EFI idle issue.....comes and goes

[Timmy390]

Your parts seem a bit mis-matched without a simple tune. Especially considering the 351w.

Eric

Tuned by EFI Guy SN95 TM04 ECU tuned and chipped.

Tim

 

[jw0747]

You replaced the heads? Did you first try something simple like resetting the base idle? If your idle is all over the place try resetting the base idle before going all over the board.

 

[Rustytruck]

Did you get a spare ECU from EFI guy? If you did maybe check with him on swapping it out. Maybe a failing capacitor on the ECU starting to act up. I saw his video on repairing these boards hes's one smart feller.

 

[Twidgeon]

I had to replace my IAC valve because mine was running at really high RPM's at idle. While I was troubleshooting, I also remember reading that the MAF sensor can cause what your describing. I actually changed my MAF sensor but it wasn't the issue so I brought it back to the guys at the parts shop. I've been buying quite a few parts from them so they didn't mind when I returned it. Have you tried a new MAF sensor yet?

 

[Tiko433]

How is the voltage? I did a motor in my sons 89 FSB it would run like crap if the voltage was low . It would crank strong so it didn't show signs of a low battery. I swapped parts for a day till I put a booster on the battery, fixed everything. Worth a check

 

[Timmy390]

You replaced the heads? Did you first try something simple like resetting the base idle? If your idle is all over the place try resetting the base idle before going all over the board.

I've replaced the heads 4 times now (long story) and it's always ran fine after the change. It was running fine and all of the sudden started this.

Did you get a spare ECU from EFI guy? If you did maybe check with him on swapping it out. Maybe a failing capacitor on the ECU starting to act up. I saw his video on repairing these boards hes's one smart feller.

No spare but Garry did crack it open and inspect. Everything was good a year ago. Not that it couldn't have gone bad since Garry worked on it.

I had to replace my IAC valve because mine was running at really high RPM's at idle. While I was troubleshooting, I also remember reading that the MAF sensor can cause what your describing. I actually changed my MAF sensor but it wasn't the issue so I brought it back to the guys at the parts shop. I've been buying quite a few parts from them so they didn't mind when I returned it. Have you tried a new MAF sensor yet?

Have not tried a new MAF yet.

How is the voltage? I did a motor in my sons 89 FSB it would run like crap if the voltage was low . It would crank strong so it didn't show signs of a low battery. I swapped parts for a day till I put a booster on the battery, fixed everything. Worth a check

Voltage appears to be fine. Cranks fine, and alt is putting out 14.2V per the volt meter. 130 amp alt.

Thanks for the suggestions
I didn't get done what I has planned to do. The spare FP regulator was not the right one. It's for a 5.8L but it has 3 mounting screws and mine has 2. Went to buy one and the aftermarket ones are not the correct part. The motorcraft CM4760 is what I need. It has an O ring seal that fits in a recess in on the fuel rail and all the aftermarket ones are come with a big gasket that does not fit the fuel rail. No one local has the Motorcraft so have to order it.

Plan is to put it back together tomorrow and check FP with my gauge.

Tim

 

[Timmy390]

OK ,so I had lots to look at and the NorthStar V8 has taken up valuable time I should have been working on my rig but helping a buddy in need has rewards down the road.

So since the 8th I replaced the IAC and that didn't help. Removed the upper intake and looked over everything. Checked all possible vacuum leaks and such. Truly there just aren't that many on my rig. Put the old motorcraft CM476 back on and buttoned everything back up with a new upper intake manifold gasket.

I did a IAC reset procedure (idled fine through out the process) with the new IAC and took her for a spin. 5 miles into the run, I hit a stop light.......rig dies when I push in the clutch....start it up, dies again....get her running and keep reving her till I get to the light and head home. Kept depressing the clutch on the way how no issues.

Parked and let it idle, no issues.....

Let it set for 5 minutes, went out and it started but would do the same ole thing, 1000rpm, dropping to 300 then die

Frustrated I disconnected the ECT sensor. Started it up and she idled fine.........shut her down, reconnected the ETC and 1000rpm, dropping to 300 then die. Repeated the connect and disconnect several times each resulting in the same thing.......connected she dies, disconnected she runs.......

Could this be a simple as a bad ECT sensor? It would explain the coming and going of the issue but is there a bigger connection between the ETC and air fuel delivery I might be overlooking?

Tim

 

[EricLar80]

Just pull the plug on the ECT sensor and try to run it. If it runs better than it does now, then that's the issue. I think you can test the ECT sensor by measuring the resistance across the pins. If it is a short, you know it's bad.

 

[Timmy390]

Replaced the ECT sensor and not change. Once it gets warm, she will not idle. Tried unplugging the O2 sensors, no difference.

Can't check the fuel pressure because the port on the fuel rail is under the edge of the explorer intake. Can't get the connector in there.

I need a drink

Tim

 

[EricLar80]

If the ECT didn't fix it, then it probably means that it is having trouble once the computer tries to go into closed loop. It will be in open loop until it warms up to about 160 or 170.

If it runs well and then goes bad, then fuel pressure likely isn't the issue.

So, you have a chip installed for the tune? Have you checked to make sure it is still connected well?

 

[Timmy390]

If the ECT didn't fix it, then it probably means that it is having trouble once the computer tries to go into closed loop. It will be in open loop until it warms up to about 160 or 170.

If it runs well and then goes bad, then fuel pressure likely isn't the issue.

So, you have a chip installed for the tune? Have you checked to make sure it is still connected well?

You just stated the exact some thing I was discussing with my buddy yesterday. Closed loop is my issue it appears. Runs like a top and pulls like a train just will not idle once warm. When the idle is surging and it's trying to die, you can hit the gas and it revs up fine.

