Motronic 1.5 Electronic Fuel Injection

[R-vin]

hi,
i have a 6cyl 3.0L OHC 12V engine with some issues, it will idle smoothly (checked with a vacuum gauge to show all ok), when the throttle is snapped, the engine revvs normally, but when the throttle is held open, it revvs dies down, revvs dies down,and continues like this, the spark plugs were removed and checked many times, even new plugs installed,new Distributor cap and rotor installed, the ignition coil was checked for spark leakage or shorting out, new plug wires put in (after i got a nice jolt from #5), engine compression tested at general 170-180psi for 5 compression cycles on each cylinder, even had all spark plugs out of the cyl head to see them sparking, the TPS sensor was checked for function>throttle closed 0.68V, wide open 4.6V, reff voltage 5.11V and throttle was slowly opened to see constant voltage increase and vice versa, Injector connectors were checked, to see battery voltage on one pin (red wire) and computer ground control on the other pin, Note, Injectors #1, #2, #3 have continuity on the computer ground control, the same goes for #4,#5, #6 >>> this goes with BOSCH Motronic 1.5 fuel injection which pulses the injectors in Banks>>> here a 6cyl, firing order 1-5-3-6-2-4, injectors 1,2,3 pulse together then 4,5,6 together and so on…

can anybody suggest what could be going on?

i suspect the fuel system, fuel filter was changed, the old one was not choked, i could blow freely thru it…to measure fuel pressure i will need to source a suitable apparatus..

could leaky injectors be causing this? (car has had a reputation of high fuel consumption), i suspect this as this evening i got a few back fires thru the exhaust/intake not too sure had a back fire here), measuring intake manifold vacuum, there was a strong vacuum, with no fluttering of the gauge needle (this says that valves etc are ok)…

i`m open to any ideas…
thanks guys…

R-vin
Rio De Janeiro, Brasil

Topic

[college man]

What make vehicle?

[R-vin]

hi,
the car is a brazil made Omega A (GM), i know in england they had this car as the Vauxhall Carlton, Germany as the Opel Omega A, here in 93 brasil GM started selling the Omega A under the Chevrolet make (completely assembled in brasil), mine particularly is the station wagon body called the Chevrolet Suprema here….
i just removed the injector rail, verified that the fuel is being sent on the inlet to the rail and the return line functions as a return line >>>> i`m here in brasil and i could not believe the quality of mechanics…99% were professionals with the VW beatle and the associated technology….. when i got this car, injectors #3 and #4 were inverted, as well as many wires cut under the dash, others stripped without being reinsulated, one in particular was next to the brake pedal and would spark every time i applied the brakes, the rear air suspension for automatic leveling or the car (rear) when carrying cargo, the air pump for this system does not work, why??? a hose from the water spray bottle was connected to its intake… no wonder the air bags blew out…..

back to the injectors, most have the plastic cover on the injector tip broken, for #5 and #6 >> missing completely… what effect would this have?

[college man]

With broken injector pieces you could have a vacuum leak/
causing a misfire. The fuel trims will also go positive trying
to add fuel.check out this link.

http://www.ericthecarguy.com/faq/solving-automotive-performance-issues

[R-vin]

hey,
while at the intake manifold/injector rail, i decided to check the wiring harnesses, to my suprise the Idle motor connector had repaired wires, one with just 2 strands of copper still making contact, repaired this and continued reinstalling the injector rail (got a kit that had new seals, the plastic tip and the accompanying plastic washer (had to buy 2 kits cause were for 4 bangers), verified no intake leaks, while doing this i realised something, the connector for the crank position sensor (engine only has this rotation sensor), the sensor wire connetor was loose in the engine harness connector… with slight movement, i would get the rough revving problem…. turns out the connector is missing the metal clip that secures the connection>>> nothing a paper clip and two pliers cant fix…. not pretty bends, but it holds the connection securely and releases when the made up metal clip is pressed…. strangely the intermittent loss of crank sensor signal trouble code was not triggered (code 19) … i am puzzled at the simple fix… but it worked, the engine revvs smoothly and when held at various revvs, does not die down, actually when held at a constant revv, i can see the varying rich and lean cycles on the oxygen sensor….

thanks for your attention…. sometimes the fix is not as straight forward…. at least i got clean injectors now 😉

warm regards
R-vin

[college man]

Glad you got it worked out.

[Author]

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