Developed a miss

[84turbojoe]

I've been picking away at my car problems but now a new one has occured.
After driving the car for 15-20 min a miss developes between 2-3k. The car is at operating temp, and the miss will go away if I down shift or stomp on it and than will return if in the above rpm range.
The car is pretty much back to stock config ex for 3' exhaust and gillis controller.
I still have factory ignition(original?)on it.
Any ideas? Thanks for the help!
Joe

[SVOeric]

My miss in that rpm range ended up being the fuel pressure regulator --

When it gets dark outside, take your SVO for a 10 - 15 minute drive, come back, and open the hood, is the exhaust manafold glowing red slightly??

I could only see mine doing this at night.  I have a new Kirban FPR from SVPU to put on tonight, this should solve my problem

 

[svobud]

might be TPS related as well.....

[johnbasler]

Check your PCV valve too

I know this is going to sound silly but several years ago I had a similar problem with my long-gone 86 SVO. Turns out the OEM pcv valve had disintegrated, clogging the pcv tube. The resulting vacuum problem made a lean condition that sounds similar to this. Since the PCV valve is tucked away where you forget about them, doesn't hurt to check it out.

Good luck.

[84turbojoe]

MISS

Thanks for the replies.
Possible!.
The car seems to be running rich(smell of exhaust) so that could be FRP or leaking injectors. The FPR is new but from what I've read that doesn't matter.
The throttle response varies throughout the peddle travel or lags in response so it could be TPS. Again, TPS is new but...
I do have a Ford PCV valve in there and it is a little old but still in one piece (will replace v/soon)

Could ignition have anything to do with it. Could it be getting old etc...???

[svobud]

have you even run a computer code check on it yet to see if there may be a sensor failure somewhere?

O2 sensor....once dead...ECU loads up the fuel.

[84turbojoe]

Run codes

Bud,
My code connector had been replaced by the flat female type connectors. The scan did not work properly, tried a few times to ensure it was not operator error.
I broke down last week and took the car to a Ford dealer to pay the $89 diagnosis fee and the first thing they found was EGR. Paid the bill, took it home, replaced it (man that thing was shot) but didn't fix the prob of the miss which I knew wouldn't but helped in other areas..lol.
O2 sensor is new, but the ECU is not. Due to the scan problem I just went ahead and replaced all sensors, figured it was time anyway.???

[jhawk]

I would change the plugs and wires first. When I first got my svo it had a similair miss. I replcaed anything and everthing except the plug wires since the previous owner had installed new ones. Someone told me change the wires even if they are new. I did. Problem solved. Now the first thing I do when a miss occurs is replace the plugs, wires, cap and rotor.

jim

[84turbojoe]

back fire

I'm starting to think that the miss is there at any rpm, just more noticeable after the is warmed up. Also, I am gettin backfiring (quite a bit) when letting up on gas peddle during normal driving. Does the back firing lead to some other problems and a really bad sign, or just running too rich. God I can smell the fuel from the exhaust. I just haven't had time this week to work on it and have to drive it to work daily but will get into this weekend. I will look at previously mentioned items, just worried about the backfiring. Thanks.
Joe

[SVOeric]

I can't remember if you have done this or not, but I think a compression check would be in order.

I would also say check the plugs, and make sure they don't have oil on them.

With the correct computer back in, and the 30# injectors back, I wouldn't think you would be running rich... You might also want to make sure the fuel return line isn't kinked somewhere.

 

[Tony]

All these are good suggestions. I would also check the cat. A clogged or messed up cat can also seem like an ignition or fuel problem. Get under there (jack-stands and a cool car for safety), and give your exhaust system around your cat a good shake... if you hear something rattling around in there (like sand or gravel), you'll have to replace it. My 85 was running like crap for a few days before I figured it out. I also checked codes, ignition and fuel before I came to that conclusion. When the exhaust shop cut it out, they had to clear debris from about 2 feet down stream of the cat... it was a MESS!

Just my .02. Let us know what it is when you track it down! Good luck.

Tony