first off hello everybody, its my first post on this site. my name is eddy and i own a 92 camaro rs. it has a 305 motor with throttle body induction. i have run across a peculiar issue with my injector spray recently. the driver side injector sprays more fuel than the passenger side injector, resulting in hard starts(flooding motor) and a really high idle(2k rpm @ 120farenhight). I have replaced both injectors and cleaned and regasketed the throttle body. what could cause something like this to happen?

 

The problem has persisted since i rebuilt the TB. car ran great before that. can someone please explain how i can troubleshoot this? ive done a bunch of searches and have not found anything similar. thanks a lot.

 

Bad injector o ring

 

Since posting this thread i have replaced the orings with new ones i had laying around. Id like to make a note that after installing the injector o rings before the injector, the spray now appears to be even. Im going to check the pattern again with a timing light later today, and ill post what i noticed. However, the injectors still are spraying a lot of fuel at idle, and the idle is at around 2000 rpm. I am under the understanding that the injectors are like switchs, turning on and off. When i watch a tbi idle correctly it seems that the injectors alternate spraying fuel, and they are not spraying fuel constantly at idle. My injectors do not do this, they constantly spray fuel into the throttle body at idle, with the throttle plates closed. The timing is set a 0 degrees. Some of the wires under the hood are exposed(as in not covered by the black materiel). i did not see any burnt wires or wires down to metal, but it would make sense to me that the plugs on top of the TB injectors have grounded wires, and they are not telling the injectors to turn off, causing constant spray. Is this possible? If so, how would i check for this? Please note that injectors are both remanufactured, and the motor does not miss, and no SES lights are visible. Any ideas or thoughts would be greatly appreciated, thanks.

 

You rebuilt your tb and the problem arose? Hows your tps? Wrong setting will cause computer to dump gas if it thinks the throttle is open. Just a thought.

 

my guess would be TPS

 

Thanks for the input everybody, and something is definately off on my tps. Upon removal of the tps the TPS lever does not look to be lining up with the grooves of the sensor. If i attempted to line the mounting holes up and install it it would fail, in order to install the TPS i have to twist it either 1/4 turn clockwise or counterclockwise. It is installed twisted 1/4 turn counterclockwise. Is this incorrect? = I made a childish image in MS paint to hopefully show you guys what im talking about. Can this lever be safely adjusted? I have a feeling that is what is causing my idle difficulties, but after inspecting the spray pattern with better lighting the right injector still seems to spray more than the left, but i think i should solve the high idle issue first. I have done a search on TPS adjustment and have run across this: https://www.thirdgen.org/tpimod2, but a bit of it confuses me. Can anyone clarify what the author of that article meant by " make your own jumper wires"? Is the jumper wire basically 3 wires into 1 so you can read the 1 wire with vom? would it look like the 3rd image installed with the tps sensor plugged in? Is this what i should do to remedy my problem? I feel as if the TPS lever is far from where it is supposed to be located and im not sure this adjustment will bridge the gap. sorry if these seem like stupid questions, im new to TBI and i want to do this correctly. thanks.

 

forgot a image

 

The 92 TBI does not have an adjustable TPS lever. When a new TPS is installed you have to twist its body by about 10 deg and turn to align mounting holes with TB. The throttle shaft engages and turns TPS spring loaded center slot. The TPS adjustment modification is applicable to earlier, lever styles TPS sensors which had a flat blade plug. Yours is compact and circular in appearance. 92 ECM auto calibrates idle position so that the old 0.6 Vdc requirement (at idle) is wider in its range (0.3 to 0.9) and idle position is determined by ECM.


A rich condition at idle is usually due to a bad CTS or a disconnected MAP sensor.

//RF

 

RF, wouldnt a bad CTS throw a SES light? The MAP sensor is connected, so i dont believe that is the problem. Later today im going to check for vac. leaks with carb/TB cleaner, and i also plan to jumper the a and b connecters on the aldl plug to see if the engine is throwing any error codes. I have yet to clean the PCV valve or the EGR, and while i doubt either of those is capable of causing a idle of 2000 rpm, im going to look into cleaning those as well.

 

Yes, indeed. A bad CTS will throw a code. However, a disconnected or a leaky hose between TB vacuum port and MAP sensor usually will not set of a code. A lower vacuum level registered by MAP sensor will result in richer mixture. Vacuum leaks are notoriously hard to find, so take your time. Bad, corroded grounds can also play havoc in sensor readings. You'll just have to go through it systematically and see if there are any broken or flaky wires, plugs.