Haven't check the chip yet good call on that. I'll go give her a look.

Also Reached out to EFI Guy on my tune. This all started after I swapped heads from E7's to GT40P's and cam from Explorer/truck/van cam to Comp 35-349-8/XE264HR. Maybe I need a tune update.....

Tim

 

[EricLar80]

Have you tried disconnecting power for 15 minutes to reset the computer? See if it runs well when warm after that. If it does, and then the problem eventually comes back, then there is more tuning to do because the adaptives are learning incorrectly.

Eric

 

[jw0747]

Have you tried disconnecting power for 15 minutes to reset the computer? See if it runs well when warm after that. If it does, and then the problem eventually comes back, then there is more tuning to do because the adaptives are learning incorrectly.

x2 I've been encouraging a reset of the base idle twice and haven't heard if it was ever tried. All the changes made including changing heads would indicate the computer probably needs to relearn the base idle.

Go here and do the steps below, "How to do it." Very simple.

http://www.muscularmustangs.com/idlereset.php

 

[Joe473]

Are you running OBII. Get a code reader and check what temp computer is seeing and look at what the tps voltage and IAC feedback is. Also look at O2 sensor voltages and confirm the right sensor is wired to the correct bank.
Check all ports on manifold for a vacuum leak and check pcv valve.

Sent from my SM-G900V using Tapatalk

 

[Timmy390]

The chip in the ECM is seated correctly.

Have you tried disconnecting power for 15 minutes to reset the computer? See if it runs well when warm after that. If it does, and then the problem eventually comes back, then there is more tuning to do because the adaptives are learning incorrectly.

Eric

Yes several times. Has not helped.

x2 I've been encouraging a reset of the base idle twice and haven't heard if it was ever tried. All the changes made including changing heads would indicate the computer probably needs to relearn the base idle.

Go here and do the steps below, "How to do it." Very simple.

http://www.muscularmustangs.com/idlereset.php

Yes tried that on Friday as well as replaced the IAC, didn't help. That's when I found unplugging the ECT sensor would let it idle fine....open loop it idles fine....closed loop, it will not idle

Are you running OBII. Get a code reader and check what temp computer is seeing and look at what the tps voltage and IAC feedback is. Also look at O2 sensor voltages and confirm the right sensor is wired to the correct bank.
Check all ports on manifold for a vacuum leak and check pcv valve.

Sent from my SM-G900V using Tapatalk

OBDI SN95 EFI TM04 ECM Checked all ports for vacuum leaks and changed the upper intake manifold gasket. OBDI reader is showing no codes. Have not touched the O2's since I installed them a year ago and it was running fine till cam and head swap.

Tim

 

[Timmy390]

Doing some reading which is not always good thing......

The Mustang guys seem to all have issues with idle after cam swaps with the 94-95 ECM. Found one that was detailing my issue with running fine till closed loop then surging and dying. Most of them running E, B and F-303 cams.

Some are/were band aiding it with raising the idle up to 900rpm or even higher. Some were running custom tunes to fix the issue. Some good info on the bigger cams not making good vacuum at idle and causing issue with the fuel pressure regulator. I got to figure out how to get under the intake and connect to the fuel rail port before I can check this.

I'm going to tray and raise the idle tomorrow and see if that helps. Also have reached out to EFI Guy for his thoughts on a new tune as he did the one I'm running now.

Tim

 

[rjrobin2002]

I went through several bugs with my efi and I added grounds, checked my sensor, replaced distributor, TFI module, plug wires, harness relays and come to find out it was simple and here is what mine were....
- For whatever reason when I hit a bump I would feel a engine surge. I wiggled and twisted my wires all over the harness and where the harness connected to the computer it would surge and die when I bent the harness. I removed it from the computer and put some grease on the computer pins and retightened it and that stopped. So twist and wiggle on your harness and see if you can make it happen.

-I still had a miss and after several months driving I started my engine in the dark and popped the hood the other day and found my number 8 spark plug was arcing to the header, replaced the plug and fixed that. So run it in the dark and look for a short.

 

[pcf_mark]

You solved your problem by unplugging the ECT. There is a spark and fuel adjustment based on engine temp (you probably knew this). When you get warmed up and enter those bin values it is not correct. You need to adjust your tune. Idle is very tricky / sensitive to tuning with EFI. For example all I did was swap a C4 to 4R70W and I needed to re-rune my spark and fuel at idle because ti would hunt (600 then to 700 then back to 600 in a slow rolling idle). A few clicks in my tune and it idles stock and I never even opened the hood. I just waited until it was warm and idling poorly then adjusted the trim on the bins or cells in the map right around there.

 

[Timmy390]

You solved your problem by unplugging the ECT. There is a spark and fuel adjustment based on engine temp (you probably knew this). When you get warmed up and enter those bin values it is not correct. You need to adjust your tune. Idle is very tricky / sensitive to tuning with EFI. For example all I did was swap a C4 to 4R70W and I needed to re-rune my spark and fuel at idle because ti would hunt (600 then to 700 then back to 600 in a slow rolling idle). A few clicks in my tune and it idles stock and I never even opened the hood. I just waited until it was warm and idling poorly then adjusted the trim on the bins or cells in the map right around there.

Yup, I think it's tune related. Seems the 94-95 mustang ECM's while faster and considered better by some, have issues with cam swaps and idle. I recall on first startup after the cam swap, the cold idle was surging a bit but that went away. I assumed it was learning and thought nothing of it.

Wish I had the equipment, software and know how to tune my own. It's just something I've never even thought about getting into. I've got a call into EFI Guy. I'm sure Garry has the cure.

Tim

 

[NYLES]

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