Misfire on Cyl #2, CEL blinking, compression test is fine?

[Vapocalyptic]

Okay guys, heres the deal. I bought what is (turning out to be) a lemon of an explorer about a month ago. It has 170k, it's a 97 SOHC v6. It drove okay, I knew it needed work, but I did not anticipate this much stress. So, let's get what I've already done out of the way...

- Replaced bolt on EGR pressure feedback sensor
- Replaced all 6 spark plugs
- Replaced fuel filter
- Replaced air filter
- Replaced intake manifold gasket (cleared codes P303 and P305)

Now, I am left with code P0302 # 2. I took it to a mechanic, they did a diagnostic, checked the coil packs, plug wire, fuel injectors, they were good. Compression came at 160 PI, they swapped the aforementioned pack, wire and injector over to # 2, still misfiring. I was told the problem lies in the valvetrain, and they would need to pull the cover to continue further diagnostic, which would cost around 400 (not including parts and potential labor)

With the new intake manifold, it doesn't idle AS rough, but still pretty bad. I'm losing power at high speeds, it backfires at high speeds, and it takes longer than usual to get to freeway speeds.

I'm at my wits end - I have very little money and live hand over fist, I just do not have 400 dollars to identify the problem. I'm coming to you today to see if 1) Getting the valvecover off really costs 400.00+, 2) what could potentially be the problem and 3) Should I just sell the damn thing?!?

Thanks everybody.

 

[Vapocalyptic]

Here is a report of the diagnostic I took it in for.

Engine scan - found codes po453, po302, po 305, tested system and found fuel tank pressure sensor connector not making contact - adjusted
found intake manifold gaskets are leaking vacuum causing air fuel mixture to be out of spec - replaced manifold
lower fuel tank and install pressure sensor, tested ok
after reassembly found cylinder number 2 still misfiring - run compression test - 160 psi
swapped spark plug, wire, and fuel injector with #1 cylinder, misfire remains
suspect vale train problem
requires removing valve cover to continue diag

 

[pcam13]

We had this problem at work. Cam was worn right out. Take the VC's off and rotate the engine over and see if and how the rockers are moving.

 

[Vapocalyptic]

Getting the valve cover off seems to be the problem... I am not mechanically inclined, so I have been asking around for a quote - I've got from 299.99 to 499.99 - just to remove the cover, NOT to continue a further diag/replacement/ETC. Bearing in mind I can GET the cover off, what should I be looking for? I know the rocker arms should be examined, the seat, and the springs, but I'm trying to avoid dumping money into this truck - it seems I should just cut my losses and stick to local public transportation til I can afford a new vehicle. I was told worst case scenario, it needs a valve build, which would not be economical or rationale at 170k.

 

[2000StreetRod]

purchasing an old vehicle

Most people have a reason for selling a vehicle. Often the reason is that the vehicle is no longer reliable and repairs will exceed the value of the vehicle. Most people who purchase a 15 year old vehicle do it because they can't afford a newer one. They hope to get lucky and get a reliable vehicle or plan to do repairs themselves to save money. Paying a shop to repair an old vehicle is often more expensive than repairing a new vehicle.

In the case of your 1997 SOHC V6 it has a variable intake system that was deleted in the 1999 models. As I recall the upper intake manifold must be removed to remove the valve covers. The intake manifold also had to be removed to replace the intake manifold gaskets which apparently you paid a shop to do. The shop should have replaced the upper and lower intake manifold gaskets since the lower ones are cheap and the additional labor is short. I think the 3rd generation and later Explorers have an integrated intake manifold which takes less time to remove. Also, I think the valve covers can be removed without removing the intake manifold. An example of why a newer vehicle may be cheaper to maintain.

A compression of 160 psi is a little low (normal for a warm engine should be about 180 psi). Were all cylinders the same? 170K miles is not excessive for an engine that has been properly maintained and not abused. I would be more inclined to suspect timing chain slip than burned valves. Is there any audible indication of timing chain rattle? Your engine has a chain from the crankshaft to the jackshaft and a timing chain from the jackshaft to each camshaft. If your vehicle has 4WD then there is another chain from the crankshaft to the balance shaft. If the timing chain related components are original your engine is getting ripe for failure.

The repairs performed to date are most of the inexpensive actions to eliminate a misfire. Now you're left with the more expensive actions: testing for a clogged injector or one with a bad electrical connector, determining why compression is low, etc. Here's a link to some ideas regarding misfire: Engine misfire procedure

Unfortunately, I think you made a poor choice in purchasing an old Explorer with the 4.0L SOHC V6 engine if you have to pay a shop to maintain it. If the rear timing chain cassette fails the cost to repair it will exceed the value of the vehicle. On the other hand, if you have a garage, some tools, and a mechanical inclination members of this forum will assist you with diagnosing problems and making repairs.

 

[drdoom]

Long ago I had a valve stick open following an extended storage. The cam follower popped out, and of course had a misfire til I patched it back together. IIRC the upper manifold had to be pulled to access the valves.