Misfire codes set then limited throttle and RPM
Starts up and idles smooth. raise RPM to about 2500 and engine gets a slight vibration and scanner registers misfires on all cylinders. Within about a second of that happening the throttle is limited and will not rev over 3000 RPM. check engine light also is flashing. Did a cam Crank sync and drove the vehicle and ran great for about 1 mile then while at Full throttle and about 4500 RPM the check engine light flashed and lost power like I just took my foot off the gas peddle. However It was still floored. when the RPM dropped below 3000 RPM the car surged from 2700 to 3000 RPM. The car drove with limited throttle after that but idled perfect and ran good to about 2000 RPM. turned the car off and restarted and the car would accelerate normal again until the the problem happened. Scoped the Cam and crank sensors and compared to know good on IATN and matched up. Did not see a variation when the problem occurred. Pulled the Valve cover and inspected the valve adjustment OK. Inspected the timing marks on the chain since right there. Looked like chain stretched maybe 1/2 tooth but scope on cam crank sensor did not show it out of time. This is a car from a car lot that they picked up at auction. So I am sure this is why it was there. Has anyone seen something like this before. Attached the cam crank screen shot.
Can you post fuel trim/Throttle graphed-data leading up to fault? Also, I can’t find your subject vehicle known-good in iATN. Are you SURE it’s marks present the same as years-past?
posted screen shots of data. shutting off #1 injector when problem occurs. In generic it has negative fuel trims.
members.iatn.net/file/view/?id… Link to 2012 accord with same motor.
Going to need tps vs o2 data during that wot run, where it acts up.
Pull a fuel sample , see if it’s contaminated.
Looked at some data. because of data groups I could not look at all the pids I wanted too at the same time. I can get the car to act up if I rev the car in neutral to about 2500 rpm and the check engine light starts flashing and then engine looses power. I went generic to look at fuel trims better. lambda on the scan tool, is it lambda or a percent? I noticed that fuel injector went to zero ms…
Robert, I am struggling with the data set however, it appears your post cat O2 sensor is contradicting your AF sensor . Perhaps this is a clue?
when the check engine starts flashing at 2500 rpm the #1 injector shuts off. That will make the O2 sensors go lean, the Front will react first then the down stream later. When the RPM drops to idle the injector starts working again. Then rev the motor again and the injector shuts off again. Shutting off the motor and restarting resets it and it runs good again till problem happens again.
You can perform a running compression test with a regular gauge. Do that, plus snap-throttle on both the suspect bad cylinder and a good one. This will show a breathing issue, liked a worn cam lobe or bad lifter. Search for Jim Morton's article on "Running Compression Testing" for more info. HTH, Aloha from Maui
Take off drive belt and retest.
Robert, Had a very similar situation on a Honda. Wound up being contaminated fuel so plus 1 on Scott's suggestion.
Did yours run great for a mile then just fall on its face? This car will wheel hop and torque steer all the way through 1st and second gear, all the way through the gears. Then a short time later fall flat on its face.
Robert, Mine would run good for awhile and would continue to run well if kept under 3,000 rpm or so. Then when you brought the rpm's past say 3,000 rpm or so it would start misfiring, flag misfire codes, and have limited throttle until key reset.
The CKP needs to be relearned nothing wrong nothing needs to be replaced idle till fan kicks on shifter in 2 ( make sure it’s in two, very important ) On a level road accelerate over 2500 rpm in 2 take your foot off the gas completely till rpm drops under 1000 next accelerate up to 5000 rpm and release the gas pedal till rpm drops under 3000 it usually takes one try and the mil stops…
Mat, The vehicle I had I cleared and relearned CKP with HDS and had no effect on issue. While I agree it is worth a shot and it is no doubt something that should be performed regardless.
Crank relearn issues usually cause a flashing light with NO real misfires, in other words, it just erroneously identifies good cylinders as misfiring cylinders. In this case he has an actual low power and drive-ability issue. Plus he said he already did the relearn procedure.
Had a very similar situation and it ended up being the crankshaft position sensor. Sensor had been replaced with an aftermarket sensor. Installed factory sensor and did relearn produce, problem gone. Just a thought.
This may have been a water car. Check the crank sensor connector and the CKP pins very thoroughly for green corrosion. This will beat you down if you miss this. Collect the crank sensor pattern on the pico at a higher sample rate per second then zoom in to evaluate. Thanks
Update: After sleeping on all your comments and seeing the negative fuel trims at idle. I was wondering if the #1 injector is over fueling the #1 Cylinder causing a power difference and leaning out the other cylinders with fuel trims. Since #1 injector was shutting off when problem occurred i swapped the #1 injector with #4 cylinder. Started the car and revved to 2500 rpm till the problem…