third coast

Oil Analysis from a Cherokee 4.0 that I am helping my son with came back with high iron and lead wear material. Iron was 96 ppm (universal average for 4.0 engine is 25 ppm) and lead in 10 ppm (average is 2 ppm). Fuel contamination of oil was found to be high at 5.8%. Oil viscosity test results showed lower than expected viscosity, most likely a result of the high content of fuel in the oil. There were 2,300 miles on oil when the sample was taken. Engine has 160,000 miles. Short trip driving in cold weather was reported. It is unknown how long the problem has been present. I expect that the oil dilution by fuel is at least in part caused by contaminated and leaking fuel injectors. The oil analysis was done prior to potential purchase and we are evaluating next steps.

I am interested in feedback from anyone that has experienced a similar situation of high wear metals in the oil and then correcting the root cause of the excessive wear. If you had high fuel content in the oil what was the cause? Did wear return to more normal numbers or did the wear rate continue to be high, indicating irreversible damage done to bearings, crank shaft, cam shaft, etc? Once bearings begin to wear excessively does the damage continue to accelerate? I am looking for those that were using oil analysis to determine before and after wear rates. If it is likely the engine is significantly damaged that would be a factor in a purchase decision and purchase price. Thanks!

Suprmn

Well, I have never gotten scientific enough to do an oil sample, but if the 4.0 has a flaw, it is rod bearing wear and eventually throwing a rod. If there has been good maintenance, I have seen these engines go 300K miles without a problem. I have a friend that pulled the rod bearings at 322K and replaced them. They were well past the copper and worn out. However, with a new set of bearings it is still running today. I would expect that the fuel contamination issue has been there awhile which probably accelerated the wear. Personally, if you like the jeep, I would purchase at a price that you would be ok with if you had to get into the engine. Then I would slap a set of rod bearings in and a set of injectors and go enjoy.

Transpoquick

High lead='s a bearing problem(in this case)

High iron='s a cylinder wall, piston ring, connecting rod problem(basically the "engine") in this case.

Something "may" be wrong.

At 160k that could just be normal wear though. From the #'s op gave it sounds like it needed an oil change.

I would change the oil a couple more times and then have another analysis done if this is a "new to you vehicle".

third coast

I think the way forward is to buy the Jeep if the price is appropriate for the problems it has. It needs a lot of other basic maintenance/repair work in addition to replacing the injectors. After fuel system work and a couple of oil changes I should be able to get a better idea if damage caused by fuel in the oil has seriously damaged the engine and if wear continues at a high rate. From there we can determine if an engine swap or complete rebuild is necessary.

Anyone have any particular recommendations for new OE type replacement fuel injectors? Rebuild of current injectors? Really not interested in higher flow rate injectors at this point.

s346k

how did you draw the conclusion of leaky injectors? simply running rich for extended periods of time will raise fuel percentage in the oil. more fuel in the oil means more wear on bearings. rich mixtures wash cylinders, as well.

Transpoquick

^^x2^^

third coast

Poor condition fuel injectors is my best guess given 160k plus miles on engine and minimal routine maintenance. Short trip driving in cold weather certainly would contribute but expect this adds to the build up of crud on the injectors. Just a cleaning of the injectors would be an option but given the amount of fuel in the oil it seems like a new or rebuilt injectors would be worthwhile. I did notice that new injectors are not inexpensive however, at around $100 for new name brand units. Are refurbished units reliable?

Tbone289

If you must, buy injectors from jhc7399 here on the forums. He has lots of satisfied customers, including me.

However, I wouldn't arrive at the conclusion that the issue is injectors without doing some troubleshooting. What's the fuel mileage like? Are the rings sealing well? Any CEL codes like o2? etc....