New Issues After Fuel Injector Change
Thread Starter
Le Mans Master
Joined: Jun 2006
Posts: 5,642
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From: One day you're a Comet...the next day you're dust... Arkansas
New Issues After Fuel Injector Change
I just changed the injectors on my near stock 1989 6 speed L98. Before the change I had a very rough idle after going into closed loop. The new injectors are new 22 lb Lucas type that fit the fuel rail perfectly. I now have a low/erratic idle on cold start. This clears up in a minute or two of coaxing. After the car warms up the idle is within normal range and smooth. I can't tell if this is caused by a overly rich mix at start up or not. I don't smell gas and the car starts right up cold or hot. BTW I have no codes.
The other thing is that my MPG and range with the new injectors are about 40% less than before on my digital dash readout. (From low 20's average down to @14's average). This doesn't seem possible. I'm wondering what might cause this. I had the battery disconnected for 3 days during the install and the ECM had some learning to do after completion.
The other thing is that my MPG and range with the new injectors are about 40% less than before on my digital dash readout. (From low 20's average down to @14's average). This doesn't seem possible. I'm wondering what might cause this. I had the battery disconnected for 3 days during the install and the ECM had some learning to do after completion.
Le Mans Master
Joined: Aug 2007
Posts: 8,735
Likes: 412
From: WV
Baddack, when I put my 383 in and changed injectors from stock to 24 lb Bosch 3 injectors my mpg reading was also way off, its reading 12-14 mpg when Im really getting around 18-20 mpg. My tuner (mseven) told me he could compensate for this in my tune..If your car is running ruff cold its running off the perameters from the ecm in open loop, maybe the cold start perameters need to be changed via a tune for these injectors....Im just guessing on the last part..Im sure someone on here knows for sure...WW
Instructor
Joined: Jun 2008
Posts: 173
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From: Norman OK
Interesting... I experienced almost the same thing when I switched over to Bosch 3s on my 91 L98/auto awhile back due to 3 bad Multechs..
My idle is a just a wee bit rocky for the first minute or two after cold startup, and a little rich, but then settles in nicely when warm.
Around town/combo driving, I still see 14-15 mpg range average on my digital, but if I do a highway trip and hit the reset before hand, I'll see in the mid to high 20's average. On INST, while coasting down, it is fun to see in the high 60's-70's for MPG..
Hadn't given it a whole lot of thought, but maybe it's time to dig in to it..
Anybody else experience this?
My idle is a just a wee bit rocky for the first minute or two after cold startup, and a little rich, but then settles in nicely when warm.
Around town/combo driving, I still see 14-15 mpg range average on my digital, but if I do a highway trip and hit the reset before hand, I'll see in the mid to high 20's average. On INST, while coasting down, it is fun to see in the high 60's-70's for MPG..
Hadn't given it a whole lot of thought, but maybe it's time to dig in to it..
Anybody else experience this?
Thread Starter
Le Mans Master
Joined: Jun 2006
Posts: 5,642
Likes: 5
From: One day you're a Comet...the next day you're dust... Arkansas
Thanks for the responses. I just got back from a quick round trip, half 2 lane highway and half freeway. The average fuel millage on the readout was exactly 17.0 MPG. Previously with the Multechs I got around 28MPG on the readout for the same trip which was right with my ealier manual calculations.
I made the entire run on cruise at 1600 to 1700 RPM. (5th gear on the 2 lane and 6th gear on I-40). Next I will do a real check of the MPG the old fashioned way. BTW, the car ran perfectly with good throttle response. I know there is nothing seriously wrong at all, I'm just curious about the cause. Especially the unstable cold idle.
I made the entire run on cruise at 1600 to 1700 RPM. (5th gear on the 2 lane and 6th gear on I-40). Next I will do a real check of the MPG the old fashioned way. BTW, the car ran perfectly with good throttle response. I know there is nothing seriously wrong at all, I'm just curious about the cause. Especially the unstable cold idle.
