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Pages: 1

lms MAF

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Posted by: lsc8

I bought a used lms maf and when i install it my car decides to act up. First off i have a cobra intake, but i didn't think that should effect it. After i put the lms maf on the car acts almost like the tranny is slipping it wont pick up, kick down, or even want to shift. Geno said check fuel pressure..it was at 30#'s at idle, so i installed a walbro 255hp pump. My pressure is now at forty, but i still have the problem. At work we have a OTC genesis scan system which has real time diagnostics that showed my fuel pressure dropping down to around 6 #'s when i kick it down but then comes back up to 40. I don't know if this is normal or how long it should take to come back up. I'm wondering if i should try a fuel pressure regulator or what? When i install the stock MAF the problem goes away, but i haven't run real time diagnostics on the car with the stock maf on it though. The maf tube is colored black on the bottom and Geno says that it should be the right one. I'm stumped.

Posted by: seanklsc

If anyone can help, its probably Geno. I just wanted to say that I installed a used LMS 80mm too, and without a hitch. Runs like a champ. I just had to run to the hardware store for a rubber gasket adapter.

Posted by: 67Continental

i have heard that you can't use a 255lph pump with a stock fuel pressure regulator. could this be your problem?

Posted by: torquemonkey

I'm going through some fuel issues right now and with the reading I have done the fuel pressure shouldn't drop like you described. According to the book, working pressure is 39#. (Mine is 30# at idle and 40# w/ vac line pulled) Either it would be the fuel pressure reg., source of vacuum or a voltage signal from the ECM.
I have a Cobra intake project in the works and only after I had gotten the parts the I find some issues that need to be resolved. Again from reading, people are reporting that they are having brake issues at low RPM. Supposedly from low vacuum signal from the intake. Could there be a relation?

Posted by: ONEBADMK8

Stupid thing but did you remember a small black rubber O ring on the mass air electronics tower when you removed it from the stock housing?

It would be at the base of the black electronics if it came out with the electronics?

If it didn't and it got stuck in the stock maf housing and you installed the electronics without this installed between them and the LMS housing then you will have problems.

Also clean the maf wires, they may have a mild coating on them.

What's the mileage on your car?
Did you replace the fuel filter?

Posted by: 98LSC32V

You can run the Walbro 255lph with the stock fuel pressure regulator no problem... did it for years...

Posted by: lsc8

the maf already came with the electronics on it but i will pull it apart and check. I was wondering about the vacuum also, because yes my brakes really suck. If the regulator was getting enough vacuum could that be why the pressure is dropping so fast? Also after i put the lms maf on if i run through the gears once after it shifts into fourth, from then on it will run ok. But the problem reoccurs after you restart the car.

Posted by: ONEBADMK8

Quote:

Originally Posted by lsc8

the maf already came with the electronics on it but i will pull it apart and check. I was wondering about the vacuum also, because yes my brakes really suck. If the regulator was getting enough vacuum could that be why the pressure is dropping so fast? Also after i put the lms maf on if i run through the gears once after it shifts into fourth, from then on it will run ok. But the problem reoccurs after you restart the car.

This used unit came of a Mark VIII? Your sure? If it came used then make sure it's Mark VIII electronics.

Posted by: lsc8

well even though i the maf's had matching part numbers i switch them along with moving a sensor and i think it has take care of my problem. The roughness is gone, im gonna take it to work tom and run diagnostics again to see if the fuel pressure is still dropping though.

Posted by: ONEBADMK8

Quote:

Originally Posted by lsc8

well even though i the maf's had matching part numbers i switch them along with moving a sensor and i think it has take care of my problem. The roughness is gone, im gonna take it to work tom and run diagnostics again to see if the fuel pressure is still dropping though.

Nice glad to hear its working out. Keep us posted.

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