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Discussion Starter · #1 ·
Hello everyone and thanks again for all the assistance with my new-to-me 1991 Isuzu Trooper 4cyl, 5 speed. I purchased the trooper last weekend in Northern Georgia and drove it back to St.Augustine Florida. The trip was 450 miles on bad tires, bad alignment, non functional oil and temp gaugues but the trooper made it back just fine. The prevous owner told me that the Timing Belt was replaced, air pump removed, and the head had some work done to it. My current issue is rough idle when started (engine hot or cold). The trooper got 21.25 MPG on the way back home, I stopped every 100 miles to check oil, etc and fueled up. From the reviews I have heard, this is what the truck got when new so everything must be functioning properly right? However, I do have an idle issue...

If I start the engine first thing in the morning, I have to feather the gas pedal to keep it running, once I start driving it around the block for a few minutes, the idle will hold around 700-900 RPM and thing are good. If shut the engine off and restart it (already warmed up engine) I experence the same stumbling. I then again have to hold my foot on the pedal at idle and drive it around, then the idle will be okay if stoped at a light for example.

There are many unknowns right now and I don't know where to effectively start troubleshooting. I have replaced all 4 spark plugs and the plugs look very nice (light TAN) in color, replaced spark plug wires and distributor cap/rotor to date. I also checked the timing and could not get it to go to 12BTDC. I had the distributor maxed to the limit at 900 rpm and would only get to 10BTDC. I did not disconnect anything and now see that had to be done.

Where do I start? Is this a vacuum leak somewhere, there are hoses all over this joker! Do I check the timing indicators and timing belt first? Any and all help is greatly appreciated. This trooper is in great condition, no rust anywhere.. I will get this thing running sweet with the forum's assistance of course.

Thanks in Advance -

Brian
 

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The first thing that comes to mind is perhaps the charcoal canister. Leave it out in the sun for a day or two to dry it out. And, since you mention it, the 2.6 does in fact have 12 miles of vacuum lines running all over the place. Any leak in that system can cause all sorts of odd/bad running.

I'd check out those things before messing with the teeth on the dizzy.

Good luck!
 

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Brian_Fisher said:
There are many unknowns right now and I don't know where to effectively start troubleshooting. I have replaced all 4 spark plugs and the plugs look very nice (light TAN) in color, replaced spark plug wires and distributor cap/rotor to date. I also checked the timing and could not get it to go to 12BTDC. I had the distributor maxed to the limit at 900 rpm and would only get to 10BTDC. I did not disconnect anything and now see that had to be done.

Where do I start? Is this a vacuum leak somewhere, there are hoses all over this joker! Do I check the timing indicators and timing belt first? Any and all help is greatly appreciated. This trooper is in great condition, no rust anywhere.. I will get this thing running sweet with the forum's assistance of course.

Thanks in Advance -

Brian
Please clarify "distributor maxed to the limit at 900 rpm and would only get to 10BTDC " There's a couple of things to check / do if you're saying what I think you're saying.
 

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Discussion Starter · #4 ·
when turning the distributor to change/set the timing, I have it turned as far foward as it go and it hits the bolt/adjusting nut. If I turn it the other direction the ingine will cough and stumble. Basically I can only get to 10 degress BTDC and the book says 12. I cant tun it any further.

Thanks in advance!
 

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If you bring the #4 cylinder up to TDC on the compression stroke, the rotor button should be perfectly aligned with the #4 electrode on the inside of the dizzy cap. You can pull the cap and very carefully observe that terminal and by using visual transference, make a mark on the outside body of the cap or dizzy base. You can also mark the firewall. To cut to the chase, I would go through the hassle of removing both timing covers, and the crap necessary to access them,

I would then use a breaker bar and socket on the large crank pulley nut and rotate the crank pulley so that the mark on the inner crank timing sprocket aligned with its match mark. Also make sure the cam timing sprocket is aligned with its match mark.

At this point, the rotor button should be aligned with the #4 electrode on the inside of the dizzy. If it isn't, gently pull the dizzy out far enough to reinsert it to the proper location. This might take 2 or 3 attempts. As you reinsert it, remember to offset it initially due to its gear is going to mesh with another gear which will cause it to rotate a couple of teeth. You'll see what I mean when you do this. If successful, you should pretty much have the same area of adjustment to the left and right in the adjustment slot.

Once these 3 critical areas are aligned, look down at the timing mark on the harmonic balancer. It should be aligned with the zero mark on the timing tab. If it isn't, scribe / paint a new line to correspond with the zero mark. The balancers are known to slip and the factory mark is no longer accurate. To manually rotate the crank, it might be easier if you remove the spark plugs to relieve the compression.
 

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Shooter,

I finally got around to removing all the stuff to access the Timing Belt and Camshaft/Crankshaft Sprockets. I am at TDC on the #4 Piston (verified by placing finger on the spark plug hole of the #4 picton and air pushed my finger off hole; also placed a screwdriver in the hole and immediately touched the top of the #4 Piston)

The Timing Mark on the Camshaft aligns perfectly; however, the Crankshaft is about 3/4 teeth over the the left of the mark. How the hell did the engine run like this and still get 21 MPG on the highway? It runs like crap on idle, car shakes, but smooths out around 1200 rpm.

