aearon

Howdy,

i bought an 88 gta with the 350 in it. When I bought it the maf was unplugged and the car would fire right up. I replaced the maf and it’s relay cleared the check engine light but now it is a bear to cold start. After it warms up it’s not a problem but sitting overnight it takes a minute or so to get it to fire. Any ideas would be greatly appreciated

GeneralDisorder

iTrader: (1)

There's a lot of terrible MAF's out there. They really don't make a quality unit for these cars anymore. Best solution is to scrap the MAF system and go to speed density. Dynamic EFI has a plug-and-play for this:

https://www.dynamicefi.com/EBL_Flash.php

GD

Tremo

I have a Delphi MAF I bought from Rockauto a couple months back. It seems to be working fine.

Tremo

I don't see how a MAF would interfere with starting. When you first start up cold, the ecu is in open loop, so isn't it just looking at the TPS and using tables until the thing warms up and goes into closed loop?

I also have heard that there are some really shitty MAFs on the market now, but that Delphi which I'm running, so far, has worked well.

Some guy over in Holland rebuilds Bosch hot wire MAFs, but you could buy 2 or 3 brand new Delphi units for the price he charges to rebuild a Bosch.

GeneralDisorder

iTrader: (1)

I think it has to do with the relay he replaced along with the MAF - IIRC the fuel pump power goes through the MAF relay also. Probably the aftermarket relay has something to do with the issue. So it's now relying on the oil pressure switch to power the fuel pump which takes a bunch of cranking.....

GD

i88aGT

I have a few relays that all test good even under load and yet they will make the car run rougher/smoother on startup. you can try swapping your relays (the two that are the same). and perhaps this is due to the aftermarket relays not being 100% original. There is a resistor(?) missing in the new ones. You can see it missing on the schematic printed on new oe relays, it's depicted as a straight line whereas the stock ones have the zigzag line printed on them.
I was able to find a relay that had the matching schematic, it was a gray relay not for the maf system, and I found it browsing high load relays for camaros online from auto stores. I never did buy it to compare tho...
I also depinned, cleaned, regreased the 3 relays. I dunno if it helped neccessarily but you will surely find the grease is nasty by now.

Tremo

Rockauto sells these replacement relays, as does many local car parts stores. I have several on hand in my parts stash. I've tested them to make sure they work. They are not too expensive.

On my firewall driver side there are 3 relays. Fuel pump, MAF power and MAF burnoff. Both MAF relays have been replaced a couple times. I'm original owner of the car and I think that fuel pump relay is the original. Still works.

i88aGT

if you have a nice multimeter you should try putting a t-pin on the signal wire from the maf and testing while running. if I remember right the voltage is between 0-2.5v on that wire depending on how much air it thinks it needs to account for. mine would periodically jump to 2.5v and stick, which was not right for a car idling. even tho I have a basic multimeter that is very slow, it was bad enough to detect. it let me know that the maf was malfunctioning.

Tremo

Yes, but the only issue with this is handing a long wire on the signal pin and running it into the passenger area of the car to look at MAF voltage while you drive, that long wire acts like an antenna and can pick up noise and cause electrical interference problems. The MAF voltage is already brought in to feed to the ecu, no? Maybe better to tap off the connector on the ECU.

You bring up another good point is the response time of the DVM. Mine is very accurate but rather slow on the updates.

GeneralDisorder

iTrader: (1)

You can use shielded wire and the MAF signal is 5v so it's not going to interfere with anything. It's also not a wave, it's a constant voltage so it's not likely to produce significant EMI.

GD

i88aGT

Huh, that's interesting, I never considered interference. I'll keep that in mind for future test endeavors. You all are a lot more pro than me doing road tests! I idled/reved it in in the driveway with the multimeter propped against the windshield, so the wire wasnt too long. Admittedly, it was a cheap, flimsy wire. If I knew how to pin where it goes into the ecu I would.
Do you have to remove the ecu to test? I know you have to be careful to avoid shorting.