420A Confused on Idle issue

[david-b]

Hey all;
I'm a long time user on AutomotiveForums and a long time reader over here, although I believe this is my first time posting.

I've got a 95 Talon ESi and have been having weird idle issues with it which is blowing my gas mileage. Basically what happens is when I'm driving, I used to pop it to neutral and the rpm would drop right down to idle and sit there no problem. What's been going on for quite some time now and just getting annoying now, is when I pop it out, say from 3k rpm, and it'll fall to about 1500rpm, and either shoot up to 2000 and slowly come down, or go from 1500 or 1200 and just surge +- 400rpm. It's most annoying. However, when I come to a complete stop, the idle drops down to ~850 and sits perfectly.

I don't remember when this started, so I couldn't tell you what I did to make this happen.

My mods are:
Ported Head & IM | 3-Angle Valve Job/PEP Valves | Crower Stage 2 Cams | Crane Springs/Tit. Retainers | OBX Adj. Cam Gears | 4-1 Tsudo Header | 2 1/2" DP | 2 1/2" Tsudo Catback | Bomz UDP | Prothan Mounts | MSD Coilpack & 8.5mm Wires | Iridium Plugs | CAI | 55mm TB | SAFC | Datalogger | Grounding Kit | Voltage Stabilizer | B&M Shifter | Drilled/Slotted Rotors | Front, Rear, Lower Strut Bars | Stage 2 Clutch
Freshly rebuilt tranny also.

What I've done:
-IAC and TPS are tested and working fine. Replaced 1-2 years ago anyways
-EGR valve is new
-No vacuum leaks that I could find
-No CEL
-Cleaned TB
-SAFC at 1000rpm is -10%

Also getting another ECU and trying that, but a couple weeks ETA for that. When I reset the ECU it does seem to help a little, but then goes back to the bad drop-to-idle


Any ideas? Thanks in advance!!

 

[1gDSM4g63]

It is most likely the BISS; http://www.vfaq.com/mods/BISS-2G.html or maybe a blown throttle gasket.

 

[david-b]

It is most likely the BISS; http://www.vfaq.com/mods/BISS-2G.html or maybe a blown throttle gasket.

420a don't have a BISS. And TB gasket is brand new along with every gasket on the head.

 

[silvreclips]

Whats up Dave, Still haven't got that thing fixed.

I know whenever my car is rolling (not in gear) the rpms stay around 1200-1300 until I completely stop. It has been that way since day one. The only weird thing im seeing is that it surges to 2k sometimes.

 

[david-b]

Whats up Dave, Still haven't got that thing fixed.

I know whenever my car is rolling (not in gear) the rpms stay around 1200-1300 until I completely stop. It has been that way since day one. The only weird thing im seeing is that it surges to 2k sometimes.

It never did that when I got it though, and for a long time. I remember it specifically because of how quickly it used to drop down to idle rpm. And listening to other cars also, they do it right.

 

[silvreclips]

I think we need to take a poll.

How many cars sit around 800-900 rpms when rolling in neutral?

Good luck on the fix, you seem to have lots of problems with that car of yours.

 

[ndsti]

Haha.. my car did that then it crankwalked just are warning though.

 

[david-b]

Haha.. my car did that then it crankwalked just are warning though.

. That sucks, but again, working with 420a... never going to happen. Although with my luck and this car, it probably would. But still... Go !!

 

[ndsti]

Read up on Iridium plugs and why their bad!

 

[ndsti]

Don't say never any car can walk!

 

[david-b]

Read up on Iridium plugs and why their bad!

Ya they're bad for high heat (nitrous) motors. I'm not use nitrous or turbo. Just all bolt-ons. They come out looking great each and everytime I change them. No melting or anything.

 

[Shadow98]

I know you said you tested your TPS, but I'd get it check out or replaced again. I had one go out in less then 6 months before...

 

[david-b]

I know you said you tested your TPS, but I'd get it check out or replaced again. I had one go out in less then 6 months before...

I just tested it with the Ohm meter or whatever. It's in the right voltage or whatever. I tested numerous times. I believe it did it with the old TPS too. Like I said, this one is nearly brand new. On the logger and the SAFC, it works fine. The old one used to show movement when nothing moved and was out of the right voltage, this one is fine though.

 

[greentrbo_95gst]

. That sucks, but again, working with 420a... never going to happen. Although with my luck and this car, it probably would. But still... Go !!

We've never heard of 420's crankwalking. Have you tried replacing the Idle Speed Controller?

 

[4UH8ERS]

Have you tried replacing the Idle Speed Controller?

