AC Stalling engine

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08-13-2010, 09:38 AM
titanescape

AC Stalling engine

I'm still having this issue, the AC blows cold as ice but always wants to stall the engine.

Mine is a 96 with a JSRC M45, JSRC air to water IC, and JSRC Headers. The car runs great but when I flip on the AC it bogs down and stalls. I can keep it alive with the gas pedal then slowly let off the gas and it will idle below 1K. Other times it will idle really rough or stall out. The AC blows cold as ice but I can't figure out the stalling issue. Ive increased the idle(I don't like it idling that high) but that still doesn't stop the problem. :confused:

I looked on the other board and all I can find is either the ISC(Idle Speed Control) or the AC Relay fan. I don't wanna just start buying parts blindly!

Thanks in advance for any help you can offer!
08-13-2010, 09:46 AM
sammm

Does it idle correctly without the AC running? Have you jumped TEN/GND and checked it?
08-13-2010, 09:50 AM
titanescape

Yes, it idles perfectly. When I jumped Ten/GND I didn't get any codes at all. The check engine light didn't blink at all.
08-13-2010, 09:51 AM
jeepinbanditrider

The increased airvolume in the intact track after the SC install causes it. I've had constant problemw with mine since I put the JR supercharger and TDR Air To Air intercooler in it. The only things I've been able to do to fight it has been to close off the idle screw (all of this is while the "ten/ground" pens are jumpered) and set it to stock idle speed with the throttle plate adjustment. Then open the idle screw until idle is around 1100 RPM then leave it that way. It idles a bit high but for the most part has helped with the stalling issue. It still does it a lot I've gotten used to just giving the throttle a blip when the RPMs get low coming to a stop light or something like that.

I think the only way I'm going to be able to cure this problem to the point that it'll run like stock is to get a standalone FM computer of somekind but I could be wrong maybe there is something I can do to fix it.
08-13-2010, 09:55 AM
titanescape

That's basically what I've done and yeah it idles a bit high but that's all I've been able to do to keep it from stalling all them time. I have the exact symptoms as you and that's what I do..give the throttle a little blip and it will idle. Sometimes rough but it will idle and I will say cool!

There's got to be some way to fix it.
08-13-2010, 10:04 AM
Electro

Was the "dual TBs" that some have tried sparked from this symptom? I don't have A/C, so don't forsee this problem... just never understood the premis for running two Throttle bodies.
08-13-2010, 10:10 AM
titanescape

Good question but I don't know about that one. Can this be related to the Idle Speed Control? Maybe it needs cleaning if that's possible.
08-13-2010, 10:16 AM
goofygrin

On the Evo, if you switched to a big cone filter, when the AC kicked on it would kill the car (a secondary fan kicks on and pulls the air out of the intake). The fix is to install a blocker/shroud that separates the intake from the area in front of the engine.
08-13-2010, 10:29 AM
titanescape

Hmmmmm..ok gg, please go on. Are you talking about the space between where the intercooler connects to the intake?
08-13-2010, 10:48 AM
sammm

I meant jumping TEN/GND to verify idle is set correctly. Sounds like that's not the problem anyway.
08-13-2010, 10:53 AM
titanescape

Well it was correct until I idled it up to about 1500. I don't want to keep it idled up that high.
08-13-2010, 11:02 AM
Titus

Quote:

Originally Posted by jeepinbanditrider

The increased airvolume in the intact track after the SC install causes it. I've had constant problemw with mine since I put the JR supercharger and TDR Air To Air intercooler in it. The only things I've been able to do to fight it has been to close off the idle screw (all of this is while the "ten/ground" pens are jumpered) and set it to stock idle speed with the throttle plate adjustment. Then open the idle screw until idle is around 1100 RPM then leave it that way. It idles a bit high but for the most part has helped with the stalling issue. It still does it a lot I've gotten used to just giving the throttle a blip when the RPMs get low coming to a stop light or something like that.

I think the only way I'm going to be able to cure this problem to the point that it'll run like stock is to get a standalone FM computer of somekind but I could be wrong maybe there is something I can do to fix it.

+1. I also got in to the habit of blipping the throttle as I put the clutch in while I came to a stop, and that would prevent a stall 90% of the time.

When I went to full ECU (LINK), all my idle issues went away... it never stalled again.
08-13-2010, 11:08 AM
titanescape

How much did that run you? So are you saying you that's what u are using for fuel management? I hate to sound dumb but I'm not familiar with that.
08-13-2010, 11:30 AM
goofygrin

Quote:

Originally Posted by titanescape

Hmmmmm..ok gg, please go on. Are you talking about the space between where the intercooler connects to the intake?

