Help! I need to figure this out!
10-16-10, 11:23 PM
#1
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Help! I need to figure this out!
Alight so I have the Fc listed in my sig which is an 88 s4 na fc and I am trying to tackle this problem that just suddenly appeared about a month or so ago. I have search so I am finally breaking down to posting since I know there is something I am missing.
The Problem:
Basically I have a hesitation when I accelerate around the regular 3800rpm mark. I have added and regrounded everything according to posts that I have found as well as Aaron Cake's guide. This problem is not always around just the 3800rpm area but that is where it is most lean. The car also will lean out to 15 or 16.5 afr when only cruising and once I give it throttle it will be decent after 4000rpms. That means around 13-14 afr which before I could dip to 12. I also have recently found that the second trailing spark plug is either firing wrong or not at all. I put a timing light on the wiring and to strobes but never shows the timing mark like the first trailing does, which is right on the mark.
Steps that I have already taken:
-I have replaced fuel filter which since I rebuilt the engine had the previous filter back wards duh!
-I have replaced spark plugs and wirings were replaced when the engine was rebuilt.
-I have tried a replacement tps, afm, ecu and had no difference. Probed the injector pins to find that they are getting battery voltage.
-I have checked fuel pressure which is 40psi with the fpr vacuum hose off and just around 30psi when plugged in.
-I have reset the timing as well as checked to make sure that the secondaries are clicking and they are when the ecu turns them on.
-I have the orifice pill in the boost/ pressure sensor which reads 3.5 with engine not running and drops in voltage as the throttle increases.
-I have taken the fuel pump out to check and see if there is any junk in the sock or tank and there wasn't.
-I currently have the safc disconnected from altering the afm so that I can get it running right and I do not have the O2 sensor hooked into the ecu which hasn't made a different in the past because I turn with the safc.
Please any help is greatly appreciated so that I can get back to driving once again!
The Problem:
Basically I have a hesitation when I accelerate around the regular 3800rpm mark. I have added and regrounded everything according to posts that I have found as well as Aaron Cake's guide. This problem is not always around just the 3800rpm area but that is where it is most lean. The car also will lean out to 15 or 16.5 afr when only cruising and once I give it throttle it will be decent after 4000rpms. That means around 13-14 afr which before I could dip to 12. I also have recently found that the second trailing spark plug is either firing wrong or not at all. I put a timing light on the wiring and to strobes but never shows the timing mark like the first trailing does, which is right on the mark.
Steps that I have already taken:
-I have replaced fuel filter which since I rebuilt the engine had the previous filter back wards duh!
-I have replaced spark plugs and wirings were replaced when the engine was rebuilt.
-I have tried a replacement tps, afm, ecu and had no difference. Probed the injector pins to find that they are getting battery voltage.
-I have checked fuel pressure which is 40psi with the fpr vacuum hose off and just around 30psi when plugged in.
-I have reset the timing as well as checked to make sure that the secondaries are clicking and they are when the ecu turns them on.
-I have the orifice pill in the boost/ pressure sensor which reads 3.5 with engine not running and drops in voltage as the throttle increases.
-I have taken the fuel pump out to check and see if there is any junk in the sock or tank and there wasn't.
-I currently have the safc disconnected from altering the afm so that I can get it running right and I do not have the O2 sensor hooked into the ecu which hasn't made a different in the past because I turn with the safc.
Please any help is greatly appreciated so that I can get back to driving once again!
10-17-10, 12:18 AM
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Yup the open I have them running off the airpump which is not blowing into the exhaust incase anyone wonders. Also my injectors were sent out to be cleaned when I rebuilt my motor as well.
10-17-10, 09:41 AM
#4
Before 3800 rpm the secondaries should read about 13volts at the respective ECU pins. At 3800 the voltage drops to about 7 volts. Does yours follow this pattern. Have you tried driving with the Boost sensor hose disconected and plugged and compared results between the two scenarios?
10-17-10, 01:08 PM
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I have checked the pins and they show around 13 volts for all 4 injectors and I do not see a change in voltage when I rev under load and the secondaries kick in. I read that it happens possible so fast that the digtial meter that I have won't see it. With the boost sense disconnected and the line plugged I get richer across the board but still shows a lean hesitation. I still can't figure out the trailing issue. I guess it is bad wiring since I have switched the wires and get spark at the port for T2. Can a plug be bad from the factory and not show spark? It still stobes though with a timing light.
10-17-10, 01:20 PM
#7
I have checked the pins and they show around 13 volts for all 4 injectors and I do not see a change in voltage when I rev under load and the secondaries kick in. I read that it happens possible so fast that the digtial meter that I have won't see it. With the boost sense disconnected and the line plugged I get richer across the board but still shows a lean hesitation. I still can't figure out the trailing issue. I guess it is bad wiring since I have switched the wires and get spark at the port for T2. Can a plug be bad from the factory and not show spark? It still stobes though with a timing light.
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10-18-10, 02:28 PM
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When I rev to hear them kick in it is when still and my boost sensor is unplugged. I checked my plug wire and get 11.5ohms and it still doesn't show the trailing mark when I use the timing light. I will try to check the voltage. I ohmed the secondaries and they checked out okay. Strange thing is with some load not WOT but medium throttle in leans out to 15-16 afr.
