1G Misfiring and GM MAF Install

[Generation1JeY]

Hey everyone, i just got my car working the other day, and ever since i have had a weird misfiring problem. The car is idling pretty good, but even at idle you can hear a little misfire if you listen close to the tailpipe, then when i'm in fourth or fifth and i give it WOT it will kinda sputter or misfire, i dunno i can't figure it out i have no idea what could be causing it, i just replaced coil-pack, plugs and wires, gapped plugs right, got 160 compression across the board, did a power balance check with the wires, right now i'm thinking either fuel or boost leaks. However, if it was a boost leak or intake leak it wouldn't affect my car at idle? so why is it misfiring a little bit at idle?

Also i tried searching, but i can't seem to find the answer, i got a 3" gm maf and a translator from a friend of mine and i don't have the installation instructions. Its one of the new versions 2.03 i believe with the plug and play setup, i'm just wondering where exactly does the rpm signal wire go? Someone told me to splice it with one of the CAS wires, but on the translator website instruction manual it says rpm signal and stuff from different places like transister pack, and also it says 2g on the instruction manual so i wasn't sure if its the same for me since i'm 1g.

Anyways, any help appreciated. Thanks.

 

[MrdB]

tap signal wire in the wire wire on the cas

 

[brute]

Double check your settings. It sounds like you might be running so rich that it's misfiring. Here's what mine looks like. This is for a 3" MAF, 450cc's, and stock everything else.

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[DSMcamaro]

http://www.fullthrottletech.com/showthread.php?t=105

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its the skinnier of the 2 black wires on the CAS.

 

[Generation1JeY]

Hey brute, i mean that on my current setup i'm having misfiring problems. Currently i just am running a stock 1g maf and stock everything else besides exhaust pretty much. I just meant that i have the equiptment to install the maft, but i haven't done it yet. Thanks though i will follow your picture.

One more questions, if you guys are familiar with datalogging. My boost is around 11-12 right now and at about 6300 rpms i'm already getting about 90% injector duty cycle. Does that make sense? I have stock 450s. I didn't figure the stock injectors would be working so hard with that much boost. could that be my problem? like faulty or clogged injectors? Also i'm getting a light amount of knock on this current boost setting at around 3500-4500 rpms, after that it seems to go away. I read somewhere someone was talking about getting light amounts of knock a little early in the rpm range when starting a 3rd gear pull early in the rpm range and giving in WOT. So is the knock normal?

 

[larsrya8]

One more questions, if you guys are familiar with datalogging. My boost is around 11-12 right now and at about 6300 rpms i'm already getting about 90% injector duty cycle. Does that make sense? I have stock 450s. I didn't figure the stock injectors would be working so hard with that much boost.

Have you done a boost leak test?

 

[Generation1JeY]

ya but i cant get it to work, i think i might have a huge boost leak or my boost leak tester is messing up because i was using a good compressor and i was pushing air through the system but it wouldn't build boost at all. I don't know what was wrong.

 

[donmagicjuan]

If possible, try positioning the source of your compressor as close to the throttle body as you can. By starting closer to the head, you will have fewer possible trouble spots. After you fix the leaks at this location, slowly work your way out to pinpoint the massive leak you're experiencing.

 

[Dream On]

I had the same problem. Ended up having some nice holes in my intercooler, biss o-ring leaked, j-pipe leaked, and probably other stuff as well. Good call on starting at the TB and working your way back towards the turbo.

 

[Generation1JeY]

what do you mean try positioning? I just have a coupler with a pvc end-cap with a tire stem pressed in that i attach to the turbo-inlet...

 

[donmagicjuan]

I mean pull off your UICP and stuff the end cap in the coupler for your throttle body elbow, then move it to the LICP (if you have the stock one) or the coupler before the intercooler. After you've identified and fixed all the leaks downstream of those locations, then try it pre-turbo again.

 

[Generation1JeY]

o ok got it. never though of doing it like that.

 

[Generation1JeY]

Ok, forget the boost test i will do that later, right now i have other stuff bugging me. My idle is not cooperating and i still have the weird misfire. I swapped throttle bodies today with my gsx and my idle is still messed up, i ground the two ecu plugs and set it right at 800, kill the motor and disconnect the grounds and start it back up and it starts idling at 1500. It doesn't make sense. And with the misfire just at idle if you listen to the exhaust out of the tailpipe you just hear it misfire every couple seconds. It will burp and sputter air out. Tommorrow i'm gonna try swapping injectors, coil-pack, transistor pack, and maybe installing my fuel pump to see if that helps at all.

Does anybody have any experience with this and know what else it could be? Plugs and wires are brand new and good, i have no check engine light, but under heavy load at mid rpms or in high gears if i give it WOT it will just kinda sputter and misfire, i would think its boost leaks but it does it at idle too so it can't be a boost leak if it does it at idle right?

 

[Generation1JeY]

Ok, got the misfiring fixed, turns out it was my coil-pack, doesn't make sense though cause there was zero physical damage to it it looked perfectly fine, no cracks in the holes where the plug wires go.

I have another question though, if my boost is at about 11, should i be geting any knock at all? when i do 3rd gear pulls i get like 3 or 4, but then if i'm on the freeway in fourth or fifth and i punch it i will get around 7 or 9 or so, is that normal? shouldn't i be getting zero?

And with stock injectors and fuel system what should my injector duty cycle go up to? it appears to be linear so it travels up with the rpm, by redline i have almost 93% duty cycle isn't that really high?

 

[donmagicjuan]

Knock counts on a stock setup along with high IDCs are indicative of boost leaks. The air escaping has been metered already, meaning that the ECU will call for more fuel than is necessary (high IDCs). If the leak is large enough, the turbo will become less efficient and heat up the air, which can potentially lead to knock. Have you done a leak test yet?

 

[Generation1JeY]

Nope not yet, but now that you have told me that i'm gonna do one today. I'm gonna try what juan told me to do, because last time i tried it on the compressor it wouldn't work for some reason, either my boost leak tester is leaking itself, or i have some big leaks cause i was using a good air compressor and i wasn't even able to build boost in the system.