L-jet richness question
10-14-2018, 05:16 PM
#1
Three Wheelin'
Thread Starter
L-jet richness question
Working through a rich running/poor fuel Econ question on the 83s L-jet.
When I got my car the vacuum limiter was taken off and the two ports off of the throttle body were capped. I have the limiter. The throttle cable is also adjusted right now so that it DOES NOT close the micro switch at is most relaxed point (idle).
Can someone explain the integration of the idle micro switch, vacuum limiter, oxs sensor, and their effect on a rich running condition with regard to the ecu?
Thanks
-scott
When I got my car the vacuum limiter was taken off and the two ports off of the throttle body were capped. I have the limiter. The throttle cable is also adjusted right now so that it DOES NOT close the micro switch at is most relaxed point (idle).
Can someone explain the integration of the idle micro switch, vacuum limiter, oxs sensor, and their effect on a rich running condition with regard to the ecu?
Thanks
-scott
10-14-2018, 11:59 PM
#3
Racer
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The micro switch will “cut off” the fuel on hard deceleration. Without the micro switch, unburnt fuel will pass through the exhaust. Without the idle switch, the rich running condition is pretty short lived and at idle.
10-15-2018, 01:32 AM
#4
Rennlist Member
Check the fuel pressure regulator and its vacuum hose for holding vacuum, and no fuel odour or leakage at the regulator. Also air cleaner for clear.
jp 83 Euro S AT 57k
jp 83 Euro S AT 57k
10-22-2018, 10:08 PM
#5
Three Wheelin'
Thread Starter
Update
so I have the new sensor in and adjusted the idle switch so it engages and no change.
next up will be the fuel pressure regulator. No leaks or anything along those lines.
perhaps something internal.
will report back. Thanks for all the knowledge and suggestions.
next up will be the fuel pressure regulator. No leaks or anything along those lines.
perhaps something internal.
will report back. Thanks for all the knowledge and suggestions.
10-22-2018, 10:29 PM
#6
Three Wheelin'
Thread Starter
One more thought...
let me describe a more complete picture of symptoms...I have been reading up on FPRs and I do not have some symptoms described by others.
1) Car is not hard to start - hot or cold
2) No smell of fuel anywhere
3) idle is very smooth at all times
4) cold start - engine idles up around 1200 rpm for about 2 min or so then drops to 700ish
5) exhaust has a very rich smell - at all times (cold start, hot start, idle, going down road, etc.
6) fuel Econ sucks
7) no smoke from exhaust that I can see (other than the initial Smoke on a cool morning until engine warms up).
i think that sums the observations. thanks all.
1) Car is not hard to start - hot or cold
2) No smell of fuel anywhere
3) idle is very smooth at all times
4) cold start - engine idles up around 1200 rpm for about 2 min or so then drops to 700ish
5) exhaust has a very rich smell - at all times (cold start, hot start, idle, going down road, etc.
6) fuel Econ sucks
7) no smoke from exhaust that I can see (other than the initial Smoke on a cool morning until engine warms up).
i think that sums the observations. thanks all.
10-22-2018, 11:30 PM
#7
Rennlist Member
Hi Scott,
It sounds to me that besides the other suggestions, you may have a poor O2 sensor signal reaching your ECU. With the O2 sensor disconnected, the car will run a little rich at all times. If you have a bad sensor or the wiring is bad the ECU will try to boost the fuel and the car will run rich.
Just an idea.
Good luck,
Dave
It sounds to me that besides the other suggestions, you may have a poor O2 sensor signal reaching your ECU. With the O2 sensor disconnected, the car will run a little rich at all times. If you have a bad sensor or the wiring is bad the ECU will try to boost the fuel and the car will run rich.
Just an idea.
Good luck,
Dave
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10-23-2018, 09:53 AM
#8
Administrator - "Tyson"
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In addition to the suggestions above, measure the resistance of the temp 2 sensor on the radiator bridge. The resistance goes up as the engine heats up and this value directly controls the pulse width of the injectors.
AFM could also be out of whack, these are wear items and should be rebuilt at some point. See Mark Anderson @ 928 International for that.
One stuck injector could also be the culprit. Check the plugs for any abnormalities.
The 9th cold start injector could be leaking too.
Personally I'd put the vacuum limiter back on. Nothing to do with this issue but it makes the overall driving experience better on the street.
10-26-2018, 11:19 PM
#9
let me describe a more complete picture of symptoms...I have been reading up on FPRs and I do not have some symptoms described by others.
1) Car is not hard to start - hot or cold
2) No smell of fuel anywhere
3) idle is very smooth at all times
4) cold start - engine idles up around 1200 rpm for about 2 min or so then drops to 700ish
5) exhaust has a very rich smell - at all times (cold start, hot start, idle, going down road, etc.
6) fuel Econ sucks
7) no smoke from exhaust that I can see (other than the initial Smoke on a cool morning until engine warms up).
i think that sums the observations. thanks all.
1) Car is not hard to start - hot or cold
2) No smell of fuel anywhere
3) idle is very smooth at all times
4) cold start - engine idles up around 1200 rpm for about 2 min or so then drops to 700ish
5) exhaust has a very rich smell - at all times (cold start, hot start, idle, going down road, etc.
6) fuel Econ sucks
7) no smoke from exhaust that I can see (other than the initial Smoke on a cool morning until engine warms up).
i think that sums the observations. thanks all.
I'd like to add here that mine will idle really high after a cold start, no matter the ambient temp. It might start around 1500 at first, then after warming up I've seen it go up to almost 2000. I noticed the AFM was not fully seated when I was looking for a different problem area, so I reseated it and poked it a little to make sure it was working properly. No change in my idle problem though. During this operation I noticed the idle microswitch is not being pressed at all by the movement of the throttle. I wasn't able to find the throttle plate adjustment, I only adjusted the slack of the cables and no change. Moving the throttle I thought I heard it closing completely, but I didn't look inside so I could be wrong.
Other notes, I have not replaced the OXS yet, there is a small leak at the fuel pump inlet have yet to fix (I'm not sure how yet), there are also many rubber hoses that are either torn or cracked and need replaced. I am on a very tight budget trying to get this car fixed lol.