bad miss at half throttle/cruise?????

[lib88stang]

I have a very bad miss at cruising speed, at about 2k-3k rpms yuo can feel the car missing and if you get into the gas just a little it get way worse but if you floor it it takes off fine. Sometimes it will backfire or pop when you get into it alittle. It doesn't do this all the time but alot. The fuel pres and tach don't drop when it starts missing bad, it feels like its going to die then it wil take off. what could this be???

could it be EGR, the sensor at the char canister???

I did look at the engine at night and the coil was arcing and all the plug wires on the pass.side and 2 on the driver side. Could this be the prob. or is it because I have an MSD box????

Please help this is very frustrating..

 

[HISSIN50]

ahh, yeah, plug wires could do it.

also pull the codes. i think you are on the right track with possible EGR/EVR malfunction too.

good luck.

 

[lib88stang]

I did pull codes and #11 system ok.

what is the EVT??

Could the arcing make it miss that bad??

 

[HISSIN50]

the EVR is the solenoid that controls the EGR.

you betcha - plug wires (and the coil wire!) could definately cause issues like you have.

since you need some new wires anyhow, i would do that first - it just might fix your problems.

good luck.

 

[lib88stang]

could it also be the sensor by the char canister (vac purge)???

If so is a 4cly stangs the same??

Also where is the EVR located

And what does the black and white connectors do(the salt and pepper on the back of the intake)???

 

[1986LX2002]

Yeah arcing wires arent good you need to fix that asap. loom up your wires the proper way too just dont let them hang and keep them seperated as much as possible to avoid crossfiring. Also check your firing order and probably wouldnt be a bad idea to check your plug gap, and if you do that index the plugs while your at it "free tiny amount of power'

 

[lib88stang]

I just replaced the plug wires, the cap, the rotor, and the coil. All MSD brand. All wires are sepparated. Still bad miss. I don't know what else to do!? Any help at all, guys?

 

[HISSIN50]

have you disconnected your ignition box and tried driving like that yet? you would not be the first to have box issues.

that is all that comes to mind - since you dont have any codes being tossed....

good luck.

 

[Schlodes]

What plugs are you running? And does anything look amiss with them when you pull them out?

Never had good luck getting Bosch Platinum plugs to work in these cars.. Would always get a light miss about 4500 RPM when more than 3/4s throttle... But wasnt as bad as what you are describing.

TPS sensor is ok? Hook a voltmeter up and look for flat spots [flat spot = voltage numbers increase steadily as you sowly open the throttle.. If theres a flat spot voltage increase stops.. then climb again.. or just dont at all..].

MAF?

 

[lib88stang]

I disconected the MSD box and it still did it, I don't have mass air, I will check TPS for flat spots. I do have bosch platinums in it but I can't see them making the car do it because it had a miss before I put them in and I had autolites in it before.

I don't want to have to take it to a shop and spend a bunch of money and it be something stupid. I have had it for 5 years and put 100,000 miles on it since I got it and never had a prob like this.

Please help thanks

 

[AznStanger3v]

sounds like an exhaust leak to me.

 

[lib88stang]

explain why that could be an exhaust leak???

 

[AznStanger3v]

bc when i had an exhaust leak, it did the EXACT same thing. im using experience in my hypothesis on this, bc sometimes experience is just better for helping.

 

[Schlodes]

If it were a bad enough exhaust leak that the 02 sensors werent reading proper...but still doubt it would cause a condition like you have.

What coil are you running?

 

[lib88stang]

I have a advance auto coil, and its brand new. I got one for a 91 gt cause I heard it was better.

I dont have an exhaust leak, but could it be O2 sensors? They are a year and a half old.

I'm tired of putting so much money in it and it not getting fixed, but it has to be something simple with either vaccum or electric.

more ideas please

 

[5.0_Gil_89]

tps, and clean your 10 pin.

 

[lib88stang]

what is the 10 pin?? Is it the white and black connectors ??

First thing in the morning I am going to check the TPS for flat spots and the O2 sensors.

Any more ideas???

 

[Raginstang]

definetly could be vaccuum leak. try checkin for one with brake cleaner and listen for engine to rev up. also check all lines and the line to the pcv valve. sounds like you might have a sticky egr valve. just some ideas. try pushin on the diaphram on the egr and see if it unsticks. test with a vacuum pump. also, I have heard that platinum plugs are terrible for these cars. when I worked at ford, we had all kinds off missfire problems from the platinums.

 

[lib88stang]

I checked for vac leaks and nothing

I checked EGR- nothing

I checked and replaced MAP - nothing

It is getting worse, The car hold back till 4500 rpms then cuts loose like it has a power band. But if I run it hard it runs fine. Just driving normal it misses and bogs then takes off if you mash the gas.

What else could it be before I take it to a mechanic??

 

[lib88stang]

I know somebody else had this problem too.

Any help please, it is driving me crazy...........