Pocket Auto Diagnostics

Pocket Auto Diagnostics will be temporarily closed until I find another work truck.

I know I haven't been posting much lately, so I wanna make a quick video because people have been asking me if I'm still working on cars. They think I'm a full time day trader now and became a millionaire. The truth is my new nick name is called Day Day Red. Anyways. Let's get back to the business. We have a 2000 Nissan Frontier. It had stopped running. The customer has changed the spark plugs, spark plug wires, and distributor. Now the engine starts but it's running like crap. I wanna bring you guys along and troubleshoot the problem together.

The Power of the FIRST LOOK SENSOR 07 Dodge Dakota 4.7 V8 w/ over 200k Miles. ~Customer concern... Check Engine Light P0306. ~Vehicle History The money light has been on for more than a year. It has no driveability complaint. The money light will come back around 100-200miles after clearing it. The customer has replaced new spark plugs just for the heck of it. Smog inspection is due, so here I am. ~Preliminary Check At idle, I can definitely feel there is a small misfire here and there. For a normal person, this is barely noticeable due to the fact that this is a V8 engine, so each cylinder only contributes 12.5% of the total engine power. Brake torque rev or drive it like you steal it, everything is just SMOOTH!!!! In my experience of dealing with this type of misfire which can only be felt at idle but not so much, the problem is usually engine mechanical like the valve clearance issues on those Hondas. ~Pin Point Testing Picoscope is ready. BLUE CHANNEL is our ignition sync for the Cylinder#6. RED CHANNEL is relative compression test, and we can see that the cylinder#6 has a lower peak than the rest of the cylinders. YELLOW CHANNEL is our intake manifold pressure pulse, and we can see that during the compression stroke on cylinder#6, the pressure waveform didn't go down like the others. That means the intake valve is leaking. Just look at the engine as an air pump. During the compression stroke, all the valves are closed, and the piston is coming up and compressing the air. If the intake valve doesn't have a sufficient seal, the air inside the cylinder will escape through the intake valve, thus the pressure inside the intake manifold increase. That's how we interpret the intake manifold pressure waveform we see on the Picoscope. ~Bottom Line There is definitely a leakage in the intake side of cylinder#6. Is it the intake valve or the valve seat? I don't know and I don't care. Regardless, the head has to come out in either case. With the help of the First Look Sensor, this diag was done under 45mins and none of the spark plugs were ever removed. The pressure waveform was taken in the brake booster hose port. I still remember early last year I had a GMC truck took me 2 days and I still couldn't find the problem. That was the car that made me want to get all these labscope stuff. F U domestic junks but also thank you.

Finally I'm done with this POS! It's a 2010 Audi TT. The car came in with 2 concerns: coolant leak and random multiple cylinder misfire. Customer stated the engine overheated on the freeway one time. He made a quick stop to a gas station and found out coolant level was low. He added 1 gallon of water and drove home without any problem. The next morning when he started the car, it had a rough idle. Check engine light was on. The car went back to normal after it warmed up. O...Continue reading

Looks like we will soon have some study material for In-cylinder pressure analysis. This is my friend's car. She told me the Check Engine Light came on this Tuesday. Sputtering at times. When I first turned on the engine, I noticed there was a dead miss. The raw fuel smell confirmed that. This V6 engine still has easy access to all the ignition coils, and I quickly found the middle ignition coil on the front bank is bad. Bought one from O'Reilly and put it in. That's easy fi...x. However, I do notice there is a random light misfire at idle and would go away as rpm increases. Looking at scan datas, the total fuel trim is at -7% which means the PCM is taking 7% of fuel away by reducing the injectors on time by 7%. The PCM has to do this #1 is to protect the CAT converter and #2 for the CAT converter to do its job. Also, I already cap the vacuum hose from the purge solenoid just to rule out a leaking purge solenoid. The MAP voltage at idle is around .8v at the low side. The OEM spec is below 1v. All my Hondas have around .9v at idle, so this car has a low .8v at idle indicates it has more vacuum inside the intake manifold. Looking at the MAP voltage is just solely for diagnosis directions only, and those voltage reading is just a rule of thumb. For those who are familiar with Honda, they'll be thinking all these are the cause of valve clearance issue, and Yes this is what's in my mind as well. It's a 3hr job and I can't sell it just because I think that is the problem. As someone who has all the scope and pressure transducers, I do not have any excuses to try-agnose. Stay tuned for Part II pressure transduce test. Let's see if I can accurately pin point where the tight/loose valves are.