So I ran a dry cylinder compression test. I got some of odd results and was wondering if anyone can throw in their two cents. My car has always had a very small shimmy while idling . Otherwise it accelerates fine. No misfires. *I pulled out the plugs in the photo below, I changed them for some champion coppers. It's running smoother but still has small shimmy .*
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Test was performed on a warmed up engine, all plugs off, no fuel, and about 6 cranks for the reading. I'm a little concerned about the reading because it's coming in high. I hear a normal range is 120-150 . Anyways, advice will be greatly appreciated.

Results:
1- 152, 155
2- 156, 156
3- 166, 166
4- 152, 152
5- 175, 176
6- 161, 162

1999 Cherokee sport, 6cyl 4.0l 4wd

 

By the way, here are the plugs that came out of it. How do they look? Anything I should be concerned about? I do see anti-seize on number 4 .

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The 4th one in the picture looks like it got some anti-seize on it that can be the problem . that plug needs to be cleaned , and then see how it runs . The compression looks ok . you can try a fuel injector cleaner and see if that helps .

 

Sorry. I forgot to mention that I changed out the plugs for new champion Copper plus . Still runs with a shinys, but definitely smoother . I'm glad to hear that you think the compression is fine . But isn't 170s kind of high? My next move is fuel injector cleaning.

 

Could be the gauge....out of calibration. Compression is fine.

ever think of just swapping the injectors for the 4 holers?

jhc7399 here on the forum sells refurbished sets.

 

So this weekend I finally got around to doing the injector replacement. Put in the 4 hole Bosch injectors that I got off ebay; lots of options on there. Read reviews and picked what looked like the best.
It was about a 1 hour job with most time being spent cleaning out the fuel rail connection and holes were the injectors connect to the engine.
I know that some people question the need for this change and there has been loads of debate about whether it helps performance or mpg, but in my case the difference was big. Acceleration was smooth, engine noise lower, cleaner idle, etc. We will see about the MPG impact.
Yes the 24 year old injectors were very dirty and the same effect could have maybe been achieved by cleaning them, but for $64 for 6, I was happy to swap out for new ones.
Later in the day I also did a full clean of distributor cap and arm connections. I do this every 6 months, just a clean, not a replacement. This also smooths out the idle.
So, all in all, a happy weekend.
Try the injectors, but clean your grounds and your distributor contacts first.

 

$64 for 6?!?! I thought they were $64 each! Are Bosch the recommended injectors? At that price, everyone should be replacing their injectors . Thanks for the suggestion.

 

$64 for 6?!?! I thought they were $64 each! Are Bosch the recommended injectors? At that price, everyone should be replacing their injectors . Thanks for the suggestion.

 

Yesi thought about swapping for awhile now but always thought it was too expensive . But after I found out that you can get them for $64 a set, it shouldn't be a question. I agree, the guage can be a little off . They're all within range of each other so it's not so bad. Thanks for your help. I will be talking to jhc7399 soon.

 

I ended up just getting some refurbished injectors from ebay :
Brand: Genuine Bosch (Gen III) BOSCH 0280156007
Connector Type: EV6
Flow Rate: Stock Flow Rate (stock replacements) - 23lbs
Impedance: High
Spray Design: 4 Nozzle

I hope these are the right specs. From what I understand, they should pop right in.

 

o ,how does it run?

 

I'll let you know, going to get them next week. I'm going to try a double ATF engine flush. I'll let you know how that goes too.