New Injectors: Five attempts to start; dead spot around 3000-3500, jerky city driving
09-09-2018, 10:45 AM
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Car: 91 1LE
Engine: LB9
Transmission: MM5
Axle/Gears: GU6
New Injectors: Five attempts to start; dead spot around 3000-3500, jerky city driving
91 LB9 w/288k miles backed by a T5. Only mods are airfoil, underdrive pulley, ported lower air box, gutted cats, and dumped bullet muffler after the y-pipe.
I picked this up two months ago and needed to get things going in a minimal amount of time to make it to a race. It has new plugs, wires, distributor, O2, cap, rotor, whatever the module is on the distributor, and fuel filter from a previous owner. TPS voltage checks out fine (even tried a new GM TPS and it was the same as the existing aftermarket one). New Bosch 2 19# injectors from South Bay (I got spooked reading the tuning issues with the 3's and didn't have time to mess with anything other than a stock replacement).
Symptoms:
It initially would take two attempts to cold start. Idled fine once started. When first giving any throttle it would bog and then take off (almost like what happens when a MAF sensor goes bad). Would have low RPM misfire/jerkiness. This was apparently an issue for some time due to all the usual suspects being replaced by a previous owner as mentioned above.
After doing some research on the forum, I called South Bay and they suggested just going with the Bosch 2 replacements if I was concerned with what I was reading online about some issues with the Bosch 3's. I've put about 400 miles on the new injectors which includes racing at the UMI event last month.
It's now taking five attempts to cold start. Idles fine once started. The initial throttle bog is gone; however, it now has a "dead spot" around 3000-3500rpm where power just cuts out unless I am WOT. Also, after driving on the highway for maybe 20-30 minutes, once going to "city" driving, it sputters, jerks, etc no matter what RPM unless I am at WOT. Again, it feels like when a MAF sensor goes to crap.
It also seems down on power compared to the stock injectors. To make that feeling worse, I also swapped in a 4th gen rear with 4.10's to replace the 3.42 third gen rear at the same time, and it doesn't seem any quicker with the 4.10's vs. the 3.42's. I've also triple-double-quadruple checked to ensure everything went back together correctly, vacuum hoses, etc.
I was thinking about calling South Bay to see if I could swap to the Bosch 3's since I am no longer under a time crunch. Thoughts?
I'd appreciate any suggestions where to turn from here.
I picked this up two months ago and needed to get things going in a minimal amount of time to make it to a race. It has new plugs, wires, distributor, O2, cap, rotor, whatever the module is on the distributor, and fuel filter from a previous owner. TPS voltage checks out fine (even tried a new GM TPS and it was the same as the existing aftermarket one). New Bosch 2 19# injectors from South Bay (I got spooked reading the tuning issues with the 3's and didn't have time to mess with anything other than a stock replacement).
Symptoms:
It initially would take two attempts to cold start. Idled fine once started. When first giving any throttle it would bog and then take off (almost like what happens when a MAF sensor goes bad). Would have low RPM misfire/jerkiness. This was apparently an issue for some time due to all the usual suspects being replaced by a previous owner as mentioned above.
After doing some research on the forum, I called South Bay and they suggested just going with the Bosch 2 replacements if I was concerned with what I was reading online about some issues with the Bosch 3's. I've put about 400 miles on the new injectors which includes racing at the UMI event last month.
It's now taking five attempts to cold start. Idles fine once started. The initial throttle bog is gone; however, it now has a "dead spot" around 3000-3500rpm where power just cuts out unless I am WOT. Also, after driving on the highway for maybe 20-30 minutes, once going to "city" driving, it sputters, jerks, etc no matter what RPM unless I am at WOT. Again, it feels like when a MAF sensor goes to crap.
It also seems down on power compared to the stock injectors. To make that feeling worse, I also swapped in a 4th gen rear with 4.10's to replace the 3.42 third gen rear at the same time, and it doesn't seem any quicker with the 4.10's vs. the 3.42's. I've also triple-double-quadruple checked to ensure everything went back together correctly, vacuum hoses, etc.
I was thinking about calling South Bay to see if I could swap to the Bosch 3's since I am no longer under a time crunch. Thoughts?
I'd appreciate any suggestions where to turn from here.
Last edited by demonspeed; 09-12-2018 at 07:40 PM.
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