zoned019

Okay, first I'll describe the problem, then I'll give you some background info on some stuff I've done recently that could possibly be related, hopefully someone can put the pieces together and help me figure out what is wrong.

When I go WOT out of 1st gear, the car has a VERY noticable flat spot from about 1k to 4k RPMs, above 5k, it takes off like a bat out of hell. It drones until 4-5k, then you get kicked back in your seat. Then shift to 2nd, 2nd feels normal, but that is probably only because 2nd doesn't start until 4k (assuming u shift 1st at 6700). (Back to 1st gear) If I only have the pedal about 3/4 the way down, it accelerates smoothly. The problem also seems to be cured by resetting the ECU...but only for about the first 10 minutes, first gear will pull hard, like it should, then it is like the ECU adjusts its timing/maps/whatever and it kills my first gear power. That part could all be in my head, but I swear, it feels that way.

Recently, I installed a 2.5" mandrel bent exhaust. I have read about people saying they lost some low end power, but I do not think this could be the issue. Plus, my car is more heavily modded than a lot of people that have a 2.5" exhaust (1.8 ECU, CAI, 61mm BBTB, Airram, headers, full exhaust).

Also recently, I have installed the 1.8 ECU (the "best" one 23940). My car is a 97 Rev A, with a 2001 engine/trans, and ECU out of a 98 elantra. I believe this ECU is what is causing my problems.

Another thing that has been going on is I think an issue with my IAC, or maybe this is another problem stemming from the ECU, I'm not really sure. When I start my car, the idle is at 2200. After about a minute, it comes back down to 1000. No CEL's. I thought that the issue was my idle adjustment screw on my BBTB (because it is broke), but I actually removed the screw entirely and so there is a little more I have to push the gas pedal before the butterfly opens, takes a little getting used to, but its fine. I drove the car like this for a long time before fixing the idle screw on the BBTB, and never had the idle at 2000, so I don't think that is the issue anymore. I do notice that when I rev, and then let off the gas, it takes the revs awhile to "step" down. Basically, it takes longer to rev down. It feels a little weird. I remember DTN having a similar issue, he said he cleaned his IAC. This would be an option except that it is routed UNDER my Airram, so it would be a PITA to have to take out and clean, especially if it only MIGHT be what is causing the idle problem.

So, are the idle and power loss problems related? Are they because of the ECU? Or is the IAC messing up, and causing funny things to happen when the car is low in the power band? Could it be the TPS? I replaced my DaeSung it with a Kefico probably about a year ago, and haven't had any issues with it..I think.

Side note, my gas mileage has seriously shot up. Like an extra 75-100 miles per tank, and I have been beating on it.

Please help, thanks guys.

StrikeEagle

Not exactly sure what's going on, but I'm pretty sure the fuel mileage increase is due to the ECU. I noticed that when I installed mine, went up 50-100mi per tank. Sounds like your problem is the ECU though. Try plugging in the 2.0 one again (don't have to remove the 1.8, just unplug it) and see if the problem goes away. If it does, then try a different 1.8L one.

REDZMAN

I doubt the power loss is due to your ECU, the 1.8L ECU is known to get RID of the flat spot around those RPM's.

Just start with the usual.

1. Check your MAF and orientation of it.
2. Check for vaccum leaks.
3. Check your PCV valve, clean it if it needs to be.

zoned019

The plot thickens..

Reset the ECU again, now the car seems to idle fine, but I still have a flat spot in 1st gear....UNTIL the car warms up. Once the engine is at normal temperature, then it seems fine.

Any ideas? Vacuum leak?

Input? Anyone?

funkypc

Try swapping your ECU back - you did put a non REV A ECU on a REV A car - It's always a possibility.
or else it could be your MAF. Try driving temporarily with it unplugged.

AGreen

Edit:
I fully read your post....
You've already done what I said to do.... owned.gif

I initially said to check your tps because that was the EXACT problem I was having with mine. Could it be the Keifco doesn't cure cancer?!!!