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Discussion Starter · #1 ·
Hello all.

I am the (almost proud) owner of a '04 24V Probe (KLDE engine). I have been restoring it fully for nearly 2 years.

The engine runs almost fine, and it has the max power it should, runs beautifully above 3000 rpm or so, but it is still a bit uncomfortable to drive in the city, because it shakes quite a bit when gently pushing/releasing throttle.

It also stumbles or hesitates a bit when hard accelerating at low revs, more during the first, colder, minutes, but this is not as annoying.

I have replaced EVERYTHING: spark plugs, wires, distributor, cap, rotor, fuel injectors, all the required VRIS, EGR valves, etc. so NO CODES are thrown by now, and in fact it passes MOT with very low CO emissions. I also measured fuel pressure, replaced exhaust pipes, cat and lambdas.... nearly half of the car is new at this point.

I have also checked the TPS and MAF sensors with an oscilloscope looking for signs of glitches, but they don't show anything strange.

I also checked timing belt and everything is perfectlyl in sync. I re-adjusted my timing a bit earlier (13ºBTDC) than nominal 10 because that seems to improve stumble at low revs/high loads.

Another symptom is that, after, say 30 min, the car starts bad, it turns but takes a while to start (like 2-3 seconds). If, after stopping it, I restart sooner (within minutes), no problem. Also, if I let it sit overnight, it starts perfect next time.

Do you think that messing around with the throttle cable tension or the idle screw can affect this? How would you continue?

Thanks for your support!
 

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Coolant temp sensor ? If the coolant temperature sensor goes bad it can send a false signal to the computer and throw off the fuel and timing calculations.
 

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Discussion Starter · #3 ·
A lot of thanks for your swift answer,.
Well, that makes a lot of sense, but I have a bit of confusion there: my car seems to have two temp. sensors, one is simply a switch for the fan/s (near the top filling neck on the engine), while the other, very close to that one, goes to the ECU and also to the instrument cluster as I understand (I know this varies from year to year, mine is a '94).
In case that the coolant sensor was bad as you suggest, wouldn't I get wrong readings in the instrument cluster? I get consistently good readings, it is down when the engine is cold and rises slowly to the middle, so I assume the sensor that goes to the instrument cluster is ok.

Also, I have higher idle when cold (but that may be the effect of the mechanical idle controller in the throttle body: from what I have read in the workshop manual, there is a coolant line passing through it used to melt a wax-controlled idle passage).
 

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Discussion Starter · #4 ·
Update to my previous post: there is a specific code (09) for the coolant temp sensor. I remember that I once disconnected my sensor and it triggered that code, so I assume it is ok. Maybe it is reading not too accurately even in that case?
 

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Discussion Starter · #5 ·
Second update (sorry): I have noticed that, sometimes, when I turn off the engine, even if it is not too hot, returning the key to pos 1 triggers the fan ON. This happens also with a cold engine, sometimes. ¿?
 

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The fan can cut on in ignition position if air con on ? Could always test the sensor operation . If timing set up correctly , should not need to adjust / advance ?


 

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Discussion Starter · #7 ·
Thanks.
The fan cuts in sometimes, no matter if the AC/ is on or off (it is usually off).
As for the temp. sensor operation, yes, it's simply a NTC, and I think I already tested it, but the symptoms my car has are compatible with a bad temperature reading. However, no codes.
I made a mistake: my car has two sensors, one with a single terminal is used by the instrument cluster only, and the other is read by the PCM to adjust engine operation and to trigger fan/s. The first one is obviously ok, I think I will try and replace the other, or simply replace it by a resistor of the nominal value for 80ºC (250 ohm approx according to the test procedures manual), and see if it runs perfect when warm.
 

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Discussion Starter · #8 ·
Well, some updates...
I replaced my ECT sensor with a fixed resistor which value corresponds to engine at operating temperature.
When I started this morning, idle was normal (not accelerated, what confirms that the PCM is reading that the engine is at operating temperature. The problem is that it is impossible to drive it, it stalls as soon as I touch throttle. So I guess that my sensor shouldn't be too bad. I had to reconnect it to be able to take my car out of the garage this morning.
I will try putting the resistor again when it is hot and check how it drives. Maybe my sensor is not totally bad but it's not reporting the exact actual temperature.

The hiccup when at very light throttle annoys me a lot. Pedal response is not linear at all. Any ideas?
 

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Check this out and the links at the bottom also . Note the mention of the fan kicking in
( Observe that as we move the sensor in one direction, there comes a point where activates the radiator fans. We leave the TPS sensor at a point close to the location where the fans are activated (but remain off).

 

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Discussion Starter · #10 ·
Thanks, I have done that procedure several times, I even used the feeler gauges mentioned in the manual to check that the fans are activated with 0.5mm opening but not with 0.15mm.
However, yesterday I noticed that sometimes I have to pull by throttle pedal up to make idle go to the nominal rpm (it is not enough to just let the gas off), meaning that perhaps my throttle cable was a bit too tight, not always letting the butterfly close completely. I readjusted it and made it looser. Will check if it runs better now, but I have fiddled with all this in the past so I am not very confident.
Also, I think that the idle screw has a role on all this. I adjusted it to just have around 600 rpm when hot and gas off (and also when hot in the test mode) but...
 

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Hello all.

I am the (almost proud) owner of a '04 24V Probe (KLDE engine). I have been restoring it fully for nearly 2 years.

