2007 Suzuki Forenza 2.0, Rough Running Engine and Overheating Issues

This 2007 Suzuki Forenza with a 2.0 came into the shop a couple of months ago with a customer concern of a rough running engine and an overheating issue. We felt pretty confident we were looking at a blown cylinder head gasket at this point; but, we wanted to "test and not guess".

There are a couple of ways to check for a blown cylinder head gasket. One way is to pressurize the coolant system and, with the spark plug out of the missing cylinder (or all plugs removed), using a bore scope in the cylinders to check for seeping coolant. Another way is to use a 5-Gas Analyzer to check for combustion gases in the coolant system. The third option, similar to the second, is to do what is called a block test.

We opted for the third option. It is a method we have used often with great success.

Before this, however, we wanted to perform a visual inspection.

When the customer drove the vehicle up to the shop, we noticed the tell-tale white smoke out the tail pipe. It was quite pronounced and the smell of coolant in the exhaust was noticeable.

The next visual inspection was of the oil. As you can see in the pictures below, the milky look to the oil is a sure sign that coolant has entered the crankcase.

We let the vehicle sit and then took the cap off the coolant tank. We noticed when we started it, fumes coming out of the tank.

Per the instructions with the block test kit, we let the vehicle run for about ten minutes and then performed the test. The kit comes with a clear tube and a fluid. The fluid is added to the tube, then you place the tube over the coolant tank opening. You apply vacuum to the top of the tube, in this case we used a hand-held vacuum pump, and apply vacuum for a minute or two. If combustion gases are present in the coolant, which they should not be, then it confirms a problem. (If there is a problem, the fluid, which is blue out of the bottle, will turn green.) Of course, it could be a blown head gasket, a cracked head . . . etc., but you confirm there is a problem that calls for a top-end engine tear down.

In the picture below, you see the fluid just added to the tube. You can see it is a light blue color out of the bottle. If the test passes (meaning no combustion gases are detected in the coolant system; hence, no blown head gasket) the fluid will remain blue. However, if the test fails, (combustion gases detected) then it will turn green within a minute or two.

Here I am showing (minus the fluid) how the tube fits on the coolant tank. (It is minus fluid because I just took the picture to demonstrate how to do it.)

As I applied vacuum (via the vacuum pump) to the top of the tube, within seconds, the blue fluid changed to green. This confirmed a failure at the mating of the head and block. Now, it was time to remove the head, send it to the machine shop and replace the head gasket.

We replaced the head gasket, timing belt and water pump and other odds and ends. Put it all back together and the vehicle ran nice and smooth. We test drove it a few miles and shipped it to the customer.

2005 Ford F150 King Ranch Edition 5.4 Misfire

This vehicle came into the shop with a customer complaint of a rough running engine, a misfire.  Customer said he was driving along on a trip and all of a sudden the truck started to misfire and run poorly.

First things first, we verified the customer's complaint.  Took the truck for a test drive and confirmed the misfire.  Next, we connected our diagnostic tool and checked for stored codes.

We pulled three DTC's.  They were P0171 System Too Lean (Bank 1); P0303 Cylinder 3 Misfire Detected; P0316 Engine Misfire Detected on Startup; and P0353 Ignition Coil C Primary/Secondary Circuit Fault.  We checked the freeze frame data and started our diagnostic.

We weren't concerned with the first code, with an active misfire on that bank, the lean code is explainable.  We needed to know what was causing the misfire.  Just a head up, on the last code P0353, the Ignition Coil C . . . C is number 3 cylinder.  Ford uses letters to correspond to the cylinders.  So "A" is 1, "B" is 2, "C" is 3 . . . "H" would be cylinder 8.  Okay, you get the idea.

Another FYI for you, Ford commonly mistakes cylinders.  So it may throw a cylinder 3 misfire, but when you start investigating you determine it isn't number 3 that actually has the misfire.  So be careful with that too.

Now, we needed to see what was causing this misfire.  Was it a plug, coil, wiring, or PCM?  With the P0353 code, any of these could be possible.

So, we hooked up our lab scope and sync probe and did some investigating.  First, let's rule out the PCM and wiring.

