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98 Protege 1.5L 5 Speed Man Fluctuating Idle RPMs



 
 
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  #1  
Old September 11th 05, 08:21 PM
rljt60
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Default 98 Protege 1.5L 5 Speed Man Fluctuating Idle RPMs

The 1.5L I just replaced ran fine but had loose rod bearing. There was no
RPM problem. The newly installed engine came with everything attached
(intake/exhaust manifolds, sensors, etc). Now at cold start-up the engine
revs to 1000 RPM and shortly later idles down to 750 RPM. Turn on the A/C
and it stays at 750 RPM. However, later when the engine is hot the RPMs
get screwy.

With clutch in or out it can fluctuate between 1000 & 1250 regardless of
A/C. Or it will stay at 1750 without A/C and drop to 1250 with A/C on.
Or it will sit at 750 regardless of A/C. Punching the accelerator will
result in it staying the same or changing to any of the other
combinations.

I pulled the new engines throttle body front end with all sensors and
valves and replaced it with the old engines front end, sensors and valves
since that unit had worked previously. There is no change. I cannot find
any vacuum leaks. I did not touch the idle speed adjust screw on top of
either front end. Is that really the idle speed adjustment screw?

I set the timing per the Haynes manual which says to put a jumper between
the TEN and GRND terminals on the test connector and set to 10 degrees
BTC. I noted that the jumper had no effect other than disabling the dash
tach to zero. Pulled the jumper and the timing did not change. Was I
supposed to see a change?

When it is warm it seems it does not get a good "power curve" feel in any
gear until 2000 rpm regardless of the amount of gas given. It feels heavy
or straining below that 2000 rpm. Is that to be expected with the 1.5L
w/5speed manual?

Is there another way I should be setting the timing (the jumper issue)?

How far should the accelerator cable wheel's tang be off of the TAS screw?
Or should it rest against the screw? I think I have heard that the TAS
screw cannot be adjusted by a layman but if I am wrong, how do I check it
or properly adjust it?

Are there any ideas for me to get this thing working right? I appreciate
any help I can get. Bill


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  #2  
Old September 11th 05, 11:56 PM
Leon van Dommelen
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Default

"rljt60" > wrote:

>The 1.5L I just replaced ran fine but had loose rod bearing. There was no
>RPM problem. The newly installed engine came with everything attached
>(intake/exhaust manifolds, sensors, etc). Now at cold start-up the engine
>revs to 1000 RPM and shortly later idles down to 750 RPM. Turn on the A/C
>and it stays at 750 RPM. However, later when the engine is hot the RPMs
>get screwy.
>
>With clutch in or out it can fluctuate between 1000 & 1250 regardless of
>A/C. Or it will stay at 1750 without A/C and drop to 1250 with A/C on.
>Or it will sit at 750 regardless of A/C. Punching the accelerator will
>result in it staying the same or changing to any of the other
>combinations.
>
>I pulled the new engines throttle body front end with all sensors and
>valves and replaced it with the old engines front end, sensors and valves
>since that unit had worked previously. There is no change. I cannot find
>any vacuum leaks.


I know from experience that the intake vacuum at idle beyond the throttle is
very strong. It does not take much to produce a leak that messes up idle.
Apparently, you can listen for it with a stethoscope. I have one but it did
not seem to work well for me when I tried.

> I did not touch the idle speed adjust screw on top of
>either front end. Is that really the idle speed adjustment screw?


Hard to tell without a Protege manual. In any case, why would it be messed
up on both ends? And why would the idle not be consistently too low/too
high if it was?

>I set the timing per the Haynes manual which says to put a jumper between
>the TEN and GRND terminals on the test connector and set to 10 degrees
>BTC. I noted that the jumper had no effect other than disabling the dash
>tach to zero. Pulled the jumper and the timing did not change. Was I
>supposed to see a change?


Probably not. The jumper is to keep the ECM from messing around with
the timing, for example telling it not to advance timing when rpm goes up.
But at least on the Miata, the ECM does not make much changes in timing
as long as the car is idling normally. I know that I did not see a change
on my Miata when I removed it.

>When it is warm it seems it does not get a good "power curve" feel in any
>gear until 2000 rpm regardless of the amount of gas given. It feels heavy
>or straining below that 2000 rpm. Is that to be expected with the 1.5L
>w/5speed manual?
>
>Is there another way I should be setting the timing (the jumper issue)?


Not if Mazda tells you to connect 10 to GND, as it does on the Miata.
Did you check that TDC is really top dead center for the #1 piston?

Unless you did what I did, (not set the timing adjustment to zero
on my Sears timing gun), I would think your timing should be OK.

>How far should the accelerator cable wheel's tang be off of the TAS screw?
> Or should it rest against the screw? I think I have heard that the TAS
>screw cannot be adjusted by a layman but if I am wrong, how do I check it
>or properly adjust it?


I believe the throttle cable should have a very small amount of slack
when the throttle is not depressed, and obviously the actual amount
of slack is then not going to make a difference for idle.

>Are there any ideas for me to get this thing working right? I appreciate
>any help I can get. Bill


Give it a few days, you may get more responses in due time.

Leon
--
Leon van Dommelen Bozo, the White 96 Sebring Miata .)
http://www.dommelen.net/miata
EXIT THE INTERSTATES (Jamie Jensen)
  #3  
Old September 12th 05, 12:45 AM
rljt60
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Thanks for the input Leon. the vacuum lines, I will replace all lines
on the throttle body tomorrow. And yes, TDC is true. And the cable calls
for 3/32" or so slack and that is where I have it with the tang against the
TAS plus I have tried slightly tighter and looser with no real change until
if just a tad too tight it really revs up fast. I'll let you know if any
change based on your input. Again, Thanks. Bill

 




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