TPITuned Port Injection discussion and questions. LB9 and L98 tech, porting, tuning, and bolt-on aftermarket products.
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For the past year my 1992 Z28 [350 TPI] has been the victim the notorious “rough idle” which has progressively gotten worse with time. The car has 90,000 original miles and has been babied with only minor bolt on upgrades [exhaust, headers, suspension, etc].
Symptoms: The car starts and runs perfect for about 20 minutes until getting up to operating temp. Then a rough idle starts but is only noticeable while the car is stopped in gear or when shifting from park to drive/reverse. It would also occasionally bog at takeoff and stall while sitting or shifting. A slight ticking would also develop that was noticeable from the interior.
I started by checking the obvious:
1) IAC – cleaned 2) TPS – checked ok 3) Fuel pump – ok 4) Fuel pressure – ok, although after priming pump and turning off the pressure would drop immediately 5) Injectors – all ohmed between 13 – 16 6) Vacuum leaks – none 7) FPR - ok
After looking around on the forums I contacted John with Fuel Injector Connection (FIC). He explained to me that the stock multec injectors are pretty much junk and that my symptoms sound like it is the injectors. He also explained to me why my car was doing what it was doing [only bad when hot]. I purchased a set of remanufactured Bosche Type III’s (22lb) with the gasket kit and installed with the assistance of the guide that is available here on thirdgen and the provided directions. Took me about 5 hours total. The injectors dropped right in and everything fit like normal. I recommend having a diversified set of ¼ inch drive extensions and sockets. Also, remember to reset the ECM as described in the directions.
Results: The car runs perfect again!!!! John was very helpful and even provides his cell number if assistance is needed. I have been driving the hell out of it for the past couple days and no relapses [although I did carry a fire extinguisher just incase I sprung a leak]
I have seen many posts on here of people with similar symptoms. It seems like they there are a million things that may cause this problems. I hope this provides some guidance for those to maybe look at the fuel injector route before spending $$$$ somewhere else.
congrats man, I run the exact same injecter and wouldnt change them for anything else period. The flow pattern of these injectors is unmatched in my opinion. John is a heck of a guy.
305 takes a 19# injector.......although, you can run a 22# injector in it and it will be fine, I would just recommend that you get an adjustable fuel pressure regulater to bump the psi down a little......unless you have a ton of mods.
P.S. the bosch 3's are pretty loud as far as injectors go in my opinion......a lot louder than the multecs, but they are unmatched in everything else about them as well.
glad to hear your car is running good again. its nice to see people posting their solutions to help others. i got my type III injectors from fic too... jon is awesome. he hooked me up last year and it helped my idle big time.
__________________ The only difference between genius and stupidity is that genius has its limits - Albert Einstein
305 takes a 19# injector.......although, you can run a 22# injector in it and it will be fine, I would just recommend that you get an adjustable fuel pressure regulater to bump the psi down a little......unless you have a ton of mods.
P.S. the bosch 3's are pretty loud as far as injectors go in my opinion......a lot louder than the multecs, but they are unmatched in everything else about them as well.
If you have a 305 you need 19lb injectors unless you want to change the tune. Installing a adjustable regulator is just a band aid and is not worth the money.
You dont have change the tune........an afpr is not a bandaid at all it is seriously needed to do any kind of tuning man....Its very worth the money, or you could make your own, but it is essential for tuning the motor lol.
i have almost the same problem in iroc. i swapped a 350 in for the 305 but now have the rough idle. i have 22lbs injectors, 350 knock sensor, 350 ESC module BUT 305 prom. could that be my problem?
__________________
1987 Camaro IROC-Z Exterior
350/700R4
T-Tops
Flowmaster Exhaust
Smoked Tail Lights
180 Degree Thermostat
2055 Hooker Headers
Front Slotted Disk Brakes with HAWKS Pads
Interior New Black carpet all around
Black Plastics all around 4th gen seats Pioneer Headunit
Pioneer 4x6 speakers in dash
Kenwood 6x9 speakers in sail panels
i have almost the same problem in iroc. i swapped a 350 in for the 305 but now have the rough idle. i have 22lbs injectors, 350 knock sensor, 350 ESC module BUT 305 prom. could that be my problem?
yea my 305 is curently stock for noy, but thanks about the injector size............... the ones i have on it noy leak when they are hot, fuel pressure wil hold when the car is cold but once it gets warm and starts dien when i turn the car off the fuel pressure drops prety quick and i just want a good set of injectors since buying 8 of then isnt cheap i want it to be worth my money
I have a rough idle,and a shimmy from the engine at speed ,I notice one of my injectors is not ticking,it ohms 17,oretty sure this is my problem,nut sure would like re assurance thx!!
For the past year my 1992 Z28 [350 TPI] has been the victim the notorious “rough idle” which has progressively gotten worse with time. The car has 90,000 original miles and has been babied with only minor bolt on upgrades [exhaust, headers, suspension, etc]. 
