Hey guys, I haven't been around much lately due to work, house, kid, etc... but I am having a problem getting my truck through VA state emissions yet again. The truck has been running fine for a 20+ year old, and it was getting consistent 28 to 32 MPG per tank average.

88' Ranger XLT, s-cab, 2.3L, 5sp

Test results are as follows and notes will be below the numbers:
1st Test
......................15mph....................... .....25mph
................Limit......Reading................ Limit......Reading
HC ppm......179.......103.....................174.... ....107
CO%..........1.52......0.12....................1.9 6.......0.17
NO ppm......1227......3767...................1121......3439
RPM.................1698.......................... ......1908
Dilution.............14.5......................... ........14.6

Notes: Timing was somewhere around 5 deg BTDC AND the cam gear was rotated clockwise 1-2 teeth. Not to mention the EGR vacuum hose had come off the valve. All these things were discovered afterwords, but the EGR hose was not discovered until just before the 3rd test.

2nd Test
......................15mph....................... .....25mph
................Limit......Reading................ Limit......Reading
HC ppm......179.......59.......................174... .....51
CO%..........1.52......0.10....................1.9 6.......0.16
NO ppm......1227......1641...................1121......1748
RPM.................1774.......................... ......2821
Dilution.............14.8......................... ........15

Notes: Adjusted timing to spec 10 deg BTDC, rotated cam gear counter-clock wise to line up with marks on the cover. Still didn't notice the EGR hose at this point, and the results were close to passing. It was suggested I adjust the timing a little more and maybe change the plugs to get it running as clean as possible.

3rd Test:
......................15mph....................... .....25mph
................Limit......Reading................ Limit......Reading
HC ppm......179.......89.......................174... .....98
CO%..........1.52......0.13....................1.9 6.......0.25
NO ppm......1227......2201...................1121......2645
RPM.................1758.......................... ......2847
Dilution.............14.7......................... ........14.9

Notes: I changed the plugs, moved the timing to 15 deg BTDC, and changed the air filter. It was just before this run on the rollers that the hose being off the EGR was spotted. So that should have really helped lower the #s but I guess not. Or was I supposed to set timing closer to 0-5 deg BTDC to lower the NOx for this run?

At this point I have re-adjusted the timing back to factory spec (10 deg BTDC), and added a bottle of cleaner to the fuel to flush it out before the next test. All signs point to "high combustion chamber temps", but the truck never gets hot, the other readings are pretty good, it is just the NOx reading that is bad. I should also mention that there are 2 KOEO codes, 31 & 67. I have never been able to get rid of these. The 67 is due to a trans swap and nothing to worry about. The 31 is EVP below voltage (I think) and I have tried new EVP sensors, new EGR valves, but no one has the EGR solenoid in stock for me to try that, and the code never goes away. Any ideas?

 

High NOX is a sign of high compression, high engine temperatures, or a lean mixture. Since you now have a working EGR system, you could try running a good fuel injection cleaner through to remove carbon deposits.

If that doesn
t do the trick, you may need a new converter to pass smog.

 

Pulling the SPOUT connector will cause the timing to remain static at whatever value you set it at. Oftentimes this is enough to significantly lower NOx, especially at higher RPMs.

 

Bear River - the high temps is exactly what I suspected, and the guys at the station said the same thing. My big problem is I don't know for sure if the EGR is working properly due to the fact that I am still getting a code 31, and I can't find an EGR vacuum solenoid for this model to see if that has any affect on the test. I put vacuum to the valve with a hand pump and it holds open so I don't think there is a problem with the valve. I also removed it with the "feeder tube" to check for blockage.... nothing, everything is clear. The EVP sensor is a Motorcraft OEM that I bought less than 2 years ago.
I do have a bottle of CRC in the tank right now so I am hoping that will help since it "claims" to have a "Guaranteed to pass". I am also not to sure that replacing the converter will have much affect on it since (correct me if I am wrong) this late 80's truck should only have a 2-way converter that won't affect NOx in the first place. I don't have a problem replacing a part if it is bad, but if the converter didn't play a part in the NOx readings from the factory I can't see how it has gone 'bad". I would agree that if there is a 3-way converter available for my truck then it would help to reduce the emissions, but it would only mask the root cause of the original problem.
Also, just as a reminder, I did a basic refresh on this engine 1.5-2 years ago when it broke a head bolt and blew the head gasket....... ahhh fun times. The head was rebuilt at a machine shop, and the block was cleaned out and put back together.

Rockledge - That is a good idea if it works. Not to sound like I am doubting you...... is that the way it works? IE - keeping the timing closer to TDC will lower the combustion temps?

Other thoughts/notes: I have not had the time to check the fuel pressure at the rail, but I was assuming the "Dilution" reading on the tests indicated I was right on the mark for Air/Fuel ratio? Yes, no? I did notice a significant drop in temps as measured by my face after moving the cam gear and adjusting the timing. The temp gauge never got above normal, but you could tell with your head under the hood that it was pretty warm under there. I am still not sure how the cam gear got rotated, but oh well, and I did realize how the timing was off in the first place. NOTE TO SELF - when using a timing light that has a built in advance **** on the back..... make sure it is still set to 0!!!!!!

