New owner, just failed GA emissions, high NOx main culprit

[leftfield6]

Greetings all, I'm brand new to the forum and to this neat little truck, a 1991 Ram 50. I bought it from my brother-in-law over the weekend, and drove it from Virginia to Georgia yesterday. It seemed to run pretty good, with the exception of what sounds like a detonation rattle whenever I was asking it to pull, like going up a long hill, or accelerating to pass.

The truck has 89K on it, and I know it just had a timing belt change a few thousand miles ago.

So, pinging issue aside, it also has a "check engine light" on, but I can't find anyone who has the right cable to read it. I thought the emissions inspection station would, but they didn't either. The ran the emissions test using the tailpipe sniffer test. It passed on some and failed big on some.

• HC ppm - Read 28, Allowable 194
• CO% - Read 0.0%, Allowable 2.19%
• NOx ppm - Read 4279, Allowable 1258
• CO + CO2% - Read 14.54, Allowable 6.00%

So, where do I begin? What are the likely culprits for the high NOx readings? I have a factory service manual on order (from an eBay auction), but it's not here yet.

Any way this is related to the timing belt change? If the belt were one tooth off maybe?

I'm hoping that whatever the fix is, it fixes the detonation noise and the emissions, I have a suspicion they are connected.

Thanks in advance for your help!!

[DroppedMitsu]

Could be EGR system needs cleaned(carb cleaner/bottle brushes/compressed air)/fixed, incorrect timing, o2 sensor bad, etc.. start at the egr

[Fordubishi]

Detonation is caused by either to much timing or cheap crappy low octane gas in most cases. If the belt was just done they might have put it 1 tooth off if they don't know mit's. Most of the time they line up the cam pulley with the edge of deck, there is a small mark just below that that is your timing mark.Maybe one of the boy's will post a pic of where the marks are so you can double check as I don't have the 4 cyl in mine.

[royster]

If the belt was just done they might have put it 1 tooth off if they don't know mit's. Most of the time they line up the cam pulley with the edge of deck, there is a small mark just below that that is your timing mark.Maybe one of the boy's will post a pic of where the marks are so you can double check as I don't have the 4 cyl in mine.

Little details like this make a world of difference. After reading this post, I looked at my own, sure enough: there's a subtle "nub" just below the top of the cylinder head. The Chilton book does not give a good photo of it. But in looking at it, I realized that if you were lining timing marks with the TOP of the cylinder head, instead of the casted timing mark, it is EXACTLY one tooth's difference. All the difference in the world.

The Chilton book DOES point out that the mark is on the head, just below the top. Not sure I would have missed this, but potentially, Fordubishi saved me a ton of agony by highlighting this detail.

Regarding EGR:

there is a labrynth passage for the EGR valve. This is a little hole you'll see in the intake manifold, and it is likely filled with carbon. By seperating the plenium from the manifold, you see this passage is pretty well blocked up there, too. But when you take the EGR valve off, you can see this is a total of 4 square inches of carbon yuck that disables the EGR to do its job properly. It takes some doing to get that carbon out of the whole passage way AND the EGR valve.

quote from: Roy's Garage

I took off the EGR and it was PACKED with crap. I got it cleaned up to where I could actually see the valve shaft. While Seafoaming the engine is great, it doesn't help the EGR to this depth, and can't: there's no way for it to reach the EGR. At 89,000 miles (boy, I'm envious) yours' wouldn't have nearly the crap mine did, and that may be a blessing to you: removing the EGR valve and clearing that passage might be as simple as spray cleaner.

I again express my gratitude for the experienced members of the forum for sharing their knowledge. I'm clearly no expert, but by sharing my own experiences, it adds to the overall view. I came here without one penny: now I'm able to at least put my two cents in.

[royster]

If the belt was just done they might have put it 1 tooth off if they don't know mit's. Most of the time they line up the cam pulley with the edge of deck, there is a small mark just below that that is your timing mark.Maybe one of the boy's will post a pic of where the marks are so you can double check as I don't have the 4 cyl in mine.

scan0038.jpg

Plugged EGR and passageway ('90 2.4l)
scan0039.jpg

[leftfield6]

Well, my EGR wasn't COMPLETELY clogged up, but pretty close. Each of the large passages was 90% closed, and the valve wasn't moving at all. I've cleaned it up with carb cleaner and wire brushes.

Considering my original emission test fail was almost 4 times the legal limit, I wonder if this one fix will get me to a passing number. Most emissions information I've found online mention the EGR as one of the main offenders of a high NOx number.

[royster]

Glad to hear you got some progress. I'm a big believer in Seafoam, and they make a spray that might help with the EGR passages. I'm prone to tell you to take the shop vac and roto-rooter the passages out with some 14-guage electrical wire while sucking up the gunk-ola. Please note that the "-ola" designation indicates a combination of funk and liquidity, so as not to be confused with "funk-inski", which solely designates funk particulate of a dry manner. "Funk-inski-ola" is really not something you want to talk to the wife about, and even some guys are squeemish about it. "Funkus Gunkus" is the very worst, because it indicates a semi-organic matter that has indiscriminate breeding habits, much like the men around East Virginia (West Virginians are another story, altogether).

