Car is 2000 TL 131K miles. Headers and Intake and TB spacer.

Over the last month or two I've had a couple of instances when the car would idle rough after first starting the car. After driving it the problem seemed to go away.

Today car in for California smog check. Easily passed emision portion of test but failed overall because the Check engine light came on during the test and gave OBD codes po302 po305 po304 and po300. All misfire codes.

Go to start car to leave and car idles super rough and dies. Try several times and the idle is so bad I can't get the car to stay running. I ask smog tech how car ran during test. He said during the test the car suddenly started to run rough during the heavy load on the dyno roller section of the test. I let car sit for a few minutes and turned it over. Rough idle but now I could keep running. Rev'd it a couple of times and got better then drove away. Car drove fine, idled normally at stop signs. Parked it came back ten minutes later, rough idle, rev'd it got a little better drove away and car seemed fine again.

Let car sit for 2 hours and started it. Started up no problem no rough idle. I'm sur the car isn't fine though. I don't want to try another smog check until I figure out what the problem is.
Ideas on what to check?

Thanks

 

misfire (per the codes) or iacv maybe?

 

done the spark plugs recently or otherwise handled the coils?
how old are the plugs and what plugs-ngk iridium? or some off brand?
harsh driving -bouncy- racetrack stuff?
Wires are all on tight at coils?

Its usually 1 coil fails and gives a multi cyl misfire code- they go without much warning too- its loss of cylinder ignition power and action on the roller wheels would be right on

buy 1 at parts store- beck arnley 50 bucks is fine
see the many threads on how to find the bad coil- but you probably know how already-own a multimeter,,

When you did the manifold spacer did you clean the IACV on bottem of TB unit?
and the egr port service of intake manifold?

Note- have to reset ECU with new coil or as you move it around,
pull CLOCK fuse on passenger end of dash for 1 minute-the secret backup power to ecu! = washes memory

once prob solved:
Now you will have to do some driving to fill the computor with enough info for testing
The smog machine knows if the system has been recently reset-
Can you believe: some people try to clear a CEL by disconnecting battery (or clock fuse for us) then fake their way thru a Ca smog test!!--not likely

If pressed for time to get restest, there is a 45 minute driving set of speeds and actions to do it fast
Otherwise a week or two driving required

 

No handling of coils recently. I thought I had changed the plugs a few years ago when I put in the headers but now that I look at the plugs I think I never got around to it and they are original to the car. This afternoon the car started up with no problems. But I went ahead and changed the plugs this afternoon with ngk Iridium. While changing the plugs I noticed 2 of the plugs were barely even finger tight. The sleeves of the coils on those plugs were very dirty and the tops of the plugs looked like they had some baked on oil on them. Possible cause?

When I put on the manifold spacer I also put on a new IAC valve which went out coincedently the same time the spacer came in. But have never cleaned the EGR ports.

As of right now with the new plugs the car seems to run fine. I think I'll put a hundred miles on it and see how it runs. I'm only 6 weeks late on my registration what's another week.

 

that's the spirit!

 

finger tight plugs will cause loss of power for sure!

(daughters car recently unscrewed and blew a plug out at 15mph, still attached to plug wire-bad noise, panic phone call-1 new plug, my trusty plug wrench and back on the road--amazing what comes loose on cars-must be time for new plugs when they jump out of the engine)

crud on the firing tip? or the top end where coil meets?
on working end would be from poor firing
on top end, dirt does get in there

did you use connector grease for the coils to plug and coil to power leads,
and a little anti sieze on the plug threads?
not required but never hurt

 

in Ca you can take your failed smog results and pay the reg/20% late fees-
get a temp window tag to avoid a no reg ticket and its fine

 

ayo bro i seriously had the like the same exact problem wit my 03 tls, i found it out to be the throttle body cable area.. i dun remeber exactly but after my boy fixed sumthing, all me CEL and idle issues were gone. if thats any help jus the story sounds jus like mine.

 

The same thing happened to me on a '99 Honda Civic. I was driving around my old neighborhood when all of a sudden I hear a gun shot-like sound from the engine and a horrible sound when I pressed the accelerator as if I didn't have exhaust manifolds on the engine!!

So I lean forward in my seat and notice two things visually: the hood was loose (as if I pulled the hood release cord) and there was a outward dent (bump) on the hood. When I pulled over, I noticed one of the spark plug had shot out of its hole so hard it dented the hood AND hood brace. I re-tightened the plug and all was good.

 

but on the TL we have coil on top of plug ignition, held on with 2 allen screws
so I dont think a plug coming out- for us- is too likely

One bad coil is most often the cause of OUR multi cyl misfire codes

 

had the same situation in my 01 tl,engine was shakin check engine light was on, happened while driving. do not drive the car untill u fix the issue as u can cause damage to the motor< at least thats what the service adviser told me when it happened.. its most likely a coil.. the pain in the ass is to figure out which one.
Good luck hope u figure it out soon

 

It's not hard to diagnose a bad coil. Swap the coil to a cylinder that does not have a misfire erase codes, see which ones come back. If problem follows to the good cylinder you now know which coil is bad. Same with plugs. Swap them around and see if the problem goes to another sensor.easy.

 

or unplug the power lead to coil and ck for rpm drop--bad coil wont change rpm

 

i have a 2000 tl, 138xxxmiles..same problem for a while car drives fine i come up to a red light, and the car idles very rough, i hateddd it, check engine light finally came on, same codes, misfires all over lol, i did the sparkplugs (NGK). ran ok for a little while, then 1 day the problem was back, so i went ahead and replaced the ignition coils (i did all 6 just because im picky about the performance of my car lol )..but it drives like its right off the lot, feels like i gained horsepower and everything lol, also clean out the EGR valve,i did mine when i did the coils, it was pretty dirty... this was back in May, and the problem has been gone since.. goodluck with it

 

ohh, and to find out which coil is bad.. leave the engine running, and 1 at a time, remove a coil, and put it back before moving on to the next.. .if the engine starts to idle rough when you remove it, IT WORKS lol.. if nothing happens when u remove the coil.. theres a problem, that coil is bad...

 

Yes nick has it. Doing it nicks way tells u

 

You have a dead cylinder. So if swapping the coils doesn't work. And the problem is still in the same cylinder it Could be plugs, or valves, loss of compression also.