Also, if that is the original MAF, it is a "early design". They were not as durable as the later design MAFs. When you replace, all GM MAFs are built to the new standard, and I am pretty sure that all the aftermarket are, too.

However, when these things reach this kinda price point, it's best to make sure everything around them is ok.

Rich Silvestris

Update: I took today off 'cause the bride and I are headed for a weekend away. I did my weekend chores last night and this AM, and I took the time to throw in the relays. Then I drove the car on a couple of errands. No SES and no hiccups!

Thanks for all the input guys. The manual is great, but it was written in 87. The guys on the forum are today's manual to me.

bogus

great!

And the 1987 manual truely does SUCK.