OK, so I've been suspecting leaky injectors for a while, so while troubleshooting a valve cover gasket problem, I decided to change my injectors to the LT1 injectors I've had sitting in my store room for a while. I cleaned them up, and put new O'rings on them. And yes, my L98 did come with 24's before anyone says that's the problem.

I took everything apart, put everything back together the way it goes, checked the vacuum lines 3 times (didn't have them on right the 1st time...also had the brake booster disconnected). Now I'm pretty sure that the vacuum lines are correct, but I'm still having a problem. Here's the symptoms.

Car starts up fine, has a rough idle (shakes the car). Car drives, but lacks any power whatsoever. If revved at idle, it will pop after the gas is let off.. Sounds almost like it's backfiring out the exhaust side. When driving, car will pop going through the upper RPM's, and car has hardly any power. It's driveable through the mid RPM range if you're easy on the throttle.

All the plugs are getting spark, and I've reset the ECM. I didn't reset the IAC because I don't think that's the problem since it has the problems in the upper RPM range and no power.

I checked the timing (with EST disconnected)....it is dead on. Revved it a little bit to see if it moved, it stayed solid.



I'm suspecting either an injector isn't firing, vaccuum problems still, or I dunno. At this point I'm open to ANY suggestions.

How would I check the injectors without pulling the fuel rail?

 

sounds like to much fuel. what pressure u running at???

 

Stock pressure, stock lb/s hr

 

Since your open to anything, this might be a long shot, but maybe some of your injectors didn't seal when you put them in the manifold. Did you hear them "snap" when you pushed them in?

 

Yah, I did...I think I'm just going to take everything back apart.

 

Well I don't know if this is a bright idea, but I heard a great way to find vacum leaks is to get a propane torch. Turn it up to high but don't light it obviously, and go around all your vacum lines and stuff, and listen for a change in idle.

 

Before you take it back apart, check to see if all the injectors are firing. Start the car, and place your fingers on the body of each injector. If its firing, you will feel it ticking/clicking. If you don't feel anything, its not firing. Also, the header would be cold at the cylinder that has a bad injector.

When I first did my TPI conversion, I had a combination of bad parts at first startup which was quite a pain to sort out. One of the things that happened to me was a very rough, shaky idle. When I mean rough, I'm not kidding, I was amazed it would stay running.

KingTal0n came over one day to try to help and figure out what was going on, and he noticed my driver side headers were still cold. Turned out I had four bad injectors on the same bank. (I later found other problems, but the injectors were causing the rough idle). The odds of having 4 out of 8 injectors go bad on one bank made me think something had messed them up. Just to be safe, I swapped ecms since I had an extra one lying around, and replaced the four bad injectors. Haven't had problems since then.

I never though a V8 could idle on four cylinders before I saw that.

 

Start and warm the engine, then try a power balance test by disabling an injector at a time. My wild guess is that you are lacking good fuel atomization or flow (lean), or have streaming injectors causing fuel puddling.

 

I will follow your suggestions before I pull it apart. It won't be today though, I already have a full schedule.

 

Turned out the #5 injector wasn't firing. Haven't put everything back together yet, guess my old injectors will be going in.

Hopefully that was the only problem.

Thanks

 

92blue when you say the headers are cold do you mean the exhaust?? I am trying to diagnose a problem I am having with my TPI and am getting no where!! (very frustrating), I have been told that the only 3 sensors used for start up in open loop are TPS IAC and CTS is that true?

 

Yes, all four primary tubes were stone cold. You could let the engine run for a minute or so with your hand on any part of the driver side header. You could walk over to the passenger side then, and you could feel the heat from a distance. In my case, all four injectors on the driver side weren't firing. No fuel means no combustion. No combustion means no heat.

1985WS6transam, PM me with some more details, or start a new thread if you like and send me the link. I'll be glad to help, but I don't want to hijack someone elses thread.

 

Got my shovel and started digging up old posts and this one seems good. My car is behaving the EXACT same way. I just replaced a head gasket and now the car only runs on the passenger side injectors. It's weird. So all 4 injectors were bad on 1 side? I didn't touch the headers yet to see if they are hot, or listen to the injectors themselves. But I removed every driver side wire and there was spark arc, but the idle didn't change. Hope you reply to this.

 

...hummm, just did a head gasket?? - you sure you set the valves right??

 

I set the valve lash the same on both sides. And idle didn't change when I pulled ALL wires from the driver side, it only changed on the passenger side.

 

Well, at the time that happened to me, I was under the impression that the 730 ECM had two injector drivers. I reasoned that one of them may have gone bad, and damaged one bank of injectors. In reality, that theory doesn't work because the 730 only has one injector driver.

Does that mean it was a coincidence that all 4 bad injectors got installed on the same side? Seems like it now.

On the bank with 4 dead cylinders, check to see if the injectors are firing, as it sounds like they are not. You should have constant 12volts on one terminal for each injector connector, and the ECM will intermittently ground the second terminal to fire the injector. With the engine running, a voltmeter will show 12 volts across the two terminals. More than likely, this is an issue of poor ground, blown fuse, damage injector wiring, etc...

 

I hate to say without knowing 100% for sure, but I think each bank of injectors has its own FUSE (I think INJ1 and INJ2 on the fuse block - I'm thousands of miles away from my car though). There are separate wires for each bank, and separate connections at the ECU, but yes, only 1 driver in the ECU (one pin probably can't handle the current, and also gives another point of failure without fully disabling the car).
Take a look there, before you tear it all up.

 

You are correct, each injector bank has its own fuse, and there is one ground lead from each injector bank to the ECM.