928 s4 problems after engine swap
05-18-2015, 02:28 AM
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928 s4 problems after engine swap
Hey,
A while ago i posted about my 88' s4 sparking randomly.
turns out because of a bad powder coated intake the internals got alot of metal scraping wich made it not have any compresion, atleast not enough to start.
people that rebuild engine's told me it was no good to try and rebuild it.
So i bought a new engine. A 1990 s4 whit 79k miles on it (the condition it arrived in makes me think it wasnt used in years)my car is a 1988 s4.
after (again) i replaced all the seals all bearings all sensors, waterpump all belts ignition cables coils yadayada...
reinstalling the new engine was a bit rough but it got in.
first time i try to start it imidetly dies after it start up.
on second attampt i keep it alive whit the gas paddle and i noticed it works delayt. When the engine got on temprature it was able to idle itself around 800 rpm.
after the fans started working we put the engine off let the oil drain and put in a new filter and new oil.
the next start take alot of cranks before it would start and again, had to keep it alive after a while It idled by it self.
so we proceed to fill the gearbox.
as soon as i selected all the gears and went back to P the engine started to go up and down in revs 800 - 1100 over and over also the guy i work with told me the gearbox hit a gear(wheels started moving) everytime the engine bounced in revs. but regardless we proceed filling the gearbox, as i put it into gear- wheels start moving i apply the brake and after 2minutes ich the engine stalls. Also restarting it was no problem(after keeping it up again for a bit).
So now i have no idea where to look. Did a sensor get damaged re fitting the engine? A feul damper or regulator? bad wiring? There is an overflow of things to chek and i dont know the 928 to well to pin point the problem(s?)
Details i might have forgotten: i removed airpump clogged the vacum unde the intake tho.
rebuild all of vacuum and used length according to cattalog. Also did the gearbox one since it actuly leakd might end up a bit shorter then used to tho.
and the thing of it bieng a younger engine so tripped over a few things like oil pressure sensor of the old car.
all the other parts i got whit the new engine i used those.
That about sums it up i think?
thanks in advance.
A while ago i posted about my 88' s4 sparking randomly.
turns out because of a bad powder coated intake the internals got alot of metal scraping wich made it not have any compresion, atleast not enough to start.
people that rebuild engine's told me it was no good to try and rebuild it.
So i bought a new engine. A 1990 s4 whit 79k miles on it (the condition it arrived in makes me think it wasnt used in years)my car is a 1988 s4.
after (again) i replaced all the seals all bearings all sensors, waterpump all belts ignition cables coils yadayada...
reinstalling the new engine was a bit rough but it got in.
first time i try to start it imidetly dies after it start up.
on second attampt i keep it alive whit the gas paddle and i noticed it works delayt. When the engine got on temprature it was able to idle itself around 800 rpm.
after the fans started working we put the engine off let the oil drain and put in a new filter and new oil.
the next start take alot of cranks before it would start and again, had to keep it alive after a while It idled by it self.
so we proceed to fill the gearbox.
as soon as i selected all the gears and went back to P the engine started to go up and down in revs 800 - 1100 over and over also the guy i work with told me the gearbox hit a gear(wheels started moving) everytime the engine bounced in revs. but regardless we proceed filling the gearbox, as i put it into gear- wheels start moving i apply the brake and after 2minutes ich the engine stalls. Also restarting it was no problem(after keeping it up again for a bit).
So now i have no idea where to look. Did a sensor get damaged re fitting the engine? A feul damper or regulator? bad wiring? There is an overflow of things to chek and i dont know the 928 to well to pin point the problem(s?)
Details i might have forgotten: i removed airpump clogged the vacum unde the intake tho.
rebuild all of vacuum and used length according to cattalog. Also did the gearbox one since it actuly leakd might end up a bit shorter then used to tho.
and the thing of it bieng a younger engine so tripped over a few things like oil pressure sensor of the old car.
all the other parts i got whit the new engine i used those.
That about sums it up i think?
thanks in advance.
05-18-2015, 05:26 AM
#2
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First of all it sounds like your idle control valve under the inlet manifold may not be working for whatever reason.
