'94 Ranger emissions failure
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Senior User
Joined: Jul 2002
Posts: 134
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From: NJ USA
'94 Ranger emissions failure
Hello, all. Long time…
’94 Ranger, 3.0L V6, 2WD, 5sp. man. 102K and counting, will be 10-yrs. old on June 10. Original battery and exhaust still kickin'.
Briefly, the pig failed emissions for excessive NOx (twice now; first time I thought the cat had cooled during engine-offs in 60 minute inspection wait line). Limit is 1227, first fail was 1270, second time it blew a 1397.
What’s funny is it passes the coordination tests (couldn’t resist the DWI analogy). What I mean is that NO codes are present during KOEO and KOER tests, gas mileage is perfectly normal at 23 MPG, and it runs like it did on day one. Plugs/cap/rotor have only 12K on them, wires only 45K. Further, based on the diagram in the engine compartment and a perusal through my Ford factory service manual, there doesn’t appear to be an EGR system on this engine.
Anyone out there who’s had a similar problem or experience that can offer some advice or direction?
As always, thanks in advance for your time and effort.
Mike
’94 Ranger, 3.0L V6, 2WD, 5sp. man. 102K and counting, will be 10-yrs. old on June 10. Original battery and exhaust still kickin'.
Briefly, the pig failed emissions for excessive NOx (twice now; first time I thought the cat had cooled during engine-offs in 60 minute inspection wait line). Limit is 1227, first fail was 1270, second time it blew a 1397.
What’s funny is it passes the coordination tests (couldn’t resist the DWI analogy). What I mean is that NO codes are present during KOEO and KOER tests, gas mileage is perfectly normal at 23 MPG, and it runs like it did on day one. Plugs/cap/rotor have only 12K on them, wires only 45K. Further, based on the diagram in the engine compartment and a perusal through my Ford factory service manual, there doesn’t appear to be an EGR system on this engine.
Anyone out there who’s had a similar problem or experience that can offer some advice or direction?
As always, thanks in advance for your time and effort.
Mike
Post Fiend
Joined: Dec 2001
Posts: 10,562
Likes: 4
From: South Jersey
SC29 HIGH NOX
NOTE:
If the vehicle was not manufactured with an EGR System take the NO path.
l Verify that the vehicle has an EGR System and appears operational.
l Verify that the EGR System has not been modified.
l Go to Section 5, EGR Pinpoint Test «HE1».
l Is a fault indicated?
Yes
SERVICE as required according to service manual direction. After service is performed, GO to «SC35».
No
GO to «SC30».
SC30 CHECK FUEL CONTROL
l For Carbureted vehicles:
-- Go to Section 5, Carburetor Fuel Delivery System Pinpoint Test Step «HB1».
l For all others:
-- Go to Section 5 Fuel Control Pinpoint Test Step «H1».
l Is a fault indicated?
Yes
SERVICE as required according to service manual direction. After service is performed, GO to «SC35».
No
GO to «SC31».
SC31 ADDITIONAL CHECKS
l Additional checks:
-- Transmission torque converter clutch operation.
-- Cooling system (after market front facia or intake air system modifications).
-- Engine running lean (vacuum leaks, low fuel pressure, etc.; refer to steps «SC23» through «SC27»).
l Go to Section 5, Emission Related Components Test Step «D1». Verify that any applicable components are functioning properly.
l Are all checks OK?
Yes
GO to «SC32».
No
SERVICE as necessary. After service, GO to «SC35».
SC32 CHECK BASE ENGINE
l Go the Engine group of the Service Manual to check engine vacuum and excessive carbon build up in the combustion chamber.
l Is a fault indicated?
Yes
SERVICE as required according to service manual direction. GO to «SC35».
No
GO to «SC33».
SC33 CHECK ALL FAILED GASES
l Have you attempted to diagnose all emission failures?
Yes
GO to «SC34».
No
FOR CO:
GO to «SC8».
FOR HC:
GO to «SC9».
FOR NOX:
GO to «SC10».
SC34 CATALYST TEST
l Go to Section 5, Catalyst and Exhaust Pinpoint Step «HF20» to perform Delta Temperature Catalyst Test.
l Did the vehicle pass the test?
Yes
VERIFY test results. If OK, GO to «SC36» to perform the baseline test. Use this information for further diagnosis.
No
SERVICE as necessary. After service, GO to «SC36» to verify repair.
NOTE:
If the vehicle was not manufactured with an EGR System take the NO path.
l Verify that the vehicle has an EGR System and appears operational.
l Verify that the EGR System has not been modified.
l Go to Section 5, EGR Pinpoint Test «HE1».
l Is a fault indicated?
Yes
SERVICE as required according to service manual direction. After service is performed, GO to «SC35».
No
GO to «SC30».
