EFI idle issue.....comes and goes

[Timmy390]

Whatca doin?..........

Wishing I hadn't changed cams......LOL Love the rig and how it runs right up to closed loop on the ECT and then it kind of sucks.....Surging idle and dying at stoplights.

Heads are fixed.....no more bubbles. Valve train fixed, no more tapping....Talked to Garry last night. He's going to play with my tune and look at the other tunes he's done with this cam and sort the idle issue out. He gave me a perfectly working tune for the combo I had and I go and screw it up with a cam swap. Self inflected.....

New tires and rims on hold till this is resolved.

Tim

 

[EricLar80]

A cam change should really only affect the idle air function if the MAF and injectors were properly tuned. There should really be no effect if the lobe separation angles of the two cams is the same.

Have you tried to reset the idle? Follow the instructions here:
http://efidynotuning.com/idleair.htm

Eric

 

[Timmy390]

A cam change should really only affect the idle air function if the MAF and injectors were properly tuned. There should really be no effect if the lobe separation angles of the two cams is the same.

Have you tried to reset the idle? Follow the instructions here:
http://efidynotuning.com/idleair.htm

Eric

Yep I did try the idle reset

Idle issues after a cam change seems to be a common issue with the 94-95 Mustang EFI from what I've read. EFI Guy gave me a few things to try and if that doesn't work he's going to tweak the tune. Lobe sep on the explorer/truck/van(also HO cam) I was running is 116 and my new cam is 114

I've read some of the 94-95 Stang guys just crank the idle up to 900 plus using the T-body set screw to get around a custom tune. Really don't want to do that. Will if it comes to it but hope it doesn't

Poured rain all day so didn't get to look at it.

Tim

 

[Timmy390]

Update......It's idling now when warm but not a proper solution.

Long story short, SN95 EFI is just an odd duck as I'm finding out the hard way.

To get the thing idling I did a modified version of the idle reset but to get the 300-400 plus RPM surge out of it, I had to adjust the TB stop screw till I was idling between 900 and 1000RPM's It still surges just a bit 50-100rpm but it's drivable. Cold idle is at 800. It's a bit slow to come back to idle but I bet that's the TPS voltage that I've not reset. I really would like the idle down just a bit.

The missing piece of the puzzle I THINK is the adjustable IAC (air bleed screw) the SN95's came with. I'm running a 97 Explorer TB and IAC which is non adjustable. The specific SN95 idle reset process I found talks about adjusting this air bleed screw.

So enter the possible long term fix......

Engine Idle Air Kit P/N: F2PZ9F939A It's a spacer that goes between the TB and the IAC and has bleeder screws so you can adjust the amount of air the IAC lets in. Basically let more air in. Developed for a totally different reason it also provides the ability to fine tune closed throttle plate idle air flow without altering the TPS. Anyone running one of these on earlier mustang EFI?

Going to give this a shot.....still might need a tune tweak

Tim

 

[EricLar80]

I used the spacer before. It worked really well to fix the idle issue I had at the time.

Eric

 

[pcf_mark]

Total Hack Alert

You could take a vacuum cap off and see how it runs. The leak may help compensate for your idle fuel issues. You could plug the hole with a piece of plastic or wood then drill it out a little at a time to get the size you want to help with your idle.

Obviously this a patch.

 

[Timmy390]

Total Hack Alert

You could take a vacuum cap off and see how it runs. The leak may help compensate for your idle fuel issues. You could plug the hole with a piece of plastic or wood then drill it out a little at a time to get the size you want to help with your idle.

Obviously this a patch.

Yup, I got that advice from my buddy with the NorthStar (we put the heads back on last night) issues as well. His words were, bigger cam needs more air. So played with that yesterday as part of my troubleshooting. The extra air did two things, raised the idle and took away the surging.

I didn't go as far as trying to set the idle down low with the cap removed but did play with the hole wide open and then with it all but blocked.

