01 Blazer with 135k miles. Blazer shows hesitation under acceleration at higher speeds (60ish), less noticeable drifting around town. Noticed small amount of coolant loss. Performed pressure test and saw water along intake manifold and valve cover. Will intake manifold leak cause hesitation? Recently installed new fuel pump. Checked fuel pressure shows 60 with key on. Drops to 54 at idle. Seems to be within spec of Haynes manual. No codes in computer. Also, just performed complete tune-up with plugs, cap, wires, rotor and ran great afterwards. MAF sensor replaced about a month ago - but computer showed code for that. I know replacing intake manifold is big job for backyard mechanic. Just trying to confirm this will take care of hesitation as well. Thanks in advance for your help.
You need to fix the intake leak first you could very well have two issue though. Lets get that leak fixed and go from there. What was the exact code number for that maf code?Vacuum leaks can cause maf codes.
Fuel pressure regulator leaking or defective fuel pump.
Foul/defective spark plugs.
Open spark plug wires.
Ignition coil/Coil packs defective.
Incorrect ignition timing.
Cap and rotor.
Note:If it doesn't apply disregard it and keep testing
December, 30, 2011 AT 1:01 AM
Ok - after many hours of disassembly, inspecting, cleaning, and reassembly the coolant leak is fixed. This included replacing intake manifold gasket, valve cover gasketes, all heater hoses and radiator hoses, new thermostat, and new valve cover gaskets too. Although I was excited the blazer started and no leaks, I was disappointed when I felt the hesitation during the test drive. On my initial post, I should also have mentioned that I replaced one vacuum line and fuel filter. Also, I did re-inspect 2 of the plugs readily accessible and they looked good. The distributor cap and rotor also looked good during my diassembly of the intake. Also started blazer in dark looking for open plug wires - but did not see any. There are still no codes showing or pending. What to do next? Your help is most appreciated.
December, 30, 2011 AT 4:51 AM
So is it a hessiation or a lack of power?Also how did you check for codes?
December, 30, 2011 AT 8:53 PM
Hesitation to me - using Actron CP9135 menu item 1 to check for codes - there is also menu 4 to check for I/M monitors - all those show ready and return no codes
December, 30, 2011 AT 9:45 PM
Have the fuel pressure checked and monitored if its within specs
December, 31, 2011 AT 4:17 AM
Have you checked the plugs and wires yet?
January, 7, 2012 AT 1:24 AM
Replaced the Throttle Position Sensor - instant results. Thanks again for all your help on this one.