Ok, this is my last attempt at fixing the svt. Then off to a mechanic. So far...replaced the iac and pcv. This is exactly what happens. First start the car up, idles around 1k, then falls to 750, then drops to 400 and stays there. Then i start driving. First stop light, she drops right to 500, then to about 250, catches itself and shoots back up to 500, then down and stalls out. This happens 60% of the time. Now if I turn the defrost of a/c on, it idles around 750 for a longer time, but then drops to 500 and stays there. No bouncing under 500. What the hell could be wrong? Could it be the fact it hasn't been tuned up in a while? Could bad o2 censors cause this since i'm pulling some codes that has to do with a lean a/f on the upstream sensors? Maybe a fuel pump problem? Could it have to do with the gaskets on the uim and lim? Or plugs? I need this fixed asap and have all of today to fool around with it and get it running like its supposed to. Any help would be great. Thanks guys.
All of the mods done so far performance wise is gutted pre cats. No codes have to do with the o2 sensors below the cats. Also, the ru-3530(think thats the number) home made intake. What else should I check? Thanks.
Brian
Throttle position sensor!
I've had the intake on for over 8 months now with no problems before. You think the tps sensor could be the problem? Any way to check it before replacing? I hate buying parts that don't fix the problem. Already spent 150 parts wise with no fix yet. I'm going to do the intake manifold rebuild today, and replace the fuel filter which hasn't been changed in who knows how long (its a 98). Also going to replace spark plugs.
I don't have my car out front, but there should be a throttle stop screw somewhere. With a different intake manifold, you are changing the breathing characteristics of the engine. The IAC should adapt for this, but perhaps the computer is confused with the new intake, and it has taken a while for the computer to adapt. Try disconnecting the battery for 5 minutes, reconnect, restart, and see if that fixes it.
If it comes back right away, or after a few hundred miles, try adjusting that throttle stop screw. Also check the TPS as another suggested. Other possibilities include the Air Charge Temp sensor and Coolant Temp Sensor (make sure to get the one that goes to the PCM, not the instrument cluster).
From my Service CD
Unique Idle Concerns Low/Slow Idle
Stalls/Quits Deceleration
Vacum lines, IAC Connections,Air filter (restricted) Air intake tubes (leaks, restrictions),
Fuel quality-octane or contaminated, Proper seating of intake manifold and
components - IAC, EGR, Electrical connections, Ignition wiring.
TPS testing
TP sensor disconnected.
Key on, engine off.
Measure voltage between VREF circuit and SIG RTN circuit at the TP sensor vehicle harness connector.
Is the voltage between 4.0 and 6.0 volts?
Ok, I replaced the upstream o2 sensor. Ran great for about 10 minutes, then the idling problem came back. The codes were clear, but that was before the crappy idling came back, and my cel light is burned out. So who knows if it came on again. Further details about whats going on are in this post made my me earlier.
Bad Idling
I have a 95 Contour 2.5L atx. When engine is cold, when I started it and put it into gear the car would almost stall and then the idle speed would eventually come back up. When car is warm I have no problems.
Replaced the throttle position sensor and the car now runs perfect.
Bob
I don't know if this helps you at all, but I have a 98 SVT and my cel light used to come on all the time, and my car would struggle when idling randomly (this would happen prob once every 3 months). I couldn't figure out what it was, but after about 9 months i realized that this always happened right before i changed my oil. Everytime i got my oil changed at 3k miles, the problems instantly went away until about 2700 after that oil change. So i guess my advice to you is, try changing your oil if you havn't done so in a while.