- This topic has 12 replies, 5 voices, and was last updated 11 years, 3 months ago by
.
-
Topic
-
Trying to trouble shoot this 2006 Scion xB and am currently scratching my head. It seems to be running hard and has some shaking going on. Even for a 1.5L engine it feels very sluggish on acceleration. I have attached a screenshot of some sensor values. This is with the vehicle warmed up. The load % from this shot is with the vehicle in park. If I hold on the breaks and have it in drive I see it go up to about 54%. There are also no codes being thrown right now. The owner states that there was an o2 issue awhile back that “might still be an issue”. To me, the bank 1 sensor 2 o2 sensor doesn’t seem to act like it should and was thinking that this would cause the symptoms I’ve outlined. (don’t worry about the other 3 not showing up, as this is a generic layout I made awhile back). I have also cleaned the MAF sensor, changed the engine oil/filter, air filter, and changed/gapped the spark plugs currently in it. The car currently has 49,416 miles on the clock.
-
Replies
-
rough engine idle is usually caused buy a imbalance of power between cylinders or cylinders not firing correctly, in order for a engine too run correctly it needs several things
1 fuel too burn
2 a correct air fuel mixture ideally stoichiometric 14.7/1
3 something too ignite the air fuel mixture like a spark
4 proper compression and relatively equally balanced compression between each cylinder.
first check spark, you can usually get a spark tester, make sure there is good spark too each cylinder, if you are getting spark check the condition of your spark plugs, since you have already replaced your spark plugs your spark plug condition should be ok, but are they gapped correctly? also make sure the ignition coils are in good condition, they are what makes the high amperage low voltage current, into low amp high voltage current for your spark plugs too work correctly, sometimes they wear out and dont produce enough spark, sometimes you may experience voltage leaks where spark is traveling somewhere ells besides the spark plug gaps… this can be caused buy bad wires or poor connections, also check for corrision too any connections, clean the corrosion up and apply die electric grease, be carful beacuse ignition systems create very high voltages, and they hurt!
check fuel pressure, if fuel pressure is low this means your engine is being starved of fuel and is not running correctly, low fuel pressure is commonly caused buy bad fuel pump, or clogged fuel filter, or even a fuel leak, in some cases bad fuel regulators can cause odd things with fuel systems, most modern sequencial fuel injection systems are between 40-60PSI but check with manufacturer specs to be sure.
check compression too each of the cylinders, compression should be roughly within specification, and each cylinder should be within 20% of each other, if one cylinder is over 20% difference in compression between cylinders there may be a compression issue, and if there is a major difference in compression with a wet test it may be caused buy warn out piston rings, if two cylinders neighboring are low in compression like cylinders 2-3 or 1-2 or 3-4 are low in compression you may have head gasket issues, low compression can also be caused buy warped valves, HOWEVER this is caused typically after engines reach high mileages 49,000 miles i don’t think you should be having compression issues unless at some time you seariously overheated your engine, this leads too blown head gaskets, takes the tension out of piston rings… screws up bearings… which causes all sorts of rough engine run.
also check throttle position sensor, MAP sensor if applicable, and O-2 sensor data, Eric has a video on 0-2 sensor scan tool checking and all that, 0-2 sensors are largely responsible for correct air fuel mixture
Thanks for the reply 13aceofspades13. I’ll go through your list as I have already check on most of it.
Spark on all 4 cylinders is good. I checked each individually and they all appeared to have about the same amount of spark. The distance they were sparking at were all consistent as well. No corrosion on any of the connections. I cleaned them up just to be sure initially though, so all is good there. The gaps are correct as I gaped them myself. I also took them out recently to verify, and they were still good.
Fuel pressure is also good. At idle it’s sitting around 45psi. The fuel pump is also showing a good resistance value.
Compression is good and pretty much equal on all cylinders.
I do see that at idle the TPS is at roughly at 11% when my foot is off. Also as far as I can tell, the MAF sensor data looks good. When I cleaned it, I also made sure to do some resistance checks on it as well and everything looked fine.
I’m going to check both of the o2 sensors again tomorrow to double check things. Just thought I would post on here to maybe get some help to check things I haven’t thought of.
Thanks again for the input ace! Hopefully someone has some other ideas.
Bank 1 sensor 1 is upstream and sensor 2 is down stream.
Check out this link on performance issues.
http://www.ericthecarguy.com/faq/solving-automotive-performance-issues
Hey Jay, When I did this a few days ago I had about the same drop in RPM from disconnecting each coil pack. I didn’t come across one that made no change in engine RPM from disconnecting.
[quote=”DaGlitch” post=77145]Hey Jay, When I did this a few days ago I had about the same drop in RPM from disconnecting each coil pack. I didn’t come across one that made no change in engine RPM from disconnecting.[/quote]
Good to know, the list ace gave is pretty thorough so hopefully you’ll find the problem there, but if not that’s a tough one :unsure:
Yea, I’ve already pretty much gone through everything Ace mentioned. At least I’m not the only one that is stumped lol
Hey Karl, This is not a California car. Hmm, I’ll have to get back under there again to look at the brands. I believe they are Bosch, but don’t take my word on that. So, I’ll get back to you on that one. Out of curiosity, wondering why you asked? Thanks!
Arrggghhh I was afraid you would say Bosch… May want to check that out… Anything but Densos on Toyotas cause problems…..
-Karl
- You must be logged in to reply to this topic.