J30 hesitation


dbrunone
07-02-2003, 10:55 PM
I have a 95 J30t with 94k miles. When the engine is cold, the car runs great. But when it warms up after about 15 minutes of driving, I get fairly uneven acceleration, especially in 1st gear, and the power drops by about 25%. When it is cold, it is very quick off the line, but when warm, I can floor it from a stop and it still feels sluggish. I have tested the EGR and coolant temp sensors, I had the injectors cleaned, had throttle bodies cleaned, replaced the throttle position sensor, and replaced the air filter. I got a little more overall power from the injector cleaning, but other than that my efforts have been futile. Also, my gas mileage is not great; this car is supposed to get 18mpg city and i am only getting 15-16. What in the world can be causing this problem??

-David

ERobles
07-03-2003, 05:00 PM
Try cleaning your mass air flow sensor - it may be dirty. I had the EXACT same problem with my 94 J (101,000 miles) What happened was I installed an aftermarket intake from Stillen. The filter on the new intake is coated with oil and the oil starts to coat the mass air flow sensor over time. After I cleaned mine I noticed a pretty big difference but got tired of having to clean it every other day (I may have made the problem worse when I cleaned the filter and coated it with too much oil) so I called a local junkyard and purchased a used one for $200. New ones will run you about $550. Ebargain auto parts sells refurbished ones but I dont know what the price is. http://www.ebargainautoparts.com
Hope it works.

dbrunone
07-04-2003, 12:30 AM
how do you go about cleaning a mass air sensor? Arent there lots of little delilcate fibers?

ERobles
07-04-2003, 10:52 PM
Just use STP air intake cleaner and gently spray any dirt and grime off. Mass air flow sensors use thermistors and platinum "hot" wires to convert the amount of air drawn into the engine into an electrical signal the ECU can read. The ECU needs to know intake air volume to calculate engine load. This is necessary to determine how much fuel to inject, when to ignite each cylinder, and when to shift the tranny. So if cleaning it does'nt help much as in my situation the sensor is most likely not functioning correctly. Also the problem only occurs when the engine is warmed up -this suggests that the thermistor (thermistors change electrical resistance as temp rises or falls) in the MAF sensor is not functioning properly and is sending false signals to your ECU therefore causing the hesitation.

jasonhanjs
07-25-2003, 03:18 PM
I have same problem with my 93 j30, someone told me it should be camshaft position sensor, I did not try it yet. I want to know your way to fix it. my email: jason_hanjs@hotmail.com

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