Ordered the Idle Air By-pass Service Kit. I'll update once it gets in and I play with it. Fingers crossed

Tim

 

[pcf_mark]

Total Hack Alert

Put your idle back to where it was and take a vacuum cap off and see how it runs. Then you can plug the nip a little off the plug to make a controlled leak to bleed air into the system after the throttle body / air meter. You can get fancy and use a hose with a little balsa wood plug and drill the hole a little bigger at a time until you get what you want.

Or you could go MegaSquirt and get control over everything using your existing set up including the wiring except the ECM plug.

 

[EricLar80]

Total Hack Alert

Put your idle back to where it was and take a vacuum cap off and see how it runs. Then you can plug the nip a little off the plug to make a controlled leak to bleed air into the system after the throttle body / air meter. You can get fancy and use a hose with a little balsa wood plug and drill the hole a little bigger at a time until you get what you want.

Or you could go MegaSquirt and get control over everything using your existing set up including the wiring except the ECM plug.

I am not sure I would recommend to do this; certainly not more than just a test. This causes un-metered air to enter the engine, which is then not accounted for with fuel. The spacer plate he ordered is the best long-term solution. You can also drill a hole (or open the existing one up more) in the throttle body plate to have the same effect as the spacer, and plug it later with a rivet or braze/jb-weld.

Eric

 

[pcf_mark]

I am not sure I would recommend to do this; certainly not more than just a test. This causes un-metered air to enter the engine, which is then not accounted for with fuel. The spacer plate he ordered is the best long-term solution. You can also drill a hole (or open the existing one up more) in the throttle body plate to have the same effect as the spacer, and plug it later with a rivet or braze/jb-weld.

Eric

The whole point of a controlled vacuum leak (by taking a vac cap off) is to provide un-measured air to alter the AFR. A hole in the throttle blade is the same as opening up the idle stop and I have never seen an EFI blade with a hole. A carb yes but that is different metering philosophy.

**Apparentiy my first post was lost in the ether but it is now back sorry about that**

 

[Timmy390]

I am not sure I would recommend to do this; certainly not more than just a test. This causes un-metered air to enter the engine, which is then not accounted for with fuel. The spacer plate he ordered is the best long-term solution. You can also drill a hole (or open the existing one up more) in the throttle body plate to have the same effect as the spacer, and plug it later with a rivet or braze/jb-weld.

Eric

Yes, read about drilling holes in the throttle plate or opening up existing but that's a non starter for me. Hoping the plate works.......

Should have just left well enough alone or went with the Explorer setup. Live and learn......

Tim

 

[EricLar80]

The whole point of a controlled vacuum leak (by taking a vac cap off) is to provide un-measured air to alter the AFR. A hole in the throttle blade is the same as opening up the idle stop and I have never seen an EFI blade with a hole. A carb yes but that is different metering philosophy.

**Apparentiy my first post was lost in the ether but it is now back sorry about that**

Drilling the hole is not the same thing because in the other case you affect the throttle position sensor when you adjust the screw.

Here is a picture of two factory Ford throttle bodies with holes in them:

http://www.explorerforum.com/forums/index.php?threads/mustang-4-6-throttle-body-on-a-4-0-sohc-explorer.139454/

 

[pcf_mark]

Well how about that! Holes in the blades. Maybe a Ford thing I'm looking at an LS7 and no holes. Interesting - i think GM does a stepper IAC and Ford uses a fast idle valve maybe that it to compensate?

You are correct opening the idle screw will impact TPS and drilling a hole will do the same thing as opening the idle screw. My point was the AFR is wrong not the idle speed. The idle is hunting because it cannot stabilize.

A vacuum cap / hose with an orifice can do the same thing it just lets air in from outside the closed loop. Because of this it actively changes for AFR because the engine is leaner. Air bypassing the throttle body that has gone through the MAF has already be accounted for. Just a different way of tuning around a problem was my point.

As I said **total hack alert** but very easy to try and un-do if it does not work.