I'm not saying it's the same issue, but it sounds similar.

Here's the X engine bay with a modded stock airbox:
http://www.hspnnews.com/images/uploa...engine_bay.jpg

And here's an example of a shield that's on an intake:
http://www.extremeturbosystems.com/i...takelarge3.jpg

You might be able to experiment with some cheap sheet material to see if it helps before buying a new ECU.
08-13-2010, 11:39 AM
jeepinbanditrider

Quote:

Originally Posted by titanescape

How much did that run you? So are you saying you that's what u are using for fuel management? I hate to sound dumb but I'm not familiar with that.

It's basically a stand alone ECU that replaces your stock ECU IIRC. I'm probably going to wind up going to a Mega Squirt setup. The Mega Squirt setup brand new ready to plug and play is about 700 dollars. If you do some shopping you can get them used for half that.

Quote:

Was the "dual TBs" that some have tried sparked from this symptom? I don't have A/C, so don't forsee this problem... just never understood the premis for running two Throttle bodies.

It mounted a second TB in the stock location after a supercharger install. It basically made it to where the intake track past the second throttle body was the same volume as before the supercharger install so the car would idle and run as normal which should solve these problems. Can't remember where the write up is though. After a SC install the "throttle body" on the stock intake is just a dummy body with no throttle plate in it. The second throttle body that you speak of added a throttle body with a throttle plate.
08-13-2010, 12:31 PM
Rob®

Quote:

Originally Posted by jeepinbanditrider

It's basically a stand alone ECU that replaces your stock ECU IIRC. I'm probably going to wind up going to a Mega Squirt setup. The Mega Squirt setup brand new ready to plug and play is about 700 dollars. If you do some shopping you can get them used for half that.

Assuming Titus has the same LINK I do, it does completely replace the stock ECU. The newer model year versions of it can be run parallel I believe, but not 100% sure of that. Few wiring changes and you're good to go.

I would highly recommend a MS over the LINK, unless you can get a LINK for $1-200 or so. I would easily trade it this afternoon for a DIYPNP (the build your own MS PNP). A friend in NJ traded his LINK straight up for a brand new PNP for his car, just because the kid wanted FM's help with tuning...I would be a very happy camper if someone made me a similar offer. I'd even take used, or the build-a-bear version of the PNP (keeping AC, so I need the PNP from what I've seen).That being said, the LINK's really not a bad standalone ECU, just very outdated and a complete PIA to run more than 18psi.
08-13-2010, 12:42 PM
Titus

Quote:

Originally Posted by titanescape

How much did that run you? So are you saying you that's what u are using for fuel management? I hate to sound dumb but I'm not familiar with that.

Back when I got mine, I had to spent about $1400 on the ECU, plus another $400 on bigger injectors (you will need this too). The ECU completely replaces the stock one.

Quote:

Originally Posted by jeepinbanditrider

It's basically a stand alone ECU that replaces your stock ECU IIRC. I'm probably going to wind up going to a Mega Squirt setup. The Mega Squirt setup brand new ready to plug and play is about 700 dollars. If you do some shopping you can get them used for half that.

The MSPNP (MegaSquirt Plug-N-Play) was not available back when I bought mine. The LINK was discontinued shortly after the MSPNP came out (likely because they could not compete on price).

Quote:

Originally Posted by Rob®

Assuming Titus has the same LINK I do, it does completely replace the stock ECU. The newer model year versions of it can be run parallel I believe, but not 100% sure of that. Few wiring changes and you're good to go.

I would highly recommend a MS over the LINK, unless you can get a LINK for $1-200 or so. I would easily trade it this afternoon for a DIYPNP (the build your own MS PNP). A friend in NJ traded his LINK straight up for a brand new PNP for his car, just because the kid wanted FM's help with tuning...I would be a very happy camper if someone made me a similar offer. I'd even take used, or the build-a-bear version of the PNP (keeping AC, so I need the PNP from what I've seen).That being said, the LINK's really not a bad standalone ECU, just very outdated and a complete PIA to run more than 18psi.

What he said.
08-13-2010, 12:50 PM
titanescape

What about the "AC Fan Relay" I read it's what tells the ECU that the AC is on. Could this be the culprit?
08-13-2010, 02:25 PM
Titus

Quote:

Originally Posted by titanescape

What about the "AC Fan Relay" I read it's what tells the ECU that the AC is on. Could this be the culprit?

I would be very surprised if you found a part that is the problem, as I suspect the community would have identified it by now.