SC30 CHECK FUEL CONTROL
l For Carbureted vehicles:
-- Go to Section 5, Carburetor Fuel Delivery System Pinpoint Test Step «HB1».
l For all others:
-- Go to Section 5 Fuel Control Pinpoint Test Step «H1».
l Is a fault indicated?
Yes
SERVICE as required according to service manual direction. After service is performed, GO to «SC35».
No
GO to «SC31».
SC31 ADDITIONAL CHECKS
l Additional checks:
-- Transmission torque converter clutch operation.
-- Cooling system (after market front facia or intake air system modifications).
-- Engine running lean (vacuum leaks, low fuel pressure, etc.; refer to steps «SC23» through «SC27»).
l Go to Section 5, Emission Related Components Test Step «D1». Verify that any applicable components are functioning properly.
l Are all checks OK?
Yes
GO to «SC32».
No
SERVICE as necessary. After service, GO to «SC35».
SC32 CHECK BASE ENGINE
l Go the Engine group of the Service Manual to check engine vacuum and excessive carbon build up in the combustion chamber.
l Is a fault indicated?
Yes
SERVICE as required according to service manual direction. GO to «SC35».
No
GO to «SC33».
SC33 CHECK ALL FAILED GASES
l Have you attempted to diagnose all emission failures?
Yes
GO to «SC34».
No
FOR CO:
GO to «SC8».
FOR HC:
GO to «SC9».
FOR NOX:
GO to «SC10».
SC34 CATALYST TEST
l Go to Section 5, Catalyst and Exhaust Pinpoint Step «HF20» to perform Delta Temperature Catalyst Test.
l Did the vehicle pass the test?
Yes
VERIFY test results. If OK, GO to «SC36» to perform the baseline test. Use this information for further diagnosis.
No
SERVICE as necessary. After service, GO to «SC36» to verify repair.
Post Fiend
Joined: Jan 2003
Posts: 9,748
Likes: 16
From: Connecticut
Hello Mike, 
As pointed out in the Ford stuff Ken posted, the way to reduce NOx is by reducing combustion chamber temperatures. Since your 3.0L doesn't have an EGR system, you are unfortunately somewhat at a disadvantage in that regard.
But as noted, other things that can cause higher temps - and hence NOx - include a lean condition (vacuum leak, low fuel pressure, clogged fuel filter/injectors), deficient cooling system, carbon buildup (increased compression), and those kinds of things. Your ignition system sounds like it's in good shape. How is your fuel pressure?
Speaking of ignition, over-advanced timing could cause high temps too, but your ECM would be keeping that in check, you have to think. On a related note, and FWIW, I've heard of people with the DIS systems pulling the SPOUT connector off in order to retard (default) the timing to 10* BTDC. Word is they pass pretty easily after doing that. I'm not sure if there is a similar trick with your DI system, but if you run out of options, it might be worth thinking about.
Just some food for thought.
As pointed out in the Ford stuff Ken posted, the way to reduce NOx is by reducing combustion chamber temperatures. Since your 3.0L doesn't have an EGR system, you are unfortunately somewhat at a disadvantage in that regard.
But as noted, other things that can cause higher temps - and hence NOx - include a lean condition (vacuum leak, low fuel pressure, clogged fuel filter/injectors), deficient cooling system, carbon buildup (increased compression), and those kinds of things. Your ignition system sounds like it's in good shape. How is your fuel pressure?
Speaking of ignition, over-advanced timing could cause high temps too, but your ECM would be keeping that in check, you have to think. On a related note, and FWIW, I've heard of people with the DIS systems pulling the SPOUT connector off in order to retard (default) the timing to 10* BTDC. Word is they pass pretty easily after doing that. I'm not sure if there is a similar trick with your DI system, but if you run out of options, it might be worth thinking about.
Just some food for thought.
Thread Starter
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Senior User
Joined: Jul 2002
Posts: 134
Likes: 0
From: NJ USA
Ken,
Thanks much for taking the trouble to list that procedure. Is that from the Ford manual? If so I should be able to find it on my CD of same, but I’ve found finding things on it are beyond tedious, as the “find” function is awful. Anyway, thanks for the effort. I’m printing it out just-in-case.
Joe,
Thanks for tips; all noted. I began my TS in the same manner, thinking it’s something forward of the cats causing the problem. But now I’m thinking it could be the cats themselves, after a call to a mechanic friend and something I found on the ‘net.
What the mechanic said was troubling. Being a pair of three-way catalysts (which I think means they reduce NOx as well as CO and HC), they’re expensive as heck (~$1,000) because they’re ONLY available from Ford. He mentioned that a Midas or Meineke MIGHT weld in a compatible, cheaper converter for less, but wasn’t sure.
The internet article gave me this little snippet.
