Coolant Loss & Hesitation

JSINES

MEMBER
2001 CHEVROLET BLAZER
135,000 MILES

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.

9 Replies

SATURNTECH9

MECHANIC
30,869 POSTS

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.

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Sunday, December 18th, 2011 AT 8:59 PM

RASMATAZ

MECHANIC
75,992 POSTS

Fix the leak and as for the hesistation might want to check the following below and also refer to this link:https://www.2carpros.com/articles/engine-hesitates

Could be caused by one of the following below

Oxygen sensor.

Catalytic converter.

Fuel injectors dirty/sticking.

Mass airflow sensor/Airflow meter.

Throttle position sensor.

Crankshaft position sensor

Knock sensor

Manifold absolute pressure sensor.

EGR Valve

Fuel pressure regulator leaking or defective fuel pump.

Fuel contamination.

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

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Sunday, December 18th, 2011 AT 9:00 PM

JSINES

MEMBER
9 POSTS

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.

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Friday, December 30th, 2011 AT 1:01 AM

SATURNTECH9

MECHANIC
30,869 POSTS

So is it a hessiation or a lack of power?Also how did you check for codes?

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Friday, December 30th, 2011 AT 4:51 AM

JSINES

MEMBER
9 POSTS

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