The ISC, is the IAC he referred to and said is in the correct voltage. Easy mistake to make as even Mitsu lists it as ISC in the parts dept.

If I am rolling in neutral though, my car does idle around 1100-1200 RPM. It will drop to about 900 at a complete stop.

When you say it "surges" is it just once and then immediatly corrects itself or does it surge multiple times in a row? Can you make it surge repeatedly or is it a random thing you can't reproduce?

 

[GabedsmT]

hey i had the same exact problem for about 2 weeks. u probably have the same throttle body i have 55mm well heres ## answer: i was so upset because i thought the TB plate wasnt closing like is suppose to and i thought i was gonna have to returned it. well after changin my idle control motor about 3 times n realize it wasnt the sensor..... i decided to work out with the screw.. i did about 3 full turns to the left(losing it) meanin closin the plate some more.. and my problem was gone! all that work takin it out about 4 or 5 times n it wasnt the damn screw . so there u go good luck... n if it doesnt work out for u, is deff the sensor on the bottom, idle control motor sensor.

 

[bullettdsm]

If I am rolling in neutral though, my car does idle around 1100-1200 RPM. It will drop to about 900 at a complete stop.

Normal. ECU reads speed sensor.

MB

 

[david-b]

hey i had the same exact problem for about 2 weeks. u probably have the same throttle body i have 55mm well heres ## answer: i was so upset because i thought the TB plate wasnt closing like is suppose to and i thought i was gonna have to returned it. well after changin my idle control motor about 3 times n realize it wasnt the sensor..... i decided to work out with the screw.. i did about 3 full turns to the left(losing it) meanin closin the plate some more.. and my problem was gone! all that work takin it out about 4 or 5 times n it wasnt the damn screw . so there u go good luck... n if it doesnt work out for u, is deff the sensor on the bottom, idle control motor sensor.

The plate closes fine all the way. It was actually sticking a little and I did some fine sanding the other day around the edges and fits even better. And no that didn't make it worse. Helped the pedal from sticking that little bit it was though.

The screw is as far out as it can. The piece that hits the screw is actually sitting inside the hole because the screw is pushed back enough. Doesn't touch the screw at all.

IAC is fine. It's new, and checks out fine.

Surges many times until I come to a stop and drops down then.

 

[Shadow98]

If the screw isn't touching the piece that opens/ closes the TB plate, your TB cable is too tight.

 

[david-b]

If the screw isn't touching the piece that opens/ closes the TB plate, your TB cable is too tight.

It's not too tight. The piece that hits the stopper is hitting the actual metal on the TB, not the screw itself. It's closed all the way.

 

[bullettdsm]

Well, it does sound a lot like a vac leak. But since you seem to have ruled that out and we are now into the "goofy" stuff. I'm wondering with the bad gas mileage and the surging (that is "helped" by resetting the ECU) if you don't have a front o2 senser problem. I didn't see anything about a cel but it wouldn't nesessarilly throw a cel.

Just a thought.

MB

 

[4UH8ERS]

Well, it does sound a lot like a vac leak. But since you seem to have ruled that out and we are now into the "goofy" stuff. I'm wondering with the bad gas mileage and the surging (that is "helped" by resetting the ECU) if you don't have a front o2 senser problem. I didn't see anything about a cel but it wouldn't nesessarilly throw a cel.

Just a thought.

MB

I can vouch for that. I have had a front o2 sensor go bad (with no CEL) and cause me to run extremely rich and have idle surge as a result. Might want to check the exhaust manifold for a leak as well, which can cause inaccurate o2 sensor readings.

Just another idea seeing as how we are running out ideas.

 

[david-b]

I can vouch for that. I have had a front o2 sensor go bad (with no CEL) and cause me to run extremely rich and have idle surge as a result. Might want to check the exhaust manifold for a leak as well, which can cause inaccurate o2 sensor readings.

Just another idea seeing as how we are running out ideas.

Actually I kept forgetting to post this, but the front O2 sensor is about 8 months old, brand new. The old one threw a CEL, so I replaced. The header is tight on there, along with the rest of the exhaust with no leaks or cracks. Been on and off the car numerous times this year. So I checked that too

These are all great ideas, but I don't know what else there is. I've gone through a ton of things and nothing. It's under about 6 inches of snow so I can't get to it at the moment. Was going to play around with that screw in the TB a little. Not til later though it looks like.

 

[GabedsmT]

you have 3 options and guarantee you itll go away:
1 mess with the adjustable screw
2 replace the idle control motor(right under the tps)
3 vacuum leak

 

[silvreclips]

I dont know man, I beleive Dave has already tried all of those.

I guess his car is just cursed