Bosch or Multecs for C4 L98 1990?
Thread Starter
3rd Gear
Joined: Sep 2005
Posts: 3
Likes: 0
Bosch or Multecs for C4 L98 1990?
C4 L98 1990.
Replaced my shorted Multecs with Bosch 0280150561-D9B back in 2005. Suffered an actual MPG drop of 25 % since then. I first suspected compression, o2, cats, egr, but all seems ok after checking. Plugs look great and no soot in the tailpipes. When I listen carefully to the engine at light load, cruising, I can feel/hear a very slight stumbling/misfire. Most people wouldn't notice it. One thought is that unburnt oxygen forces BLM to rise. Acceleration and idle is ok. Could it be anything with spray pattern? I havn't tried new Multecs because of the price but there's soon not much left to try. Has anyone seen this kind of problem and tried swapping back to good Multecs? I would appreciate info about the result before buying new OEMs.
Typical idle values:
PROM 5061
Spark adv: 14
Inj pw: 1,8 ms
Int: 131
Block: 139, 2000rpm 153
MAP: 38kPa (0,66v), key on 102kPa (4,92v)
ECT: 106
MAT: 42
Oil: 101
Replaced my shorted Multecs with Bosch 0280150561-D9B back in 2005. Suffered an actual MPG drop of 25 % since then. I first suspected compression, o2, cats, egr, but all seems ok after checking. Plugs look great and no soot in the tailpipes. When I listen carefully to the engine at light load, cruising, I can feel/hear a very slight stumbling/misfire. Most people wouldn't notice it. One thought is that unburnt oxygen forces BLM to rise. Acceleration and idle is ok. Could it be anything with spray pattern? I havn't tried new Multecs because of the price but there's soon not much left to try. Has anyone seen this kind of problem and tried swapping back to good Multecs? I would appreciate info about the result before buying new OEMs.
Typical idle values:
PROM 5061
Spark adv: 14
Inj pw: 1,8 ms
Int: 131
Block: 139, 2000rpm 153
MAP: 38kPa (0,66v), key on 102kPa (4,92v)
ECT: 106
MAT: 42
Oil: 101
Safety Car
Joined: Jan 2004
Posts: 3,783
Likes: 15
From: Northern California
Buy a set of the Bosch III injectors from supporting Vendor FICINJECTORS AKA: Jon Banner
Check out the injector videos at the top of the page shot by Jon. Many members have bought these new style injectors including me and have had Great results! These are the Best value replacement injectors for the L98. At only $169 a set, they can't be beat.
Check out his website. www.fuelinjectorconnection.com
Check out the injector videos at the top of the page shot by Jon. Many members have bought these new style injectors including me and have had Great results! These are the Best value replacement injectors for the L98. At only $169 a set, they can't be beat.
Check out his website. www.fuelinjectorconnection.com
Last edited by GKK; Oct 11, 2008 at 01:20 PM.
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
C4 L98 1990.
Replaced my shorted Multecs with Bosch 0280150561-D9B back in 2005. Suffered an actual MPG drop of 25 % since then. I first suspected compression, o2, cats, egr, but all seems ok after checking. Plugs look great and no soot in the tailpipes. When I listen carefully to the engine at light load, cruising, I can feel/hear a very slight stumbling/misfire. Most people wouldn't notice it. One thought is that unburnt oxygen forces BLM to rise. Acceleration and idle is ok. Could it be anything with spray pattern? I havn't tried new Multecs because of the price but there's soon not much left to try. Has anyone seen this kind of problem and tried swapping back to good Multecs? I would appreciate info about the result before buying new OEMs.
Typical idle values:
PROM 5061
Spark adv: 14
Inj pw: 1,8 ms
Int: 131
Block: 139, 2000rpm 153
MAP: 38kPa (0,66v), key on 102kPa (4,92v)
ECT: 106
MAT: 42
Oil: 101
Replaced my shorted Multecs with Bosch 0280150561-D9B back in 2005. Suffered an actual MPG drop of 25 % since then. I first suspected compression, o2, cats, egr, but all seems ok after checking. Plugs look great and no soot in the tailpipes. When I listen carefully to the engine at light load, cruising, I can feel/hear a very slight stumbling/misfire. Most people wouldn't notice it. One thought is that unburnt oxygen forces BLM to rise. Acceleration and idle is ok. Could it be anything with spray pattern? I havn't tried new Multecs because of the price but there's soon not much left to try. Has anyone seen this kind of problem and tried swapping back to good Multecs? I would appreciate info about the result before buying new OEMs.
