Q: I just bought a truck to replace one I loved but recently totaled after flattening a Prius that pulled out in front of me. It's a 2009 Dodge Ram with two-wheel drive and a 5.7-liter engine _ almost the exact truck I had.
I've been working through a list of things in need of fixing and noticed this truck, compared to the old one, doesn't idle as smoothly once warmed up. It does run well at other speeds, though. I've caught it up on all the other maintenance stuff, such as plugs, filters and fluids. And I've run a couple of bottles of injector cleaner through it. It passed a smog just fine when I bought it, so I'm a little puzzled about the idle being different. Any ideas?
_Sal A.
A: There are quite a few reasons an engine might idle rough.
I've learned that one of the first things you should do is check for any pertinent service information. If it's known that your particular vehicle is prone to certain issues, or technicians report a high rate of success with a certain procedure, I research these possibilities before plunging into other tests and procedures.
In your case, Chrysler issued a technical service bulletin just as this truck model was released for sale with a procedure to mitigate idle roughness. It's worth a look!
If your present truck was an early build for the 2009 model year, it might benefit from a powertrain control module, or PCM, software update, which should raise the idle speed from 584 rpm to 638 rpm, likely a sweet spot for smoothness.
You should be able to confirm the fix has been made by checking the warmed-up idle speed with a scan tool or an accurate tachometer. A more sure way is to check the existing software calibration using the scan tool. This is best done by a dealer or independent shop.
Let me know how this pans out. Meanwhile, I'll start creating a checklist of possible causes and solutions if you need more help.
Q: My 1990 Toyota truck has always run great. I've always been able to count on her to turn over, start and get me where I need to go.
The other night, though, she stalled out at a stop sign. I put her in park, she turned over, but as I moved the gearshift, she stalled. That happened several times. I hated to leave her on the corner but I would like to have an idea of what might be wrong before a mechanic decides to rake me over the coals.
_Marianne Chavez
A: This is a shot in the dark, but we can try a few things.
It sounds like the truck starts but dies when you apply any load against the engine.
Try this: Apply a small amount of throttle as the truck starts and see if you can accelerate the engine up to perhaps 2,500 rpm in park or neutral. If it stalls out, I'm thinking there might be a fuel pump problem and a tow will be necessary. If it revs up OK, try applying a smaller amount of throttle, perhaps 1,200 rpm, as you place the transmission in drive. If it keeps running, try driving it a bit, always keeping a small amount of extra throttle applied as you return to idle. If this helps, there's probably a fault occurring with the idle control system. If the engine bogs down or quits, I'm back to the fuel pump hunch.
It sounds like your bigger issue may be finding a repair shop you trust and like. How about recommendations from friends or social media ratings? Insist on clear explanations. Automotive Service Excellence, or ASE, technician certifications are good to see, as is Automotive Service Council membership. A second opinion is hard to get when it's a tow-in situation.
