redfish0 Posted May 18, 2005 Share Posted May 18, 2005 I have a 99 gs300 with 112k on it. Best car I have ever owned and I have had no propblems until now. I recently had maintenence performend on my car to include timing belt, serpentine belt, oil/filter, air filter, plugs, transmission fluid, etc. It ran great before but now there is an issue when I drive through the 40-50mph range. At about 40 mph if I try to accelerate gently the car coughs and hestitates and almost shakes. Once I get to 50 mph all is well. If I accelerate vigorously between 40-50 mph I have no problems, just gentle acceleration, like after I coast through a toll plaza causes a problem. Curiously my mpg has gone down as well since the service was performed. App. 415 miles per tank and now about 350. Any thoughts? I disconnected the battery overnight to reset the computer which was ineffective. Any thoughts? I thank you all in advance. Quote Link to comment Share on other sites More sharing options...
TurboGS300 Posted May 18, 2005 Share Posted May 18, 2005 Check TPS, O2 sensors(as it's about time to replace them). Also run a can of seafoam throught the fuel tank and through the vacuum line for the throttlebody. <_< Also check the coolant temp sensor for the ECU. Quote Link to comment Share on other sites More sharing options...
ColinBarber Posted May 18, 2005 Share Posted May 18, 2005 What plugs were used? Quote Link to comment Share on other sites More sharing options...
redfish0 Posted May 18, 2005 Author Share Posted May 18, 2005 Check TPS, O2 sensors(as it's about time to replace them). Also run a can of seafoam throught the fuel tank and through the vacuum line for the throttlebody. <_< Also check the coolant temp sensor for the ECU. ← I used plugs from autozone. they were platinum dual post bosch 2. Should I have used others? Quote Link to comment Share on other sites More sharing options...
redfish0 Posted May 18, 2005 Author Share Posted May 18, 2005 I have a 99 gs300 with 112k on it. Best car I have ever owned and I have had no propblems until now. I recently had maintenence performend on my car to include timing belt, serpentine belt, oil/filter, air filter, plugs, transmission fluid, etc. It ran great before but now there is an issue when I drive through the 40-50mph range. At about 40 mph if I try to accelerate gently the car coughs and hestitates and almost shakes. Once I get to 50 mph all is well. If I accelerate vigorously between 40-50 mph I have no problems, just gentle acceleration, like after I coast through a toll plaza causes a problem. Curiously my mpg has gone down as well since the service was performed. App. 415 miles per tank and now about 350. Any thoughts? I disconnected the battery overnight to reset the computer which was ineffective. Any thoughts? I thank you all in advance. ← since I am a neophyte, pleae tell me what the TPS is and I will check it. Quote Link to comment Share on other sites More sharing options...
Lexusfreak Posted May 18, 2005 Share Posted May 18, 2005 Check TPS, O2 sensors(as it's about time to replace them). Also run a can of seafoam throught the fuel tank and through the vacuum line for the throttlebody. <_< Also check the coolant temp sensor for the ECU. ← I used plugs from autozone. they were platinum dual post bosch 2. Should I have used others? ← I would have stayed clear of Bosch plugs personally & used either NGK or Denso platinums or iridums. The Bosch plugs are certinaly not helping things here. B) Quote Link to comment Share on other sites More sharing options...
TurboGS300 Posted May 18, 2005 Share Posted May 18, 2005 TPS is Throttle position sensor! Irridiuns are the way to go in plugs, however the boschs will work as long as they are cross referenced to OEM. I don't think the plugs are your problem, unless they are too cold a plug. Quote Link to comment Share on other sites More sharing options...
redfish0 Posted May 20, 2005 Author Share Posted May 20, 2005 Thanks Turbo. I will give it a shot and see if it helps. Is there a computer I could it up to in order to find out exaxctly what is wrong? Quote Link to comment Share on other sites More sharing options...
TurboGS300 Posted May 20, 2005 Share Posted May 20, 2005 Yes, the dealership or any good repair shop should have one. <_< Quote Link to comment Share on other sites More sharing options...
chuckb Posted May 20, 2005 Share Posted May 20, 2005 I'll bet it's your new plugs. I've heard of the same thing happening when oem iridium plugs aren't used. I would first put oem ngk or nd plugs in and see what happens. Quote Link to comment Share on other sites More sharing options...
redfish0 Posted May 23, 2005 Author Share Posted May 23, 2005 i have noticed one additional feature of this problem. I want to share it with you all who are knowedgable and see if it sheds further light for diagnostic purposes. I noticed that the first 10 minutes after strting the cold engine the engine does not cough or hesitate during the 40-50 mph range. After 10 minutes or so the problem surfaces and stays that way the rest of the day. Perhaps it is the plugs and I will start there. Any other thoughts with this new info? Quote Link to comment Share on other sites More sharing options...
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