Coast to Coast: Fault Diagnosis and Lessons Learned

This report is LONG overdue! I had drafted it, then forgot about it. Oops! What follows is my recollection of a engine fault that my GTI suffered while pulling a trailer on its first Coast-to-Coast trip. I have a series of entries about that trip, starting with this entry. We wound up on the side of the road during a night time mountain climb about 2500 miles into the trip. The roadside stop was very brief. We were climbing a mountain pass and probably should have been in a lower gear. We had experienced a check engine light a day or two earlier, also while in a climb at only 2500 rpm. However, this time the EPC light came on, the Check Engine Lamp (CEL) was flashing, and the car’s behavior was terrible. I was certain that I could restart the car and drive gently. After pulling-over and restarting, I decided to stay in a lower gear with the trailer in the mountains. I pulled codes with my OBDEleven app and found cylinder #3 misfire and “hide cylinder” DTCs. I cleared the codes and continued west.

It had been a LONG time since I last diagnosed a spark engine since I had been driving diesels for 20 years. But I did recall that VW ignition coils, aka “coil packs,” had been problematic in the past. I was disappointed to learn that the VW dealers in Fresno do not carry coil packs. Apparently, they’re a warehouse-only item. That was shocking since I considered coil packs to be a consumable item. But there’s another explanation: Inventory costs money; plus, supply vs. demand. With older generation VWs, the coil packs ARE consumable items because they fail frequently. However, I now know that Mk7 coils fail far less often. As a result, dealers don’t need to keep them on the shelves. Anyway, I ordered a full set to see if they resolved my problem. The parts department said they’d have them the following morning.

The coil packs were waiting at opening time, as promised. I went to the parking lot, where I had hidden my car behind a truck, and changed them out in a stealthy manner. NO JOY! Damn! Well, the next step was exactly what I had planned: a dealership visit. The service advisor was very accommodating and got us in right away. He appreciated that he didn’t need to explain so much to me and that I had provided a thorough report about my problem. He came out from time to time to get approval for different levels of troubleshooting. In short, the fault did not move from cylinder #3 when the tech moved coil packs or spark plugs to different cylinders. He checked engine compression and leak down; both were good. He inspected the cylinders with a bore scope and saw nothing abnormal. He noted that the low-pressure fuel pump (LPFP) output seemed below standard, but he wasn’t sure if it may have been a sensor trick that the APR tune used to drive more pressure from the pump. Yes, I disclosed that I am tuned! I didn’t want my ECU tune to be overwritten during a technician’s guess for answers.

He suggested that I have the LPFP and its controller replaced for another $750. Surely, they’re not BOTH bad! However, the tech didn’t have the tools (or expertise?) needed to discriminate between the two components. “So, let’s just replace them both. It’s only the customer’s money, right?” Of course, neither part was in stock, nor could they be there for three days (it was a Friday). I asked how a bad LPFP could affect just one cylinder. The service advisor could not explain. He said that if the LPFP and controller did not fix the problem, then the dealership would work with VW tech support, who would require the car to be returned to stock before proceeding. THAT was a show-stopper for me, especially with my stock downpipe and other parts being 3000 miles away.

I asked if the car was safe to drive; he said it was okay. I had already extended our stay an extra day and did not want to add another three days or longer. So, I paid the $320 diagnostics bill and left. It sucked that new coil packs and $320 worth of troubleshooting didn’t resolve my issue. But at least I knew the engine wasn’t damaged. Thankfully, I had decided to clean my intake valves before the trip so that I could possibly avoid any intake-related issues. Can you imagine what kind of guesswork the dealer would have done with my current issue if I hadn’t been able to tell them that the intake was freshly cleaned?

Once I was free from the dealership, I called my local mechanic, Euro Pros in Yorktown, Virginia. Given the dealer’s troubleshooting so far, he immediately jumped on the #3 injector and agreed that the car was safe to drive since it could be driven gently without triggering the EPC indicator. Talking to my mechanic ignited a few memories from my old days in gasoline-powered cars. The conversation had me wondering why a trained dealer technician didn’t focus on the #3 cylinder and get to the injector. The experience reminded me that some shops will just throw parts and customer money at a problem until something works. Never mind all the wasted parts… the customer gets to keep those while the shop keeps the money.

I drove the car another 3500 miles, trailer and all, before being able to visit Euro Pros. As diagnosed over the phone, the #3 injector was at fault. I had all four injectors replaced. Euro Pros also found a thermostat housing leak that wasn’t there before the trip. In summary, I now have four new injectors, a new water pump, a new thermostat and housing, plus fresh coolant. Knowing what I know now (hindsight, right?), I’m still wondering why a trained VW dealer tech wanted to pursue fuel pump AND controller replacements before eliminating all cylinder #3 suspects. It’s too easy to think they just wanted to make more money from me. I hope it was just incompetence, though who’d want that from a dealership? I’m glad I knew enough to say NO!

