Unsolvable Idle Problem

[stutz43078]

Ok, let's start with the history of the car:

-The car is an automatic 91 gst
-My friend bought the car 2 years ago
-The water pump was bad
-He replaced it
-When he started it, he was getting idle surge
-He noticed the intake cam gear had a missing tooth
-He replaced it
-Before he put on the belts back on, he found another car he wanted more
-About a year after that, a year ago, he sold the car to me
-When I got it all it needed were the belts put on
-I decided to do a full build due to the missing cam gear tooth
-I found no signs of bad timing, but continued a full rebuild
-Went with the 1g rod 2g piston combo along with 2g cams
-Did the balance shaft delete
-Removed the emissions, power steering, and air conditioning
-Rebuilt the 13g turbo
-Installed a translab shift kit
-Finally got everything bought, built, and in yesterday afternoon

Ok, now the problem:

-I started the engine
-The rpm's jump to about 1700
-Then within about 3 seconds the rpm's climb to 2100
-At 2100 rpm the check engine light comes on and the engine dies

Some side notes:

-Seems as if the ecu is killing the engine because the rpm's just drop with no rough idle or misses
-Also no unusual sounds coming from anything in the engine bay

Things I have tried and done:

-I have read and tried terry's idle surge page:
Terry's Talon Troubleshooting Tips #3 - Fast Idle (aka. Idle Surge)
-I have ruled out that this isn't a typical case of idle surge
-I have tried a new idle speed controller
-I have tested the throttle positioning sensor
-I have tried two different mass air sensors
-I adjusted the cam angle sensor and it did change the rpm that the engine was jumping to, so I assume it is working
-I have checked my vacuum lines and intake/intercooler hoses multiple times for any sort of leaks, and installed all new hose clamps
-Installed new grommits on the injectors
-I have tested the fuel pressure regulator
-I double checked all my connections, even disconnected each primary sensor seperately to make sure that they would give me a no start symptom
-The knock sensor, o2 sensor, and pcv ar all new
-I losened my throttle cables and made sure the throttle place was all the way closed
-The only other thing I can think of is year old gas, but I assume that it would be getting poor idle, not high idle with that issue.

I think that is all. If anyone has any other suggestions, they will be greatly appreciated. This is my first dsm so I could be missing something quite simple. I know I need to check the check engine light, but I have no access to a OBDI scan tool set up for a mitsubishi. Thanks in advance.

 

[agentorange313]

maybe this will help

1G BISS Adjustment

 

[92AWDHX40]

Did you do a boost leak? ??? Idle issues are known there as well.

 

[TSi Kid]

See if you can get ahold of another ecu so that you can check if yours is bad. Definitely do a boost leak test because it could be a combination of things.

 

[gusu]

The EGR, uncleaned throttle body, and some valve on the US only DSMs also cause idle surges. My EGR was causing a idle surge, my uncleaned throttle body is causing one now, and for my friend he had to order a plate for his throttle body to block something off. I can't remember what it is though.\


Oh, I also forgot a failed ISC will eventually cause the caps on your ECU to leak. Even if the caps are replaced the embedded lines on your board could be damaged from the acid. Basically it wouldn't be repairable at that point.

 

[stutz43078]

maybe this will help

1G BISS Adjustment

I can tell it has be tampered with, so I played with it a bit, and it's not making any difference. I know that once I can get her to idle I will need this though, thanks.

Did you do a boost leak? ??? Idle issues are known there as well.

I don't have a boost leak tester, even though I'm rather confident that it's not a leak. I have visually inspected everything a couple dozen times now, but it could be, I'll try to borrow my friends later this week if I don't figure it out by then. Thanks.

See if you can get ahold of another ecu so that you can check if yours is bad. Definitely do a boost leak test because it could be a combination of things.

I forgot to mention that my friend actually tried replacing the ecu, but it didn't make a difference. It was used though so who knows. This will probably be a last resort thing though because all the guys I know around here own 2g's so I'll have to purchase the ecu. I am starting to lean towards it being the problem though. Thanks for the advice.

