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  #1  
Old 05-27-2004, 10:48 PM
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Cold and warm engine performance

Ok when i first start my svx I let it run for at leats 30 secs to get the oil flowing and then start on whatever journey i am on. The car seems to have great throttle response and has great acceleration, but when it gets warmed up, the car seems to be much more sluggish. I am reading codes for 2 knock sensors, could this be a link to my problem. Also as i was typing this i thought about my cone filter maybe just sucking hot air. Anyway when i was at the track , i was running 16.4 all night but i decided to disconnect my battery and try a run when i first started it after the batt was reconnected. I ran a 15.9 and i still think it should be running better. Anyway whats your advice??
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  #2  
Old 05-28-2004, 02:00 AM
deruvian
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When the engine is still cold, the ECU resorts to a preset air/fuel map . When the engine warms to its normal operating temperature, the ECU starts paying attention to the MAF and knock sensors and what-not in order to adjust the air/fuel ratio on the fly.

Your MAF sensor could be shot, giving the ECU false readings (or no readings, for that matter). If you are getting check engine codes for the knock sensors, then that is almost certainly your problem though. When the knock sensors notice detonation or start to go downhill, the engine will retard the timing in order to keep things safe for your engine internals.

This would explain why the car ran a little better after the ECU memory had been cleared... It hadn't yet decided on whether or not the knock sensors were bad.
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  #3  
Old 05-28-2004, 07:33 AM
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Search for time slip times and you will find lots of info about times. I agree, new knock sensors needed but it will not help your times.
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  #4  
Old 05-28-2004, 07:43 AM
red95svx
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The SVX really isn't a 1/4 mile car. It's too heavy and not geared for a jack-rabbit start. Don't feel bad though. There are some exotic cars that aren't that great at the 1/4 mile either. Instead these cars (like the SVX) are fast once they get going, which works out well on the highway!!



p.s. It's rare to have both knock sensors go bad at the same time. You are running at least 91 octane right?



Dave
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  #5  
Old 05-28-2004, 07:51 AM
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tomssvx, your engine is in a state known as 'safe mode' since your CE light is on due to the knock sensor error codes. I actually have the same thing happening with my SVX - I have 6 new spark plugs and 2 knock sensors that I'll be installing on June 5th which will fix the problem...

What deruvian mentioned about the ECU using a preset code when the engine is cold is correct. Drag racers have done this for years, that's why when you're waiting in the staging lanes at the track, you'll see several people with their engines off and hoods open.

FYI, 'safe mode' dials back timing and you lose about 20hp (from my understanding). Keeps things from getting ugly if detonation starts to occur...

-Chike
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  #6  
Old 05-28-2004, 10:14 PM
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i know the svx is not a drag racer so please don't lecture. Thank you for info on safe mode but if i were to get rid of the CEL it would remove the safety mode and run correctly right?? then that would help my engine performance. Also don't think im a rooky at the track, those cars with the popped hoods and engines off are really just trying to cool the enigne down, even a completely factory car will overheat easily if dragged a few times with the car running and hood closed in the staging lanes.
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  #7  
Old 05-28-2004, 10:16 PM
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Quote:
Originally posted by red95svx
The SVX really isn't a 1/4 mile car. It's too heavy and not geared for a jack-rabbit start. Don't feel bad though. There are some exotic cars that aren't that great at the 1/4 mile either. Instead these cars (like the SVX) are fast once they get going, which works out well on the highway!!



p.s. It's rare to have both knock sensors go bad at the same time. You are running at least 91 octane right?



Dave
I use NJ 93 point octane and the sensors were reading codes when i got the car. the previous owner really let the car go down hill. Now i am just trying to catch up w/ repairs. so far its been 2 02 sensors new front diff both wheel bearings and some other things that were never touched.
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  #8  
Old 05-29-2004, 07:15 AM
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Hey I don't think anyone was trying to lecture, just share their thoughts on the issue... I for one plan to drag race and AutoX my SVX, but I'm staying away from doing this until I take care of the needed maintenace on my car.

I don't think the drivers with popped hoods are trying to prevent their cars from overheating - although some may be. When I did that with my Lightning, it was to get my engine temp back down into the cold region before my next race. If I got to the starting line w/out my engine completely heated, I consistently ran 0.1s faster - and I didn't have a CE light on in my truck.

Anyway, a 15.9 in the 1/4 isn't bad at all for an SVX. I see no performance mods listed in your sig, are you still stock?

-Chike
Quote:
Originally posted by tomssvx
i know the svx is not a drag racer so please don't lecture. Thank you for info on safe mode but if i were to get rid of the CEL it would remove the safety mode and run correctly right?? then that would help my engine performance. Also don't think im a rooky at the track, those cars with the popped hoods and engines off are really just trying to cool the enigne down, even a completely factory car will overheat easily if dragged a few times with the car running and hood closed in the staging lanes.
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  #9  
Old 06-03-2004, 10:52 PM
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im still stock but u missed the most important part of my sig. fwd
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  #10  
Old 06-04-2004, 08:57 AM
tancred
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LOL, my car is wayyy faster when cold, which makes me feel bad because its not up to temp and i love it when its cold...SO much faster..
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  #11  
Old 06-04-2004, 09:17 AM
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FWD or not, 15.9 is not bad at all. FWD SVX's tend to be faster due to their lighter weight, but traction plays a bigger factor.

-Chike

P.S. Fix your knock sensors and I'm sure you'll be running mid 15's or faster (with good traction).
Quote:
Originally posted by tomssvx
im still stock but u missed the most important part of my sig. fwd
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Last edited by Chiketkd; 06-04-2004 at 09:24 AM.
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  #12  
Old 06-04-2004, 09:21 AM
tancred
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Its called ICE get a big ass bag put it on your CAI and let it just sit there in between runs....works best with used with Nitrous...
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  #13  
Old 06-07-2004, 06:55 PM
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ice is not the best idea on a hot engine. Could cause craking or warping in the aluminium. Just a heads up. New knock sensors on the way and also the fwd had a 3.70 final drive so that also adds to the 1/4 mile time.
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  #14  
Old 06-07-2004, 07:46 PM
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Tom,

How many miles are on your SVX? The knock sesnors may be causing the CE light, but the problem may be a miss-firing spark plug... I changed out my spark plugs and the right knock sensor this weekend - and I honestly felt the problem was with an old spark plug.

FYI - the factory plugs are good for about 100K miles. If the previous owner did limited maintenance, then the spark plugs may be the original ones.

The 3.70 gears in the FWD models are good for acceleration, but can make traction off the line that much more difficult. I'm sure you'll run a much faster 1/4 mile time when your CE light is off.

Good luck!

-Chike
Quote:
Originally posted by tomssvx
ice is not the best idea on a hot engine. Could cause craking or warping in the aluminium. Just a heads up. New knock sensors on the way and also the fwd had a 3.70 final drive so that also adds to the 1/4 mile time.
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