Got the 69 running with EFI...kinda....surging bad at idle

[streetgrande69]

Well I'm doing a Mass-flo EFI conversion on my 69 351w. for those of you not familiar with the system its a 90'sih ford system with a later modle GM LS1 style maf that fits into your air cleaner.
Any way it uses all stock sensors and actuators so now this is easy....you diagnose it just like a stock 90 mustang.

so this is where i need some help.

started the new motor...fresh rebuild this weekend. went ok except that at idle...it surges real bad and after a few seconds it dies. So does anyone know what the problem might be? I couldn't even set idle or timing because i can't keep it runing. fuel gage on the regulator reads a constant 39 psi.

any help...would be great! I will be getting a code reader this week so hopefully that will help!

 

[Ronstang]

I am not familiar with that system or the sensors it uses per se but your problem sounds line a bad/dirty idle air bypass/idle speed control or whatever they call it on this system.

 

[streetgrande69]

I am not familiar with that system or the sensors it uses per se but your problem sounds line a bad/dirty idle air bypass/idle speed control or whatever they call it on this system.

Hey there Ronstang...hot down there this time of year......I'll be in Splendora in August.

everything in this system is the same as a 90 mustang. the idle air sensor is a stock unit from a 90 mustang it's new.
here is a link to the system
http://www.mass-floefi.com/mass-flo.html

 

[Ronstang]

I would see if you can borrow an extra Idle air bypass solenoid then to test with as that sounds like the cuplrit Eric. New units do not always function as planned.

Not too hot lately as it has been raining all the time. What time in August? I am building a Griggs GR-350 to be delivered to CA. We are leaving Aug 15 so if you are here earlier maybe you can come by and check it out.

 

[Ronstang]

How can you double post????

 

[streetgrande69]

I'll be there late August so looks like I'm gonna miss ya....thanks for the tips...

 

[bnickel]

might also be the throttle position sensor. if the sensor is not set in the right range it could cause surging at idle. that is a fairly common problem on 4.0l jeeps.

 

[roan65]

There is several things it could be. Check the 5.0 section. They have a sticky thread on surging idle.
need to pull codes to see whats up
Take off IAT and clean it.
Check for a vac leak
make sure you have good voltage while the car is running.
make sure you have good grounds, and lots of them!

I just put EFI in mine and the charging system was acting up. It would run then go into a surging mode and die.

 

[KiwiGT]

Mass Flo

If you purchased a Mass Flo system from Chris at Quality Roadsters give him a call. He has a reputation for standing behind his product and giving excellent after sales assistance in resolving issues like this.

 

[lauras70mach1]

Set your TPS (car doesn't have to be running for that)

Check for vacuum leaks.

 

[ForceFed70]

Another vote for vacum leak.

 

[gonzothegreat]

I got a MegaSquirt system.
http://www.fordmustang.co.uk/index.php?folder=/022-Pictures/EFI/pictures/
video of the engine running:
http://www.fordmustang.co.uk/pictures/03-videos/video/Kermit65/efi.wmv

and I have a high idle, still trying to fix it.

 

[ForceFed70]

I got a MegaSquirt system.
http://www.fordmustang.co.uk/index.php?folder=/022-Pictures/EFI/pictures/
video of the engine running:
http://www.fordmustang.co.uk/pictures/03-videos/video/Kermit65/efi.wmv

and I have a high idle, still trying to fix it.

That's the nice thing about speed density. The only thing that a vacum leak does is cause a high idle...

Check for vacum leaks.... also check your IAC, and try adjusting your throttle stop if you have one.

 

[gonzothegreat]

cheers buddy for your tips, I will do it tomorrow

 

[ARTTII]

Any progress update for us yet?

 

[streetgrande69]

nothing yet...i am having trouble getting codes using the check engine light.....i need a code reader before much happends.

 

[66HertzClone]

nothing yet...i am having trouble getting codes using the check engine light.....i need a code reader before much happends.

I have no problem at all getting codes from my system, remember you need to connect the jumper wire before you turn the key on. All the codes in the MassFlo instructions show up for me when I run the codes, even the first time thru before I started the engine.

 

[streetgrande69]

it's not that i can't get the codes it's that i guess i just have trouble understanding the blinking light or i just don't trust myself on what i get. i know there is timing and such between the blinks....just i get lost about half way through. i got my hand on a good scanner todat that a good friend at jmc motorsports loaned to me. i'll hook it up tonight and check the codes.

 

[ddonaca351]

Well if the system is a 90' (like my 5.0) then the "throtle body airflow" scalar will not be correct with a 351. This setting as well as the map for the IAC flow and several others will not be correct. These change with displacement, cam, idle speed, etc... The changes are many of what custom chip burners do to get good idle quality on aftermarket engines (dyno time is well worth the money). These are the figures which tell the computer how much air is being sucked in by the motor at idle, and how much the IAC is supposed to add to achieve a given idle rpm. For instance the IAC also holds a higher idle setpoint until you get below 7mph in order to keep the motor from dying on rapid deceleration. Check tweecer.com for these and many more fun pitfalls of latemodel computer tuning issues...

The stock program also specs out a 672 rpm idle, now if your engine can not idle at 672 (many good cams can not), then the computer will have an embolism trying to get it down there. Also be advised if the IAC does not give the controll the computer wants then it uses engine timing to do the job. (so don't be suprised if your timing is all over the place at idle) I set my idle speed to 880 rpm in the program (tweecerRT) and this solved most of my idle issues.

Another trick that the latemodel guys use sometimes is to rotate the MAF, as turbulance through it can sometimes cause a problem. This may not be possible/practical in your case since its inside the aircleaner.

The surge can also be caused by the O2 sensors cooling off at idle (with long tubes) and causing a rich condition (but this *seems to be* most common on 94/95 systems). If you have shorties, this is unlikely.

Also check the wire in your MAF to ensure that its clean (isopropyl alcohol ... GENTLY!!!!!) If you run a KnN, the oil film from the filter coats the wire in the MAF and screws up the readings to the computer.

The TPS voltage that you are looking for is LESS THAN 1.0vdc. (k.o.e.o : key on engine off) Anything above 1 puts the computer into "part throtle" mode. (I run .90 at the sensor, some say .97-.99 but what if your meter isnt exactly the same as the computer...?!?! )

The coolant temp sensor can also contribute, as well as the air charge temp sensor, but these are fairly rare. And of course a bad O2 sensor... but the codes will show that (trouble shoot the first code first. dont start with the last one and work backward)

The other ideas listed above are valid, but I thought I would add some not mentioned yet... and f.y.i. the dreaded "surge" is fairly common with cams, heads, etc... untill the computer is tuned.

Good luck, hope its just a bad sensor.
Dave-

 

[streetgrande69]

i'm getting a 11 and 66 code...maf below min. voltage??? so i'll give chris at mass-flo a hollar.

i'm hoping that chris at mass-flo has engineered this system so that it would work with my 351w....i have read nothing but good stuff so i still have faith!