Typical idle values:
PROM 5061
Spark adv: 14
Inj pw: 1,8 ms
Int: 131
Block: 139, 2000rpm 153
MAP: 38kPa (0,66v), key on 102kPa (4,92v)
ECT: 106
MAT: 42
Oil: 101
Drifting
Joined: Oct 2006
Posts: 1,554
Likes: 13
From: Romeoville IL
I like my Multecs and will keep them as long as I can. Do you have Bosch II injectors? I don't have the part numbers. What is the fuel lbs rating on them. You may have 24 lb, stock is about 22 lb. The Ford injectors are sometimes rated at a different fuel pressure as well.
Burning Brakes
Joined: Aug 2006
Posts: 1,061
Likes: 99
From: Seattle WA
Are you measuring MPG by the trip computer or manually by recording miles & gallons at fill-ups? If your bosch injectors flow different at GM fuel pressures than stock multecs, the computer will think it's injecting more or less fuel and throw off the trip computer.
Supporting Vendor
Joined: Mar 2008
Posts: 1,762
Likes: 14
From: Cumming Ga
C4 L98 1990.
Replaced my shorted Multecs with Bosch 0280150561-D9B back in 2005. Suffered an actual MPG drop of 25 % since then. I first suspected compression, o2, cats, egr, but all seems ok after checking. Plugs look great and no soot in the tailpipes. When I listen carefully to the engine at light load, cruising, I can feel/hear a very slight stumbling/misfire. Most people wouldn't notice it. One thought is that unburnt oxygen forces BLM to rise. Acceleration and idle is ok. Could it be anything with spray pattern? I havn't tried new Multecs because of the price but there's soon not much left to try. Has anyone seen this kind of problem and tried swapping back to good Multecs? I would appreciate info about the result before buying new OEMs.
Typical idle values:
PROM 5061
Spark adv: 14
Inj pw: 1,8 ms
Int: 131
Block: 139, 2000rpm 153
MAP: 38kPa (0,66v), key on 102kPa (4,92v)
ECT: 106
MAT: 42
Oil: 101
Replaced my shorted Multecs with Bosch 0280150561-D9B back in 2005. Suffered an actual MPG drop of 25 % since then. I first suspected compression, o2, cats, egr, but all seems ok after checking. Plugs look great and no soot in the tailpipes. When I listen carefully to the engine at light load, cruising, I can feel/hear a very slight stumbling/misfire. Most people wouldn't notice it. One thought is that unburnt oxygen forces BLM to rise. Acceleration and idle is ok. Could it be anything with spray pattern? I havn't tried new Multecs because of the price but there's soon not much left to try. Has anyone seen this kind of problem and tried swapping back to good Multecs? I would appreciate info about the result before buying new OEMs.
Typical idle values:
PROM 5061
Spark adv: 14
Inj pw: 1,8 ms
Int: 131
Block: 139, 2000rpm 153
MAP: 38kPa (0,66v), key on 102kPa (4,92v)
ECT: 106
MAT: 42
Oil: 101
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Advanced
Joined: May 2007
Posts: 82
Likes: 1
From: LA California
It would crank but not run.
Multec 1 injectors (PN 17086544) were used in Corvettes from 1989 through 1999. High alcohol content fuels and cleaners are known to erode the insulation on the injector coils, leading to a failure. To make a long story short, on my car the injector 2 coil failed when it got hot and prevented the engine from starting.
If you search this forum, you will find many posts by people who have replaced original Multec injectors with Bosch Design III injectors, part number 0-280-155-700.
If you look closely, you can see the part number on the side:
Bosch also produces an identical injector for Ford under part number F4SE-A1B. I replaced the stock Multecs in my Corvette with Ford F4SE-A1B’s.
An original Multec next to the Ford F4SE-A1B
A close-up of the part number: F4SE-A1B:
According to Injector Flow Rate tables on the Internet ( http://users.erols.com/srweiss/tableifc.htm ), stock Multec injectors, sometimes called 22 lb. injectors, flow 235.9 cc/min @ 43.5 psi. Ford/Bosch replacement injectors, sometimes called 19 lb. injectors, flow 226 cc/min @ 43.5 psi, although this seems to depend on who is doing the measuring.
These injectors also seem to be quite popular with the Bimmer, Volvo, and Saab crowd. There is an interesting thread here: http://www.m42club.com/forums/showthread.php?t=233&page=3
There are many vendors who carry these injectors; a few include:[LIST=1]
P.S. I have two Lhasa Apso's: one named Chevy, one named Ford. I love 'em both.
Last edited by Grumpy; Oct 12, 2008 at 10:22 AM.
Le Mans Master
Joined: Feb 2005
Posts: 5,146
Likes: 3
From: The Motor City
The 90-91 map cars are more sensitive across the board to changes, which does have an effect on fueling through out the load range vs rpm.
Also, is the 14* @idle w/est dis-connected ?
Last edited by mseven; Oct 12, 2008 at 11:11 AM.