I am a little puzzled by your description of the sequence of events- you say you started the engine, warmed it up and then changed the oil and filter- this seems a little strange- I would think after an engine rebuild you would have new oil and filter in place before you started up- please clarify.
You also say you ran the motor and then eventually you filled the gearbox with oil. I presume you have an automatic gearbox- [correct?]. Presumably this had the original oil in it and you changed the old for new- is that a correct synopsis of events?
The air pump is a bit of a non entity. As I am aware there are no significant differences between the 88 and 90 engines that would impact your change out [the earlier 87 model had a different fuel pressure regulator but not the 88 I believe] - doubtless others can/will comment if they know differently. There may be a slight difference in compression ratio?
Rgds
Fred
I am a little puzzled by your description of the sequence of events- you say you started the engine, warmed it up and then changed the oil and filter- this seems a little strange- I would think after an engine rebuild you would have new oil and filter in place before you started up- please clarify.
You also say you ran the motor and then eventually you filled the gearbox with oil. I presume you have an automatic gearbox- [correct?]. Presumably this had the original oil in it and you changed the old for new- is that a correct synopsis of events?
The air pump is a bit of a non entity. As I am aware there are no significant differences between the 88 and 90 engines that would impact your change out [the earlier 87 model had a different fuel pressure regulator but not the 88 I believe] - doubtless others can/will comment if they know differently. There may be a slight difference in compression ratio?
Rgds
Fred
05-18-2015, 05:59 AM
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When i got the engine it was enmpty so basicly new oil > first start > new oil again did this to remove any dirt or water that may or may not was inside the engine.
An automatic yes. I had to add some. it already was new but after disconecting the radiator there wasnt enough oil left inside.
The only major diffrence i heard about is that they started using gt pistons in 90' engine for a "treu" 10,0:1 compresion
An automatic yes. I had to add some. it already was new but after disconecting the radiator there wasnt enough oil left inside.
The only major diffrence i heard about is that they started using gt pistons in 90' engine for a "treu" 10,0:1 compresion
05-18-2015, 06:19 AM
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The 90 cylinder heads have more reinforcement over a couple of head bolts as earlier models had some tendency to crack.
What you say makes sense. Investigate the ISV as I advised you about in the initial post and check whether the contacts on the throttle position switch are working- both for idle and WOT [less important at this stage].
Do you have a set of wiring diagrams at your disposal? If the ISV is not working it defaults to a typical mid range position to support idle but of course does not work correctly for cold starts. You should also check the temp 2 sensor resistances for given temperatues- do you have that info?
Rgds
Fred
What you say makes sense. Investigate the ISV as I advised you about in the initial post and check whether the contacts on the throttle position switch are working- both for idle and WOT [less important at this stage].
Do you have a set of wiring diagrams at your disposal? If the ISV is not working it defaults to a typical mid range position to support idle but of course does not work correctly for cold starts. You should also check the temp 2 sensor resistances for given temperatues- do you have that info?
Rgds
Fred
05-18-2015, 06:38 AM
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Got all the wire diagrams yes.
i'll chek the temp 2 sesnsor since its still the old one.
the ISV seems hard to ge by, the intake manifold have to come off again i assume?
this wont have effect on my gearbox problem or does it?
Gz
i'll chek the temp 2 sesnsor since its still the old one.
the ISV seems hard to ge by, the intake manifold have to come off again i assume?
this wont have effect on my gearbox problem or does it?
Gz
05-18-2015, 07:32 AM
#6
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If you have to replace the ISV then the inlet manifold has to come off to get at it but let's try to find out first of all whether it is working [or not].
Check that the idle switch is working- see sht 10 of the 88 wiring diagram- field P81. One contact goes to pin 2 on the LH plug and the other to pin 3. The switch itself is located at the back of the inlet manifold next to the MAF. As you ease the throttle you should be able to hear the micro switch making/breaking contact. At idle I believe this contact should be made and it will track to earth. Whatever way round it is you should be able to detect the make or break in the circuit. This tells the computers that the ISV has to operate. /the other contact is for the WOT - this is a simple make or break contact arm and a soldered joint in the body is notorious for failing. Make sure the idle contact is working correctly. If the idle switch is not working it could be caused by the cable not being adjusted correctly [i.e. if the cable is a little too tight the contact is not made]. The throttle cable adjustment is critical in that there is very little room for error- too tight and idle does not work- too slack and you do not get the butterfly to the fully open position. If the idle contact does not work this can also be caused by incorrect setting of the idle switch position. This is held in place by two little screws and has to be set so that the slightest movement of the throttle plate makes or breaks the contact. Adjustment of this item at the very least needs the manifold lifted a few inches to be able to get at the screws if my memory serves me correctly.
