4g61t.org

Hey Guys,

So the car started and moved today with the 4g63 in it. I did notice a problem though. When trying to rev up the car it revs up to 1500rpms then drops down, revs up to 1500 then drops down. This happens when I hold the gas down. If i keep tappiong the gas when it gets closes to 1500 rpms i can make it over and rev the car up normal after that. If it falls below 1500 rpms it does the rev up and rev down thing again.

If i unplug the mas air flow meter the car will rev up just fine. No hicups at all.

My question is.. Is the 4g61 air flow meter different then the 4g63 air flow meter? The one in the car right now is from a 61.

I was also thinking I might have a vac leak somewhere, so when the air flow meter is plugged in that's why it drops. I dunno.

I'm lost! =)

Thanks,

Michael

Yes. The 4g61 MAF is smaller. Are you running on a 1.6 or a 2.0 ECU? What injectors? You've probably got a vacuum leak too somewhere if it's surging that much. Any CEL's?

vfaq.com

http://www.dsm.org/how-tos/tttt/tttt3.html
http://www.vfaq.com/index-main.html

Look at the two links.
I believe the MAF is different also.

http://www.4g61t.org/forum/viewtopic.ph ... 78#p210078

I think this is the exact problem.

2.0L ECU. I'm going to try a 1G MAF and see if that works.

I'm pretty sure it's not the ISC Controller. I've had that problem on about 30 1G's heh. I think it's the bad combo of ECU and MAF. Thanks for the link. VFAQ has been a saviour for me for the last 10 years.

The 4g61t maf is different, as it runs at different Hz signal both at idle and at higher RPM's. You have to match 4g61t ecu's with 4g61t MAF's, and 4g63t (1g) MAF's with 4g63t (1g) ECU's if you are just plugging in everything as if it was factory. You can run a C53a 4g61t car (motor and harness) with a 4g63t (1g) ECU, 4g63t (1G) MAF and 450cc injectors direct plug and play and you will have no issues.

I run the 1.6 ECU in my car with a 2.0 MAF and it runs great. I also have 660cc injectors and tune it out with an S'AFC and a wideband. The smaller MAF and larger injectors balance themselves out, but I'm still leaned out a good 20% on the S'AFC. With the addition of a 2g MAF it would almost be perfect.

I don't think it's the MAF! I plugged in a 2.0L maf, and fired it up and tried to drive around the block. Same thing! The car would start to climb in RPM and then fall on it's face. Right at 1500 rpms. Anyone have any other ideas?

I'm wondering about the 3 solenoids on the firewall now. I unplugged and removed them. I'm going to try to put them back on tomorrow and see if that helps? Are they needed?

I can't start the car right now, because it has no exhaust and is damn loud. The neighbors hate that =)

Those solenoids are only there for emissions, and serve no other purpose. It won't effect the way the car runs.

Sounds great to me. Man. I need to figure out what would cause the rev to drop with the maf plugged in. But when the maf is unplugged rev just fine

Another question. The code on the ecu says it's a 90 ecu. The ECU was rebuilt on it as well. Could it be a non 90 ecu? Do you think that would cause the problem? I heard you can switch to wires? Or would the car not start at all?

What year wire harness are you using? If it's a '90 ECU with a '91+ wire harness you would have issues. If it's a '91+ ECU and you're using a '90 harness you'd also have issues. Pins 6 and 14 need to be swapped if you're using a '91+ ECU with a '90 harness. If it's vice versa, I really don't know what you'd have to do. I've heard that '90 ECU's in '91+ cars actually work ok for some reason, but I've never tried it.

Do you know what the issue would be? The ECU is a 90 (2.0L), the harness is a 89 GT harness, the maf is a 2.0L

I'm going to open the ecu tomorrow and check it out. It seems wierd i'm having this problem.

You shouldn't have a problem with that ECU and wire harness combo. Maybe you have a large boost leak, or the ECU could be broken in some way. I had a problem similar to this, the ECU I was using had a dead MAF circuit, but the car immediately threw a CEL as soon as it turned on for the MAF.