[TorkRollN]

I have a 93 Notchback with 5.0 & 5 spd manual.
It has a surging idle. Maybe only 100-500 rpm surging range.
When it starts up I have to give a very slight amount of pressure on the throttle to keep the rpm up. Otherwise it will sit there and surge, getting worse until it quits. If I hold my foot on the gas pedal with a slight amount of pressure for a minute the idle stabilizes. But once you start driving the surging will return when you come to a stop sign and it drops to idle. Plus it just isn't making the power it should. This car is stock but use to really put you back in the seat when you accelerated. It just doesn't give me the same happy feeling anymore.

I did a KOEO test and do not seem to be able to get code 11 at all. But it does display code 63.

Then I try the KOER test and get code 98 and code 63.

This car use to be ALOT of fun. I'm looking for help to get it back to running the way it use to.

Any ideas?

Thanks,
Barry

[Danno]

Mine does something similar. I just got it tuned at the shop and even after they spent a couple days just tuning it, it still does it (although it's not all the time now like it used to be). Before I took it to the shop I did a fair amount of searching on the topic and there are a lot of good posts that tell you a lot. Start with those and try to determine if there's a specific area that might be causing it. If it makes you feel any better, my car runs awesome now, even with the surge, and the shop was saying that the Fox Body mustangs are real touchy at idle. One little voltage swing somewhere will cause it (apparently).

[TorkRollN]

OK,

I had a friend tell me how to diagnose the TPS with a voltmeter, over the phone. We determined that the TPS was putting out only .3 volts at idle. Sometimes I could not even get a reading it was so low. This seems to make sense with the code 63 I was getting. So got a brand new TPS and installed it. Adjusted TPS to .92 volts. Surging problem seems to have gone away !

Now, I am having a problem where I have to push the gas pedal very slowly or it seems to stumble and stops making any power. Doesn't try to quit but unless I lift off the gas pedal and come back on slowly , it won't accelerate. And even when I do get it to accelerate nicely it still doesn't seem to have the pull that it should. I'm guessing because I can't go to absolute full power.

So, now I have to figure put how to diagnose this issue...

Barry

[TorkRollN]

Also, I cleared the previous codes.

Now I get code 94 and 44. But, I don't think my AIR system is hooked up , which makes perfect sense with those two codes.

I used to have a H pipe, with no cats. The car ran and sounded really good back then. But, We installed two cats into the system. Ever since then the car has just not run properly. Always seems down on power.

I just need to get this thing to pass the emissions test here in AZ so I can rip those damn cats off and put a new H pipe back on.

Barry

[allmotor92lx]

Are the cats you put on used if so they might be bad

[TorkRollN]

Well,

A friend told me to clean the MAF. I had already checked it with a voltmeter to make sure it was functioning propely and it seemed like it was. But when I pulled the MAF out it was covered with like a 1/32 inch of black carbon on the leading edge of the front wire element in the MAF. Cleaned it with some CRC electric parts cleaner. My throttle response instantly cam right back. Car now has full power and is JOY to drive now !

So, the new TPS fixed my idle surge and cleaning the MAF restored it to original power on the top end.

Barry