[leftfield6]

Glad to hear you got some progress. I'm a big believer in Seafoam, and they make a spray that might help with the EGR passages. I'm prone to tell you to take the shop vac and roto-rooter the passages out with some 14-guage electrical wire while sucking up the gunk-ola. Please note that the "-ola" designation indicates a combination of funk and liquidity, so as not to be confused with "funk-inski", which solely designates funk particulate of a dry manner. "Funk-inski-ola" is really not something you want to talk to the wife about, and even some guys are squeemish about it. "Funkus Gunkus" is the very worst, because it indicates a semi-organic matter that has indiscriminate breeding habits, much like the men around East Virginia (West Virginians are another story, altogether).

I'm from western Virginia, which is very different from Wast Virginia.

[leftfield6]

Some progress, but I still failed the retest.

Took it back in today for a retest after cleaning out the EGR valve. $5 worth of carb cleaner and 30 minutes of time accomplished this:

Old reading: NOx ppm - Read 4279, Allowable 1258
New Reading: NOx ppm - Read 2020, Allowable 1258

So, I've cut it almost in half. I think next steps are to maybe spend a little more time cleaning the EGR, but also check and set the timing. Also a little SeaFoam in the tank when I fill up tomorrow.

Suggestions?

[leftfield6]

I found the OBD1 plug today, hooked up my old school voltmeter and pulled this pattern of pulses:

long-short-long-short-short-short-short, then it repeats.

If I follow (or think I follow anyway) the instructions on the wiki page for how to read this, it adds up to a code 25, right? Barometric pressure sensor?

However, if I follow the very muddy instructions and diagram in the Haynes manual, I'm not so sure, it seems like following their instructions for deciphering says it is the throttle position sensor.

Can someone confirm my inderstanding of how to read this code? First time trying to decipher the morse code of an OBD1 vehicle.

Thanks in advance!!!

[royster]

I can only offer a note of sympathy while we wait for forum experts to respond, Leftfeild. I don't even HAVE a voltmeter, and I wouldn't know what I'm looking at if I did. This is what I have to learn next. It was suggested I invest in a "DVOM".

The Haynes manuals really are frusterating when it comes to crucial details.

And on this forum, it's hit-or-miss for those with knowledge to respond. Always grateful when they do, but sometimes we are forced to just forge ahead on our own. I know nothing about the barometric sensor, but for the problems you're experiencing, I'd look into the throttle positioning sensor...not sure what you can do about it except have a look at it. If it's working I suspect you'd be able to see it wiggling the accellerator cable on the intake (I saw this on mine during warm up). From the experience with my '90, there's not a lot you can do to enhance the sensor's performance. I HAD to remove mine in order to get the valve cover off. I did spray it with MAF spray to clean off the dust. I also keep a can of electrical connection cleaner spray in the garage: spraying the inside of the connectors helps assure good connections where grease might have built up.

[noahwins]

I'd trust the wiki more than Haynes. If BARO is flaky, that definitely could create the high NOx condition you're experiencing. In the intake plumbing.

[DroppedMitsu]

You only add up the longs(and shorts) right after each other, if theres a short in between the longs it means those are two seperate codes, so I believe you have two codes, you need to listen to them a little longer and write it out a little longer to see if the same pattern keeps repeating. It looks like you have codes 11 and 14, which l+s= 11, l+s+s+s+s=14. That would be o2(which would def throw emissions readings off) and Throttle position sensor(could also affect emmis, might just need adjusted or might need replaced)

[Merrill]

Do a full tune-up. It will make a world of difference in passing emissions. Plugs, wires, cap, rotor, PCV, fuel filter, air filter, oil change. Do all of it at once - not separate. Then clean the throttle body and intake with TB spray/cleaner and adjust your timing. Most O2 sensor codes relate to a problem NOT being the O2 itself. They simply tell you the O2 is reading outside of its parameter.

It has been for ever since I have dug through the OBD1 codes so I'm not much help there, but mechanically - do a full tune-up. The piston slap knocking sound will go away after the full tune-up is complete and the timing set correctly.

[leftfield6]

Today, I proceeded to disassemble the intake boot/pipe assembly, and then I cleaned the bejeesus out of the butterfly valve and the upper intake area. An entire bottle of TB cleaner. It was nasty in there. I removed the EGR valve and sprayed some in from that side too. I started the truck up and volumes of white smoke were produced as it coughed and sputtered back to life. After the smoke machine died out, the truck seemed to be running a little smoother. before I had a slight stumble and shake at idle.

