89 trooper compression test/idle issue

[89TrooperPeep]

I recently bought this thing for a great price because it isn't passing emissions in my state. High NOx. It also has an idle problem where it will die in idle if the ac and fan are not on. I assume the two issues are related. 233k miles. 4ZE1.

In trying to fix it, I did a compression test today and got these results, but I'm not sure what they mean and I'm hoping someone can give me some clues.

1- 150
2- 143
3- 133
4- 165

I know they are technically in spec, but should be within 10-15% of each other.

This might not be related, but I'm including this info just in case. I just tested the emissions again today and it was still a fail and I have done these things between my last fail and today:

-Replaced catalytic converter(it had the original cat I think)

-Replaced all coolant hoses and replaced the coolant.

-Replaced the crankshaft seal

-Found a few vacuum lines that went nowhere and put them where they belonged/plugged them(smog pump is gone so I plugged those hoses)

-messed with the EGR valve and it moves just fine, but it does look original

-replaced fuel filter

-replaced coolant temperature sender.

-oil change

[DSUZU]

What I don't see is VALVE ADJUSTMENT. If this hasn't been done, it should be. Yes, this can cause emission problems too. I'll add more later. Dennis

[Shawn Anthony]

Im suspecting you have burnt valves. however start by checking the timing and adjusting if needed.
Next adjust all the valves. The perform another compression test using the 1 pump/over 5 method. Record the first pump pressure then the 5th. ONLY the 5th. This will reveal in more detail what is going on. Then get back to me for the nest step in proper troubleshooting

[DSUZU]

When you adjust those valves, have a torque wrench and a 10 MM Allen socket handy. Set the torque wrench for the final head bolt torque and pull each head bolt until the wrench clicks or reads the correct torque (this is retorquing the head bolts). It NEVER hurts to check head bolt torque.
For emissions inspection, a new set of plugs often helps. You want to see good, sharp edges on your plug electrodes. Because you have a low idle, it might be a god idea to replace the PCV valve. Make sure it is the correct one as there are many that look correct. As Shawn mentioned, the timing should be set to factory specs. Many set the timing to "best running" and often, this is too far advanced, this too can cause high HCs. Be aware that on many 2.6s, the harmonic balancer can or has slipped, so it is also possible that timing mark may be off (there is a cure, but we can go into that later if needed) Be sure all of those vacuum hoses go to the correct places. After all else, there is an idle mixture adjustment screw that adjusts idle mixture. It is located at the top rear of the throttle body. I recommend no more than a 1/4 to 1/2 turn, and then road test before making any further adjustments. The stop screw for the throttle plate (sealed with red glue) should never be messed with. Finally, a good long hard drive to heat that cat up before hitting the inspection line. Dennis

[89TrooperPeep]

Thanks I will do the timing and valves ASAP

[89TrooperPeep]

Just an update: the timing was way off, but we were not able to get it lined up. Roted the distributer clockwise as far as it would go and it got closer but was still about an inch to the left of the 12 degree mark. We think the harmonic balancer slipped. Now we've found that whoever worked on this car before left a socket on the bolt for the harmonic balancer. It's stuck on there good. Ugh.

[itsmehb]

Sounds like it may have slipped. Most have. My 89 only was off maybe 3 degrees. Only way that I know of is to remove the lower timing cover. Then line up the upper cam gear and lower crank gear. Then when you reinstall the lower timing cover the zero TDC mark and the mark on the timing cover will only line up if the damper has not slipped. If the mark on the damper is off paint it black and file a new mark agreeing with the zero TDC mark.

[89TrooperPeep]

UPDATE: We fixed the timing and adjusted the valves.

Did another compression test and the results are extremely consistent. They were all consistently 90 on the first crank and 145-150 on the 5th crank.

The car still isn't running right though, and it seems like the first cylinder might be misfiring. Once the car is warmed up, it idles at a shaky 600 RPMs or 1,000 if the AC is on.

I'm not sure what to try next and am open to any suggestions.

[Shawn Anthony]

great news the compression is up where it should be. that even 90 PSI on the first pump across all the cylinders is extremely valuable information as now you verified that your funky idle is not due to the internal part of the engine.

how do you know its cylinder #1?

SO...... here is the next couple steps.

1, verify that there is no intake leaks. do this by spraying brake clean on the intake manifold, injector seals and vacuum hoses. Dont forget the intake piping after the MAF sensor, throttle body, upper plenum and brake booster. pinch off the vacuum tube that leads into the cab that operates the HVAC components.