 

[Timmy390]

Initial testing has proved very positive. Installed the Idle Air By-pass Service Kit and can get the idle down and no more surging. She also settles back to idle much quicker now...

More testing to do and some "fine" tuning but my rig idles cold and when warm now. Got the idle down to 700. When my electric fan kicks on the idle goes up 100rpms but the fans are controlled by the SN95 ECM so I'm sure it's normal.

Tim

 

[RnrdTheFox]

Initial testing has proved very positive. Installed the Idle Air By-pass Service Kit and can get the idle down and no more surging. She also settles back to idle much quicker now...

More testing to do and some "fine" tuning but my rig idles cold and when warm now. Got the idle down to 700. When my electric fan kicks on the idle goes up 100rpms but the fans are controlled by the SN95 ECM so I'm sure it's normal.

Tim

Can you post a link to where you got the Service Kit. FWIW, I have the exact setup as you down to I think the same cam except I stroked my to 393. When my engine builder and I got on the phone with comp cams they warned about the lobe separation and rough idle with EFI. We ignored that and proceeded since the cam showed good low end torque that I wanted. I never had the surging idle like you have when going into closed loop, but I spent many hours getting the best possible idle set and tuning things in the computer. It doesn't like it below 850 and will die if I take it much lower. It is very drivable now and oh so fun when I hit the throttle. But, if I can get it down to 650 - 700 that would be awesome. Thanks.

 

[EricLar80]

Can you post a link to where you got the Service Kit. FWIW, I have the exact setup as you down to I think the same cam except I stroked my to 393. When my engine builder and I got on the phone with comp cams they warned about the lobe separation and rough idle with EFI. We ignored that and proceeded since the cam showed good low end torque that I wanted. I never had the surging idle like you have when going into closed loop, but I spent many hours getting the best possible idle set and tuning things in the computer. It doesn't like it below 850 and will die if I take it much lower. It is very drivable now and oh so fun when I hit the throttle. But, if I can get it down to 650 - 700 that would be awesome. Thanks.

https://www.amazon.com/gp/product/B000O0TJ4Y

 

[Timmy390]

Can you post a link to where you got the Service Kit. FWIW, I have the exact setup as you down to I think the same cam except I stroked my to 393. When my engine builder and I got on the phone with comp cams they warned about the lobe separation and rough idle with EFI. We ignored that and proceeded since the cam showed good low end torque that I wanted. I never had the surging idle like you have when going into closed loop, but I spent many hours getting the best possible idle set and tuning things in the computer. It doesn't like it below 850 and will die if I take it much lower. It is very drivable now and oh so fun when I hit the throttle. But, if I can get it down to 650 - 700 that would be awesome. Thanks.

Got mine off ebay
http://www.ebay.com/itm/BRAND-NEW-O...ash=item541dc0b205:g:xSEAAOSwPhdVSaye&vxp=mtr

I did some additional tinkering with this and now have it idling at 750-800. She bumps up 100 RPM when the cooling fans kick on. At 700 I had a small issue with it on hot startups. The idle would drop low and stumble on startup then settle back down. I didn't like that so I bumped it up just a notch. It did fix my surging issue and return to idle when coming to a stop is much quicker than before.

This is from Garry "EFI Guy" on how he setup my tune
Your base idle speed is 672. But you will rarely see it that low. The PCM will add to desired speed for various conditions like temperature, time since start, dashpot, a/c, fan, etc... It only bumps idle speed 50 rpm for A/C. I would expect you to see around 750 most of the time.

I do wish it idled just a bit lower than it does now and it did before the cam swap. The cam just like more air at idle.

The kit has two adjusting screws. I have one closed off and one adjusted as needed. The kit says to knock out the "plug" for 5.8L but the kit was designed for one purpose and I'm using it for adjusting to my cam so I left the plug in.

I'm sure I'll end up tweaking on it some more but for now it runs great and I'm loving it.

Tim

 

[pcf_mark]

Thanks for updating the thread I learned something.