I should have just left things alone but a few weeks ago I picked up a 2004 Corolla with 168k miles with minimal maintenance. First thing I noticed was a fast idle, it would start around 2500rpm and just sit there, no CEL though. After doing some research most suggested an intake gasket, since it was cheap I figured it couldn't hurt. I also confirmed the plugs and PCV were never replaced so I added those to my list. So this afternoon I installed a new intake and throttle body gasket, new PCV and new NGK iridium plugs. When I started up the car the fast idle was gone but now there was a noticeable stumble. I pulled a plug to confirm P/N was right and it matches mfgs site, checked PCV and even tried the old one...no change. I haven't pulled the intake back off yet but I guess that will be tomorrow. The other thing I noticed is when I moved the car a few feet I seemed to have no brakes, so I am wondering if a vac line got screwed up. Any suggestions on what I could check/recheck? Got to believe it is something on the intake side but can't imagine what could have improved the high rpm but caused all these misfires.
P0300 and P0304
- Thread starter wlepse
- Start date
How do the plug wires look? At 168k they may be leaking voltage or arcing across the engine instead of firing the plug. Get a multimeter and check the resistance of the coils and make sure those are in specification. That is where I would start.
Vacuum leaks won't cause misfires. The misfires are occuring because something is wrong with the ignition circuit.
By no brakes, do you mean the pedal is really stiff? If it is, check the hose from your brake booster and follow it, make sure it is hooked up and if the line has cracks in it, replace it.
Vacuum leaks won't cause misfires. The misfires are occuring because something is wrong with the ignition circuit.
By no brakes, do you mean the pedal is really stiff? If it is, check the hose from your brake booster and follow it, make sure it is hooked up and if the line has cracks in it, replace it.
Wires seemed fine but I will double check again tomorrow...maybe when I moved the cable cover I pinched something. Do you know what resistance the coils shoild measure?
But again the car drove fine before these "repairs" it just had a cold start fast idle, so I am having a hard time believing a car that previously drove fine w/o a CEL now has misfires on all cylinders from something pre existing.
As for the brakes...they were fine three weeks ago but now feel like they have lost all boost. I realize this shouldn't cause an issue with misfires but since this happened after the work I am wondering if there are common lines that break. I know on my Audi...some hoses break if you look at them wrong...wondering if there are known trouble hoses.
But again the car drove fine before these "repairs" it just had a cold start fast idle, so I am having a hard time believing a car that previously drove fine w/o a CEL now has misfires on all cylinders from something pre existing.
As for the brakes...they were fine three weeks ago but now feel like they have lost all boost. I realize this shouldn't cause an issue with misfires but since this happened after the work I am wondering if there are common lines that break. I know on my Audi...some hoses break if you look at them wrong...wondering if there are known trouble hoses.
I guess anything is possible but the hoses are shaped and I only removed one side so I don't think you could mix them up. Also don't think they are related to brakes since the are connected to intake...but maybe I bumped something. I will have to poke around tomorrow and maybe pull the intake again to see if something looks off.
For as little as it would cost, I would suggest replacing all the vacuum lines associated with the brake booster. You might also want to look at VSV operation.
As far as misfires go, are you getting codes for all 4 cylinders, a code for multiple random, or what? Perhaps you somehow got the wrong plugs? NGK or denso should be the OE. Cross reference your part numbers
As far as misfires go, are you getting codes for all 4 cylinders, a code for multiple random, or what? Perhaps you somehow got the wrong plugs? NGK or denso should be the OE. Cross reference your part numbers
As post below mentions the codes are for random and in each cylinder. In my OP I did mention cross referencing the plug with mfg site and it was listed. Besides in the past when I got the wrong plug I was ok until engine got hot and it started to pull timing....this is a cold start issue. Since I am seeing it on all cylinders and I seem to be missing vac I am wondering if I have a major leak on the intake which is causing misfires due to different airflow than maf and if leak is bad enough I won't get vac. Hoping to tear it apart this weekend but with mothers day I might not get a chance. But I will update once I figure it out.
Well I think I found it. I disconnected the throttle body from intake and intake from head. As I was pulling it out I noticed something different. Previously I removed the lines from the intake as I removed it...there is one on the backside and it seemed loose. Sure enough that line was off at the other end. My guess is I worked it loose trying to get at it but it didn't come off until I reinstalled the intake. Started it up, rpms came down and were nice and steady...brakes also have boost. Cleared the code and don't expect it to return.