Emission Problems with '91

Hey Ya'll,

I got a '91 351(5.8L) that won't pass emissions. I've had it in two shops and they can't seem to figure it out. The last shop I had it at said the emissions were fine while the truck idled but as soon as it was taken out on the road it started pumping out the CO. Everything I read say that it's due to the air/fuel mix being too rich. I wish it was as simple as turning a **** but unfortunately it's not since it's all ECM controlled with a bunch of sensors and solenoids all over the place.

Anyhow, it has a new cat on it, the first shop told me it was bad so I had it replaced which didn't fix anything. I've been seeing some posts about the fuel pressure regulator, and thinking that may be the problem.

Any thoughts or suggestions?

Thanks

Ed

Have you tried higher octane gasoline, I've even heard of people running aviation fuel. Also there is something out there called guaranteed to pass.

yo,

try a DIY Code Check by Ryan

Even if the Check Engine Light is not on - "Don

Madmax-- I dumped some of that crap in there last year and it passed. I dumped some in there this year and it failed. Go figure. Thanks for the advice.

miesk5 -- that's some good info...I haven't yet looked into but when I find the answer I'll post it on here... or rather when the mechanic finds it cause right now I've got zero time to monkey with it.

Thanks for the help! You guys Rock!

Ed

oh also check your egr, they have a tendency of getting stuck and causing problems, alot of the pollution control crap on my truck is faked but I still pass emissions. Also I believe you can have the fuel/ air mixture modified by having the computer reprogrammed. First thing you should check though is the O2 sensor, I ran my truck for a month without one and you could smell it was running rich, **** with a lighter you could blow giant fireballs out of the exhaust. Even if the sensor itslef is good it could be dirty or the connection could be messed up, I once managed to snag the wire for mine on some brush while driving down railroad tracks to get around an accident.

Oh if you only have about 2 or 3 gallons of gas in the truck try dumping ALOT of that crap in the tank, shouldn't run it that strong but if theres only a gallon or two you can drain it by removing the line to the fuel filter, turning the key on and jumping two pins on a connector under the hood Miesk5 should be able to point them out to you. just drain it into a can and set it aside for next year.

I ran my truck on aviation gasoline 115/145 last time I took it to inspection which is basically 115 octane. Also it almost never goes bad unlike regular pump gasoline, but it's hard to get they almost completely stopped making it in the early 60's.

If I were looking at stockpiling a couple thousand gallons in case of a fuel shortage, I'd be looking at something like 100LL which is basically strait 100 octane gasoline with a tiny amount of lead. It keeps for a good 5 or 10 years with no appreciable degradation, and it's the most commonley available AVGAS around. Normal pump gasoline starts to lose the light fractions in a month, after two years it's basically a benzene/kerosene mix. Might still run in diesels though.

I've got another problem now... the damn truck won't start. I don't hear the pump sending any fuel when I turn the key so I'm thinking it's the fuel pump. The thing I don't understand is that I had the pump replaced less then 2 years ago. They shouldn't go bad that quick should they?

madmax -- Yeah, I use my Bronco the same way... Bush came into town and they closed the underpasses under the highway he was traveling on. I got out my truck switched it into 4x4 and drove over the median/hill. I wasn't going to wait there, that's why I drive the Bronco. So what's with the fireballs out the exhuast? What would you do, spark a lighter at the end of the tailpipe?

I miss driving my Bronco. ;-(

One more question, what oil do you all run? I'd been using 10W-40. I looked under the hood and saw an emissions controls sticker. On it, it said to use 10W-30. You don't suppose the difference in oil is causing it to fail emissions?

Ed ;-)

Hey All,

I'm getting the Bronco from the shop today. They said the truck passes emissions when it's not in overdrive. It comes on automatically in my truck so I need to figure out how to turn that damn thing off before I go have it tested. Emission people turn the truck off before they test it so it comes right back on. Any advice on dealing with the emission people. I'm going to let them have it.

Fuel pump relay was the culprit for it not starting.

Anywho thanks for all the help with this. The blurb on how to check codes should come in real handy in the future.

Ed ;-)

Take it to another emissions inspection station and tell them you don't want them to use overdrive because It doesn't shift properly into 4th and you don't want to risk further damage to the transmission.

and for the flaming exhaust, with the O2 sensor not plugged in it ran WAY too rich so much that I could light the exhaust with a lighter if I wound it up and then let off the throttle, as the engine wound back down you could light it.

So when I got it from the shop they had taken care of the emissions for me. I'm ****** off cause I spent a whole lot of money that I didn't need to.

So I call the emissions place and talk to some guy responsible for QA. He looks into all the times it was at the emission test centers and tells me that he's not convinced that testing it in overdrive was the problem and blah blah blah.