The base gasket between TB and intake is prone to leaks - so expect to replace it. Just take your time inspecting engine bay.

//RF

 

RF, I just looked over my car and id like to give you a better idea of how the car is running. I sprayed the PCV valve with cleaner and verified it was in good operating condition. I then checked all the emissions hoses for proper routing and no obvious visible cracks. The vacuum line running to the temp sensor on the stock airbox is plugged by a bolt. This line is labeled in the emissions sticker as "S". Please note i had the airbox assembly removed to view the spray pattern, so the IAT sensor was not in use. The motor was cold and had not been started since yesterday. I started the motor and after a few brief revolutions it fired, but was running at very low rpm(500 or so) in park. I stepped out and observed the spray pattern. The motor was not surging at all and was running smoothly, with no backfiring, misses or smoking. The injectors looked to spray correctly, and they were not constantly spraying fuel, but alternating in short bursts, without any leaks. I heard a click clack noise from the injectors which i understand to be correct operation. I gave it a few short bursts of throttle and it was responsive, but i noticed as the motor warmed up(around 3 minutes later) the idle had increased to around 800 rpm and the injectors were spraying a continuous burst of fuel that was puddling up on the throttle plates. The temperature at this point was approximately 120-130. Sometimes when i revved the motor at this point it would respond well to increased throttle, but if i let off completely it would drop a little lower than its idle rate for a brief moment and quickly jump back to idle.(Ex- with motor idling at 900 rpm i rev motor to 3000 and let off throttle completely, rpms drop to 800 briefly and quickly rise back to 900) Note- At this point I begin to notice the spray pattern between the two injectors is uneven, though the spray is uniform, the pass side injector is spraying very little, like what i noticed at lower rpms, and the driver side is spraying fuel in at an increased rate. As i let the motor warm to operating temperature further the idle increases gradually past 1000 rpm and after the motor reaches about 160-170 temp units the motor rises idle rpm at a noticeably faster pace until it reaches about 1800 rpm, where it idles up to 220 temp units. I used a paper clip and joined A & B on the aldl connecter and observed that it is throwing a code 13."Oxygen sensor circuit open or no activity" Reading that is kind of like chinese to me as ive never diagnosed obd1 or any other system for that matter. What differs between "no activity" and "circuit open"? can someone break this down.

The motor was in park the entire time, timing set to 0* and during the different idle rpms i spritzed carb/TB cleaner around the base gasket and it didnt seem to effect idle, even under long, continuous spraying.

 

Well, let make sure that you are getting Code 13 to begin with. When you install a paper clip into ALDL between terminals A & B, ignition in run position you should see SES blinking as follows :

12 12 12 pause 13 13 13 pause 12 12 12 pause 13 13 13 -> repeating.

Code 13 basically states that O2 voltage is too low or not oscillating between rich- lean voltage levels (0.8 <-> 0.2) once engine reached operating temperature and 2 minutes of engine run have passed. Usually causes are:
harness short to ground
poisoned O2 sensor (spilling antifreeze is a big no-no) - o2 voltage is stuck just below 0.45volts.
cold O2 sensor - do not install single wire O2 in full length headers.

Depending on your abilities troubleshooting O2 voltage is relatively easy with DVM. O2 sensor is located on the driver side exhaust manifold, above oil filter.

Timing on LO3 should be set with EST plug open - 0 deg TDC. Once you set it re-connect EST plug, clear ECM by disconnecting battery for about 30 seconds with engine off. At idle, timing should be bouncing between 16 and 20 deg (use dial back timing light makes it easy to observe).

//RF

 

I just replaced the IAC unit. now my car purrs like a kitten. I misinterpreted code 12 as code 13(embarrassing) I noticed my IAC was bad when i ran the car and it hurt my ears to listen to the huge vacuum leak the IAC was causing by not functioning properly, lol. RFmaster, it was really cool of you to throw in your .02. It really saved me a lot of time and i feel much more comfortable working with my cars induction system. My camaro runs a lot better now that i rebuilt the TB, it is a very noticeable difference.

 

Well, glad that you got that squared away! No worries - just enjoy the drive...