I have a bad misfire so today I did a few tests, what is your interpretation of the compression tests?

I did both dry (first) and then wet (added oil) and got the following average compression readings (3 tries per)


DRY WET
Cylinder 1 96 105

Cylinder 2 110 127

Cylinder 3 95 116

Cylinder 4 100 110

Cylinder 5 110 120

Cylinder 6 100 120

Note: the wet test was performed by adding about 15cc of Lucas power steering stop leak oil (thick oil I happened to have available).

My understanding of these results are:

1. At the low end of the acceptable compression range.

2. The variation in compression between cylinders is acceptable.

3. The increase in compression from the addition of oil points to worn rings.


I am currently running mobil 1 high mileage 5w30 full synthetic; based on these results, perhaps I should run a higher viscosity oil. I recently changed the oil after 5k miles and if I remember correctly, I had to add a quart of oil (possibly 2?) over that time/miles. So it is burning/leaking some oil; however, it doesn't smoke and there aren't oil spots/leaks under the car. Note that I have only put about 7k miles on the car since buying it 14 months ago.

I also feel that these results wouldn't be the cause of my misfire problems.

Although not a great picture, here are the plugs. cylinder 1 looked different than the others, but none looked really bad and none were oily.

[IMG][/IMG]

So what do you think?

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1999 Mazda B3000 3.0L 2WD AT FFV extended cab 213k miles. Purchased 4/1/2014.

Did the plugs fix the misfire? If not I guess wires and then ignition coil would be the next steps assuming it's nothing major.

Well since the plugs are pretty new and in good shape, I didn't replace them again. This study as to evaluate compression to see if there was an issue with rings or valves relating to the misfire.

I am going to take the truck to a shop so they can perform computer diagnostics on it. The misfire has been getting worse over the past few weeks to the point where it is now backfiring when I accelerate hard so it isn't very driveable.

I am suspicious of the injectors and/or cats. Nearly everything else has been replaced. But that is why I wanted to ask here about the compression test results here to see if people think the integrity of my 220k engine is ok (or adequate perhaps).

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1999 Mazda B3000 3.0L 2WD AT FFV extended cab 213k miles. Purchased 4/1/2014.

I had a misfire a couple years ago and just took it to Advance and had them pull the code. Misfire cylinder 1. I pulled plugs that looked good but changed them anyway along with wires and ignition coil and it cleared it up with no issues since.

I have an appointment at a shop today in a few hours for them to hook it up to their computers and see what they can find. I'll report back. When I called them, they felt that 100 PSI was low, but they also doubted my compression gauge (well it is HF afterall, lol).

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1999 Mazda B3000 3.0L 2WD AT FFV extended cab 213k miles. Purchased 4/1/2014.

Have you replaced the cam sync ?

yes.

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Well here is the news from indy. mechanic confirmed low compression. said it was valve seats something something. said could replace heads, but considering 220k miles, said not practical. he said whole engine should be replaced.

He also noted transmission is bad and again at 220k miles, needs to be replaced.

I was hoping he would have found that my compression readings where wrong and there was a solution to my misfires. But no, it is due to low compression.

I guess I will watch craigslist for an engine and tranny. part of me just wants to walk away. I have been working on this truck as a build project for the past year. Honestly, I got carried away fixing stuff and replacing parts on a vehicle with 220k miles that didn't run right and slippy transmission.

oh well.

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1999 Mazda B3000 3.0L 2WD AT FFV extended cab 213k miles. Purchased 4/1/2014.

Put it up for sale and get something better to drive.

Hmmm definitely low, you can either get a new rebuilt engine, or try a quick fix. I heard Restore helps slow or stop blow by filling cracks on the cylinder walls. Worth a shot and can be found at the auto store. Saw some impressive reviews stating it brought back compression numbers similar to yours back to operational. Some people actually did a before and after test. Otherwise it looks like a swap or rebuilding the engine

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Ford ranger 2001 edge, 3.0 vulcan, manual transmission, 3.73 open diff., 29" tires, 1.8 ratio Harland Sharp roller rockers, fender pod filter intake, MSD ignition wires, thrush glasspack, last catalytic comb delete, Electric fan, Nitrous Express wet kit 50 shot atm (soon to be supercharged, eaton m90, custom designed supercharger adapter intake by me )

Change the oil and filter with 40w, change the transmission fluid (drain and refill, not flush), top off all fluids and be sure everything is in good working order, put a 4 Sale sign in the window and list it in the local paper, look for a replacement. It's a 99 model vehicle. Putting that much $$$$$ into it is a very poor financial decision. This is the best advice you will get.