After that make sure the ISV connector is made correctly. Without the correct tool this plug can be tricky to connect correctly- you think it is connected but in fact it is not- this is very difficult to get at or indeed to see. In situ testing of the ISV is possible but the procedure involves the use of an oscilloscope.
Rgds
Fred
Check that the idle switch is working- see sht 10 of the 88 wiring diagram- field P81. One contact goes to pin 2 on the LH plug and the other to pin 3. The switch itself is located at the back of the inlet manifold next to the MAF. As you ease the throttle you should be able to hear the micro switch making/breaking contact. At idle I believe this contact should be made and it will track to earth. Whatever way round it is you should be able to detect the make or break in the circuit. This tells the computers that the ISV has to operate. /the other contact is for the WOT - this is a simple make or break contact arm and a soldered joint in the body is notorious for failing. Make sure the idle contact is working correctly. If the idle switch is not working it could be caused by the cable not being adjusted correctly [i.e. if the cable is a little too tight the contact is not made]. The throttle cable adjustment is critical in that there is very little room for error- too tight and idle does not work- too slack and you do not get the butterfly to the fully open position. If the idle contact does not work this can also be caused by incorrect setting of the idle switch position. This is held in place by two little screws and has to be set so that the slightest movement of the throttle plate makes or breaks the contact. Adjustment of this item at the very least needs the manifold lifted a few inches to be able to get at the screws if my memory serves me correctly.
After that make sure the ISV connector is made correctly. Without the correct tool this plug can be tricky to connect correctly- you think it is connected but in fact it is not- this is very difficult to get at or indeed to see. In situ testing of the ISV is possible but the procedure involves the use of an oscilloscope.
Rgds
Fred
05-18-2015, 08:19 AM
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As soon as i'm back in my garage i'll you know if it worked.
as u mentiond ISV i went on a little research, and apparently its a sort of valve wich can get dirty.
the state of the inside of the manifold of wich this ISV came was properly dirty so i'm also think it could be jammed. But first i'll try your steps above. The removing of the intake is a real pain.
thanks alot for the detaild information!
i'll keep you upto date.
as u mentiond ISV i went on a little research, and apparently its a sort of valve wich can get dirty.
the state of the inside of the manifold of wich this ISV came was properly dirty so i'm also think it could be jammed. But first i'll try your steps above. The removing of the intake is a real pain.
thanks alot for the detaild information!
i'll keep you upto date.
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05-18-2015, 08:47 AM
#8
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The worst part about removing the manifold is the ISV connection if you do not have the correct tool. Nowadays I leave the circlip off the connector. I have purchased two connectors- one male one female to make an extension that can be undone outside the manifold.
I had a problem with my ISV many years ago and was told it needed replacing. I grabbed the bull by the horns- pulled the inlet manifold and removed the ISV. /it had effectively seized due to some kind of dry black powdery substance stuck in there [I expected oily gunge]. I cleaned the stuff out with a rag on the end of a wooden spoon handle and gradually the shuttle started to move freely. Squirted a bit of WD40 over the shuttle and then it moved freely, boxed it up and some 14 years later it is still working problem free.
There is a method to test the ISV in situ using an oscilloscope.
Regards
Fred
I had a problem with my ISV many years ago and was told it needed replacing. I grabbed the bull by the horns- pulled the inlet manifold and removed the ISV. /it had effectively seized due to some kind of dry black powdery substance stuck in there [I expected oily gunge]. I cleaned the stuff out with a rag on the end of a wooden spoon handle and gradually the shuttle started to move freely. Squirted a bit of WD40 over the shuttle and then it moved freely, boxed it up and some 14 years later it is still working problem free.
There is a method to test the ISV in situ using an oscilloscope.
Regards
Fred