Bad miss at 30-35mph

[86VickyLX]

Hmmmm...the website I was looking up the codes on doesn't say it but when I look at the code definitions on this forum it says #34 is Insufficient EGR flow/Excessive exhaust back pressure; or EVP voltage above closed limit(SONIC)/PFE sensor voltage high or out of range. (O)(R)(C)

I've noticed my car has a rotten eggs smell sometimes. Is is possible my EGR valve and position sensor is fine and I have a bad or plugged catalytic converter?

Bad converter or it's running very rich.
I'm gonna lean towards running very rich, since it's been there since the beginning. I'm also gonna bet, if you do a cylinder balance test, you will find that one cylinder fails.

[gadget73]

you dont have a flow sensor, just a position sensor.

31 PFE or EVP circuit below minimum voltage of 0.24 volts.
33 EGR valve opening not detected.
34 PFE or EVP circuit has intermittently failed above the closed limit of 0.67 volts.


31 is usually a bad or wrong position sensor
33 is usually either a bad egr valve that doesn't hold vacuum or a vacuum leak between the regulator solenoid and the valve itself
34 is usually either a bad or wrong position sensor, or a chunk of crap holding the valve open a little bit

92 would be explained by a leaky injector. Yank the plugs on that side. If one is noticeably darker than the others, thats probably the dud injector.

[PushnFords]

Bad converter or it's running very rich.
I'm gonna lean towards running very rich, since it's been there since the beginning. I'm also gonna bet, if you do a cylinder balance test, you will find that one cylinder fails.

I'm only getting a rich code on one side (Bank 2). I pulled the plugs right after I got the car to check the gaps and they were all clean except #4 which had deposits on it. Not sooty like overly rich...more like oil contamination deposits. I tried to do a cylinder balance test but it won't do it with existing codes.

you dont have a flow sensor, just a position sensor.

Oops...knew that...mistyped....

31 PFE or EVP circuit below minimum voltage of 0.24 volts.
33 EGR valve opening not detected.
34 PFE or EVP circuit has intermittently failed above the closed limit of 0.67 volts.


31 is usually a bad or wrong position sensor
33 is usually either a bad egr valve that doesn't hold vacuum or a vacuum leak between the regulator solenoid and the valve itself
34 is usually either a bad or wrong position sensor, or a chunk of crap holding the valve open a little bit

92 would be explained by a leaky injector. Yank the plugs on that side. If one is noticeably darker than the others, thats probably the dud injector.

I'll swing by the JY during a lunch break this week and grab another EGR valve/position sensor or two and try them out.

As for the leaky injector...I described the plugs above. Would a cylinder burning oil trigger a rich code? None of the plugs looked like they were getting too much fuel. If it helps at all I went on a 375 mile trip a week ago and got 19mpg according to my calculations and 18 according to the trip computer. That was with some city driving and a vacuum leak bad enough it was making my heater go full hot on every hill.

[gadget73]

fuel economy sounds decent. You might pick up a rich code from burning some oil but it would likely be smoking visibly all the time. Could just be the O2 sensors are toast. They do lose accuracy over about 60k miles.

[PushnFords]

I was going to test the O2 sensor but damn...they have 130K on them and RockAuto has them for $10. I might just replace them in a week or so. Gotta get back to the paying projects first although I'll keep messing with the EGR. Yesterday morning I didn't wear a coat outside. By dinner I was wearing a light shop coat. At 11pm I was shoveling 3.5" of snow off the drive. When I got home today at 5pm I was wearing a light coat unzipped and the drives were all bare. JY is going to be a mud pit.

[1990LTD]

I need to replace mine...couldn't do it when I tried since they're bastards to reach. Hateful fucking things.

[91waggin]

o2 sensors won't cause misfires on these things. All they do is tweak the fuel mixture slightly when the computer is in closed loop. They don't have enough of an impact on the computer's mixture decisions to cause a real bad misfire on these cars.

[PushnFords]

With CV EGR valve and HO position sensor
34 - EVP sensor out of range
92 - System running rich, Bank 2

Since I got the above readings I haven't touched a thing on the car mechanically. I took it for maybe a 10 mile drive two nights ago but only at 15-25mph because of heavy snow. Today I drove it the 2 miles to work and home. I've noticed when I start it up the engine instantly revs pretty high and then sets back down to a normal idle. I just rechecked the codes and got 41, 91, and again the 34. I'll put a few highway miles on it and recheck...still going to try and grab another EGR valve.

