ringting Posted June 11, 2012 Report Share Posted June 11, 2012 Request for wisdom on possible root causes of poor performance when driving uphill BACKGROUND Daily drive is 100 miles round trip in Southern California, eastbound in morning & westbound in afternoon. Travel time is 50 minutes in morning and 60-65 minutes in afternoon. Issue has developed over last 3-4 weeks. Up to now the car had strong acceleration and good gas mileage of 21-23 mpg. Basic tune-up has been done, vacuum lines replaced, small leak in rad and temperature keeps hitting 225 when in slow moving heavy traffic so I pull heat (DS fan seen working). Purchased car a year ago when odometer read 61,000, now it reads 81,000. First owner was elderly lady driving vehicle roughly 120 miles per month. PROBLEM Roughly 35-37 miles into drive home, engine temp is around 150, speed has been 65-70 for at least 15 minutes. Experience some delayed/sluggish acceleration in morning. Road Condition: 2.5 mile uphill with roughly 5 degree grade Toll road so surface well maintained Vehicle Performance: Loss of speed Engine surges Transmission alternates between 3rdand 4th gears Throttle held wide open Engine: 3.8L (Vin L), Option Code is L27 Transaxle: 4T60-E, Option Code is M13 I own 1994 BuickRegal Service Manuals, Volume 1 and Volume 2 I do NOT own a scan tool so open to suggestions on what to buy I am a basic weekend mechanic with manual tools CURRENT THOUGHTS 1) Vacuum Leak 2) Fuel Pump 3) Fuel Filter 4) Fuel Regulator 5) Something in Transmission 6) Need to spend more time reading manual Quote Link to comment Share on other sites More sharing options...
AL Posted June 11, 2012 Report Share Posted June 11, 2012 Could also be a coil pack that is weak under load... A clogged cat could be the case as well as those usually show signs of failure when your under load... I recommend taking your car on a wide open throttle run and see if anything feels odd... If it has a misfire at higher rpms or if the check engine light comes on to give you a code to start diagnosing with Quote Link to comment Share on other sites More sharing options...
95 vert Posted June 11, 2012 Report Share Posted June 11, 2012 I say clogged catalytic convertor Quote Link to comment Share on other sites More sharing options...
ringting Posted June 12, 2012 Author Report Share Posted June 12, 2012 Thank you gentlemen, I shall read the manual on these ideas and do visual inspection followed by test drive as recommended. It does seem to struggle when underload. This puppy use to fly by everyone on the uphills so .... Quote Link to comment Share on other sites More sharing options...
ringting Posted June 18, 2012 Author Report Share Posted June 18, 2012 Time spent visually inspecting the engine resulted in correcting two places. 1) Exhaust manifold connection for cylinder 5 had two loose nuts 2) Generator was installed incorrectly, Bolt on fire wall side was there but not through body. This placed higher tension on belt. Work done with noticable benefit * cleaned the gounds under IC Work done without evidence of improvement A) Fuel filter, always some benefit to changing filters Spark plugs 1, 3, 5 cleaned More next week, plan is replace rad and service cooling system along with "refresh" the Throttle Body assembly. The goal is ensure no vacuum leaks. Quote Link to comment Share on other sites More sharing options...
RobertISaar Posted June 18, 2012 Report Share Posted June 18, 2012 if i were you.... i'd look at just replacing the plugs entirely. Quote Link to comment Share on other sites More sharing options...
ringting Posted June 19, 2012 Author Report Share Posted June 19, 2012 While normally I would agree, right now want to ensure vehicle is worth maintaining. The more I work on it the more I discover this puppy has had major things done. Clues like incorrectly installed generator, wires retaped, and NEW frame parts under PS of engine concern me. New plugs installed within 7500 miles. Point to pulling them was to find possible root cause of rough idle, while out took the time to clean & check gap. Rough idle gone, mostlikely due to closing gap in exhaust manifold. One bolt was 1/4 inch out and the other just loose. Cylinder 1 & 3 were tight. Cleaning gounds under Ignition Control well worth the time as this vehicle is very close to were it should be. Remaining gounds will be done next weekend along with prep work for major cooling system service. Current rad is repairable however might just buy a new one. And probably Low Coolant Sensor. 1994 Service Manual Volume I page 6B-18 Figure 24. Comments? Any words of wisdom regarding the Transmission Oil Cooler (hose, steel lines, connectors) 1994 Service Manual Volume I page 6B-2 Figure 1. Oh and what is the story on Throttle Body Coolant system. Keep or plug? Reason for asking about Throttle Body is might remove and rebulid (new seals/gaskets) top of engine to ensure no vacuum leaks. One last question: Anywhere to get details on O-ring sizes and material requirements? Quote Link to comment Share on other sites More sharing options...
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