Motor idle surges and loss of power.

[rsross314]

Ok yet anouther problem with my freshly built 420. Cranked it up for the first time after the timming was done and rechecked , the car fired up and would idle at 3500 rpms and surge between 2k and 3500 radicaly. Started messing with some plugs checking everything , i have the egr block off plates if that makes any difference , and unplugged the top plug behind the t/b and it didnt affect it untill i unplugged the bottom plug and it stoped surgeing and held idle but at 3k. Plugged them both back up pulled the bat to see if anything would reset and cranked it back up now it idles at 1k but when the gas is pressed the idle drops and is impossible to drive more then a few feet. Also noticed that the entire time my intake was loud as crap , i work at a shop and have never heard anything that loud sucking in air , but again when the gas is pressed the intake gets quiet and you cant hear that much untill you let off and again it starts geting loud. Any ideas? I was thinking at first maby the computer was bad but im not sure now. Its a 95 rs

 

[VelocitàPaola]

Are you sure the timing is spot on?

 

[rsross314]

Yea its been checked and rechecked. Would that affect it in that way though?

 

[VelocitàPaola]

It would make for a bad idle and loud intake.

 

[XMasta19]

How exactly are you doing this "check and recheck"?

The timing can easily be mixed up and done incorrectly...

 

[rsross314]

I did the timming the first time and was 2 teeth off and had it done at a shop and then when i got it home turned the crank by hand to check the marks.

 

[rsross314]

Ok woke up this morning to get my car towed and the car fired right up still idleing at 3k but once i tried to back it up to get it on the truck it droped down normal and drove great. Still had it towed just incase and once i got home it did the same thing high idle but once the clutch was released and started to move it functioned normal. Could this be a ecu problem i read something about they run ok untill warmed up with the ecu going out , it was in the 30s this morning. Or maby a vacum leak?

 

[XMasta19]

If you start the car and just let it idle...will it stay on for 5-10min etc, just really high?

 

[rsross314]

Yeah it will drop low after about 10 mins or longer and start stuttering real bad. But untill then it cranks and stays at 3k-3500 but will drive decent for awhile.

Just took my ecm out and apart , first thing i noticed was a label on the out side with this word for word. " WARNING WARNING Software Uptadet Warranty"
After thinking about how hard it must be to rebuild an ecu if you can not spell update i opened the case and it was all screwed up. So im getting a new one this week hopefully this is the problem.

Changed the ecu same problem. checked a few vac lines and it didnt help. Im thinking it may be a line though. any ideas?

The vaccum lines are correct (- the one for the egr as i have a block off kit). Also just replaced the ISC and TPS , idle is steady but at 3k rpm , made sure it wasnt the cable holding the tb open. I could realy use some help , The only lines missing are to the egr and the plugs also for the egr. I cant figure this thing out. There is a VERY loud hissing from the air going into the hole for the isc too , is that normal?

Update: Just swapped my old ecu back in and it started Perfect and idle was at 900 steady no problems untill again the motor heated up and it now just shuts off. When it was running good it would rev steady and respond to the throttle but now it just stutters and barley moves even at WOT and will die off.

 

[brassc2007]

It is a possibility that it could be a sensor. the sensors read differently as they warm up so it could possibly be reading fine when cold but after a short warmup period the sensor could be throwing the wrong reading to the ecu i would suggest test you sensors when they are warm and see if they are throwing a reading that is in the factory operating range if not replace them and see what happens. good luck

 

[aljohnl]

so did you find an answer? My 95 rs does EXACTLY the same thing. I'm on my second computer. Its almost like it has its own mind. I was putting home from a test drive going like 1 mph then bam! About broke my neck. The idle surges bad when warm too, like the comptrr is pulsing the idle motor open and close.

 

[Kimiko]

I have a 95 Eclipse GS with the same problem. I have so far changed the MAP sensor, the Idle Air Control motor and I have replaced all the vacuum lines to ensure that I do not have a leak. I just found some information on a different site that might be helpful. I happen to have a leaking radiator and have noticed that as the day goes by, my idle problem gets worse. I have a feeling that the paragraph I am posting below is the reason because when I top off my radiator in the morning, the idle problem does not happen. I am going to replace the radiator and see if this fixes the idle problem.

Our cars have the coolant temp sensor at the top just next to the radiator cap and the thermostat. I can only assume that when the coolant level drops, the temp sensor can no longer send proper info to the ECM. Please read below and check your coolant levels.



"The idle can be too high for several possible reasons. A high idle speed is caused by excess air entering the engine. THis can be due to a leaking vacuum hose, a failed intake manifold gasket, or any other place on the engine where air is being sucked in.

The computer controls idle speed by opening and closing a valve called an idle air control. THe IAC allows a specific amount of air to enter the engine at idle. If the IAC valve is faulty and not responding to the commands teh computer is sending, it can cause idle speed to be too high. Also, the computer depends on being able to accurately measure engine tempeature to be able to calculate an accurate amount to open the IAC valve. So, a faulty engine coolant temperature sensor, a faulty engine thermostat, wiring problem with the coolant temperature sensor circuit or a low engine coolant level (coolant too low to contact the temperature sensor in the engine) can all result in a higher than normal idle speed."

 

[RSTeclipse97]

I sorta have a simular problem only in reverse. When i first start my car it lobes like its gotta big cam in it and after a minute smooths back out. I talked to my local dealer and a buddy that works at a speed shop and they both said it was more than likely the temp sensor on the back of the motor. That sensor tells the ecu how lean or rich to run and the small sensor on the thermo housing is for the gauge. If i were to try and start and leave right away my car wants to just die and not really go to good but it will atleaste move

 

[Locke]

The temperature sensor on the back of the engine (intake manifold) is the IAT sensor, which meters the temperature of the incoming air charge. The information from this sensor is vital for correct calculation of airmass.

Test it.

There are two temperature sensors on the thermostat housing, both measuring coolant temps. The small one drives the gauge, while the larger one provides information for the ECU.