[PushnFords]

Since I got the above readings I haven't touched a thing on the car mechanically. I took it for maybe a 10 mile drive two nights ago but only at 15-25mph because of heavy snow. Today I drove it the 2 miles to work and home. I've noticed when I start it up the engine instantly revs pretty high and then sets back down to a normal idle. I just rechecked the codes and got 41, 91, and again the 34. I'll put a few highway miles on it and recheck...still going to try and grab another EGR valve.

Ok...I drove out of town on the highway and back home (about 8 miles) and checked my codes: 41, 91, and 34. Installed an EGR valve, position sensor, and vacuum reservoir I pulled off of an '89 Town Car and drove another 8 miles....still have the same codes.

I've got a shop manual ordered but if anyone has any info or suggestions on tracking down that EVP code I'd love to hear it.

[PushnFords]

Ok...I drove out of town on the highway and back home (about 8 miles) and checked my codes: 41, 91, and 34. Installed an EGR valve, position sensor, and vacuum reservoir I pulled off of an '89 Town Car and drove another 8 miles....still have the same codes.

I've got a shop manual ordered but if anyone has any info or suggestions on tracking down that EVP code I'd love to hear it.

Pulled the Town Car EGR valve back off and welded up the port so the pintle moves but no air/exhaust flow. Now I get 41, 91, 34, and 13.

[91waggin]

Make sure if you make any repairs, you disconnect the battery for a few minutes to clear codes.

[PushnFords]

Make sure if you make any repairs, you disconnect the battery for a few minutes to clear codes.

I hadn't been doing that...oops. If I fix a problem that is causing a code how long will it take for the computer to turn the code off? I guess I thought since it as a KOER test it only picked up active problems...the miss is still there.

[86VickyLX]

I hadn't been doing that...oops. If I fix a problem that is causing a code how long will it take for the computer to turn the code off? I guess I thought since it as a KOER test it only picked up active problems...the miss is still there.

KOER test picks up stuff that's happening as it runs through the self test, if you have a code during this time, it's happening right now.

In regards to the EVP, do you have a voltmeter? I'd be willing to bet that the voltage that the computer is seeing is higher than .65 volts.

41 and 91 are lean codes, whatever you did now it's running lean on both banks.

Code 13 means basically it's idling too high. Which normally means either the idle screw has been fucked with, or you have a vacuum leak. The lean codes are making me lean towards a vacuum leak.

Can I make a suggestion, quit throwing parts at it. Everytime you change something, it seems to be putting problems somewhere else.

Here's what I'd do first. Find out where the vacuum leaks are. That should get rid of codes 41 and 91.

Code 13 should also be gone.

Lastly comes the EGR valve. If you have a voltmeter we can continue.

[johnunit]

... yeah you're gonna get a few codes if you weld up the EGR port.

[PushnFords]

KOER test picks up stuff that's happening as it runs through the self test, if you have a code during this time, it's happening right now.

That is what I was thinking....

In regards to the EVP, do you have a voltmeter? I'd be willing to bet that the voltage that the computer is seeing is higher than .65 volts.

Yea I have a full set of tools. I'm used to either old stuff or OBDII though. I'm assuming that voltage is from the EGR position sensor?

41 and 91 are lean codes, whatever you did now it's running lean on both banks.

Yea...I have no idea why I went from rich on one bank to lean on both...nothing I changed should have done that.

Code 13 means basically it's idling too high. Which normally means either the idle screw has been fucked with, or you have a vacuum leak. The lean codes are making me lean towards a vacuum leak.

Can I make a suggestion, quit throwing parts at it. Everytime you change something, it seems to be putting problems somewhere else.

I quit and ordered a shop manual! Total changes from stock currently is the removal of some of the vacuum lines for the charcoal cannister and smog pump, HO IAC valve installed, and the '89 Town Car EGR installed with the port sealed off. I have the stock parts I can put back on. Nothing changed during the last swap of those parts so I tend to think they are ok.

Here's what I'd do first. Find out where the vacuum leaks are. That should get rid of codes 41 and 91.

Code 13 should also be gone.

I'll start looking for the leak asap. I've fixed quite a few but I think I still have at least one in the dash...maybe more elsewhere.

Lastly comes the EGR valve. If you have a voltmeter we can continue.

I do....