So she runs, now for the problems.

Ok, so my cars starts, runs, and drives. However, it falls right on its face at like 4k rpms, it just kinda jerks and doesnt want to go faster. Heres what I think. The temp guage isnt reading anything so I think its always trying to warm up (constant 2k idle) and so its running pig rich and thats why its not running very after like 4k rpms. Could it be fuel cut? Its got a big 16g at stock boost with the BCS mod (it said the BCS mod raised it 1-2 PSI so it should be running like 11 or 12 PSI), it has those FP2's and an extrude honed IM. I dont think its flowing enough air to be hitting fuel cut, but I dont know. Maybe a boost leak? Any other ideas? I think its the temp sensor not working right, but I could be (and probably am) wrong.

Ok, so my cars starts, runs, and drives. However, it falls right on its face at like 4k rpms, it just kinda jerks and doesnt want to go faster. Heres what I think. The temp guage isnt reading anything so I think its always trying to warm up (constant 2k idle) and so its running pig rich and thats why its not running very after like 4k rpms. Could it be fuel cut? Its got a big 16g at stock boost with the BCS mod (it said the BCS mod raised it 1-2 PSI so it should be running like 11 or 12 PSI), it has those FP2's and an extrude honed IM. I dont think its flowing enough air to be hitting fuel cut, but I dont know. Maybe a boost leak? Any other ideas? I think its the temp sensor not working right, but I could be (and probably am) wrong.

sounds like a boos leak, but you never know, it's a dsm:evillol:

I had exactly the same symptoms, and it turned out to be the EGR solenoid. It was cracked right on the nipple where the vacuum line attaches. I just blocked off the egr and the symptoms went away. IDRC what led me to the solenoid, but it won't hurt to check it out. ;)

I have a blockoff plate already. Maybe a bad gasket? I'll check.

Also, in line with your temperature theory, try unplugging the coolant temp sensor and see if symptoms change (after you've checked the egr). If the symptoms don't change, it's possible that the sensor may be bad. I don't know how much control over the fuel the coolant temp sensor has though, a good bit probably. On a side note it is one of the things that tells the EGR solenoid to energize however, not that it matters when it's blocked off. Are you sure your temp gauge even works?

Yes, it worked fine the last time it ran. When it came out of the car the last couple times, I didnt take off the waterneck dealy before hand so I bent the prongs on the temp sensor. Well, I am like 95% sure one (or both) of the prongs arent making it into the connector holes. I think I am going to bring a mirror so I can look at them good, then straighten as necessary. To make sure it works, I am going to probably cut off the connector and hook the wires up directly to the sensor and see what happens. Or I will just stick wires in the connector, thats a better idea ;). I'll throw a new gasket on the EGR blockoff plate as well, and I will do a boost leak test in the morning or night depending on how lazy I am.

As far as fuel control goes with the temp sensor, Matt said it will run richer while warming up. Well, since the temp sensor isnt working, its trying to warm up all the time judging by the constant 2 grand idle. Hopefully when I fix the boost leak, EGR valve deal, and temp sensor it'll run good enough do do a good idle-redline pull and be road ready.

Also, (OT) those 2g front calipers help stop really well, she stops pretty quick.

As far as fuel control goes with the temp sensor, Matt said it will run richer while warming up. Well, since the temp sensor isnt working, its trying to warm up all the time judging by the constant 2 grand idle.


Hmmm, 2k though? That's the part that sounds strange since we are talking about a colant temp sensor. I have a 96 corolla, and I have wired a potentiometer in series with the colant temp sensor. I can control the fuel to some degree, I can make it run so rich that smoke comes out the pipe, or I can lean it out enough that it dies. The RPMs never vary more than about 400, and it won't make it idle over 1000rpm. That's what I meant by how much control the sensor has over the idle. Is it really capable of throwing the car into fast idle? Weird........

Well, Mikes DSM idled at 2k for a brief period of time before it got warmed up too. I am headed out there now, I'll direct wire the sensor and do a boost leak check and see if that helps. I'll just idle it in the garage and see if the coolant temp changes. If it doesnt, I'll go give it a couple pulls and see how it runs.

So I fixed the boost leak (I have a T in a vac line for when I get my boost guage, well, I just capped of the part of the T I wasnt using and the cap came off) and fixed the water temp guage (you know that little wire between the temp sensor and the block? yeah, forgot that). I took it for a drive, she pulled ok, but not as hard as I thought it should. It seemed to maybe miss every once in a while, I'll just get the plugs gapped right and see if that helps. Also, I am going to have the ignition timing set so that I know its right. Gotta fix the oil leak too. Now my problem is the idle. It idles at like 2k all the time, even when warm. WTF? I remember reading to unplug the TPS and just adjust the BISS? Is that what I should do?

