Car will not run with MAF connected

[Brian Farrugia]

Guys,

I am new to the forum but have had an 87 GN for 10 years. I recently ran into a problem that i cant figure out and I hope that someone can give me some ideas on what the issue could be.
A little background on the issue: it started when my radiator cracked and some coolant was sucked into the intake. the next day the car would not run for more than a minute with the MAF connected. I know the simple answer here is the MAF and it was an issue as the voltage was bouncing around significantly. I replaced the MAF with a stock rebuilt unit and it seems to function properly (voltage increases and decrease up and down the rpm range) but the problem persists. I cleaned the throttle body so it is not carbon and there does not seem to be a vacuum leak. When I start the car it runs rough and stumbles when you increase the rpms but will smooth out, if you let it drop back to idle the car will bog out and stall. I checked the TPS and MAP sensors and they seem to function properly, i get 5v at all the sensors signal wires and grounds look good too. Again, when you disconnect the MAF the car runs fine using the MAP and TPS sensors only.

Car is mostly stock, has a brand new 350lph fuel pump, turbo has been upgraded and puts out 25psi but it is set to peek at 18, has an 80s chip in it cant tell you much about that. has fuel pressure, boost and knock gauge in it. other than that i am blind.

Thanks for any help!

 

[John Larkin]

Somebody recently had their MAF plugged in backwards causing havoc. Replacement MAFs are not always consistently good. The IAC idle air control value under the throttle body can cause issues if it is carboned up. Might consider cleaning that with some solvent or carb cleaner. And the TPS needs to be set properly as well. You should do some reading here: http://www.gnttype.org/techarea/maintenance/maintpage.html and here: http://www.gnttype.org/techarea/ecmsensors/ecmpage.html

 

[Brian Farrugia]

Somebody recently had their MAF plugged in backwards causing havoc. Replacement MAFs are not always consistently good. The IAC idle air control value under the throttle body can cause issues if it is carboned up. Might consider cleaning that with some solvent or carb cleaner. And the TPS needs to be set properly as well. You should do some reading here: http://www.gnttype.org/techarea/maintenance/maintpage.html and here: http://www.gnttype.org/techarea/ecmsensors/ecmpage.html

I cleaned the valve and idle control under the throttle body, thought that may be it too. You are right about the replacement MAF's the first one I got had a signal stuck at 2v no matter what happened, the one I have in now seems to function properly.
How can i test the MAF to see if the 24v/signal and ground are located properly?

 

[Turbo6inKY]

Guys,

I am new to the forum but have had an 87 GN for 10 years. I recently ran into a problem that i cant figure out and I hope that someone can give me some ideas on what the issue could be.
A little background on the issue: it started when my radiator cracked and some coolant was sucked into the intake. the next day the car would not run for more than a minute with the MAF connected. I know the simple answer here is the MAF and it was an issue as the voltage was bouncing around significantly. I replaced the MAF with a stock rebuilt unit and it seems to function properly (voltage increases and decrease up and down the rpm range) but the problem persists. I cleaned the throttle body so it is not carbon and there does not seem to be a vacuum leak. When I start the car it runs rough and stumbles when you increase the rpms but will smooth out, if you let it drop back to idle the car will bog out and stall. I checked the TPS and MAP sensors and they seem to function properly, i get 5v at all the sensors signal wires and grounds look good too. Again, when you disconnect the MAF the car runs fine using the MAP and TPS sensors only.

Car is mostly stock, has a brand new 350lph fuel pump, turbo has been upgraded and puts out 25psi but it is set to peek at 18, has an 80s chip in it cant tell you much about that. has fuel pressure, boost and knock gauge in it. other than that i am blind.

Thanks for any help!

the stock ECM doesn't use the MAP sensor. It's temperature, MAF, O2, TPS, and RPM.

Unplug the MAF and it goes to a limp-home table that just uses TPS and RPM. So if it runs better with the MAF unplugged, it's a pretty good bet that's your problem.

Parts store MAFs are garbage even if they work, they don't work for very long. Your solution is going to be a newer MAF and a translator.

 

[Brian Farrugia]

the stock ECM doesn't use the MAP sensor. It's temperature, MAF, O2, TPS, and RPM.

Unplug the MAF and it goes to a limp-home table that just uses TPS and RPM. So if it runs better with the MAF unplugged, it's a pretty good bet that's your problem.

Parts store MAFs are garbage even if they work, they don't work for very long. Your solution is going to be a newer MAF and a translator.

Thanks for the Reply,

When you say temperature, are we talking about the IAT sensor or do the water temp play a role in this? Are the only sensors on the MAF circuit the IAT and MAF or is there something I am missing. How quickly should the IAT adjust voltage, it seemed to be slow to change values and took overnight to get to -18c = 25,000 ohms value

 

[Turbo6inKY]

Both IAT and coolant are taken into account, but the IAT is only significant at the extremes. Coolant temp has by far the most impact on the fuel calculations.

 

[Brian Farrugia]

Both IAT and coolant are taken into account, but the IAT is only significant at the extremes. Coolant temp has by far the most impact on the fuel calculations.

I had to put that stop leak crap in the rad to get home, could this have screwed up the sensor? what is the test method for the coolant temp sensor?

 

[TexasT]

You are way into this. and I commend it but as above the MAF is most likely your problem. My stock one worked great until it didn't. The problem with the reman units and even the original ones is calibration. The reman isn't calibrated to the turbo Regal, it is just generic, and the original ones are thirty yrs old.

Take the advice and drop the coin on the translator and newer maf. It is much easier even with the adapters to get it installed. Especially if you are planning to drive it.

 

[Brian Farrugia]

You are way into this. and I commend it but as above the MAF is most likely your problem. My stock one worked great until it didn't. The problem with the reman units and even the original ones is calibration. The reman isn't calibrated to the turbo Regal, it is just generic, and the original ones are thirty yrs old.

Take the advice and drop the coin on the translator and newer maf. It is much easier even with the adapters to get it installed. Especially if you are planning to drive it.

Thanks guys, I will take the advice. What car and year does the Translator work with? I would like to get the MAF local as the exchange rate is terrible right now so I need to know what to ask for.

 

[TexasT]

I get gm units at the wrecking yard. Only thing is you will have to see if you can locate the "jumper" that goes between the old plug and new style plug on the newer maf. Translator is a translator. Only one kind that I know of.
Just have to decide what size you want or can find and the couplings to get it plumbed into the intake tube. I bought the couplings and tbolt clamps off eBay. I like the suburban/truck maf. I'll have to measure I think maybe 3" or 3.5" don't remember. Just have to know so you can set the switches on the translator correctly.

 

[Anthony P]

choice of today's MAF => either a 3 inch or 3-1/2 inch.

3 inch is from LT1 engine, it's a black plastic case, reference GM 19217202, Delco 2134527.
part #'s, info, etc => https://www.rockauto.com/en/partsearch/?partnum=19207202

3-1/2 inch is from LT1/LS1 platform. black plastic case, reference GM 19217203, Delco 2134657. some units are aluminum bodied.
part #'s, info, etc => https://www.rockauto.com/en/partsearch/?partnum=19207203

the 5-wire to 3-wire adapter comes with the new MAF. see pics on rock auto and vendors below...

http://www.fullthrottlespeed.com/turbo-buick-v6-performance-parts.html?cat=355

https://www.highwaystars.net/air-intake-fuel-delivery/

pigtail wiring adapter is also available separately from full throttle, Casper's probably has it as well as these guy's https://www.psiconversion.com/produ...tails/PIG-1019.html#panel-product-description

translators available thru all the vendors as well.