Tech To Tech
Author: Brian Manley
Subject Matter: Going the extra mile
Issues: Malfunction indicator light, stripped cylinder threads
Your customers expect authoritative advice. So check out these examples for making their cars better than new.
Our customers rely on us for our wisdom and experience, and this is of upmost importance when we have a chance to make their vehicles better than new. Two recent examples illustrate opportunities that I had to improve my customers’ machines.
1997 Chevrolet Suburban
This half-ton carryall came to us with an illuminated malfunction indicator light (MIL), accompanied by P0300 (random misfire) and P0304 (cylinder 4 misfire) codes. During our test drive, the MIL also flashed.
With 180,000 miles, a plethora of possibilities existed for the root cause, so I began with a GM original: the Strategy-Based Diagnostic Chart.
A thorough visual check was followed by checking for published diagnostic checks and a search for technical service bulletins (TSB) that revealed one for “Rough Idle After Start: Unstick or replace central sequential fuel injection (CSFI) poppet valves, or convert to multiport fuel injection (MFI).”
Those TSBs outlined the procedure for cleaning the vehicle’s poppet valve injectors and further advised, “Poppet valves may stick open or closed; in either case, the specific cylinder will be misfueled, resulting in a cylinder misfire condition.”
Before I tackled any TSB for injector cleaning, I needed to stay true to the basics of diagnosis and start with the simple things. Scan data revealed that long-term fuel trim for bank No. 1 was high, indicating that there was “misfueling” on that bank. So a lean condition existed (Figure 1).
In addition, scan data showed multiple misfires in history for cylinder No. 4 (Figure 2).
Since I had a definite misfire on cylinder No. 4, I performed a test for spark and compression with acceptable results. What made more sense, though, was a lean issue on bank No. 2. I performed a quick test for any leaks in the intake with my LeakMaster smoke machine, but I didn’t see any stray smoke escaping. I wondered if I might have a candidate for injector cleaning or upgrade.
At that point, I ruled out other options, so pursuing the TSB was my next logical step. After pricing, I gave my customer the choice of either cleaning or replacing the vehicle’s fuel injectors and, considering the mileage on the truck, she chose the upgrade.
My experience agreed with her decision. I’ve seen several of these upgrades make a marked improvement in engine performance for my customers. With an approval for the work in hand, I popped off the top of the intake to reveal the view in Figure 3: The original central sequential fuel injection (CSFI) “spider” assembly that had been reliable for a long time but wasn’t then.
When I received the box holding my new, upgraded “spider,” I laid it out next to the extracted one (Figure 4) to demonstrate the differences between the two. The newer version has been improved to mimic a multiport system, holding an individual electrically-operated injector for each cylinder.
2004 Mini Cooper
My customer towed his cool little Mini with only three spark plugs, having recently experienced an over-zealous plug installation artist. We examined the stripped threads in cylinder No. 3 and weighed our options. Ultimately, we had to break the news to the owner that the cylinder head had to be removed for a proper thread repair.
Repairing those damaged holes on the vehicle is rarely successful, and I had stopped attempting to do so. So I explained to my customer that we could repair all of the holes with replacement thread, making all of them stronger and more durable for the long term (Figure 5).
Because I have little experience working on Mini Coopers, I solicited some advice from a friend who works in BMW/Mini service at a local dealership. Unfortunately, he had no special repair tactics for these 1.6-liter engines, so I sold the customer a head removal and repair, and we had all four spark-plug threads replaced with Time Sert thread repair inserts.
These are heavy-duty threads and much stronger than the originals. I’m always confident in this repair, and our machine shop does an A-plus job with this type of work.
Ultimately, as service repair professionals, our customers look to us for authoritative advice and repair knowledge, and often our deep databases of repair information contain ways that we can make our customers’ cars better than they were when they left the factory.
What cool upgrades have you performed for your customers?
