P0740, Low Idle, and other issues
 

Hey all,

New to the forum, so go easy on me. Seen a lot of helpful info on here and was looking to get some advice.

I just bought a 99 v6 a/t EX from a Brian O'Conner wannabe. It has 94k miles on it and the engine purrs like new. The tranny was "rebuilt" by a horrible shop 3k miles ago. I have yet to drain and fill the tranny with Honda fluid, but it's on my list.

The main question I have is regarding the idle. I'm not 100% sure whether the idiot that owned it before me messed up the needle when he put the Mugen cluster in or if it really is idling low, but the needle rests on the peg when idling. I'm leaning towards low idle because I can see the lights dimming when braking, accelerating, and when I turn on the A/C and when i press the accelerator, the needle moves immediately.
What I think it could be:
1) AEM SRI. Dirty filter, or something else to that effect
2) 1 Muffler is gone. Yes. Gone. There is a hole where it should connect to the Y-pipe. It is aftermarket, not sure what kind yet.
3) Vacuum leak. I hear some sort of hissing(ish) from where the timing belt is. wondering if the timing belt normally sounds like that?
4) Torque converter.

My question is, which of these would be the most likely cause a VERY low idle?

Any help would be appreciated.

P.S. The shift control shaft seal is leaking pretty decently (noticeably, even with the engine off). Could this cause the torque converter code? I know it's a long shot, but maybe it has low hydraulic pressure because of this?

Thanks!

P.p.s. I have tried adjusting the idle with the helms method. I tested the TCC solenoid as well (ohms and 12v (thanks to cruising this forum)) and it's good. I know it's my torque converter, not trying to figure that one out anymore.

Also, somewhat of a dumb question, but would it hurt to plug the other exhaust hole? Or would it cause issues because it's going through the Y-pipe?

Anyone? Any opinions? Could use some! :)

Have you cleaned the Idle Air Control Valve and throttle plate (both sides)? IACV can get stuck closed or blocked w/ crud and not allow bypass air to control idle speed. Result is low idle/stall condition. If AC depresses idle speed, the something is wrong w/ idle air flow.

P0740 is a "hard to fix" code. Basically you have an internal hydraulic fault that is preventing torque converter from locking as intended. There are numerous parts that can cause the fault. Only good news is you can live w/ P0740 for as long as you can tolerate the incessant Check Engine Light. You can turn it off and it will come on again as soon as you reach 55 mph. TCM detects slippage between wheels and crankshaft (torque converter not locked) and sets code.

Hissing could be PCV, brake booster, or other large vacuum lines. It could also be a loose tensioner bearing on timing belt. Check all vacuum lines carefully. You can spray throttle body cleaner and listen for an idle change to find leak site.

good luck

Thanks for the reply! I was hoping for you and/or poorman. Lol

The IACV was replaced when the trans was rebuilt along with a few other things. There is no stall, which confuses me even more, and I'm not completely sure whether the idle drops w/ AC or not, but it definitely vibrates more. It may be that I can't see it dropping because its already pegged. Any ideas where I can find that weird driver head? Or anything that is able to imitate it without stripping it? I would like to clean the throttle body just in case though.

As far as living with the P0740, if it is the Torque Converter, wouldn't that destroy other parts of the tranny? If its a hydraulic issue, then I can see it being live-able, but wouldn't it throw shavings into the tranny?

Checked the PCV valve already. I have the helms, but I can't seem to find any vacuum diagram that I can understand. When you say spray throttle body cleaner, you mean on the hoses or in the throttle body itself?

Plugging the exhaust, bad idea? Thinking of duct tape until I can find a replacement.

Thanks again for the advice!

Low idle speed is caused by lack of air flow. A dirty throttle plate may restrict small amount of air bypassing the throttle plate. IACV is usual culprit or passages to/from the IACV. A very dirty air filter might cause low idle.

P0740 can be caused by faulty internal valves and modulators. Also by check valve in the torque converter, all inaccessible to external repairs. Why would metal result from torque converter failing to lock. Clutches are source of small amount of filings seen on tranmsision drain plug.

good luck

No clue, that's why I'm here. I haven't the first clue when it comes to transmission issues. So even with shift hesitation, it should be nothing to worry about, at least for a while?

Leaving work today I noticed that before it was warmed up, and coasting in neutral, idle was dead on. As soon as I braked, the idle dropped slowly until, when I stopped, the idle was back to it's pegged position. Possibly brake booster? Haven't seen anything in the helms about that, but then again haven't looked in the brakes section.

Thanks for your time!

Vacuum levels may affect idle, but air flow is what determines idle speed. See previous post.

good luck

Ok, so IMO, the K&N on the AEM SRI is not dirty enough to restrict flow. I haven't tried cleaning the throttle body/plate yet, but will and report back as soon as I get time. Will I need to bleed the coolant system after or not? Haven't thoroughly looked at the tb disassembly procedures yet.

EDIT: Forgot to mention that, following procedures in helms, adjusting the idle speed VIA the screw has no noticeable difference. Followed the procedures to a T for several full turns either direction.

Update: disconnected battery, removed intake, disconnected MAP, removed TB with minimal disconnections, and wiped down with what I had available at work (damp rag). Put everything back together, turn the ignition and it just turns over and over.

No big deal. Happened when I put the car up to check for trans leak and I figured fuel drained back a little. Turned to off, turned back to II, no fuel pump whine. Same thing that happened before, but a couple tries had it whining again and started right up. Not this time. Traced it all the way to an open between PGM-FI main relay connector pin 1 and ECM pin A15. Awesome. Gonna have to tear the dash apart for this one.

But now I'm leaning toward the idle problem being on the electrical/fuel side. Any thoughts?