Help us help you. By posting the year, make, model and engine near the beginning of your help request, followed by the symptoms (no start, high idle, misfire etc.) Along with any prevalent Diagnostic Trouble Codes, aka DTCs, other forum members will be able to help you get to a solution more quickly and easily!
Hi everyone I'm new here, I recently bought a ford cmax 2008 that has an engine hesitation only on acceleration. I've bought a forescan elm cable to plug it in however it shows no dtc codes. I have access to live data however I'm not sure what I'm looking for. So I thought I'd come to the pros. Doee anyone have any advice for me on how to diagnose this fault? I really appreciate any help thanks very much.
If you have the ability to record and graph the live data for the following engine pids
Maf, map, o2 sensors (all of them) rpm, fuel trims (long and short term), vvt timing if applicable, ect, iat, iac, turbo pids if applicable.
Post this and we can see what us going on. If needed record a video and load it to YouTube and post the link here for us to view.
I recorded this from forscan today the first part is the sensors you mention then I flipped to throttle position sensors on idle. Any help would be much appreciated thanks.
I believe it said open loop for the open loop/closed loop fuel trim info. When does it hesistate on acceleration with engine cold or warmed up? Both?
If you have the capability start recording those pids again from cold engine till warmed up and the issue occurs. Then save the data for the whole trip. The main things to look at is grams/sec maf reading, rpm, fuel trim ST and LT. I did not see an issue with iat, ect, tps, or o2 sensors though you were switching between screens pretty quick. ST Fuel trims showed a positive 9 which after a throttle snap is normal though when recording stuff like this you want to make sure you record the engine restabilizing afterwards as well.
From the looks of the data nothing is out of the ordinary, however you might want to pull spark plugs and check the gap, as well as check maf for dirt on the wires inside maf and clean with a qtip or acid brush with maf sensor cleaner.
O2 sensor Bank one sensor two looks like it is having an issue from that pic. That i would look into / test. i also noticed the ohm reading is higher compared to bank 1 sensor 1.
The other thing i noticed is timing is at 37.5 degrees at idle i would say to look at service info for what it should be or an identical vehicle to compare to.
From what i am seeing your o2 sensors are having an issue i would first reccomend testing fuel injectors (pressure drop test with fuel injector tester) (ohm testing) (injector waveform test with ocillascope). This could be a partially clogged injector or a o2 sensor or a dirty throttlebody/ intake manifold runner control issue (tar buildup in intake manifold preventing adequate airflow on acceleration.) Typical of higher milage cars over 80000 miles.
Thanks so much that helps alot il start looking into injectors etc. I took a a video today of just the o2 sensors on idle and revving. I agree something does not look right il upload the video. Thanks again
You may want to check your time base typically i'll run a 1000 or 4000 ms screen which is 1 to 4 seconds. If to short of a time base may make it look off. I cant tell what time base you ran just an observation.
Also if your 02 sensors are heated (you should see 4 wires going to each o2s if heated if not it will have 2 wires going to each) if they are heated you will want to check voltage at fuses to see if it is receiving 12 volts. If it is then your data suggests the o2 heaters are dead on both o2s. If no 12 volts supplied to fuse you will need to back track the wire to find the issue.