So I pulled the negative battery cable off, waited a few minutes, and re-attached. Started it up, took it for a drive. Check Engine light came back on after about 10 minutes. Same pattern as above.

long-short-long-short-short-short-short, then it repeats. I let it repeat 5 times, it's the same exact pattern over and over.

Oil change two weeks ago, new distributor cap, rotor, plug wires, spark plugs, fuel filter, all done at the same time.

[lush90]

When you disconnect the battery, my understanding is that computer resets to original settings. You should let truck idle for 10 to 15 minutes after reconnecting battery to let truck get up to temperature and run its diagnostics to adjust for engine component wear, etc.. This on board self adjustment is one of the big advantages of the on board computer.

[camoit]

thats a code 14 we might have somthing around here telling you what it is. I vaguely remember seeing somthing about a code page.

[DroppedMitsu]

I already told him he has codes 11 and 14. Which are o2 and TPS

[leftfield6]

Yep, I assuming the 02 sensor is coding just because it's reading something from upstream, so I'll be checking out the TPS today. I'm hoping there is a way to check to see if the TPS itself is bad, or if it just needs an adjustment.

When the CEL came back on during my test drive yesterday, it was a little different from what I remember from before. Not sure if there is a clue here.

• Started off with cold engine
• went about 2 miles, engine now near operating temp, still no CEL
• at a stoplight, CEL came on, so it came on at idle
• when light changed, I accelerated, CEL went off
• at first shift (1st - 2nd) CEL flicked on, went back off
• same as I shifted to 3rd, but from that point on it stayed on.

Is there a clue there?

[royster]

I just get a sense that this might be related to the engine coolant sensor.

Not sure that replacing the o2 sensor would make volumes of difference, but they cost about $20 and install easily if you pre-soak the exhaust connection for it with PB Blaster or Liquid Wrench.

These are just gut feelings, and I have learned from this forum to not just "throw parts at" the truck, although with my semi-rebuild, I DID replace all those sensors.

[DroppedMitsu]

You need to check the voltage that the tps is reading with the throttle closed i believe. There is a certain range the voltage is supposed to be in with the throttle closed and also open. In the manuals which can be found on the forums it tells you the exact specs. The TPS can be adjusted by turning the tps counterclockwise or clockwise in rotation. If you can't get it to read the correct value with adjustment than the TPS is bad

[pennyman1]

slide either paper clips straightened out or sewing needles into the back of each wire on the connector of the TPS and read the voltage with the key in run postion, but motor not running. Same procedure forany TPS the voltage settings are the only difference

[Merrill]

Mitsu TPS's are very VERY fickle. They need to be pretty much dead on when setting otherwise it will "idle hunt" (revving up and down at idle). It will also throw off fueling and other settings. I usually tell people not to mess with it unless they absolutely have to.

The throttle closed position (0%) is actually a large range. If you don't have it dead on, it will add problems. If you have a bad TPS already, you will just make things worse. The best bet is to replace the TOS and try setting it if you are certain it is bad. The TPS doesn't randomly adjust itself, so if it is throwing a code because the TPS is bad (not in conjunction with, or a resulting code based on another problem), chances are it's just needs to be replaced, not adjusted.

[leftfield6]

So, just to update the thread, I finally gave in and took it to a shop. Here's the word.

• The EGR valve itself is fine, but the EGR solenoid is bad.
• My TPS is bad, it has a number of drop-outs in what should be a smooth linear change in voltage.
• O₂ sensor is bad, it's probably the original one from the factory

The shop is tracking down parts. They have a supplier who says they can get the parts, but they didn't get prices back to the shop before they closed today. I'm expecting this to not be cheap, but I am running out of time to get the vehicle registered. I'm traveling on business the next two weeks, so no way I had to keep chasing the gremlins.

Same shop is also replacing the flex-pipe in the exhaust system.

When all is done, hopefully I will have a perfectly running 90K mile truck!! It will still be ugly, but who cares.

[BradMph]

Don't feel to bad, My MR2 got it's last smog test and failed so off to the mechanic to give him a $200 donation. The mechanic simply adjusted my timing and charged me $150 for this. Then the thief says, if it doesn't pass, bring it back and we'll drop the other $50 in and I'll give you a waiver for the test. In our state the smog recheck was free, but I had to take it to a authorized smog mechanic to have it worked on because of the laws here. So, I got dry-banged for $150, but it passed and I Never have to get the car tested again. Both my vehicles are exempt from test, but not exempt from some nosey cop that says lift your hood, it's your lucky day. Modifications to the engine can cost upward of $2000 if and officer writes up the ticket. The laws have changed here in Washington State as well. From this point on, all vehicles from 2009 and newer must be equipped with California regulation smog devices. It's all about the money pretty much because if it was all about clean air, we be cracking Mexico's ass for their vehicles that run no smog devices. Mexico City being one of the smoggiest cities in the world.