cold start rev

[akcc]

during cold starts, my camry xle v6 1999 revs at 1.8k-2k rev on cold starts, is that normal? my brother's camry le 4 cyl 1999 revs at 1.2k-1.3k and drops down to 1 after 1 minute where as mine drops after 3 minutes, is that normal for my camry to do something like this?

[fenixus]

1mz-fe are known to rev higher at cold starts. my '02 1mz does exact same thing, even at 60F at cold start the initial revs shoot up to 1,600-1,800rpm while 5s-fe at same temperatures does only 1,200rpm tops under same conditions.

both cars have new ECT for EFI sensors and proper idle speed once warmed up (no IAC valve problems).

it's normal.

[akcc]

alright, thanks, i wasn't sure because i saw many other camry's and they didn't rev as high as my car during cold starts so i got a bit worried.

[fenixus]

well, usually you see cars (1mz) being re-started after some driving (warm start), and it no longer does that then.
it's happening only when you start it dead cold, cold start being defined as starting the car after it's been sitting for at least 8 hours.

There must be some threshold coolant temperature after passing which ECU no longer commands it to rev as high (on start) as it would when car was dead cold.

Originally Posted by akcc

alright, thanks, i wasn't sure because i saw many other camry's and they didn't rev as high as my car during cold starts so i got a bit worried.

[akcc]

actually, it was same camry same conditions, because my friends own camrys from 1998 to 2001 and they all have different revs with similar mileage as me and it was left to sit after a day, this wasn't just once or twice, its all time. but regardless of that, i am glad to hear that it is normal.

[fenixus]

likely he's got a different ECU with different programming. even same year/model of car have multiple sub-models (emissions, immobilizer, trim dependent, transmission, engine, etc.) and different ECU can behave differently.

even updated software (e.g. from later year which still matches) on ECU for same exact model/year/specs can be totally different. have seen that with wife's car ECU (factory vs replacement from later year).

[pmesfun]

Look into doing this.

http://www.automotiveforums.com/vbul....php?t=1014511

[fenixus]

higher engine revs at cold start are there for a reason. sticking a fake resistance reading into that circuit to lower the initial RPM will only make the warm up process longer (running RICHer until warmed up).

I wouldn't dare messing with ECT feed for ECU, it's one of primary inputs, it can screw up engine real bad if things go wrong ...

Originally Posted by pmesfun

Look into doing this.

http://www.automotiveforums.com/vbul....php?t=1014511

[pmesfun]

Originally Posted by fenixus

higher engine revs at cold start are there for a reason. sticking a fake resistance reading into that circuit to lower the initial RPM will only make the warm up process longer (running RICHer until warmed up).

I wouldn't dare messing with ECT feed for ECU, it's one of primary inputs, it can screw up engine real bad if things go wrong ...

Wouldn't the ECU send less fuel?

[fenixus]

yeah, actually it could send less fuel than needed during warm up phase. however this is not based only on ECT for EFI readings. ECU relies also on AFR/oxygen sensors readings, so it's hard to say what it would do.

anyways, cheating on coolant temperature during warm up can't be good in a long run.

I don't care about higher engine revs when car is cold. it's there to help it warm up faster and become more efficient faster than with a "mod" (it's a poor idea to mod that thing).
with this mod on the car will be warming up god knows for how long and what's worse ECU will think the car IS already warmed up, so it will switch to commands for a fully warmed up car (different patterns and fuel maps and trans shift points than when cold).

IMHO, that mod is asking for trouble.

Originally Posted by pmesfun

Wouldn't the ECU send less fuel?

[pmesfun]

Originally Posted by fenixus

yeah, actually it could send less fuel than needed during warm up phase. however this is not based only on ECT for EFI readings. ECU relies also on AFR/oxygen sensors readings, so it's hard to say what it would do.

anyways, cheating on coolant temperature during warm up can't be good in a long run.

I don't care about higher engine revs when car is cold. it's there to help it warm up faster and become more efficient faster than with a "mod" (it's a poor idea to mod that thing).
with this mod on the car will be warming up god knows for how long and what's worse ECU will think the car IS already warmed up, so it will switch to commands for a fully warmed up car (different patterns and fuel maps and trans shift points than when cold).

IMHO, that mod is asking for trouble.

I will like the shifts points to be normal, that is so annoying. I know my friend's ES300 has regular shifts points at cold temperature so it shouldn't harm anything.

So in summary, the ecu will think the engine is warmer than it actually is. All settings will adjust to what they would be at temperature. I never let the car warm up, just get in, choose a song on my iPod, turn on A/C if needed and GO. I might try this after asking the user if any negative effects has happened since then.

[fenixus]

choice is yours. only thing that ECU will think car IS ALREADY warmed up (around 250ohm on ECT sensor on average) while it will be still stone cold (normally up to 5-12K ohm on ECT sensor depending on climate/weather conditions) ...

Originally Posted by pmesfun

I will like the shifts points to be normal, that is so annoying. I know my friend's ES300 has regular shifts points at cold temperature so it shouldn't harm anything.

So in summary, the ecu will think the engine is warmer than it actually is. All settings will adjust to what they would be at temperature. I never let the car warm up, just get in, choose a song on my iPod, turn on A/C if needed and GO. I might try this after asking the user if any negative effects has happened since then.

[pmesfun]

Originally Posted by fenixus

choice is yours. only thing that ECU will think car IS ALREADY warmed up (around 250ohm on ECT sensor on average) while it will be still stone cold (normally up to 5-12K ohm on ECT sensor depending on climate/weather conditions) ...

Is that a bad thing? Texas is always hot.

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