What do you all think? Would overdrive be an issue or not? I just know that when it's in OD and I try and pass someone it's a real dog until it kicks down to that 3rd gear. And it doesn't alway kick down right a way.

chuckles1856 said:

So when I got it from the shop they had taken care of the emissions for me. I'm ****** off cause I spent a whole lot of money that I didn't need to. So I call the emissions place and talk to some guy responsible for QA. He looks into all the times it was at the emission test centers and tells me that he's not convinced that testing it in overdrive was the problem and blah blah blah.

What do you all think? Would overdrive be an issue or not? I just know that when it's in OD and I try and pass someone it's a real dog until it kicks down to that 3rd gear. And it doesn't alway kick down right a way.

Click to expand...

yo C,

is the Check Engine Light or tranny OD light on? or did you or the "mechanics" do the self test for codes that light off the CEL?

OD shouldn't be a factor.

now, what tranny do you have?

some info:

The E4OD four speed automatic transmission is used in F and E series trucks, as well as AOD and AOD-E/4R70W four speed automatic transmissions. To determine which is used in your vehicle, follow these guidelines:If the shifter has a P-R-N-OD-D-1 pattern, the transmission must be an AOD (applicable to 1980-1993 vehicles). If a 1989-1993 truck has an Overdrive Cancel Switch and a P-R-N-OD-2-1 shifter pattern, then it is equipped with an E4OD transmission. With the possible exception of some 4R70W equipped 1993 E-150 vans with 5.0L SFI engines (The existence of a 1993 4R70W van is unsubstantiated). 1994 and later vehicles with four speed automatic transmissions will all have an Overdrive Cancel Switch and a P-R-N-OD-2-1 shifter pattern, but may have either an E4OD or a 4R70W transmission. All 4.2L, 4.6L and some 5.0L engines use the 4R70W transmission, while diesel, 4.9L, 5.4L, 5.8L, 6.8L and 7.5L vehicles always use E4OD

miesk5 -- looks like I've got an E40D, from taking a look at the shifter pattern and I also have the OD Cancel switch. I don't have a check engine light on. The tranny OD light is on only if you manually switch it there, thus if it's on you're not using OD. I guess the mechanics got the codes but I'm not sure.....I just went out and grabbed them....let me take a look at the link you sent and see what they mean

From what I can gather from the codes (might not be right first time doing it watching the CEL:

32 --EVP circuit below minimum voltage of 0.24 volts.

34 --PFE or EVP circuit above the closed limit of 0.67 volts.

51 --ECT sensor signal is greater than the Self-Test maximum of 4.6 volts.

54 --ACT sensor signal is greater than the Self-Test maximum of 4.6 volts.

61 --ECT sensor is less than the Self-Test minimum of 0.2 volt

87 --Fuel pump primary circuit failure. When the FP relay was activated by the EEC, voltage was not detected on the control circuit.

95 --Fuel pump secondary circuit failure. The EEC senses infinite resistance to ground from the fuel pump on the Fuel Pump Monitor circuit.

96 --Fuel pump secondary circuit failure. The EEC did not sense battery voltage on the Fuel Pump Monitor circuit.

Oh forgot to mention... tranny was rebuilt 2 years ago. I know they put a shift kit in. When talking to the guy about it he said they mainly put them in to improve lubrication. So, I wouldn't think that it would affect kicking down from overdrive. In any case the truck has always performed less than optimal from OD to 3rd. Or is my opinion. ;-)

chuckles1856 said:

Oh forgot to mention... tranny was rebuilt 2 years ago. I know they put a shift kit in. When talking to the guy about it he said they mainly put them in to improve lubrication. So, I wouldn't think that it would affect kicking down from overdrive. In any case the truck has always performed less than optimal from OD to 3rd. Or is my opinion. ;-)

Click to expand...

ok,

I think it's time to get another self test by you or the new shop; have to clear codes first;

for now;

32 --EVP circuit below minimum voltage of 0.24 volts

EGR Valve Position (EVP) Sensor Operation & Testing, Ford by tomco-inc.com http://www.tomco-inc.com/Tech_Tips/ttt19.pdf

Code 34- EGR voltage above closed limit - Failed sensor, carbon between EGR pintle valve and seat holding the valve off its seat. Remove the EGR valve and clean it with carbon remover. Prior to re-installing see if you can blow air through the ****** side of the EGR by mouth. the egr is not closing properly which can cause detonation. remove the egr and clean off any carbon built up on it with carb cleaner and a brush if necessary.

And a test that requires break-out box, etc.

EGR Valve Position (EVP) Sensor & EGR Vacuum Regulator Solenoid (EVR) Testing for Codes 31, 32. 33. 34. 35. 38 or 84 Source: by Dustin S (Dustball, Mellow Yellow, Mr. Laser Boy) at ylobronc.users.SuperMotors.net

DTC 34 means that the PFE voltage is too high. This could be the result of a clogged exhaust or the PFE sensor itself

51 --ECT sensor signal is greater than the Self-Test maximum of 4.6 volts

Open circuit in harness

Sensor signal short to power

Damaged PCM - no way!...lol..let's not get into this!

