Well, as it turns out, I put another MAF on Saturday. Now I'm back to getting both code 33 & 44. I did order the MAF power relay but haven't gotten it yet. Don't know if it is bad but, through recommendations, thought I would change that at the same time. Don't know if it'll make a difference.

Just have to back away and think about this for a while. Its starting to get a little frustrating!!!!!

 

"I only paid for the BOSCH MAF sensor once, and that was 2 years ago. It went bad a week ago as I explained earlier, and is guaranteed for lifetime at Discount Auto. I simply took the receipt and got a another one. If it fails again in the 2 or more years from now, I just go and get another one. Didn't have to spend $700. Ha ha"

That may be true but is it a Genuine Bosch Part? The 'core' as you put it is the Sensor, the rest is just a plastic tube. And you do realize it is a used part that has been refurbished? When I said they are $749 - I meant a factory NEW part. Good luck (BTW, I sold the one I had in storage).

 

Did you ever check the B+ input to the sensor? From the relay, you should have 12v to heat the sensor up to the regulated temp so it can react properly to the incoming air. The pin escapes me, but check all pins with a voltmeter with switch on. Let me know. [8D]

 

The best that i can tell, all the voltages on the MAF are reading OK. Going thru the trouble flow chart, i get:

- Step 3 -- jumper ALCL term. D to 12v and probe MAF harness E with a light to grd. Light turns on
- Step 4 -- with ignition ON, MAF D reads 0v
- Step 5 -- with ignition ON, MAF C reads 5v

This is telling me everything at the MAF terminal is OK.

When the car is cold, it starts greats and idles great. When the temp. reaches about 145, there is a distinct stumble in the engine, just for a second, and the SES goes on. If I immediately shut the engine off and read the code(s), I get a 33. If I then drive the car for a while and check the codes, I'm seeing both 33 & 44. Now this is all with a known good MAF.

Could the ECM be causing the problem? This engine does have a Crane RV cam, which is a very mild cam. I wouldn't think that would be the problem.

The other thing I just noticed is that there is .08v on MAF term. D (from the burn off relay) when the car is running and the MAF connected. When I shut the car off, it increases to .11v for a second or two, then drops to 0v. I didn't think there would be any burn off voltage on the MAF until the engine is OFF.

Could a vacuum leak be causing my problem? I've gone over all the vacuum lines I could find and didn't find any leaks. Went as far as using the "hose to the ear" trick to check for leaks around the intake/exhaust manifolds. The only small leak I found was where the EGR pipe goes into the exhaust header where the crimp ring holds it in. There was a very small leak there. Other than that, didn't find anything else.

 

Well, your next test is probably going to involve a scan tool. Need to know what your block learn and intergrator counts are. If they are higher than 128, say 140 -150 counts, then the ECM is trying to fatten the fuel mixture up. Block learn is known today as Long Term Fuel trim and Intergrator is Short Term Fuel Trim. If you have a known good MAF and your supply voltage and grounds are good, and you have 4 -5 v on signal wire with KOEO, then I would say ECM. Since your car is a 86, the only rebuilt ECM I would trust is a A/C Delco. GM had lots of probs with the 86 model computers because it was the 1st year of the High Data Rate. They had trouble rebuilding their own ECM's, hence they turned it over to A/C to rebuild them. Matter of fact, most early scan tools had special adapters for "GM TPI", and they still had trouble reading data. I have 2 scan tools with adapters that won't read my '86, but I have a new one, by Mastertech, that does it great. Sorry to get so technical, but am trying to explain it the best I know how. [8D]

 

Don't worry about getting technical. I appreciate the help. INCIDENTALLY, WHAT SHOULD THESE COUNTS BE? Assuming the ECM is trying to fatten the fuel mixture and its not happening, does that assume the ECM is bad? May sound like a stupid question, but just trying to get me feet on the ground. I'm an old "carb" guy and haven't had much exposure to FI repairs.

I am going to take the car to a friend of mine today that has a scan tool. Maybe we'll be able to spot what is going on. From some of the test results I had gotten when running through the code 44 trouble shooting chart indicated a possible bad ECM. I was getting only .17v at the O2 sensor (chart indicates any voltage less than .35v is a possible short in Ckt 412 or a faulty ECM---checking out 412, i didn't find any shorts).

I'll let you know what I find out.

Again, thanx for your help and patience!!!!

 

What scan tool does he have? If it is a Snap On, it will not work on a 86. OTC has 1 that will, the Genisys or my Mastertech. Remember, if you replace ECM, go with the Delco remanned. Also, remember to pull your prom out of the old one to put in the new one, because the do not come with a prom chip. [8D]

 

Don't know what model scan tool he has. But will find out today.

 

Be sure and check for vacuum leaks with carb spray around injectors where they are inserted in the manifold also. Orings get old and hard and don't seal well and cause intake vacuum leaks. [8D]

 

What voltage do you get harness side unplugged?