96 Jimmy Hesitates

[dwausa]

So I was on my way to work today when I noticed the car hesitating when I put my foot on the gas. At first it accelerates fine but when the rpm meter gets to around 1,800RPM it jolts into the next gear. Then the car smooths out and i get smooth acceleration. However, when I came to a traffic light and had to stop when the light turned green the car hesistated and the RPM meter was going back and forth from around 1,700RPM to 2,200RPM and the car sort of staggered up to around 30MPH. Beyond 30MPH it was fine. Eventually the car stopped doing this. On my way home from work the car was fine, no hesitation at all. Its done this before completely at random but ONLY on my way to work in the morning, never during the day or at night. The car idles at around 600RPM, nice and smooth. My service engine soon light is on but for error code 404, something to do with the evap system. The light goes on and off whenever it pleases and I get it checked everytime, same code all the time, so I have come to ignore it. It's been doing it for the past 3-4 years, fortunately the lights never been on when I have had an echeck .

My dad rode with me earlier today and the car did the same thing it did yesterday (hesitating etc...). He said it might be a missfire but he doubts its the transmission. Spark plugs have been replaced within the last 10,000 miles, I have my oil changed every 3,000 miles (valvoline maxlife for the last 3 years, no leaks), I believe the transmission fluid has been changed at 135,000 miles (not sure, dad estimated this). I did check all the fluid levels and they look fine, according to the haynes manual the transmission fluid looks the right color and doesnt smell like its burnt. The fuel filter was replaced at 145,000 miles. The car currently has 151,000 miles on it.

Im probably going to take it to ProCare this weekend and have them check it out. Im most certainley not mechanically inclined, most ive done on the jimmy is change the air filter (last week actually) and check the fluid levels., everything else I leave to procare as i trust them.

[CanukGMC]

Originally Posted by dwausa

So I was on my way to work today when I noticed the car hesitating when I put my foot on the gas. At first it accelerates fine but when the rpm meter gets to around 1,800RPM it jolts into the next gear. Then the car smooths out and i get smooth acceleration. However, when I came to a traffic light and had to stop when the light turned green the car hesistated and the RPM meter was going back and forth from around 1,700RPM to 2,200RPM and the car sort of staggered up to around 30MPH. Beyond 30MPH it was fine. Eventually the car stopped doing this. On my way home from work the car was fine, no hesitation at all. Its done this before completely at random but ONLY on my way to work in the morning, never during the day or at night. The car idles at around 600RPM, nice and smooth. My service engine soon light is on but for error code 404, something to do with the evap system. The light goes on and off whenever it pleases and I get it checked everytime, same code all the time, so I have come to ignore it. It's been doing it for the past 3-4 years, fortunately the lights never been on when I have had an echeck .

My dad rode with me earlier today and the car did the same thing it did yesterday (hesitating etc...). He said it might be a missfire but he doubts its the transmission. Spark plugs have been replaced within the last 10,000 miles, I have my oil changed every 3,000 miles (valvoline maxlife for the last 3 years, no leaks), I believe the transmission fluid has been changed at 135,000 miles (not sure, dad estimated this). I did check all the fluid levels and they look fine, according to the haynes manual the transmission fluid looks the right color and doesnt smell like its burnt. The fuel filter was replaced at 145,000 miles. The car currently has 151,000 miles on it.

Im probably going to take it to ProCare this weekend and have them check it out. Im most certainley not mechanically inclined, most ive done on the jimmy is change the air filter (last week actually) and check the fluid levels., everything else I leave to procare as i trust them.

EVAP code huh. I had the exact issue with my jimmy. It was a big sluggish when accelerating and I had a check eng light on. We found it was an "evap code" but after hours of hunting down the ACTUAL root cause it turned out to be the valve ontop of the gas tank that relieves the pressure as fuel is pumped out. It may be the same thing on yours. With mine it wasn't letting air IN so as I pumped fuel out (especially when accelerating) I was building up massive amounts of vacuum in the gas tank which made the fuel pump work overtime and would cause fuel starvation. I dunno if you have the same issue, hth.

[dwausa]

Originally Posted by CanukGMC

EVAP code huh. I had the exact issue with my jimmy. It was a big sluggish when accelerating and I had a check eng light on. We found it was an "evap code" but after hours of hunting down the ACTUAL root cause it turned out to be the valve ontop of the gas tank that relieves the pressure as fuel is pumped out. It may be the same thing on yours. With mine it wasn't letting air IN so as I pumped fuel out (especially when accelerating) I was building up massive amounts of vacuum in the gas tank which made the fuel pump work overtime and would cause fuel starvation. I dunno if you have the same issue, hth.

was it sluggish accelerating all the time? or was it occasionaly/random.

[CanukGMC]

Originally Posted by dwausa

was it sluggish accelerating all the time? or was it occasionaly/random.

Random unfortunately. The best way to tell IF it is that valve is to have them hook up a vacuum reader to the gas tank and see how many bars of mercury it's pushing when running. The valve may be on it's way out and sometimes fails sometimes doesn't. Also it can't hurt to hook up a fuel rail pressure tester to see if you are getting a constant fuel pressure to the rail.