The engine runs almost fine, and it has the max power it should, runs beautifully above 3000 rpm or so, but it is still a bit uncomfortable to drive in the city, because it shakes quite a bit when gently pushing/releasing throttle.

It also stumbles or hesitates a bit when hard accelerating at low revs, more during the first, colder, minutes, but this is not as annoying.

I have replaced EVERYTHING: spark plugs, wires, distributor, cap, rotor, fuel injectors, all the required VRIS, EGR valves, etc. so NO CODES are thrown by now, and in fact it passes MOT with very low CO emissions. I also measured fuel pressure, replaced exhaust pipes, cat and lambdas.... nearly half of the car is new at this point.

I have also checked the TPS and MAF sensors with an oscilloscope looking for signs of glitches, but they don't show anything strange.

I also checked timing belt and everything is perfectlyl in sync. I re-adjusted my timing a bit earlier (13ºBTDC) than nominal 10 because that seems to improve stumble at low revs/high loads.

Another symptom is that, after, say 30 min, the car starts bad, it turns but takes a while to start (like 2-3 seconds). If, after stopping it, I restart sooner (within minutes), no problem. Also, if I let it sit overnight, it starts perfect next time.

Do you think that messing around with the throttle cable tension or the idle screw can affect this? How would you continue?

Thanks for your support!
You should also check the oxygen sensor.
 

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Discussion Starter · #12 ·
When I bought it approx 5.000km ago, I had inversion errors for both oxygen sensors, so I replaced them with Denso new ones, and no errors since them, so I assume they are ok and operating.
It is like if the changeover from closed-loop to open-loop was not clean or something ¿?
 

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You are assuming that the ECT will fail as go-no go. The ECT can go wrong in several ways. It works by the change in resistance with the change in temperature. I personally don't know the numbers for an automobile, but I work with similar sensors in the HVAC industry. They can internally short, ground, or corrode causing resistance to be much higher or lower than what it should, The can even swing radically making it appear as a loose wire. To confirm it's condition, you should find out what it is sending as a signal to the PCM. Knowing the resistance (or voltage drop, which is what the PCM actually reads) is not necessary if you have reader that can feed you live data. See if the temperature going to the PCM makes sense.
 

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Discussion Starter · #14 ·
Thanks, CatSkinner.
Yes, I know that the ECT is a NTC (I am an electronics engineer) and that they may fail in different ways. However, I have tested its resistance at ambient temperature (25ºC approx) and at full warm engine temperature, and the values are quite close to the specifications in the manual (around 200 ohm for normal operating temperature), so even if it is not performing exactly as per its nominal curve, at least it should run perfect at operating temperature provided that this would be the problem, so I am starting to discard it (although, due to its low cost, I may end up replacing it).
 

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Good to know. Most don't realize how the thing works. You also said this:
Also, I have higher idle when cold (but that may be the effect of the mechanical idle controller in the throttle body: from what I have read in the workshop manual, there is a coolant line passing through it used to melt a wax-controlled idle passage).
. Have you tested the IAC? Unless you screw in the base idle further than it's capacity, the idle screw will no longer be a factor once the engine is running. It doesn't directly fit all of your symptoms, but it directly fits some. It's a start.

 

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Discussion Starter · #16 ·
Thanks, Catskinner.
I assume the IAC valve is ok since idle is ok and it is a bit higher when the engine is cold. Also, there my car doesn't throw error codes for the IAC valve. Anyway, what other tests can I perform on it?
 

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I would confirm 0° TDC is actually top dead center for #1. I've seen harmonic balancers be off a few degrees, especially if anyone has taken them off. Also, compression test, it's a 94. Timing belt, any idea when it was replaced, they're supposed to be good for 100,000 miles, but I often see them go early. Lastly, outside the box, what are the odds it's not a stock cam?
 

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I would confirm 0° TDC is actually top dead center for #1. I've seen harmonic balancers be off a few degrees, especially if anyone has taken them off. Also, compression test, it's a 94. Timing belt, any idea when it was replaced, they're supposed to be good for 100,000 miles, but I often see them go early. Lastly, outside the box, what are the odds it's not a stock cam?
As suggested earlier in the thread , if set up correctly there should have been no need to advance settings from specs . to get it to run better .
 

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Discussion Starter · #19 ·
Thanks both for your ideas and time!
I checked for proper timing belt alignment when I bought it (in fact, one of the cams was retarded by two teeth). So I had it corrected and now it's perfect (checked all the alignment marks, etc).
I didn't know that the crankshaft pulley could be off by a few degrees from cyl. 1 TDC, they are keyed so I assumed that it can't be assembled wrong ¿?
In any case, checking that is not a difficult test to do so I will...

As for compression, I measured it with a cheap compression meter and got 12 bars on the front cylinders (2, 4, 6) and 10 on the rears (1, 3, 5). But I think that the difference was due to the fact that I couldn't press on the gauge properly when measuring at the back and I had to use a hand-tightened rubber extension tube that screws on the spark plug holes. So I re-measeured one of the front cylinders with this same method and then I also got 10 instead of 12 bars, so I assume that all of them actually measure around 12. which is ok.

I re-adjusted throttle cable as I mentioned and I also re-calibrated throttle idle sensor using 0.15 and 0.5mm gauges as per the manual, let's see if that improves hiccuping a bit.
 
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