Tech / General EngineIs your car making a strange sound or won't start? Thinking of adding power with a new combination? Need other technical information or engine specific advice? Don't see another board for your problem? Post it here!
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I'm having a problem finding information on testing a MAF sensor on a 1989 IROC-Z. Due to the cost of them I would like to test it before purchasing a new one. Would sure appreciate some info on the matter! The car I'm working on has no error codes stored in the ECM but won't start unless I prime it with gas then it runs terrible but it will run. I know better then to dump gas accross the MAF sensor so I know I have'nt ruined it yet this way. But the car has been worked on by other people and who knows what they have done. I bought this car from my little brother and it quit running around 3 years ago. He spent over $1200.00 having it worked on by other people (PROFESIONAL MECHANICS) and nobody could get it to run. They all said it needed a new wiring harness or it was shorted out in several locations and they would have alot of time and money invested ect... Well I've been working on cars for over 25 years and enjoy doing it so I bought it and decided I'm going to fix it myself. Well I took it home and after about 2 hours of trying to get it to run or do anything but give me erratic codes I decided to get back to the basics since the PROS couldn't seem to get it fixed with all the high tech stuff they had. Well long story short I checked the timing and they had it in 180 degrees off. As soon as I installed it properly all the erratic stuff corrected itself "who would figure". Well now after I put all the car back together after the last so called mechanic worked on it (it sat at his shop for over 3 months after which we had to go get it and haul it home all tore apart, wiring out of the harnesses, computer hanging by the wires ect... ) P.S he only charged $450.00 for his services!!! I think you all get the point. Anyway I have the car where it will start but it has to be helped to do so by priming it with gas. I have good fuel to it 43 LBS in the fuel rails, my noid lights flash properly when running. I've checked all the pinouts on the ECM for voltage and everything tests out. I,ve checked the TPS voltage is fine, Ect... Basically I've tested about everything and all tests fine but I can't find the info on how to test the MAF sensor with my volt tester, and I'm not the type of person to just throw parts at this car. Heck!!! thats what everyone else has been doing and it didn't work for my Brother. This car only has 60,200 miles on it and ran great before it quit 3 years ago. He was going down the Hiway and it just shut off. I believe that the ignition module is what actually was what went out that day. I had the old one that the original mechanic took out tested and it was bad. But I'm affraid that after the mechanic put the distributor back in 180 off he started probing and guessing and probully ruined some of the sensors. I've seen a MAF sensor go out before by people squirting fluid accross them and I'm thinking the PRO Mechanic did this. I can see what looks like squirt marks inside the intake. I would sure take any help I can get to figure this one out. When I prime it with fuel it will start right up, run good excellerate properly for about 7 or 8 seconds till the extra fuel in the runners is used up, Then it will just idle roughly. If I open the throttle it will start to rev up then run out of fuel and die and it will have to be primmed again to get it to start back up. If I don't touch the throttle it will stay running rough but not die. I've let it run for over 20 minutes and During this time the injectors are pulsing properly, the fuel rail is holding around 40 lbs of fuel pressure, no error codes are being created????? Please Help!!!!
Can you datalog? That would be the easiest way. You could then see the maf voltage.
Heres something that might help. This is the calibration table from the 'vette ARAP prom. Shows the output voltage vs. flow. You should see around 7 or 8 grams/sec at idle with around 40-50 g/s when you blip the throttle. If it can do that then Id look elsewhere for the problem for now. One thing that can help is to gently clean the wires with a light solvent, althogh the stock mafs have screens at both ends, which woudl make getting to the wires hard.
Disconnect the electrical connector on the underside of the MAF. Should run fairly well, although a bit rich...if your problem appears to go away, look at the MAF, MAF relays, poor connections, etc. If it runs the same/has the same issue, MAF (and circuitry/components) probably isn't at fault.
Also, MAF cars are a bear to start and run properly with any leaks between it and the TB, like a cracked MAF hose, poor seal, etc.
Originally posted by Vader Datalogging is all good and great, but it doesn't differnetiate between a failing MAF and failing connection between the MAF and ECM.
Thats why I was asking if he could datalog. If the computers A/D is seeing the MAFs output, then you definatly know that the system is reading in a signal. Alternativly, you can test the output right at the ECM connectors to make sure its getting a signal.
The only thing I can say is from my own experience. This may or may not do you any good. I had a 350 ZZ1 motor installed with an accel computer. About... a few months after that, I was driving down the road and... the car shut off. Dead as a doornail. I came to find out the accel dfi computer was fried.
The... <insert terribly offensive word of choice here> shop I had the original and repair work done at claimed accel said I jump started the car backwards, fried the computer and wouldn't cover the replacement and made me pay 500 for a new computer. This being back in 1994. Anyway, that last bit won't help anyone, I just wanted to complain, lol.
You might wanna look at the computer, especially if you have any aftermarket computer eq attached to it or some such.
First of all I want to Thank You guys for the info it is well appreciated. I've been working on this for a few days and haven't been getting very far. And as for datalogging dimented24x7 as of the present time I can't but on monday I will be able to. I'm making up a patch cable to solder into the wiring under the dash so I can hook my laptop up to it and watch the computer. I have a 1995 Corvette that I run CAT software on and know how to write spread sheets and input it into my Prom ect.... I haven't gotten it done on this car yet because I thought I would have it running before now and didn't have the info to compare it to anyway. Thanks alot for the charts it gives me what I've been needing. My brother has my laptop borrowed and lives 50 miles from me and I'll get it back from him on monday. He has a 1994 Firebird and we have been both writing bin files and trading them back and forth for a couple of years now. Therefore I'm pretty comfortable with the fact that my ECM is good. It isn't acting bad and I can usually tell real quick or not if one is or not. Until monday I'll hook up the car the way Vader suggested and test it. I sure appreciate the pictures and everything you provided it take time and effort to do this and it is appreciated. I'll let you folks know how it tests out in the next day or so. I'm kinda thinking that the MAF is going to test out fine though, but want to be certain before I continue on to the next step. If I find the MAF to be good I'm going to pull the fuel rail and injectors and check them. I've already done all the voltage tests ect... and I have 13.67 volts at the injectors and 43lbs of fuel pressure and they have a good visual pulse when i hook up my Noid lights on them. I'll wait till after I run the laptop on it though so I can see the pulse in action. A little more accurate than looking at my Noid lights flash. Anyway "Thanks Again" for all the info folks. I've been working on cars for 25 to 30 years and really enjoy doing it as a hobby. I just became a member of thirdgen a couple of days ago and think this is a great site!!!! I never knew it even existed. A friend of mine told me about it and I've spent several hours so far this weekend just browsing around it and have even tried to help a few others out with what I know. It sure is neat to have found this site!!!! I see that there area several divisions around the country you guys ever get together for events and stuff????? Best Regards: cabsales1
