2.3L ('83-'97) New Long Block - Low Compression in Cyl. #3

[darwood]

Hi All - Looking for some help diagnosing some issues with a newly installed long block in my '92 2.3L Ranger.

Background: I bought the truck from a guy who just had a new long block installed. Less than 200 miles on the new motor. After installing the motor it was running really rough at low idle and had no power at low RPM. However, once it came up to temperature, it ran much better and drove ok. In addition to the new long block, also installed EGR & MAF sensor. Before I got it the guy took it to a mechanic for diagnosis and this is what he found:

- Codes: 157 MAF Too Low, 327 EGR/DPFE, 332 DPFE, 334, EGR.
- Fuel pres. good @ 35-40 psi
- Plug wires, injectors, & ignition control module all check good
- Compression: Cyl. #1 160 PSI, Cyl. #2 155 PSI, Cyl. #3 120 PSI, Cyl. #4 160 PSI
- Leak Down: Cyl. #3 has 15% leak down compared to other cylinders
- Vacuum gauge and misfire are in sync

I have pulled the engine and torn it down but I'm not seeing any obvious signs issues. Given the low compression in Cyl. #3 I'm wondering if there is an issue with the valves on that cylinder or an issue with the rings. Not sure what else it could be. I didn't see any obvious damage to the head gasket. I find it unlikely that the rings would be bad in a newly built motor. One thing I did notice is that the exhaust valve on #3 has a different color than the rest. 1, 2, & 4 have a more white-ish color while #3 has a darker reddish color. With both valves closed on that cylinder I sprayed brake cleaner in both ports but didn't see anything leak past the valves.

I'm wondering if I should take the head to a machine shop and have them inspect the valves. Any input here greatly appreciated!

Thanks!

 

[Dirtman]

When you say "new" do you mean a new crate motor, a new remanufactured motor, or just a different engine from a junkyard?

 

[darwood]

Dirtman - It is a re-manufactured long block purchased from Rock Auto and built by ATK Engines in Texas.

 

[Dirtman]

I would be in contact with them before touching it. At 200 miles it should still be well within warranty and doing anything else may void that. Its not uncommon at all for remanufactured engines to be faulty on arrival. See if they will work with you first.

 

[darwood]

I have a warranty claim with them. They will take it back, inspect it and IF they deem that it is a manufacturing mistake, they will send me another one. I have 2 concerns. If they claim there is nothing wrong with it then I am stuck with the cost of getting it shipped back to me from Texas and will still have to figure it out. Also, the whole process could take a month or more. Second concern is getting a second motor from them that is faulty. I would feel more comfortable working with a local shop even if I do have to pay a little more.

 

[RonD]

Whats #3 cylinder look like inside, i.e. no scratching or marks, and piston feels tight, no slop, feels like #2

Set head upside down and fill all the chambers with water, see if #3 leaks

Could be a Cam or rocker issue, not opening valve fully or not closing it soon enough, bad lobe
A rocker can slip holding valve open too long or ??

 

[Fredness]

Ditto.
Betting cyl 3 valves need some love, which means they all do.

New head, old block forces more air passed the old rings, accelerating ring failure.
Old head, new block forces more air passed the old valves, accelerating valve/seat wear.