Has a stumble at 3500 like someone turned the key off

[88foxvert]

k so the vacuum part is normal

the 02's do affect the ltft (long term fuel trim) which overtime updates the fuel tables to adapt to your engine....but if you just changed the computers and assuming you disconnected your battery when you did that I don't think it would have enough time to affect the WOT tables that bad....

the part you're talking about with the fuel pressure is kinda sounding like a clogged fuel filter.....when you go WOT (big need for fuel) it bugs out but if you go slow and easy its ok......

yes, but I've changed the fuel filter twice already and it did not remedy it...

and I installed the new e-bay walbro 255 pump two years ago but the car has set for most of that time driven less than 50 miles.........


here's the maf test results:


#1 vpwr to ground 11.87

#2 maf sig to ground 100.2 kilo
maf sig to maf return 129.2 kilo

#3 maf sen voltage .920




before I drove it to get parts the
last koeo codes: 81,82,85

cm codes : 19 ,41, 91

koer: 41,91,33

cylinder balance test is 90-90-90

 

[88foxvert]

and no spark leak seen at night......

 

[allballsmustang]

did you check for possible fpr failure... typically if they fail you may have fuel coming out of the port that the vacuum line hooks too...that may cause your fuel pressure issue... the first bbk regualtor i had installed when i built my motor failed within a week of installing it and after i replaced it i havent had a problem since...

 

[88foxvert]

did you check for possible fpr failure... typically if they fail you may have fuel coming out of the port that the vacuum line hooks too...that may cause your fuel pressure issue... the first bbk regualtor i had installed when i built my motor failed within a week of installing it and after i replaced it i havent had a problem since...

no sign of fuel in vacumme line ......

 

[allballsmustang]

you said your running a msd super coil? are you by any chance using one of those power tower adapters on the top of the coil for the coil wire?

 

[88foxvert]

nope its a msd streetfire looks just like the oem one.....

 

[allballsmustang]

you've got me stumped without actually seeing it in person...

did you say it does it in closed or open loop?

 

[88foxvert]

yeah i,ve been stumped for a month now.........pulled the codes this morning and koeo 81,82,85 cm codes 14 ,29 33, 96



took my son to school and then pulled the codes on the way, from 0 to 2800 rpmseems to runs fine 2900 rpm spits sputters check engine light flashes seems to be getting worse or mabey I'm just so burnt out , code 14 in cm is for pip failure guess I should start there the code 41 and 91 is not in cm anymore but shows on the koer test I have new 02 sensors but I dont think that is it and I'm not going to change them until I figure this out....gonna go try to find another dizzy to try , I had tryed a buddys dizzy with the other eec but have not tryed it since the eec change... wish there was more input on here there are a ton of like threads but no one posts what fixed it....


also this is an 88 gt which was s/d I used a eec harness from a 89 gt are there any eec wires that need moved or is this plug and play ?? someone mentioned the s/d didnt have the wires for the vss or fuelpump secondary circuit.......and I would have to move some wires I cannot find any info to verify this.........any help??

 

[allballsmustang]

im not 100% on this, but i believe on a mass air conversion the map needs to be converted over to a barometric pressure sensor? maybe someone else can correct me, just a thought

 

[Black1987Stang]

not sure about 88's but my 87 didnt come with a vss so I couldn't hook one up to the eec, the only prob you might have is stalling or surging when coming to a stop and you get the vss code.

For the fuel pump circuit add on you need to tap into the fuel pump relay power and run it to pin 19 at the computer so it knows when the pump is running or not. I ran mine for a while without this and even had the vacuum line still on the map sensor and didnt feel any difference.

For a maf conversion all you need to do is unplug the vacuum line to the map sensor and and plug it so theres no vacuum leak and thats it for that sensor.

 

[88foxvert]

there is a vss on my 88 I was just under there and checked it out....

map sensor vacumme is unplugged and the hose is capped...

I swapped dizzys agian seemed to help a little but still bucks and jerks and almost dies


I took the old dizzy out and checked the hall effects sensor ??armature??? and it had some nicks in each one of the tabs on the inside like it was hitting the ??stator?? I dont know if im calling the pieces by the right name so bear with me...

 

[88foxvert]

FUEL PUMP MONITOR SIGNAL
This signal called FPM2 is used to monitor the voltage going to the fuel pump. It will generate an error code in the EEC if it's not connected but "shouldn't" cause a problem. Splice into one of the 2 pink/black wires going to the relay located under the driver's seat and insert the other end into position 19 of the EEC connector.


confirmed continueity via dvm from pink and black to eec pin #19

 

[DocG]

I'm finding this thread interesting....but having a hard time with the jargon since I'm a noob to engine tech.

What's the dizzy you're referring to?

I just picked up a 92 LX with a built 306 that is having similar issues. Seems to stumble at times, backfires on decel, surges at idle, CEL comes on at what so far seems like random times, voltage drops, vac pressure goes a little nutty..... I obviously haven't take the same amount of time to diagnose anything yet or find patterns in the symptoms....because it doesn't seem to run quite as bad as yours, but sounds similar.

 

[88foxvert]

well besides finding that the armature was at sometime hitting the stator on the inside...and thus I replaced it with a different dizzy....

and then I decided to test the msd coil I put in I tested my original and it ohmed out ok but the msd did not so I swap back in the oem one...

now with any acceleration even free reving it it breaks up bad pukes out black smoke from the exhaust chech engine light flashes like mad ,and while this is happening the fuel psi drops to 30 psi then comes backto 39 ,and after closer inspection whilst free reving whens its not cutting out it seems the fuel pressure drops a couple of pounds instead of raising....


I think its time to drop the tank....

 

[88foxvert]

I'm finding this thread interesting....but having a hard time with the jargon since I'm a noob to engine tech.

What's the dizzy you're referring to?

I just picked up a 92 LX with a built 306 that is having similar issues. Seems to stumble at times, backfires on decel, surges at idle, CEL comes on at what so far seems like random times, voltage drops, vac pressure goes a little nutty..... I obviously haven't take the same amount of time to diagnose anything yet or find patterns in the symptoms....because it doesn't seem to run quite as bad as yours, but sounds similar.

dizzy= distributer

 

[Black1987Stang]

dizzy= distributer

dizzy=distributer=distributor

 

[DocG]

dizzy=distributer=distributor

Thanks fellas....one thing I didn't even think about!

 

[allballsmustang]

well besides finding that the armature was at sometime hitting the stator on the inside...and thus I replaced it with a different dizzy....

and then I decided to test the msd coil I put in I tested my original and it ohmed out ok but the msd did not so I swap back in the oem one...

now with any acceleration even free reving it it breaks up bad pukes out black smoke from the exhaust chech engine light flashes like mad ,and while this is happening the fuel psi drops to 30 psi then comes backto 39 ,and after closer inspection whilst free reving whens its not cutting out it seems the fuel pressure drops a couple of pounds instead of raising....


I think its time to drop the tank....

id check that pump, that doesn't sound normal...

 

[88foxvert]

dropped the tank and all looked ok tryed to install a new pump but it was bad out of the box
it ran but pumped no pressure..reinstalled the old pump with a new hose and I have 40psi.

also installed new summit bill. distributer still has the same issues.....mabey even worse now

 

[WHT306]

TRY THE PICK -UP COIL IN THE DIST. BUT ITS PROBABLY EASIER TO REPLACE THE DIST. INSTEAD
HAD MY CAR DO SAME THING. OR ITS THE COMBINATION OF THE PICK UP COIL AND IGN. MOD.