Rough idle but plenty of power..

[diablodude64]

My car is a 91 240sx with a newly rebuilt ka24de. I know this has been covered about 4,000 times but I am on my last temporary and need my car to pass the emissions test. Here is the problem, it has a rough idle but still has lots of power. The hydrocarbon content standard is 220 yesterday when I had my car tested its hydrocarbon content was somewhere around 3300. I know a bit over...... I pulled some codes from the ecu and replaced the engine coolant temp sensor and I tested the knock sensor and it was bad. Luckily I had another one so I put it in (very fun by the way). I tested the maf sensor and it works great. I reset the ignition timing, checked the sparkplugs, and checked the injectors, everything works. Any help would be awesome. Thanks, Kyle

[S13Joe]

zerothread/254123

[diablodude64]

Thats not the problem, thats to easy... It sounds like an engine with a big cam. It does not idle to low though. Also when I come to a stop the rpms go down and sometimes the engine will stall.

[samxini]

I'm having the EXACT same problem with mine.

From what I've heard (haven't had time to test yet) it might be the IACV that's just dirty and needs to be cleaned.

If you do figure out what's wrong let me know and I'll do the same.

[diablodude64]

Alright I will...

[diablodude64]

As I have been calming down from the day, I have been thinking about possible problems. I took the iac off yesterday and cleaned it and I am thinking that that or a vacuum line around it is the problem.

[1sikS13]

as far as a vacuum leak spray carb cleaner or similar around known vacuum lines and the engine should rev higher for a short period of time. If this happens vacuum leak is your problem. Check the area where you sprayed the carb cleaner look for cracked hoses etc. I had a similar problem when a vacuum line from below the throttle body was going bad. It went from the metal line below the throttle body to the intake tubing.

[diablodude64]

Alrighty then... I fixed the problem. It was what I thought it was... On the iac, part of the gasket was broken.. I had a new one already so I put it on and started it up and with a few adjustments, it runs awesome!
Modified by diablodude64 at 9:02 PM 1/11/2009