10-18-10, 05:01 PM
#11
When I rev to hear them kick in it is when still and my boost sensor is unplugged. I checked my plug wire and get 11.5ohms and it still doesn't show the trailing mark when I use the timing light. I will try to check the voltage. I ohmed the secondaries and they checked out okay. Strange thing is with some load not WOT but medium throttle in leans out to 15-16 afr.
10-18-10, 05:20 PM
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I ran the car once with the boost sensor electrical plug off and it ran rich. Then to simulate load I unplug the vacuum line but cap it and also unplug the tps. I took a flat head screw drive and held it to each injector and both began clicking around 3800rpms.
10-18-10, 06:47 PM
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If you have it any other way it is working 'against itself".
A Buddy's Car experienced Hesitation issues having his Afm Cranked Sideways.(flat on both sides,Instead of the Rounded parts on each side).
.By the way:If you are using an Induction type Timing Gun,you have to get it "just right" on the plug wires or it will look like the plug is not Firing,when in Reality It IS.
10-21-10, 12:45 AM
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Alright got to check my voltage on secondaries and the lowest it hits is 10 volts hitting the throttle hard. I checked the plugs and the seem to be blackish brown so far not too lean. Only saw 15 on my wideband the last outing. With no o2 readings getting to the ecu shouldn't I still be somewhat rich though?
10-21-10, 05:57 PM
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Alright so I took it for a ride metering the secondaries and the primaries. The secondaries would stay at 13volts until the 3800 transistion when giving it hard throttle most I saw it drop was 9 volts. The primaries do the same expect one time I say 4 volts 
. Other than that seems to drive okay but leans out to almost 16 afr with light to medium throttle.
. Other than that seems to drive okay but leans out to almost 16 afr with light to medium throttle.
10-22-10, 07:45 PM
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So I will try this again. Does the engine lean out pretty easy if no O2 sensor is being read? I never had this problems before. It sat around 14-15 cruising.
10-22-10, 09:25 PM
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Alright another ride taken and I was able have it run decent except I notice the voltage dropping on the primaries. I see at idle 12 volts then with throttle it can go to 10. Now in fourth gear not around when the secondaries kick in I don't know if it dropping to 7-8 volts is normal. Anyone ever experienced this?
10-23-10, 12:35 AM
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But should the primaries drop if im not to the point where the secondaries kick in? I mean 4th getting on the freeway and punch it. The voltage drops from 13 to 10 or 9 even under 3800rpms.
10-23-10, 12:40 AM
#22
Taken from the thread provided.
""VON....Got me. Does not fit my preconceived notions.
JBREEZY....The car has to hit 3800 rpm and also have a load on it and I believe that is accomplished by the boost/pressure sensor leting the ECU know there is a heavy load on the engine. With judicious application of the throttle you can achieve over 80mph without the secondaries coming on line. With BULLINACHINASHOP application of the throttle they'll come on at 3800rpm. If you had two meters connected, one to the secondary and one to the primary, you'd see prior to 3800rpm, the voltage on the primary steadily drop from about 11.5 down to as low as 4v prior to 3800 being reached. When 3800rpm is reached the voltage on the primary will jump from the 4v to about 7v. At that same 3800rpm you'd see the secondary, which prior to 3800rpm would be around 13v, jump to the same voltage as the primary when it switched at 3800rpm i.e. the 7v mentioned above. Then both voltages will drop at the same rate. Those are not exact figures. Just close. EDIT: The above is what I see on a daily basis. I have two cheap RadioShack meters connected to the primary and secondary output wires. If someone violently disagrees, have at it. I have no books that tell me how this car works. Only what I've read on this site and what I observed on my car.""
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Last edited by HAILERS; 03-24-02 at 12:18 PM.
""VON....Got me. Does not fit my preconceived notions.
JBREEZY....The car has to hit 3800 rpm and also have a load on it and I believe that is accomplished by the boost/pressure sensor leting the ECU know there is a heavy load on the engine. With judicious application of the throttle you can achieve over 80mph without the secondaries coming on line. With BULLINACHINASHOP application of the throttle they'll come on at 3800rpm. If you had two meters connected, one to the secondary and one to the primary, you'd see prior to 3800rpm, the voltage on the primary steadily drop from about 11.5 down to as low as 4v prior to 3800 being reached. When 3800rpm is reached the voltage on the primary will jump from the 4v to about 7v. At that same 3800rpm you'd see the secondary, which prior to 3800rpm would be around 13v, jump to the same voltage as the primary when it switched at 3800rpm i.e. the 7v mentioned above. Then both voltages will drop at the same rate. Those are not exact figures. Just close. EDIT: The above is what I see on a daily basis. I have two cheap RadioShack meters connected to the primary and secondary output wires. If someone violently disagrees, have at it. I have no books that tell me how this car works. Only what I've read on this site and what I observed on my car.""
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Last edited by HAILERS; 03-24-02 at 12:18 PM.
10-23-10, 03:01 AM
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I will give that a shot. What is your thinking behind that? I think one trailing wire might be bad like I mentioned earlier because I get spark from the coil but no timing signal. If I switch the t1 with t2 I get the one not working to work and the other not working. Might order a new set of wires. Still this shouldn't be causing the problem I am experiencing with leaning out.