Idle Problems after Spark Plug Replacement
 

A couple months ago I bought a 1991 NA. It had an aftermarket dual exhaust with no cats. I wanted to get it to pass the emissions test so I had 2 cats welded in place. It still failed the emissions test, but overall has improved. The car is running really rich, so I thought there might be an ignition/spark plug problem. I pulled a spark plug and it had a ton of carbon on it. Rather than clean and replace, I just bought all new NGK plugs and some Duralast wires. I replaced them one at a time.

Ever since I did this, the car idles really rough. It has always fluttered, which I understand might be due to a TPS being out of whack. I plan to get that adjusted. The real problem is that it won't idle once it warms up. I have to constantly tap the gas to keep it running. I did not have this before I replaced the plugs and wires.

Before I did the spark plug replacement, it NEVER died when idling whether it was cold or warm.

Could it be that I did something wrong? Maybe I clumsily knocked a vacuum hose or could the plugs or wires be bad or loose? I did them one at a time so there was zero chance of mixing up the leading and trailing. I'm also sure I got the plugs right with leading/trailing.

What can go wrong when you replace spark plugs? I'll check all my work again once I get home today, I just wanted to start a thread to see if there was any common issues after spark plug replacement.

Are you sure you got the right plugs? First i would clean the old ones, put them back and see what the engine does. If it's running fine then you bought the wrong plugs. Wouldn't be the first time they tried to sell me the wrong ones;) Still no improvement then check your leads, maybe accidently you switched the trailing and leading?

The proper spark plugs for a stock setup would be 6's and 8's or 7's and 9's if for a turbo or modded engine. Look at the packaging to verify this. Your car might need a simple tune up to go along with the new wires and plugs.

double check and make sure u put the plug wires on the right plugs.

Checked my spark plugs again
 

I bought NGK BUR7EQ and BUR9EQ, which is what NGK's website recommends. I made sure the Leading and Trailing was right. I will double-check anyway.

I have a spare leading and trailing coil. I tried swapping them out one at a time and there was no difference.

Set the TPS to 1 volt (Green/Red wire) after the engine is "completely" warm. Not close to warm, but completely.

Buying Duralast plug wires was a mistake IMO. Like going to WALMART for a good suit. Even on my daughter's old 4 cyl. Camry they didn't last a month. Consider getting a set of OEM NGK wires.

Thanks for the suggestion. You are right, I need to do this so I will try tonight.

What do you think of the resistance method of adjusting the TPS? I haven't ever adjusted a TPS, so I'm sure anything is better than where it is right now.

I read about the resistance method here:
http://fc3spro.com/TECH/HOWTO/TPS/tps.html

lol... Nice analogy. I had a feeling it might be, that's why I sent ahead and shared the brand I purchased. The NGK Wires weren't in stock at the time and I wanted to have them immediately. That will be the last time I cheap out or get impatient. Even if this isn't the problem, I hate the thought that it could be.

I wonder if Wal-Mart will take my suit back. :lol:

Checking to see if the sensor is within spec via an ohm method is okay but the FSM stipulates that the G/R wire at the ECU should read 1 volt.