We checked battery voltage at the PCM with key off and with at KOEO, both showed good.  So wiring seems to be fine.  What about the driver in the PCM?

That's where our lab scope and amp probe come into play.  The picture below shows two traces (one red and one green).  The red trace is through the amp probe connected around the power feed.  This wire was accessible in the steering column and was fairly easy to get to.  It is a dark blue wire with light green tracer.  The green trace is our sync probe, allowing us to know which cylinders are which.  In this case, we were connected to number one cylinder.  With that info we could go by the firing order if we saw any problems in the patterns.  Here, what matters, is that all 8 cylinders are accounted for.  You will notice there are 8 red "lines" between each green "line".  This would suggest the PCM is onboard and functioning.

Now, we need a closer look to see where the problem lies.  The below pic shows a zoomed in view of the above pic.  Notice the difference in appearance of the two sets (3 spikes each) of red traces.  The first is nice and pointed, the second image (to the right) sort of curves over to a point and then drops straight down and then straight back up.  The first one is a known good pattern.  The second is a view of a shorted secondary ignition component: either plug or coil.  I know these trucks and engines are known for bad coils, but you have to follow the evidence to make a proper diagnosis and the right repair.

The next pic is an even more zoomed in look at the known good pattern.

The pic below is the faulty pattern . . . again, notice the differences between these last two images.

As I said earlier, these vehicles are known to mis-identify the offending cylinder.  So, we moved our sync probe from cylinder number 1 coil (control wire) to cylinder 3 coil (control wire), the cylinder that is supposedly the misfiring cylinder.  Below is the pic of this.

Based on the above pic, we knew it was indeed cylinder 3 that was the misfiring cylinder.  So, in this case, the PCM had the right cylinder pegged all along.  Now it was a case of determining if it was the spark plug or the coil that had shorted.

It turned out to be the spark plug.  The plugs had been replaced about a year ago.  So, we removed that one plug and replaced it with a new one.  We also ended up replacing another coil because it showed signs on the scope of weakness.

Started the truck and it ran like new.  Took it for a test drive, allowed the monitors to run, double checked no misfires being reported, lean situation straightened out with the misfire no longer present, cleared the codes, and shipped the truck.

2003 Mercury Sable 3.0, Misfire

This Sable came into the shop with a customer complaint of a misfire, hesitation at idle and under a load (going up a hill).

Scan data showed a misfire DTC and an active misfire on the engine.  These engines, in both a Sable and Taurus, are notorious for faulty ignition coils.  This custome decided to replace the ignition coil and plugs and wires (they were original).

Here's a look at the engine.

The front three plugs and wires are easy to get to.  The rear plugs and wires are underneath the upper intake (plenum).  The ignition coil is on the back side, underneath the plenum.

The ignition coils on these vehicles that I have dealt with that are faulty always have a crack at the base.  The easiest way I've found to do a visual inspection for this is with a small mirror and a light.

I confirmed this coil indeed have a crack in it.  To remove the coil and the plugs and wires I next got the plenum up and out of the way.  I first disconnected the air breather hose and from the throttle body.

 

 

 

I just leave it on the vehicle over on the side.

I next remove the vacuum lines and electrical connector from the EGR DPFE, which is on the right side (passenger) of the plenum.

I then remove the EGR valve.

Next, remove the plenum bolts.  There are eight of these.

Once they are removed, to save some time, I simply raise the plenum up and using a strap, I secure it up our of the way.  By doing this, I don't have to actually remove it completely from the vehicle.  Just be careful with the two hoses coming up and connecting to the plenum so as not to damage or break them.

Now that the plenum is out of the way, we can easily see the ignition coil and the rear plugs and wires.  At this point, remove the rear plugs and the ignition coil with a torx bit.

 

Here is the ignition coil off the vehicle.  The crack causing the misfire is visible.

 

 

Once the ignition coil and plugs and wires are replaced, simply torque the plenum back down and reverse the order of removal to reinstall.  (The plenum has rubber gaskets, which should be reusable.  Simply wipe them and the mounting surface clean and reinstall.)

 

 

After reinstall, I cleared the codes and took the vehicle for a test drive.  The misfire was now gone and the vehicle was operating properly.