The first picture is the Camshaft.
photo.JPG


The second picture is the Crankshaft.
photo.JPG


I also noticed that when I move the harmonic balancer to the left or the right, that the crankshaft timing gear does not move at the same time, there is some play. Is this normal? Is the Crankshaft pully worn, should it immediately move when the crankshaft is moved?

It appears that whomever replaced the timing belt did not do it correctly. Also, the harmonic balancer timing mark is off and per your last post, I now know how to fix that.

What is your advice?

Thanks
-Brian
 

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Air comes up and out on both exhaust and intake stroke. Stronger air on intake because both valves are closed. Looks like it's off more than that. Since you have all that crap out of the way, why don't you rest it. If need be, I'll post the two pages from the factory manual on the procedure. If you do that, they should definitely align and the rotor will point @ #4 inside the dizzy. If it doesn't, it might just take 1-2-3 attempts to set the dizzy; no biggy. Let me know please. Once it's all set, don't be concerned with the balancer mark. When everything is dead on and the balancer mark is not aligned with zero on the timing tab, just make a new mark at zero.
 

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Discussion Starter · #9 ·
Thanks shooter. I am going to reset everything like you suggested. Here is where I am concerned.

I slid on the harmonic balancer and used it to turn the enine to align the timing marks. What I noticed was that when I started to turn the balancer, the Timing Belt Crank Pully did no move at the same time (like there is about 1/2 play in either direction when turning).

Is this normal? I can see that whomever set the timing the first time had everything correct, but once the tensioner was release on the belt, it moved it over 3 teeth to the left (1/2" play like menitoned above).

So , should the timing belt crank pully move at the same time the harmonic balancer is turned. It seems to me like there should be zero play between the crank/harmonic balancer and the crankshaft timing gear.

Is this a common wear item?

Thanks for all the assistance! I really like these little 4 cylinder engines, just want to get this baby purring!!!
 

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Discussion Starter · #10 ·
Shooter,

Here is a video that I took to further show what I am experiencing. The angle is bad, but notice that when I rotate the harmonic balancer, the timing belt is not moving in the background.

 

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As normal for me, I ain't clear on this. The balancer and crankshaft move immediately and the crank sprocket takes a second or two to begin moving with them?
 

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If you're saying there appears to be "slop" in the crank timing sprocket, it sounds like the slot for the woodruff key is worn out of spec. That should be detectable. If the balancer is in the way, remove it. Grasp the timing sprocket and try to move it. If the sprocket has slop, the sprocket is probably defective and not the key welded to the crankshaft though I guess it could be.
 

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Discussion Starter · #13 ·
Yes, there is slop when I turn the harmonic balancer, the crankshaft timing gear does not move at the same time. I will take the belt off tomorrow morning, remove the crankshaft timing gear and inspect for wear. I think this is my problem why the damn thing runs so rough on idle. I will take a few pictures of what I found to fopefully give something back to the forum on what I have found.

Thanks-
 

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If and when you install a new sprocket, clean the shaft well and the pulleys. Smear a light coat of antiseize on the shaft, install the pulleys and make sure everything is torqued properly.
 

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I would first check with JLEMOND (forum member here). Actual name is Jerry. Super guy, knows Isuzus inside/out, has many, many parts, good prices, speedy shipping. Send him a PM.
 

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Shooter,

Found exactly what we thought it was.
1. The woodruff key was not in the right position, it was about 1/8 foward on the crankshaft, thus the crankshaft pully notch did not have 100% of the key in the crankshaft pully notch.
2. This caused the front of the crankshaft pully to wear a notch in it and wore a grove in the woodruff key.
3. This is the cause of the exessive play between the time the harmonic balancer is truned and when the crankshaft sproket moves.

Here are a few pictures to explain what I am talking about. I am so glad that I did what you suggested, I would be chasing my tail if I did not do this. I hope that this engine runs like a top when I am done.

Now that I am at the front on the engine, I plan on a new timing belt, tensioner and water pump. Is there any benefit in replacing the oil pump while I am here. The engine has 154k on it.

photo123.JPG

photo1234.JPG
 

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Discussion Starter · #19 ·
Update for everyone. Last weekend the replacement parts cam in. (new crankshaft timing sprocket and woodruf key). Both of these were worn that it was causing the timing to be off by at least 15 degrees. While I had everything removed, I replaced the water pump, timing belt, sprocket and woodruf key. I set the timing marks to #4 TDC, verified with the distributor, put the new belt on, all timing marks were good. The harmonic balancer did shift on the hub so I scribed a new line at 0 degrees BTDC. I also took this opportunity to adjust the valves by following the procedures in the factory Service Manual. When I started the vehicle after the replacement of the worn timing parts, the vehicle ran much smoother, no more shaking at idle so I feel a nice sense of accomplishment and thank everyone (especially Shooter) for assisting me.

In my quest to get this 91 trooper running smoother, I have a few other issues that I need some assiatance with. I will post these questions as new topics. Thanks again everyone.
 
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