2, thoroughly inspect the spark plugs, spark plug wires, cap and rotor. you are looking for holes and cracks. Also check the timing.

get back to me with your findings and feel free to ask me any questions during the process.

[89TrooperPeep]

Thanks. We pulled all the spark plugs wires while it was idling and there wasn't a noticible difference in how it was running when cylinder 1 wire was pulled, but it's hard to say when it's already not running well. It definitely sounds like one or some are misfiring.

We inspected the rotor and spark plugs wires and they were fine. The cap, there was a small amount of corrosion I scraped off, but it looked fine. The spark plugs are new, they probably have been in for less than 2 hours of run time.

I did spray carb cleaner on a lot of the areas you mentioned for vacuum leaks, but not everywhere so I will check that out tomorrow! So far the only leak was a 3-way vacuum hose connector that only had hoses on two of the tips that would have gone to the cruise control if I had it, but plugging that didn't do anything.

[89TrooperPeep]

Well there doesn't seem to be any vacuum leaks. We replaced the distributer cap and rotor today just because it was cheap. The old rotor looked worn as heck, but replacing them made no difference.

I'm guessing now that this might be the fuel injectors because:

1. The car has 230k+ miles and the fuel injectors look original.

2. High NOx only on the emissions test. Everything else seems fine. High NOx indicates high combustion temperature and maybe lean fuel mixture.

3. Sounds like cylinder 1 is misfiring. It sounds like it's not misfiring anymore when I pull the spark plugs wire for cyl 1. My research suggests the fuel injectors can go bad on one cylinder and cause it to misfire. Compression, spark, valves, and timing have all already been checked.

Anything else it could be?

[Shawn Anthony]

You are on the right track.

after you verified the injector o ring is not passing air into the manifold do the fallowing vitrification..
Switch injector #1 with injector #2 the run the engine. if your misfire moves to cylinder #2 you know injector #1 is faulty.

[89TrooperPeep]

I could do that... Or I could get that fuel injector cleaner stuff and run that through it for 300 miles or so and see if that fixes it.

What would you recommend?

It's either hours and hours of driving to burn through the fuel injector cleaner OR hours and work taking off the common chamber and draining the coolant and everything involved with getting to the fuel injectors.

If I find the injector in cylinder 1 is the issue, I then have to either run fuel injector cleaner anyways or replace it which means getting to the injectors again.

I'm torn.

[Enemigo]

How big of a deal would it be to replace the injectors anyway? Are there other things you can check, or would like to replace anyway, on the way to doing the injectors?

[89TrooperPeep]

I've never done it before, but I've heard getting the common chamber/intake manifold off and on again is a pain.

[89TrooperPeep]

Back to square 1. I used an engine stethoscope to listen to all the injectors and they are all clicking the same as they should. I got the fuel injectors cleaned by a local shop. I replaced the iridium spark plugs with copper after the fuel injectors got cleaned at the suggestion of the shop mechanic.

Same issues persist. If the ac is on, it will run smooth enough for a minute or so, then turn to rough idling. If the ac is off, it will stall out or just barely run at low RPMs until it is warmed up. If the engine is warmed up it can run with the AC off.

99% sure there is a random misfire on cyl 1 only. The tachometer moves up and down when it is rough idling, but stays steady if the cyl 1 spark plug wire is pulled.

I'm looking for any suggestions as to what to do next.

[Shawn Anthony]

When this problem is active i recommend wiggling the IAC electrical & the MAF sensor electrical connector. Check for cold intake leaks, and verify your idle validation switch is functioning properly.

[89TrooperPeep]

THE PLOT THICKENS

I think I know what's causing high NOx in my Trooper...maybe...

Today I realized I have no EGR pipe from the exhaust to the manifold. It's very badly plugged with a loose O2 plug on the exhaust and is not plugged at all on the common chamber. There isn't even a fitting any more on the common chamber, just a threaded hole I can stick my finger in. That could be a vacuum leak too right?

I really want to get a new pipe and put it on for emissions purposes and because I already spent $30 on a new egr valve and I want to get some use out if it... Problem is that this car has an aftermarket header. I don't know if the standard egr exhaust pipe will fit, if I can even find one (I've done some light searching and can't seem to find a pipe that looks right).

What do people normally plug the common chamber with when they do an EGR system delete?