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Sadly, I have no fuel trim reader, so I’m using a multimeter the best I can.
Symptoms: Low power, dragging, rough idle, poor acceleration, EXTREME gas consumption. Takes a good while to get up to speed past 40 mph. There doesn’t seem to be a misfire. Just a very consistent, rough and sick sounding engine. Almost diesel-like. Especially on the passenger side near the valve cover/exhaust manifold area. This area kind of smells like exhaust.. Like a really dirty bbq grill. Also, My RPMs kind of fluctuate between 500-700, 700 RPMS being normal.
It all started with these symptoms, and eventually the car died. My diagnosis pointed to a failed fuel pump. I thought maybe all of the problems would go away after doing a replacement. I replaced the fuel pump, and the car ran again. However, I still have the same symptoms. Here are the tests I did.
-Ignition: Spark plugs, wires, ignition coil all good.
-Fuel: Fuel pressure reads at a steady 32 psi and holds for one minute after shutting the engine off. (Specs are 30-45 psi)
-Air: Vacuum test is okay. No smoke from anywhere.
-Alternator okay.
-Battery okay.
-No broken valve springs.
-Cleaned the MAF sensor.
-Replaced cracked DPFE sensor hoses.
-Checked air duct/filter housing.Tried to test the crank and cam sensor, but I don’t think I was doing it right. It read 0 while manually cranking for both. But if that was the case, it wouldn’t run at all.
Decent compression.
Cylinder 1 – 155
Cylinder 2 – 170
Cylinder 3 – 175
Cylinder 4 – 175
Cylinder 5 – 175
Cydliner 6 – 150Now.. I suspected that this could very well be an exhaust issue. 4 o2 sensors, and 4 cats. I thought I possibly had some exhaust back pressure. I ran a gauge to the bung hole, but the gauge oddly stays at a constant 0, unless I rev the engine to around 2000 RPMS, which is when it hardly even reached 2 psi. This makes me more inclined to believe I have a leak. But this happens on both sides. I made sure that the connection was tight. I also removed the front 2 o2 sensors, and I felt like the RPMS were more steady.
I also ran a pressure gauge from the exhaust hose that goes to the DPFE sensor, and had the same outcome.
Could it be possible that I have an exhaust leak, and not exhaust pressure? If not, then what other tests could I run without a fuel trim reader?
Thank you
from your symptoms I’m thinking fuel delivery problem not from fuel pump. Excessive fuel consumption and steady psi on fuel pressure. No fuel smell? Fuel pressure should increase with more RPM. Do snap throttle test. PSI should go max then dip and level off. Pull the pressure regulator vacuum hose, PSI should go up (same as max throttle snap PSI). If fuel present in vacuum hose or nipple of pressure regulator you have a bad pressure regulator. In any event you should not have any drop in fuel pressure, that would be a bad pump but you replaced that so you should not have a drop.
EGR open at low RPM will cause problems as well. This could be secondary problem. Do fuel first.
You can use DVOM to watch 02 sensor movements but its hard and does not give the results/data you’re asking for. With excessive fuel consumption, 02’s are going to be reporting rich condition PCM is going to respond by trying to take away fuel to compensate.
Thanks for the reply jkreutzer!
So, I’m going to go ahead and call myself a big noob for doing this. I’ve been doing everything ass backwards with this vehicle. This is/was my most challenging diagnosis, and it all just threw me for a loop.
I basically thought that perhaps the issue was a bad valve because of what my vacuum test indicated. I took the vehicle apart, all the way down to the cylinder head and found nothing wrong. But in hindsight, I didn’t check the regulator, and didn’t care to think that the exhaust could possibly have been the issue. I was a bit overtaken by other variables, so much that I ignored it. This has been a huge lesson.
Timing components are fine, valves have been tested at a shop, and nothing seems wrong. Once I put this piece of work back together, I will check out the fuel regulator.
In the meantime, here’s a video of what the car sounds like. Ignore the whining noise coming from the power steering!
Here is the vacuum gauge pinpoint test I did a while back. I did a bit of research, and this indicates that it could be retarded ignition timing?
at this point no diagnostic can be done until you have the engine back together and running. fluctuating RPM is usually due to a vacuum leak. had an engine with a blown head gasket between two cylinders idle and sound the same as yours but vacuum reading was very low. normal vacuum is between 17 and 22 and steady.
I would throw out all previous thoughts as to what is wrong until the engine is running again. if it was a head gasket, low readings on 1 and 6 are suspect, you’ll know it when engine running again. check all vacuum lines. one that is pinched or collapsed but not cut open can cause problems.
forgot to mention… the coil pack on the V6 mustangs from 94-2000 were known to be really bad and cause much of the problems you described. You mentioned that the ignition coil was good, but make sure, test the pack, make sure you have a good strong spark coming from each coil tower. You might consider taking it to a professional and having it checked out.
Thanks again. I discovered something this evening while inspecting the camshaft synchronizer… The magnet that sticks into the camshaft position sensor had fallen out right into the camshaft! Also, the camshaft had a lot of play, where the interrupter had a wobble to it. I read that these are a bit common in these type of Fords.
Sorry, it’s been a while. The Mustang is up and running and FIXED. I think this entire deal was a domino effect. The source being a failing fuel pump. My theory is this that the fuel pump began failing, therefore causing the spark plugs to eventually lose their integrity, getting worse by the day. My camshaft synchronizer had a really bad wobble to it, but never chirped. Went ahead and replaced that as well. Runs MUCH better now.
Now I just need to take care of a rear main seal and transmission leak.
For a minute there I didn’t think that I’d get this car back.
Thanks for your time!
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