Very Rough Idle-All Parts New

[EuroFanatic]

First of all, having to post in the noob section is very annoying when I have my car torn apart in the garage and need it running asap and have to wait for answers for days before someone sees the question...


1996 Eclipse GST 2.0T

Starts after about 4-5 cranks, then will idle VERY rough. Burns very rich. After it warms up, the idle spikes to about 3k and holds. Only way to drop it is to shut the car off.

No vac leaks, replaced EVERY vac hose and pressure tested the boost pressure system. New plugs and wires. New air filter. No modifications besides an air filter put before the MAF sensor.

No check engine light, key on off ect method pulls no codes. Also with a Matco scan tool it says no ECM present, but the ECM is there, I can see it. Would run without it. If I unplug the connector to the computer on the MAF the car drops idle to a manageable level and evens idle. Plug it back in and the car idles waay high again. Seems like its in its own limp mode and runs VERY rich (black smoke) and I cannot get to the CEL to diagnose why.

Is there anyway to force the data link connector to give up its information? Are there any ideas on what could cause this?

 

[92AWDHX40]

Terry's Talon Troubleshooting Tips #3 - Fast Idle (aka. Idle Surge)

this for idle, do you have a wideband, i would find another way to check the cel, take it autozone is my next guess.

 

[92PandaTalonTSI]

Also with a Matco scan tool it says no ECM present, but the ECM is there, I can see it.

That might be the problem. I know the ECM on the 96s don't seem to go bad, but you never know. It doesn't hurt to take the ECM out and check it. It definitely doesn't take long to get to and doesn't hurt to check. Compare it to the ECMs on this site.

ecurepairhome [ECMTuning - wiki]

 

[EuroFanatic]

One of my fuel relays were bad. Does anyone know how to jump one to make the pump come on? I just tried to start it and the pump wont even try.

 

[CrawlinZX14]

Replace the relay. Or you can run a hot line from the battery back to the fuel pump with atleast one inline fuse near the battery. Then run that into a relay, run the signal wire into the relay as well, ground it, and the output for the relay will connect to the fuel pump. Do a search for a 1g fuel pump rewire mod and im sure you will get the just of it. I dont know the terminal post numbers off hand to do it, but sounds like your wiring took a crap. Use a DMM to check for how much voltage your getting at the relay, and at the pump. Chances are thats where your problem will be in the fuel pump.

The idle issue could be a bad MAF sensor. or a bad ECU. Could also be a TPS thats not right either. Telling your ecu that you need more fuel than you actually do because the TPS and MAF are not communicating the same info. Thus making it run super rich and almost like limp mode.

Did you make sure your TPS is correctly installed and set properly? It says all parts new in your title is why I am asking. If its off, it can cause issues.

 

[EuroFanatic]

Ok. I got the datalink to work properly finally. The CEL was for the MAP sensor. Flagged that immediately. I replaced the MAP and it runs MUCH smoother and not overly rich anymore. It still has a slight hiccup but I can set the idle to 600 and it wont die anymore. I have it now about 750 but there is still a slight miss.

If I simply run a on off switch to the fuel pump will that work instead of a relay? Or does it need a signal to run the fuel injection properly?

Also my TPS was set to 15% open with engine off and 16% with engine on. I dropped that down to about 1000rpm and used the setscrew on top to drop it the rest of the way.

It it possible to run a BOV instead of a recirculating valve without tuning? The guy I bought it from had an aftermarket one with it, but I dont want to put it on if it will bog down or anything...