86 S4 NA - cold start idle issue
#1
86 S4 NA - cold start idle issue
Just rebuilt the engine, prior to the rebuild it didnt have the issue... I'm not sure where to look. First order of business, I can start the car and sometimes it'll idle up to 3000 RPM, other times it wont. how do I resolve that?
Second, on a cold start regardless if it idles up or not, once it tries to drop down it sputters and stalls. I can take a video if it would help. I hear no vacuum leaks indicating thats the issue. The car holds a wonderful 7-800 RPM idle after about 5-10 seconds of tapping the throttle lightly.
Second, on a cold start regardless if it idles up or not, once it tries to drop down it sputters and stalls. I can take a video if it would help. I hear no vacuum leaks indicating thats the issue. The car holds a wonderful 7-800 RPM idle after about 5-10 seconds of tapping the throttle lightly.
Last edited by driftxsequence; 05-08-15 at 11:39 AM.
#2
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iTrader: (1)
3000rpm start up is normal when cold. I believe it won't do it in (EDIT) *GEAR*. It's pard of the AWS (accelerated warmup system). The ecu applies a sidnal to a relay to the air bypass valve. (Not the same as the BAC valve, which maintains idle as load varies on idle)
See if ur AFM is plugged in. If it is, jumper the yellow fuel check connector nearby and see if it now stays running.
See if ur AFM is plugged in. If it is, jumper the yellow fuel check connector nearby and see if it now stays running.
#4
Moderator
iTrader: (1)
Some will set the idle higher than normal on a rebuild until the engine builds enough compression.
The 3000 rpm cold start is based also on what the temp switch at the bottom of the radiator reads. If the coolant is below a certain temp then the high idle rev won't initiate, if above it will.
The 3000 rpm cold start is based also on what the temp switch at the bottom of the radiator reads. If the coolant is below a certain temp then the high idle rev won't initiate, if above it will.
Last edited by satch; 05-08-15 at 12:46 PM.
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#9
I have tested with my rotary diagnostics test and pulled 95 psi on the front rotor and 100 psi on the rear.
I had a recommendation to check the coolant sensor behind the waterpump. If that has a poor connection it defaults to the engine reading "normal temp" and in turn means less fuel is being injected.
I did come across something the other day saying idle issues tend to be more pronounced with lightweight flywheels. I do have a lightweight flywheel, whereas I had a stock one before being rebuilt.
I had a recommendation to check the coolant sensor behind the waterpump. If that has a poor connection it defaults to the engine reading "normal temp" and in turn means less fuel is being injected.
I did come across something the other day saying idle issues tend to be more pronounced with lightweight flywheels. I do have a lightweight flywheel, whereas I had a stock one before being rebuilt.
#10
about 4000 miles on the engine. still starts and dies. sometimes on warm starts the idle hunts like the TPS is off (probably is since I adjusted it a tiny bit) but that shouldnt cause it to start and die like in the video....
Anyone else have any ideas? Coolant temp sensor maybe? I had someone mention if the sensor is bad or not making a good connection it'll operate as if its always warmed up - and in this case that would kinda make sense since its lean on cold starts.
Anyone else have any ideas? Coolant temp sensor maybe? I had someone mention if the sensor is bad or not making a good connection it'll operate as if its always warmed up - and in this case that would kinda make sense since its lean on cold starts.
#12
Theoretical Tinkerer
iTrader: (41)
Do you still have it installed and adjusted correctly?
My car does exactly the same thing as you describe above. But that is because the thermowax puked all over itself. FYI, the wax is pink.
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ncds_fc
New Member RX-7 Technical
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08-15-15 10:06 AM