TPITuned Port Injection discussion and questions. LB9 and L98 tech, porting, tuning, and bolt-on aftermarket products.
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hey guys i have a 91 z28 5.0 5 speed that might need injectors. the idle is rough all the time and i have already changed the o2 sensor, tps, IAC valve, coolant temp. sensor, map sensor and checked all the vacuum lines and still no luck with fixing the rough idle. i'm hearing it is likely i need injectors considering they look all original. it does have a hypertech thermomaster chip in it, but other then that the engine is a reman. that is stock other then underdrive pulleys and a cooler fan switch. which injectors are good to use on that set up, Accel, Bosch, 19lb, 23lb?
thanx
Ohm'ing them out first is a good idea. Also you can take a long screwdriver, put the tip on an injector and the other end on your ear. You can hear them fire. See if they all sound the same.
If they look good, take a timing light and put it on each plug wire one at a time. See if it flashes evenly on every cylinder at idle. If not, it's probably a bad pickup coil in the distributor (assuming your plugs and wires are good). I've seen them cause lots of flaky idle problems.
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hey guys i have a 91 z28 5.0 5 speed that might need injectors. the idle is rough all the time and i have already changed the o2 sensor, tps, IAC valve, coolant temp. sensor, map sensor and checked all the vacuum lines and still no luck with fixing the rough idle. i'm hearing it is likely i need injectors considering they look all original. it does have a hypertech thermomaster chip in it, but other then that the engine is a reman. that is stock other then underdrive pulleys and a cooler fan switch. which injectors are good to use on that set up, Accel, Bosch, 19lb, 23lb?
thanx
If it boils down to the fact that you need injectors we will be more than happy to help you. We carry all size bosch design lll's. We are a sponsor of this forum and we are here to help. Take a look at our "new version" of the bosch design lll that would be a direct fit, no fitment or height issues. We worked for a long time to develop this. It is clean, and it is professional. NO OTHER COMPANY HAS IT!!! WE ARE THE ONES WHO DESIGNED IT! info@southbayfuelinjectors.com
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Last edited by southbay08; 11-05-2009 at 10:20 PM.
Ok I will ohm test them and see what they sound like as well. They are supposed to be between 13 and 16 right? If I end up needing injectors ill def call FIC and deal with them. and also if its a bad pick up coil then the cylinders wont all fire evenly? and the car does have new plugs wires cap and rotor.
The most important thing you are looking for is that they are all within the same spec as each other (and between 13-16, depending on temp). TPI is a batch fire system, meaning the ecm fires on entire bank of injectors at the same time, so your 4 right bank injectors fire at once and the 4 left bank ones fire at once. If one injector on one bank has a less resistence than the other 3, it will run richer than the other 3 and cause the other 3 to run leaner since electricity takes the path of least resistence. If the batch with the bad injector is on the drivers side bank with the o2 sensor, it could even be causing the other bank to run less than optimal since the ecm will be seeing a different a/f ratio than what the passenger bank is putting out due to the bad injector on the drivers side bank.
Also keep in mind that a 1991 car has the bad fuel injectors. There were 2 different brands used in the entire run of tpi cars, one type from 85-88, another from 89-92. The later ones are regarded as much cheaper and likely to fail.
Id say new injectors is $200 well spent on your car even if none of them are terribly bad right now.
ok thanx man, i will prob end up buying new injectors anyway since its a good idea to replace the stock ones, but do u know anything about symptoms of a bad pick up coil?