Well the proper way to set the idle is to ground the timing adjustment pin near the battery as well as ground pin 10 on the OBD connector (third one up from the bottom on the right hand side). This throws the ecu in idle adjustment mode and centers the ISC motor. then adjust the biss screw to a 750 rpm idle. then unhook the grounded pins. Make sure you do this on a warm engine. If the idle has never been set this could be your idle problem. I know my car idles at like 2000 at startup! so annoying, but then drops done when warm. I think my ISC is screwed

The coolant temp sensor failing will tell the ECU your coolant is at -40 degrees F. It's amazing how much fuel it will add in this situation! Ricer's car last week would hardly even idle with all that fuel. Like Loeman said, it won't raise idle to 2k though. The fast cold idle requires more air, and that comes by way of the FIAV (Fast Idle Air Valve) which is open with cold coolant and closed when it's warm. Sounds like you got that fixed though.

Nate posted on how to set the BISS. I've never done it that way, since I use DSMlink to do it. But that is the correct idea. On a 2g you have to use a factory scantool to force the ISC to the center of its travel, but the 1g does have that cool diagnostic mode you can force on. The 95s had a similar pin, but it seems to only affect timing as far as I could tell.

Nate, your problem sounds less like an ISC and more like an over sensitive FIAV perhaps. If the ISC works, it will just do what the ECU tells it to, and wouldn't be temperature dependant (aside from the fact that ISC can go open at full temp, which would probably cause the opposite of your problem). Ideally you would log ISC position (short term) and the Learned Idle Adjust position (long term ISC position) and see what the ECU is trying to do.

hmm see I wondered that myself about the FIAV but when I did the turbo conversion I through on a used turbo TB and it did the same thing. Thats why I kinda ruled out the TB. its wierd when I start the car cold it idles at like 2000 and if I let it sit to warm up for a few the idles will slowly drop to around 1100. However if I flutter the gas a bit when cold...idle surge starts and continues till it warms up a bit! its wierd! now that I think of it I think my ISC is good cuz at hot idle when I turn the steering wheel a bit it does kick up the idle. I know when my car is sitting at a 1000 rpm idle the isc is only at about 9-10% open and when cold its completely closed (according to the computer) are these numbers right? also is there a way of testing the FIAV?

Hmm. If two FIAVs did it, I wouldn't rule it out, but the chances of that being the cause go waay down :)

Is it idling at 2000 on "cold" start in warm weather? How long is it taking to come down? The ECU will force a high idle for a short time even when it's warm out and the engine is warmed up. I just want to make sure that what you are seeing is actually unusual I guess... I know you know what you are doing, but this seems strange. I'm not familar with % values for the ISC, but 9-10% for normal idle and fully closed when cold seem very different from what I see on my car. Perhaps the BISS is open too far compounding the open FIAV? (Even a good FIAV should be open somewhat in summer before the coolant is up to temp). The idle surge tells me that something is not what the ECU expects it to be. I'd start by closing the BISS a turn or so and see what happens (watching the ISC position as you did before).

haha I was one step ahead of you. I actually did that the other day and I think it has definitely reduced the idle surge problem when cold (engine cold, outside air hot). In fact it hasnt idle surged in the last couple days. When it idles at like 2000 rpm itll take about 5 minutes to drop completely to about 1100 (about fully warmed up) now if I start driving it only about a miunute after start up, the isc opens up a bit and as soon as I put in the clutch the idle jumps to 2500! haha its insane! it almost seems like a vaccuum leak but I've boost leak tested the intake track and its come out pretty good (a bit of minor leak through TB shaft seals). As for those % values, thats what mmcd for palm reads

I've got to think a bit or research why the ECU keeps setting my idle at 2k when the car is moving. I get something similar to what you see but only when moving. I can get rid of the surge by raising the Coasting Fuel Cut rpm above what it idles at, but that doesn't fix the root of the problem. I've been putting this off for a long time :) The EVO doesn't like the 2g ECU too much, or vice versa. Perhaps in my efforts I'll come across something that applies to your situation. I know the idle system pretty well on these cars, but not well enough I guess :)

Ya I'm not sure if this applies with your setup but I know I had a hacked mas before and it was causing way to much unmetered air and was causing a lean fast idle and often major idle surge. Is there any way this could be causing your problem and since your just richening it up, more fuel + more air = faster idle?