The EGR, uncleaned throttle body, and some valve on the US only DSMs also cause idle surges. My EGR was causing a idle surge, my uncleaned throttle body is causing one now, and for my friend he had to order a plate for his throttle body to block something off. I can't remember what it is though.\


Oh, I also forgot a failed ISC will eventually cause the caps on your ECU to leak. Even if the caps are replaced the embedded lines on your board could be damaged from the acid. Basically it wouldn't be repairable at that point.

Well I know the throttle body is shutting all the way and it wasn't all that dirty. The EGR was removed with the emissions and it has a block off plate there instead. Not sure what valve you are speaking of though. The ISC is working, I tried a new one today and did an ohm test on the older one, but it very well could be the ecu behind this. Thanks.

 

[92AWDHX40]

I thought i had ok bl didnt they were in places i didnt think of especially since my fmic install. Block off plate mine leaked there a t lot 3 times to fix it but not its sealed.

 

[stutz43078]

I thought i had ok bl didnt they were in places i didnt think of especially since my fmic install. Block off plate mine leaked there a t lot 3 times to fix it but not its sealed.

Could this kill the engine though? I mean I know this would give me weird idle, but could the ecu be killing the car just because the idle is too high? I'll def try to get it from my friend either tomorrow or wed. I only see him at school which is an hour drive.

 

[Tyeler18]

Go make a boost leak tester. Everyone says they don't think they have any boost leaks, but you can't see air escaping. It will cost like $10 to make. We really can't help a whole lot until we know that your system is holding pressure.

 

[stutz43078]

Go make a boost leak tester. Everyone says they don't think they have any boost leaks, but you can't see air escaping. It will cost like $10 to make. We really can't help a whole lot until we know that your system is holding pressure.

I have a friend that has one but he lives an hour away. We go to the same college though so maybe I can get a hold of him this week. I planned on doing one once I got the car idling to begin with, but I never heard of boost leak killing an engine because of high rpm's, usually it's poor/rough idle due to boost leak. You honestly think that it could be the problem?

Quick question, would a bad wire to the oil pressure switch and oil pressure sending unit cause the engine to shut off? Found a nick in the wires. Also as an update, I found all the test procedure for all the primary sensors and I'll be doing those test as soon as I am out of class tonight.

 

[stutz43078]

Ok. So finally broke down and started taking things apart. When I pulled off my crank pulley and checked my timing, I realized it jumped 2 teeth on the crank sprocket. Went and head and got a better belt and going to redo it tonight. I'll post the results either tonight or tomorrow.

 

[And_44]

Well that could diffently cause the idle issue and dying. Did your buddy also change the hydraulic belt tensioner when he did the pump? If unsure could be reason why timing jumped in first place.

 

[stutz43078]

Well that could diffently cause the idle issue and dying. Did your buddy also change the hydraulic belt tensioner when he did the pump? If unsure could be reason why timing jumped in first place.

He didn't but I did. I ordered a new timing kit. I didn't set the tension correctly, I read it wrong the first time through. Honestly I got lucky here. Stripped crank pulley bolt though in the process of changing the belt, so I have to order a new crank gear and wait for it to get here... bleh... :/

 

[TSi Kid]

I'm going to go ahead and say that this was probably your problem
If the problem still persists then look into swapping in a good ecu.

 

[banishedmunk]

There is no need for an OBD1 tester to pull a code. ECU Code Checking

 

[stutz43078]

Ok. So when I fixed the timing, I accidently stripped a bolt on on in the timing gear for the crank pulley. After waiting a week for the new part finally got it on last night, and fixed the timing, but I am still having the same problem. Idles around 2k for roughly 5 seconds then it dies. As I said before, if I touch the gas pedal it dies immediately. I did notice though, that I can get it to rev up by manually moving the throttle plate, but it still dies after about seconds.

There is no need for an OBD1 tester to pull a code. ECU Code Checking

I forgot to mention that I had done this process after I started this post. It isn't showing any codes.

I'm going to go ahead and say that this was probably your problem
If the problem still persists then look into swapping in a good ecu.

The code it gives you when there aren't any problems is suppose to mean the ecu is good. Would it be giving me that code even if the ecu were bad?