Improper harness connection

Damaged sensor

Remove the ECT sensor, If you see some rust in it clean it by sanding the surface using a fine grit sandpaper, Also check the connector and wiring. Reinstall and check for codes, if some are present change the unit.

or for the tekkies, which are not in man shops....

Using signal simulation, disconnect sensor and simulate 1.0V on sensor signal circuit. Simulated 1.0V signal and scan PID voltage value should be similar. If voltage is similar check sensor, if voltage is not similar check related circuit and PCM.

87 (oc): FP relay circuit failure- suspect inertia switch, fusible link, FP relay.

95 (oc): Fuel Pump Monitor circuit problems, processor to pump motor ground. Suspect inertia switch, FP relay, harness.

96 (oc): FP circuit failure, battery to processor.- check batty cables, connectors,grounds for corrosion,etc.

*** my INSERT ket was clicked while drinking coffee; so I overwrote following...

54 (orc*): ACT (Air Charge Temperature)/IAT (Intake Air Temperature) sensor voltage too high, indidcating -40degF. Suspect shorted sensor, harness.

61 --ECT sensor is less than the Self-Test minimum of 0.2 volt;

indicates coolant temp greater than 250 deg F.

miesk5 -- just to make sure I'm following correctly... I should do the following:

1) clear the codes

2) perform another self test and get codes

I'm assuming that if I disconnect the battery the codes will be cleared? Should I need to run the truck before I gather the codes again?

ps -- darn coffee ;-)

chuckles1856 said:

miesk5 -- just to make sure I'm following correctly... I should do the following:
1) clear the codes

2) perform another self test and get codes

I'm assuming that if I disconnect the battery the codes will be cleared? Should I need to run the truck before I gather the codes again?

ps -- darn coffee ;-)

Click to expand...

freakin' coffee! lol..and this freakin' laptop w/a bad battery!

yo chuckles!

To clear the Keep Alive Memory, disconnect the negative battery cable for at least 5 minutes. After the memory is cleared and the battery reconnected, the vehicle must be driven at least 10 miles (16 km) so that the processor may relearn the needed correction factors. The distance to be driven depends on the engine and vehicle, but all drives should include steady-throttle cruise on open roads. Certain driveability problems may be noted during the drive because the adaptive factors are not yet functioning.

by Chilton

use the Self Test & Connector Location & pics, Bronco & Ford BEST PROCESS WITH DIAGRAMS Source: by Ryan M

by disc. batty, you'll lose radio pre-sets and drive cycle stuff, but that is ok if you don't mind the radio

gl!

Ok .....I know it's been a long time coming but here's the deal....

Truck developed a coolant leak from the intake manifold. I tore into it and replaced those gaskets along with the ERG gasket, PVC, intake gasket, plenum gasket and some vacuum line I snapped. Oh and also new cap and roter and t-stat.

After I got it done I had to get emission test done on it and just knew it was going to fail. 4 month old gas and dirty oil, but I figured what the **** I've got to start somewhere as far as the emissions go.

To my pleasant surprise it passed and passed rather well. The things that were different were:

1) I told the guy doing the test to test it out of overdrive ( since this is what the shop told me the problem was last time )

2) I left the air supply tube/hoses off from the air cleaner to intake

My thought behind no air filter is that it could be restricting the air flow making for a rich air/fuel mix. And the truck had been failing with a rich mix so I thought maybe that would help.

I've also noticed that since I've got it all back together it runs warmer than it used to. I have to wonder if this is because of the new t-stat. Like the old one was just sort of stuck open and allowing the coolant to flow more freely.

I read that if the engine thinks it's cold it dumps more fuel in the engine to try and heat it up, like at startup. Thus this could have been my main reason for the rich air/fuel mix.

My question after all my ramblings....Do you think that the problem of my truck running rich was the t-stat? Or was it the greater supply of air by by passing the air filter?

I don't know why this is bothering me so much but it is.

The thermostat may not have been your only problem, but it sure wasn't helping. Fuel injected motors are designed to run at a specific temp. zone. When the engine is cold, the ECM allows for a rich mixture, leaning it as needed as it warms up. If it doesn't warm up, it doesn't lean out. Thats why I tell customers NOT to shut their pre 96 car off in the inspection lines.

Yeah, and the emissions people here have a sign that says keep vehicle running then when you get to a certain point in the line they take all your paperwork and turn the vehicle off and let it set for a while. Somehow that just seems like it defeats the purpose.

Right now my temp gauge sets right in the middle of hot and cold, well within normal range.

Just wondering how warm other Bronco's are running?