87 S4 fuel delivery problem - too rich!
03-29-2002, 02:27 PM
#16
Three Wheelin'
When the '87 had the problem, it could idle. As soon as I hit the gas it would stumble and die. If I eased on the gas, then I could slowly bring up the RPM but all sorts of smoke would come out. Honestly, this was a few years ago so it could have been white smoke. It did, however, make my eyes burn.
04-01-2002, 02:14 AM
#17
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suggestion. Unplug the MAF and see how it runs. If it doesnt effect the engine as you unplug it, then you may have found the problem. When i was trouble shooting what turned out to be a bad LH brain, i unhooked my MAF, the car ran but ran roughly and had a VERY rich exhaust. It would respond to throttle inputs but not too smoothly and again ran very rich. The second i plugged it back in, the engine smoothed out and the richness whent away.
having had 2 LH brains "go south" they all fail differntly as i think Mike mentioned. My first one just quit one day in the parking lot. I went to start the car and there was nothing but the spastic clicking of my injectors firing under the hood. Second time was a faint hesitation in the power under load or the engine would suddnely loose power when just cruising along for no apparant reason.
Best way to solve that is an LH swap.
Its not always convenient but the best way to trouble shoot this stuff is have access to "swappable" pars. That way you can immediatley eliminate the big items and then go on to the nit picky stuff... coils, vac leaks, Fuel pressures etc etc.
Between the the LH brain and the MAF they pretty much control the enigne really, best get them out of the way first <img src="graemlins/yltype.gif" border="0" alt="[typing]" />
having had 2 LH brains "go south" they all fail differntly as i think Mike mentioned. My first one just quit one day in the parking lot. I went to start the car and there was nothing but the spastic clicking of my injectors firing under the hood. Second time was a faint hesitation in the power under load or the engine would suddnely loose power when just cruising along for no apparant reason.
Best way to solve that is an LH swap.
Its not always convenient but the best way to trouble shoot this stuff is have access to "swappable" pars. That way you can immediatley eliminate the big items and then go on to the nit picky stuff... coils, vac leaks, Fuel pressures etc etc.
Between the the LH brain and the MAF they pretty much control the enigne really, best get them out of the way first <img src="graemlins/yltype.gif" border="0" alt="[typing]" />
04-02-2002, 06:19 AM
#18
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Join Date: Feb 2002
Location: uk, cornwall, where it rains - mostly!
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hi
i sympathise with your problem, i too have LH problems. my '84 euro is still with the local bosch experts. car would start and idle fine, but would not drive, over rich, rough and lumpy.
so far:
refurbished and balanced injectors
new LH ECU
complete strip down and r&r of inlet tract.
fuel pressures all ok
ignition system checked - new ngk 'V' plugs.
results:
starts and idles fine, will not drive, over lean and rough! gone from too rich to too lean!
my car does not have oxygen sensors....the inlet tract is coming off again, because there is an air leak somewhere....if you spray butane over the 'spider' the engine revs increase.....so despite a very careful reassemble of the entire inlet tract, there is an air leak somewhere!!!
i wish i had access to substitute parts to swop out.....it would make diagnosing problems so much easier. just one step at a time, and sometimes a back step!
i wish you luck with yours.
regards
johnb '84 euro s (yet to be driven in anger)
i sympathise with your problem, i too have LH problems. my '84 euro is still with the local bosch experts. car would start and idle fine, but would not drive, over rich, rough and lumpy.
so far:
refurbished and balanced injectors
new LH ECU
complete strip down and r&r of inlet tract.
fuel pressures all ok
ignition system checked - new ngk 'V' plugs.
results:
starts and idles fine, will not drive, over lean and rough! gone from too rich to too lean!
my car does not have oxygen sensors....the inlet tract is coming off again, because there is an air leak somewhere....if you spray butane over the 'spider' the engine revs increase.....so despite a very careful reassemble of the entire inlet tract, there is an air leak somewhere!!!
i wish i had access to substitute parts to swop out.....it would make diagnosing problems so much easier. just one step at a time, and sometimes a back step!
i wish you luck with yours.
regards
johnb '84 euro s (yet to be driven in anger)