Possible bad injector.

ElrodKTPQ_89 · Aug 28, 2014

So today I took my car back out to the shop to finish my brake job. Keep in mind that the car has been running pretty good here lately. So I left from my house and went maybe 3 miles to town and stopped for prolly 30 minutes to eat. Left the BBQ place and headed to the shop and saw my friend and his co-workers parked behind the paper mill here and I stopped and talked to then for about ten minutes. Up until this point the car had zero issues. When I leave from talking to them and proceed on to the shop my car started running like crap...low rpm miss and just like it had no power. So I eased on to the shop and got everything done there. When I left the car was still acting up so I stopped by a local mechanic friends shop and let him check it out. He said it sounds to him like a bad injector on my drivers side. Possibly stopped up or not working at all. My plugs and plug wires are all brand new, but I'm going to check all my plugs tomorrow just in case. So for now the car is back home and parked until further notice.

Now, tomorrow my friend will be coming home for the weekend and he's bringing me my Cobra intake I just bought. The intake has 24lb. injectors and fuel rails etc. with it. I was initially gonna wait until a later time to change intakes, but if I have to tear the intake down anyways to get to my fuel injectors...would it make sense to go ahead and just swap from factory intake to my new Cobra intake and injectors? I know I'm still not 100% sure just yet that it is an injector causing the problem, but if it is it would seem like a perfect time to go ahead and do my swap. The only major thing I'm concerned with is that the motor is still in it's break in period...maybe close to 300+ miles on it since it was rebuilt. Would changing my intake setup so soon cause any issues?

Suspect · Aug 28, 2014

dont stress it.. swap it.

btw whats this break in period stuff.. i get my shht started and it goes right on the dyno.

CC'S95GT · Aug 28, 2014

Get a Noid light to make sure the injectors are getting the pulse.
If all 8 are firing Then use a digital thermometer on the header to make sure all 8 are firing and hot.

ElrodKTPQ_89 · Aug 28, 2014

Suspect said:
dont stress it.. swap it.

btw whats this break in period stuff.. i get my shht started and it goes right on the dyno.

Lol that's some tough stuff there! But yea I was told to put anywhere from 500-1000 miles on the motor then change the oil and be good to go.

CC'S95GT said:
Get a Noid light to make sure the injectors are getting the pulse.
If all 8 are firing Then use a digital thermometer on the header to make sure all 8 are firing and hot.

Is a Noid light the test light you plug into the injector harness? And I will try all that this weekend.

ttocs · Aug 28, 2014

did you leave it running while you were talking to your friends or was it off? I am not a motor expert by any means how does that story lead to the diagnosis of specifically the drivers side injector?

ElrodKTPQ_89 · Aug 28, 2014

ttocs said:
did you leave it running while you were talking to your friends or was it off? I am not a motor expert by any means how does that story lead to the diagnosis of specifically the drivers side injector?

When I stopped at the mechanics shop yes I let him drive it down the road and see what it was doing and then he popped the hood and listened to it. He just said 'sounds like it's coming from this side.'

ttocs · Aug 29, 2014

gotcha. I was more curious as how I could tell later if I had the problem and didn't understand what I didn't see in the story above.

ElrodKTPQ_89 · Aug 29, 2014

Ok I think I'm with you now. Another thing I forgot to say in the first post: if I do decide to go ahead and swap intakes, while I have it down that far I wanna go ahead and do my roller rockers too. So I'll be upgrading to 1.7 RR's, and a Cobra intake with 24lbers, 65mm TB and a new MAF that is coming with it. Think my computer will take well to all of that or is that more of just a 50/50?

toyman · Aug 29, 2014

Short story is it will run but not well. The GT ECU is programmed for 19# injectors. So without changing the pulse width (PW) the 24# injectors will flow more fuel at the programmed PW. The ECU, based on the O2 signal, may be able to compensate for the extra fuel. Your best and probably cheapest solution would be to instal a Cobra ECU (J4J1).

CC'S95GT · Aug 29, 2014

ElrodKTPQ_89 said:
Is a Noid light the test light you plug into the injector harness? And I will try all that this weekend.

yea.

whiplash473 · Aug 30, 2014

What CC said 8 posts up + you can rent then from damn near any auto parts store.

RichV · Aug 30, 2014

Another quick trick is to go out for a drive around the block, then take a IR temp gun and measure each header right at the head. If one is significantly cooler than the rest, that's where the injector issue is. The color of the plug will tell too.

Also look for obvious stupid stuff like cap/rotor, plug wires, and plugs. Could be a failure of one of those.

ElrodKTPQ_89 · Aug 30, 2014

RichV said:
Another quick trick is to go out for a drive around the block, then take a IR temp gun and measure each header right at the head. If one is significantly cooler than the rest, that's where the injector issue is. The color of the plug will tell too.

Also look for obvious stupid stuff like cap/rotor, plug wires, and plugs. Could be a failure of one of those.

I'm gonna try the temp gun here in just a little bit once the rain stops here. And I haven't had a chance to pull the plugs and check them yet but I'm gonna do that today also. Everything else is brand new only a few hundred miles on them (dizzy, cap & rotor, wires etc.).

RichV · Aug 30, 2014

If the temp test shows a misfire on a specific cylinder, inspect everything on that one. Plug, wire, tower on cap, etc.

ElrodKTPQ_89 · Aug 30, 2014

Thanks Rich! I'll give it all a shot and let you guys know what turns up.

In other news, my intake was delivered today!

Im still a little hesitant on doing the swap before being 100% sure on what's causing my issue. As I was told by a friend, if I just tear it down and swap everything and I'm still having issues then it's gonna be harder to figure out where it's coming from than if I had nailed it down to begin with.

RichV · Aug 30, 2014

Looks like you have adjustable FPR and a rail gauge, that's nice.

I would try and get to the bottom of the issue before swapping. Clean that sucker up a little.

ElrodKTPQ_89 · Aug 30, 2014

RichV said:
Looks like you have adjustable FPR and a rail gauge, that's nice.

I would try and get to the bottom of the issue before swapping. Clean that sucker up a little.

Yep all of the above, 65mm TB, and a MAF to go with it all for $150. And it's definitely about to be cleaned up and repainted. It's gonna look good on there when it goes on!

RichV · Aug 30, 2014

Great deal! I got mine for like $230, just intake. But it is the fancy polished Motorsport SVO version, it does look good polished.

I've seen the SN Cobra intakes for as high as $500 since they are so hard to find.

ElrodKTPQ_89 · Aug 30, 2014

Yea I couldn't believe the guy let all that stuff go so cheap! I'm glad I waited and found this one instead of buying an explorer intake. The SN Cobra upper looks worlds better!

ttocs · Aug 31, 2014

I could not agree more that the cobra looks 100x better then the gt40. Do yourself the favor of polishing it and you will really be happy. Mine is almost done and can't wait to see it next to the polished vortech and the polished mezier electric water pump and all the black trim around it.

While it is out though if your waiting its not all that hard to gasket match the lower to lightly port it yourself.