It is has always been my suspicion that the problem lies in the stock ECU not accounting for the added throttle volume that the Intercooler adds. For a 1.6 Miata, the ecu uses the AFM (Air Flow Meter) to judge how much air has gone through the throttle body, and it makes an assumption on how much air the engine will suck in once the throttle body has closed based on the volume of the intake manifold. When you move the throttle body over for a supercharger, you add the volume of the crossover pipe, and adding an intercooler adds a bunch more volume. My theory is that the ECU does not realize that the engine is sucking in this extra air (because it does not know it is there), and is therefore not adding enough fuel. Add the drag of the A/C, and it stalls out.

With an aftermarket ECU like a LINK or Megasquirt, the ECU uses a MAP (manifold absolute pressure) sensor. By actually knowing the pressure of the air in the manifold (rather than predicting it like a stock ECU), it can accurately determine the fuel needs to keep the engine running regardless of the presence of an intercooler.

Anyway, thats my theory.
08-13-2010, 02:43 PM
titanescape

Man, that's the best explanation that I have heard and it actually makes perfect sense.

I was on that other board and I think those answering might not have read the part where I said I have a SC. Personally I don't think it's the relay for the simple fact that the AC runs fine and blows cold air. When I flip on the AC the reaction is just what you are saying, it's like the computer doesn't know what to do.

I was sure hoping it wasn't an expensive fix..it's annoying and I like everything to work properly but not wanting to drop a few hundred to make it right. Fall will be here soon ad I won't even need AC!
08-13-2010, 02:45 PM
titanescape

One more question Titus..you mention a 1.6, I have a 1.8 does that make a difference?
08-13-2010, 02:47 PM
jeepinbanditrider

If you can find the dual tb thread you might find a cheaper solution than going stand alone ECU. Though there is a MSII on sale over on the pointy board classifieds for 550 dollars. Not super cheap but a few dollars off a new fully built one. I don't want to go MS cause of the money issue but I want to go to the big boost kit in the future and figure I might as well go MS just to save myself some hassle.
08-13-2010, 03:12 PM
Titus

Quote:

Originally Posted by titanescape

One more question Titus..you mention a 1.6, I have a 1.8 does that make a difference?

1.8 Miatas use a MAF (mass air flow) sensor instead of an AFM. It is more accurate than an AFM, but it is located before the throttle body (like the AFM) and is measuring the volume of air going in to the throttle body (like the AFM) so I would think the same theory should apply.
08-13-2010, 03:24 PM
Titus

Quote:

Originally Posted by jeepinbanditrider

If you can find the dual tb thread you might find a cheaper solution than going stand alone ECU. Though there is a MSII on sale over on the pointy board classifieds for 550 dollars. Not super cheap but a few dollars off a new fully built one. I don't want to go MS cause of the money issue but I want to go to the big boost kit in the future and figure I might as well go MS just to save myself some hassle.

The dual throttle body should solve the problem as it would reduce the throttled volume back to just the intake manifold, but it sure seems odd to me to add complicity as a band-aid with no other gains. Switching to an aftermarket ECU gives you an instant power boost of about 15 hp, allows you to tune your engine to run much safer (by controlling timing), and just happens to fix the stalling issue as a fringe benefit. I would go so far as to recommend an ECU BEFORE intercooler and big boost kit. Heck, with an ECU, you don't even need the big boost kit... just pulleys. My install stages were Supercharger -> Big boost kit -> Intercooler -> ECU/Injectors -> pulley upgrade. If I was to do it again, I would have gone ECU -> Injectors/Supercharger -> Intercooler -> pulley upgrade 1 -> Pulley Upgrade 2.
08-13-2010, 03:37 PM
Rob®

Quote:

Originally Posted by Titus

The dual throttle body should solve the problem as it would reduce the throttled volume back to just the intake manifold, but it sure seems odd to me to add complicity as a band-aid with no other gains. Switching to an aftermarket ECU gives you an instant power boost of about 15 hp, allows you to tune your engine to run much safer (by controlling timing), and just happens to fix the stalling issue as a fringe benefit. I would go so far as to recommend an ECU BEFORE intercooler and big boost kit. Heck, with an ECU, you don't even need the big boost kit... just pulleys. My install stages were Supercharger -> Big boost kit -> Intercooler -> ECU/Injectors -> pulley upgrade. If I was to do it again, I would have gone ECU -> Injectors/Supercharger -> Intercooler -> pulley upgrade 1 -> Pulley Upgrade 2.

What he said.

I was going to suggest a standalone before the boost increase, but wasn't sure if that was the recommended path for a supercharger (makes the most sense to me, knowing what I know). Freeing up the intake track and being able to tune timing more than just retarding base timing is worth the buy in price alone. Add datalogging to the mix, and it's even more worthwhile.