Idle all over between 500 to 2200 and stalling

[DlaSerM]

Ok this is my fist post I hope I amin the right forum.

First let me say I am no amature at mechanic work and have been messing around with my car ever since I got it about 4 years ago. Its a 91 laser with a hacked MASS, K&n air filter, and my own 2 1/2 in turbo back exhaust I made with high flow cat and sport muffler, basically car is stock. I have just got done putting a rebuilt motor in it; this would be my 4th motor job on one of these cars. All the sensors that are on the motor(CAS, Ign modual, coil, IAC, etc.) are all different from the previous motor I pulled. All the sensors check out fine and I have checked TPS adjustment and closed throttle position switch which checked out ok. Already done boost leak test and found no leaks. All the injectors sound like their firing right. Rebuilt computer put in april of 2007.
Now that I got all that out of the way heres the problem. The motor doesent even have 500 miles on it yet. The idle was fine when I very first started it but after about 60 - 70 babied miles the idle started to jump all around. It would go from about normal to around 2000 to 2200 and kind of surge/miss back and forth between 2k and 2.2k . then if I hit the gas it sometimes would go back to normal then slowly rise back up and do the same thing. Then if I shut the car of and started it a minute later it would barely idle, at about 450 to 500 or stall out. If I hit the gas when it was idling low like that it would either comeback down and stall out or start to climb again and surge/miss at 2k to 2.2k . Any help is Greatly Appreciated due to this is my daily driver and my only other vehicle is my truck with a 460 that devours the gas and is making me broke.

sorry so long but I wanted to try to get every detail for a good explination of my problem.
thanks in advance, Jesse...

 

[DlaSerM]

I know I'm a new member but I would appreciate it VERY much if someone could give me an idea. I have searched this site for 2 days prior to writing this post and although I found numerous posts about idle problems, none of them were close to my problem and alot of them never had a solution that fixed the problem.

once again any help is greatly appreciated, Jesse....

 

[DlaSerM]

could someone please give me a thought on this problem???

 

[szl98gst]

I had similar problem with my gst before. It was the ignition coil going bad, and had 2 cylinders werent firing at all. Also, check your spark plug wires, make sure they are in the right order.

 

[snailspool]

Perhaps a boost leak test would help. Can you borrow a logger from anyone and get some data? It really sounds like an air problem. Try unplugging the maf and see if that makes a difference.

 

[DlaSerM]

Perhaps a boost leak test would help. Can you borrow a logger from anyone and get some data? It really sounds like an air problem. Try unplugging the maf and see if that makes a difference.

I have already done a boost leak test and didn't find any leaks. I don't know anyone in my area that has a logger or anyone that is even into these cars. I'll try the maf tonight. The idle has only been high when the car is cold and when it warms up it won't stay running it will stall. When I go to start it it will fire up for about 2 seconds and stall out. it will fire up and stall 2 or three times then it won't fire up unless I hit the gas and stay on the gas a little to keep it running. Kind of like it isn't getting enough fuel. I kind of thought the fuel pump but I didn't think it would make the car idle high when cold. I am going to pull the fuel tank and pump out of my parts car and throw in this weekend just to see if it helps. I need to replace my tank anyway due to a hole in it. I will post my findings.
thanks for the thoughts.

 

[DlaSerM]

I had similar problem with my gst before. It was the ignition coil going bad, and had 2 cylinders werent firing at all. Also, check your spark plug wires, make sure they are in the right order.

I have brand new wires and plugs. And of course I have the wires in the right order it would be pretty hard to mess the order up. The car does run and drives ok other than the high, low idle and stalling out. I do have another coil I could swap on it to see if it helps. I'll let you know my results

 

[Captain D]

Did you check the idle speed control motor with a multimeter to make sure all 4 coils are within limits? The ISC opens a passage in the throttle body that allows air to bypass the throttle plate at idle. If a coil is bad or if the passages are clogged the amount of air going to the engine at idle could be reduced. The area around the throttle plate could be dirty reducing the amount of air that is suppose to slip between the plate and the housing at idle. Do you have a mechanical boost gauge that will show you the amount of vacuum you have at ilde. It should be around 17 to 20, any less vacuum could be a vacuum leak. If you pulled the injectors out when you rebuilt the motor did you replace the bottom seals on the injectors? The ECU could be bad, do you have one you can swap out?

 

[fwspin]

I had this same problem years ago it was my idle speed controller.

 

[tbonitz301]

I have brand new wires and plugs. And of course I have the wires in the right order it would be pretty hard to mess the order up. The car does run and drives ok other than the high, low idle and stalling out. I do have another coil I could swap on it to see if it helps. I'll let you know my results

i also have a gst that did the same thing. i would check/clean your ISC,brake booster vacuum line, fp regulator vacuumline buried under injectors, and clean the egr.

 

[bugeye]

I had this same problem years ago it was my idle speed controller.