 

Well, check out: How to pull the SPOUT connector - SHOForum.

 

Interesting read. Thanks for the link. Most of it is just opinion, but then there were a few folks that posted real numbers. That part was encouraging since it is $28 a pop each time you go for a test. Like I said, I don't mind replacing parts if it is needed, but it seems even if pulling the spout for the test gets my by, I am still having some sort of an issue that is raising the combustion temps, or so it seems.

I don't know if anyone remembers, but 2 years ago I couldn't get this thing through emissions for the same freaking thing: https://www.ford-trucks.com/forums/5...al-issues.html I do remember taking it to the Ford dealer, and paying way too much to have the timing set and re-inspected. They couldn't tell me how they got it through, nor could they tell me how they adjusted the timing. At the time I had been looking for that stupid spout connector for weeks with no success. When I got the truck back, it had passed, but had no guts below 55 mph. A month or so later I finally found the spout up by the battery on the passenger's side, and once I checked the timing they had it set at 0/TDC base timing.

Anyway, after re-reading part of the thread above...... is it true that the EGR doesn't even activate until 25+ mph????? If so then it can't be the problem at 15 mph and maybe not even at 25 mph! What gives?

 

According to wikipedia (who's info you sometimes have to take with a grain of salt), two way catalytic coverters as you mentioned "were also used on spark ignition (gasoline) engines in USA market automobiles up until 1981, when they were replaced by three-way converters due to regulatory changes requiring reductions on NOx emissions."

If that's right, since your truck is an '88 you may indeed have the 3-way one.

Here's the article: Catalytic converter - Wikipedia, the free encyclopedia

 

Well, Wikipedia is a bit out of sync with reality, as no manufacturer that I know of still makes two way cats, all manufacturing shifted to three way catalysts around '95-'96, over ten years ago.

All OEM catalysts made after 1983 used some form of three way catalyst, either by using air injection, or oxygen cycling.

Have you checked or cleaned the MAF sensor? A bad MAF will most often cause a lean mixture, which will significantly raise NOX emissions. Plugged injectors or low fuel pressure will also cause the same problem. Vacuum leaks will also cause NOX problems.

 

Bear River - Thanks for the info. I kind of figured it wasn't until circa OBDII days that cars came with 3 way converters.

Also there is no MAF on this model. I am not sure when they started, but the 88' 2.3L didn't have it. As for the rest, the majority of the sensors & hoses are new'ish (>2yr). The stuff that is likely original:

IAC
MAP
FPR
Injectors
EGR vacuum solenoid
Fuel pump - high pressure
Fuel pump - low pressure

 

MAP sesnors kind do the same thing as MAF, but not as accurately. If you get a vacuum leak, it will tell the computer that there is more air going into the engine than there really is, or that the engine is always under heavy load. This can cause emission related issues, but will most often cause a rich mixture. Because there is a matching amount of air, you will get clean combustion, but all gases will be higher than normal and you will also have a fast idle. However, if the sensor goes bad and indicates there is more vacuum then there really is, you will get a constant lean mixture and excessive ignition timing.

 

Well another $28 later, and it finally passed! It wasn't pretty, but I'll take it.

I may, or may not have used Rock's advise to pass. And the numbers were sill a little strange this time around:

......................15mph....................... ......25mph
................Limit......Reading................ Limit......Reading
HC ppm......179.......55.......................174... ......57
CO%..........1.52......0.09....................1.9 6........0.24
NO ppm......1227.....1185....................1121.... ...613
RPM.................1735.......................... ......2827
Dilution.............14.9......................... ........14.9

The NOx at 15 mph just squeaked by, but the 25 mph was great. I am wondering if the 1/2 tank with fuel system cleaner in it is to blame for some of the #'s. The instructions did say to run the whole tank out and fill up again before testing. Well that would be at least another 200 miles, and I was 2 weeks over-due for my tags. Definitely driving on borrowed time, and I wasn't looking to attract Johnny Law.

Hey Bear River can you email me the cost of a direct replacement "3-way" converter for my truck? Thanks.

 

If it helps the most significant player in NOx reduction is your EGR valve. The injection of exhaust gases acts as a filler (displaces O2) to create a little bit richer mixture that will reduce combustion temps and reduce NOx emissions. Being you are having problems with your EGR system I would correct that first. I think converter replacement at this time would be pre-mature being your other emission control systems are not working properly.

 

I would agree, I guess I missed your earlier post about the EGR. A bad EGR will definitely increase the NOX.

 

Peter94 - Yea, I realize the intended function of the EGR. The problem is I get a code 31 that doesn't go away even if you change the EVP, the valve is only 2 years old and it holds vacuum when you pump it by hand. The only other component in the system is the solenoid, and no one seems to have it in stock. Special order only, and the code 31 isn't supposed to have anything to do with it.

Bear River - It isn't certain that the EGR is bad, but yes I did mention that there is a code in the computer that complains about something in the EGR system.

Can anyone tell me for sure when the EGR activates? If it only comes on over 2000rpm (for example) then it won't do anything for the 15mph readings. Or is it speed activated?

 

the EGR valve on your truck is vacuum operated. With your truck running, apply vaccum to the EGR valve, it should change the RPM of the engine. If not then you most likely have a clogged EGR passage somewhere.