Converters are also vulnerable to contamination. As a converter ages, its operating efficiency can decline as contaminants accumulate inside on the reactive surfaces. Particularly bad are phosphorus deposits from oil burning (worn valve seals, guides and/or rings), or silicone deposits from internal coolant leaks (cracked head or block, or a leaky head gasket). As the contaminants build up, HC, CO and NOX emissions begin to rise. Eventually, the converter’s ability to destroy pollutants falls to the point where it does little or nothing to clean up the exhaust. There’s no effect on engine performance, but the drop in emissions reduction may cause the vehicle to fail an emissions test.
Now keep in mind I’ve got an engine with a propensity to burn some oil (why else would Ford put an oil-level sensor in the oil pan?) and a personal habit of engine braking, causing a consumption rate of a quart per 1,500 since June 10, 1994. Also, note the “no effect on performance” in the above. Many of the possible causes you list (which I’d seen as well) should cause some adverse effect on performance.
So, while I hope I’m wrong, I’m leaning towards bad cats. Maybe a good solution is a whole new exhaust (I think Ken has and likes the Gibson system) with someone else’s cats. But I still have a problem putting $1K into a truck worth about $3K, at best.
The immediate plan is to throw it on the tester one more time -- this time at the garage -- making sure the cats are plenty warmed-up this time. I’m also going to check one other thing, that of coolant temperature. Since I changed the thermostat 2 years ago and added a small hole to it, the engine takes longer to warm-up and doesn’t get quite a hot as it used to, at least based on the gauge. I’m wondering if this slight difference is enough to muck-up emissions, so it needs to be ruled out.
Finally, to address your other points: Carbon was cleaned out awhile back to cure a slight ping (success), and I personally had to TS an intermittent fuel pump relay last year, so I bought a gauge and know the pressure is right on. As for the SPOUT trick…interesting. Maybe as a last resort, but I honestly do care about emissions and would rather fix the problem. NJ has enough polution.
Glad to see you and Ken still providing good advice to all on the forum, and thanks again to you both for the assistance.
Mike
Thanks much for taking the trouble to list that procedure. Is that from the Ford manual? If so I should be able to find it on my CD of same, but I’ve found finding things on it are beyond tedious, as the “find” function is awful. Anyway, thanks for the effort. I’m printing it out just-in-case.
Joe,
Thanks for tips; all noted. I began my TS in the same manner, thinking it’s something forward of the cats causing the problem. But now I’m thinking it could be the cats themselves, after a call to a mechanic friend and something I found on the ‘net.
What the mechanic said was troubling. Being a pair of three-way catalysts (which I think means they reduce NOx as well as CO and HC), they’re expensive as heck (~$1,000) because they’re ONLY available from Ford. He mentioned that a Midas or Meineke MIGHT weld in a compatible, cheaper converter for less, but wasn’t sure.
The internet article gave me this little snippet.
Converters are also vulnerable to contamination. As a converter ages, its operating efficiency can decline as contaminants accumulate inside on the reactive surfaces. Particularly bad are phosphorus deposits from oil burning (worn valve seals, guides and/or rings), or silicone deposits from internal coolant leaks (cracked head or block, or a leaky head gasket). As the contaminants build up, HC, CO and NOX emissions begin to rise. Eventually, the converter’s ability to destroy pollutants falls to the point where it does little or nothing to clean up the exhaust. There’s no effect on engine performance, but the drop in emissions reduction may cause the vehicle to fail an emissions test.
Now keep in mind I’ve got an engine with a propensity to burn some oil (why else would Ford put an oil-level sensor in the oil pan?) and a personal habit of engine braking, causing a consumption rate of a quart per 1,500 since June 10, 1994. Also, note the “no effect on performance” in the above. Many of the possible causes you list (which I’d seen as well) should cause some adverse effect on performance.
So, while I hope I’m wrong, I’m leaning towards bad cats. Maybe a good solution is a whole new exhaust (I think Ken has and likes the Gibson system) with someone else’s cats. But I still have a problem putting $1K into a truck worth about $3K, at best.
The immediate plan is to throw it on the tester one more time -- this time at the garage -- making sure the cats are plenty warmed-up this time. I’m also going to check one other thing, that of coolant temperature. Since I changed the thermostat 2 years ago and added a small hole to it, the engine takes longer to warm-up and doesn’t get quite a hot as it used to, at least based on the gauge. I’m wondering if this slight difference is enough to muck-up emissions, so it needs to be ruled out.
Finally, to address your other points: Carbon was cleaned out awhile back to cure a slight ping (success), and I personally had to TS an intermittent fuel pump relay last year, so I bought a gauge and know the pressure is right on. As for the SPOUT trick…interesting. Maybe as a last resort, but I honestly do care about emissions and would rather fix the problem. NJ has enough polution.
Glad to see you and Ken still providing good advice to all on the forum, and thanks again to you both for the assistance.
Mike
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