+1 on the ISC. Mine went out on the talon and caused the idle to spaz out on me and then the car would stall out at idle. I replaced it and the car is running fine now.

 

[talon187]

+1 for the isc i just had the same problem i would drive between 1k and 1.5k rmp and sometimes shoot up higher changed the isc and no issues

 

[DlaSerM]

I have already swapped the ISC out with one I kno was ok. Still the same problem. I do not have another computer to swap into it. I have made a FIAV block off plate to do some testing but I'm not to sure of what it will run like when I put it on. I was wondering if anyone had any input on the block off plate. I was thinking if the problem is in my computer which is screwing with the ISC and I put the block off plate on blocking off the ISC and the FIAV would this tell me if it was in the computer? And also how should I expect my car to idle/run like?

Thanks for the input...

 

[tqmx1]

If you have no history on the ECU I would have the Caps changed on general principle. You are looking at some parts in there that people were having go bad 10 years ago so if they lasted this long they were living on borrowed time.

It's a fairly inexpensive repair and if it's not it, one more item to scratch off the list.

 

[DlaSerM]

If you have no history on the ECU I would have the Caps changed on general principle. You are looking at some parts in there that people were having go bad 10 years ago so if they lasted this long they were living on borrowed time.

It's a fairly inexpensive repair and if it's not it, one more item to scratch off the list.

My ECU I just got back in march of 2007. It was a rebuilt unit from a reputable shop on ebay. I'm not saying it isn't messed up or anything; I guess you never know it could be the problem.

 

[Ravenous]

I would also check the coolant temp sensor... Mine went out last year and the car idled high and the car had issues running cold and starting up warm. I checked my logger to diagnose the problem and the temp showed -17 degrees if I recall correctly. This was also immediately after a rebuild, I pulled the connector and put three 10kohm resistors between the contacts and that allowed me to start. It could be a long shot because I don't remember my idle going that high but hey its something that hasn't been mentioned yet. they connectors also have a habit of breaking but looking fine.

 

[tqmx1]

My ECU I just got back in march of 2007. It was a rebuilt unit from a reputable shop on ebay. I'm not saying it isn't messed up or anything; I guess you never know it could be the problem.

Sory I missed that on my first read through. One thing I had luck with one of mine was to reajust the TPSand then opened it a little bit more (just a bit more air blead) and then used the BISS to ajust the RPMs.

One other one have you gone over the EGR system. It half way sounds like the valve is hainging open causing the low speed problem.

 

[DlaSerM]

One other one have you gone over the EGR system. It half way sounds like the valve is hainging open causing the low speed problem.[/QUOTE]

I puled off the EGR valve last night and checked it with my vacuum hand pump and it works fine. The inside was very clean still from cleaning it out during the engine rebuild as is the ports in the intake.

on a different note I put on the FIAV block off plate, which I blocked off the ISC also, and The Idle is perfectly fine after adjusting the BISS. I found my old ISC I took off when all this started and it had a Bad coil in it. The ISC I replaced it with which I just took off last night was fine, but I think the bad ISC did something to the computer which was freaking out the good one I put on. So the problem is fixed for now My computer is still under warranty so I am going to send it back to have it tested and fix if there is somthing wrong.

Thanks for all your guys input.

 

[tqmx1]

I know another dumb one, Did you unplug the battery and let the ECU go through a cold reboot?

 

[DlaSerM]

I know another dumb one, Did you unplug the battery and let the ECU go through a cold reboot?

Yes I already tried that. it was one of the first things I tried. It did nothing. thanks for the thought tho.

 

[97 gst turbooo]

so the ISC was the problem. i have a 2gb gst and i havent had any problems for 3 years. now as of today it starts up cold idle fine then it idles around 900rpms. then i touch the gas and it drops to 200rpms then drives fine and idles back to 200 and sometimes bounces and will idle at 9 then back at 2. my car is also only runnin 14-15 in vac. it sounds like there is a vac leak behind by the a/c compressor but i dunno if its just the compressor spinning making that noise.

 

[DlaSerM]

so the ISC was the problem. i have a 2gb gst and i havent had any problems for 3 years. now as of today it starts up cold idle fine then it idles around 900rpms. then i touch the gas and it drops to 200rpms then drives fine and idles back to 200 and sometimes bounces and will idle at 9 then back at 2. my car is also only runnin 14-15 in vac. it sounds like there is a vac leak behind by the a/c compressor but i dunno if its just the compressor spinning making that noise.

I don't believe the ISC itself was the problem. The ISC I took off when I installed the FIAV block off plate tested out to be fine. Either the problem was in the FIAV, which I dont think so, or it is in the idle control circuit in the ECU;which I believe it to be. After installing the FIAV block off plate my car idles fine after a little turn of the BISS. My ECU I got is still under warranty so I'm going to send it back to have them test it out and see if it is in the ECU. When I get it back I will post my results of there tests to let you know if it was the ECU.