EFI Cutting out at 3500rpms

[TDavis]

Well first off ill just say I have had a nightmare with this whole swap but I finally feel like I'm getting somewhere with it. It's a 90 Merc Marquis motor running on a Mustang A9L comp. At idle with the vac hooked up to the regulator the fuel pressure runs about 31psi with it unhooked it runs right at 40psi. I'm running a single inline pump Airtex number E8445 rated at 45-65psi and 35gph. Do I need a bigger pump or should I start looking for problems elsewhere? Any input is greatly appreciated.

 

[Pedestrian]

What injectors are you running? Orange or Tan?

 

[av bronco]

Do you have any way to moniter the fuel pressure when driving?

 

[ransil]

Check pressure when under load, power braking should do it. Might need to remove the hood and tape the fuel gauge to something so you can see it.

 

[TDavis]

Orange injectors. Well it's not totally ready to drive yet so I haven't been able to try that yet. BTW Timing is set at about 13 Degrees.

 

[70EB]

Could be fuel pump or ignition related.

Losing pressure under load could be a sign of a failing fuel pump. Your pressure of 31 is a little low, should be more like 36-38. Could be the FPR.

Other causes could be a ground issue, arching spark plug wires, or coil. Check all your grounds as everything related to the computer can be affected by a poor/missing ground.

Have you run any codes yet? That might narrow down the issue.

 

[PaulC]

I've debugged two EFI swaps that were cutting out at 2500-3200rpm and its been the Hall Effect sensor, aka the pickup coil, in the 5.0 distrib.

not being able to witness the 'miss', sometimes a reason to think its ignition would be that its a hard miss. versus at rpm when fuel goes lean the motor usually just falls over, quits making power and won't pull any more rpm, and almost dies. with an ignition issue it cuts out hard and really stumbles the motor more. oh, plus with insufficient fuel under load you're likely to get a lean backfire back thru the intake.

'tis another avenue to debug.

 

[67EB_in_619]

PaulC brings up a good point.. you say it is cutting out.. please describe. Also, you went straight to the fuel pump/pressure.. do you have a reason to believe it is a fuel delivery issue?

 

[TDavis]

Well I went to a larger E2000 inline truck pump and it didn't change much, so I borrowed a Snap on scanner from a friend and it said that the Baro sensor was out of range. I noticed that it was black smoking worse the more it ran. So out of curiosity I unplugged the sensor and the black smoke instantly stopped. The sensor was new but I thought what the heck ill take the one off my girlfriends DD 5.0 and try it. I got the same results with it too. I'm wondering how can I test to make sure that it is getting reference to the computer. I purchased the harness off of ebay like a fool and it has been nothing but problems from the get go. Help before I put a carb back on this thing!

 

[ransil]

do you have a vacuum line connected to the Baro sensor??

 

[TDavis]

nope no vac line

 

[HGM]

That should be a MAP not a BARO.. You need a vac line to it..

 

[TDavis]

If I wasn't running MAF then it would be a MAP and it would need a vac line but since I am it is a Baro. The girlfriends bone stock 5.0 stang doesn't have and vac going to it either.

 

[Viperwolf1]

Well I went to a larger E2000 inline truck pump and it didn't change much, so I borrowed a Snap on scanner from a friend and it said that the Baro sensor was out of range. I noticed that it was black smoking worse the more it ran. So out of curiosity I unplugged the sensor and the black smoke instantly stopped. The sensor was new but I thought what the heck ill take the one off my girlfriends DD 5.0 and try it. I got the same results with it too. I'm wondering how can I test to make sure that it is getting reference to the computer. I purchased the harness off of ebay like a fool and it has been nothing but problems from the get go. Help before I put a carb back on this thing!

Time to bust out the volt/ohm meter. Check the Vref voltage going to the BP sensor. It should be 5V. Check to make sure the signal return wire goes to ECU pin #46 and BP output goes to pin #45.

The diagram is here: http://fordfuelinjection.com/?p=6

 

[HGM]

If I wasn't running MAF then it would be a MAP and it would need a vac line but since I am it is a Baro. The girlfriends bone stock 5.0 stang doesn't have and vac going to it either.

Ah, didnt catch the MAF.. Thought it was a '90 5.0..

 

[TDavis]

Well I checked out the Baro sensor and everything seems good there. The problem wound up being I was sold a what was supposed to be a MAF mustang computer a while back and apparently it wasn't. I decided to try it the other day and never changed back to my A9L. So once I switched it back over the Baro problem was gone. I still am getting a few codes and it wont rev past 3500-4k. It seems like an ignition problem because the more I rev it starts popping and cracking through the exhaust not the intake. Some codes that are really catching my eye (besides all the egr codes) are Code 10 Snap throttle, Code 12 Cannot control RPM during ER Self-Test high RPM check, Code 13 Cannot control RPM during ER Self-Test low RPM check. ?:? I'm out of ideas.

 

[Viperwolf1]

Maybe something to do with the idle air control.

 

[TDavis]

I actually thought the same thing so I switched it out with another one. Didn't change at all.

 

[73azbronco]

The code 10 "snap throttle" is not a code, it is a command- literally telling you to blip the vehicle throttle. Snapping the throttle open is required to run one of the tests. If you don't do it, you get the 538 code.

The self-test diagnostic routine is pretty good at catching intermittant TPS failures and storing them for the KOEO test. The KOER test should catch any dynamic conditions with the TPS.

Do you have a high idle speed?

Maybe vacuum leak? Bad IAC? IAC failing to fully close?

 

[TDavis]

I did have the idle screw turned up because when you first start it after resetting the computer it wants to start, run for about 5 secs then die unless you hold the throttle. I think it was idling at about 1,100. I've sprayed the crap out of it checking for any kind of leaks and haven't found anything yet.