Anyway, the car runs great after receiving competent attention, even now that it’s been over 35,000 miles since the repairs! Minor engine fault aside, I did learn some lessons during that trip. I’ll detail them now and wrap-up this trip series:

1) I have no regrets about taking a trailer on that trip. However, I would have brought my enclosed cargo trailer if I had realized what a hassle the baby trailer would be. Given its homemade wooden lid, I felt compelled to unload anything valuable each evening when we stopped, which was most of the cargo. Loading/unloading was even more cumbersome once we acquired more cargo in California because of the externally-stacked tubs. Using the cargo trailer, which seemed too large for the job at departure time, would have been a huge time-saver because we could have left most cargo locked inside its more-secure enclosure.

2) Bringing the rooftop cargo box meant this was the first time that the roof rack had been mounted long-term. The rack’s extended use led to mineral deposits under the mounting pads, which marred the paint on the roof. I had considered paint protection film for the mounting pad areas. Now, I will certainly apply the film. Ironically, if we had brought the enclosed cargo trailer, we wouldn’t have needed the rooftop cargo box because everything could have just fit in it… and remained locked inside for the entire trip.

3) I travel with tools and minor parts. But there’s a fine line between having “enough tools” and carrying too much weight. There’s one tool I wish I had, but didn’t: a spark plug socket. In my opinion, anything beyond basic tools just just carrying too much. Still, it would have been nice to have been able to move spark plugs between cylinders to troubleshoot. Regardless, there will always be something beyond my capabilities. These days, if I’m on the road and away from home, I’m financially sound enough to just pay a mechanic if I’m in a jam, just as I did on this trip.

4) It’s my practice to drive “one gear down” from normal when pulling a trailer. However, it’s very flat where I live and I found myself towing in too high of a gear while in the mountains. I don’t always follow the “shift” recommendation on the instrument cluster. After all, it wants me in 6th gear at just 45 mph, regardless of load or terrain. I can say with certainty that indicator should be completely ignored when towing. When towing, I found the car to be most happy between 2500-3300 rpm. That meant fourth gear at 55 mph, fifth gear above 65 mpg, and avoiding sixth gear altogether.

5) Perhaps the biggest lesson learned, which I didn’t apply at all, is renting a van or truck instead of doing what I did. Well, if I did that, then this wouldn’t be a story or video series about my GTI, would it?  😉  Less obvious, but perhaps more important, is the fact that one-way van rentals leaving California are ridiculously expensive these days! Remember, rental companies charge per-mile/per-day on one-way rentals. The cost could have been more, less, or a wash. I probably would have felt compelled to take the most direct and economical routes if I had been renting by the mile. Driving my own car/trailer, I could take whatever route I wanted and detoured to see interesting attractions. I’ll stick to the GTI and trailer. Even if it was more expensive for this mission, it’s far less expensive on a daily basis!

Speaking of driving expenses, we drove a total of 7422 miles, not including the trip to Chincoteague for the Atlantic Ocean photo. During the main trip, we burned 322 gallons of premium unleaded fuel for an overall average of 23 mpg. Yes, there were several tanks where we achieved just 19 mpg. But we also saw 26 mpg at slower speeds, particularly in CA. I had estimated that we’d get 28 mpg. The 5-mpg error cost an extra $100 in fuel, but it wasn’t anything we couldn’t handle. I won’t share hotel or food costs since they would be the same regardless of my choice of car.

Okay, this has been a lot of information. I hope someone finds some benefit from it.

Blissful Driving,



About Scott

I grew up near Houston, TX and served in the U. S. Coast Guard for over 30 years. I have an electronics background and continue to work in the electronics engineering field. I taught myself the basics about automotive systems as well as how to perform some of my own maintenance (cars and bicycles). I became involved with Amateur Radio and computers in 1995. The explosion of technology has made my job and several of my hobbies quite interesting. My hobbies include Volkswagens, bicycling, photography, electronics, amateur radio, web management, and reptiles. Visit my websites to learn more.
This entry was posted in Maintenance, Problems, Road Trips. Bookmark the permalink.

2 Responses to Coast to Coast: Fault Diagnosis and Lessons Learned

  1. Hi Scott. Standard misfire diagnosis would normally involve switching coil, plug, AND injector – each to a different cylinder. Not sure why the VW tech only moved two components? Perhaps those injectors are a pain to get in/out?

    Once the warranty is over, I rarely darken the door of a dealer. If I can’t fix it myself, I find a good independent shop to do the work. Obviously, if you’re on the road, you get help where you can. Otherwise, I avoid the dealer service lane when ever possible.

    • Scott says:

      Thanks for writing. Swapping injectors is a very expensive process due to the amount of disassembly required to access them. For the labor cost to swap injectors, verify anything, and then access them again, one might as well just replace them. 😉 Once everything other than the injectors has been eliminated as suspects, simply replacing the injectors (said as if it’s “simple”) seems to often be the right answer. It could be that the tech was too lazy to disassemble to access the injectors and wanted to try the “easy” stuff first.

      As for avoiding the dealer, I agree! However, as you said, things change when I’m on the road and far from home. In that case, I’m inclined to find a VW specialist first (who may be booked) and then a VW dealer. On that trip, I was visiting to attend my mother’s memorial service and to retrieve some of her things, particularly her cats. Her memorial was the next day and I had no time for messing around to search for the right mechanic. I went to the dealer because it was fast. Believe it or not, they can sometimes be cost-competitive… so long as you get a competent tech. 😉 Take Care!

Leave a Reply