Sick Van

[EZHIKER]

I have been having sporadic symptoms for months now. Van would run flawlessly most of the time and occasionally would have loss of power, a bit of a stumble and then normal power through the power band, never stalling or difficult to start. Initially I only noticed the stumble after driving considerable distances, I would reach my freeway exit without issue and then stumble after the traffic stop. Now it is sick all of the time. Seems as though it is running of 3 cylinders or less, a bit rough at idle, little or no reponse in the middle of the power band.

I am getting Trouble Shoot CODE #11: 1) Air Conditioner Switch; 2)Throttle Position Sensor Circuit; 3)TPS; 4) Neutral Start Switch; 5) ECU.

I Swapped spare ECU and TPS without any change in symptoms. Neutral start Switch was replace 3 years ago (OEM), that leaves the TPS circuit and A/C switch.

What else is involve in the TPS circuit? A/C switch? not really sure were to start with this either. Any helpful hints or advice is welcome. I've been searching for obvious vacuum leaks, air hose checked out good no cracks. I'll check O2 sensors, plugs & wires next. Back to the manual.

[timsrv]

A bad TPS can cause your van to run dirty (emissions) and can have a negative effect on economy/power. Over time it can also lead to cat failure, but it will not effect your van to the degree in which you describe. As for it being bad or good, unless you swapped in a new one and adjusted it properly I'd be more surprised if it were good (I see bad TPS units all the time). Did you reset codes after you swapped it? Perhaps this code is just left over from before.

If I had to guess, I would have to say the code 11 is most likely a separate issue from the more serious runnability problem. I would ignore the possibility of an AC switch (unless of course you're trying to track an AC problem) and I would also ignore the possibility of a bad neutral safety switch (unless it won't crank when you try to start or it will start while in gear).

It sounds to me like there's something else going on, but the question is what. Intermittent problems are hard to find so in a way it's good that it's becoming more consistent. There are several things that can cause these kind of runnability issues without triggering a code. It could be fuel related but based on the way you described it I'm leaning more towards electronics. Since you already swapped ECUs I think it's safe to rule that out. The coil or igniter in my mind would be the next things to look at. There is also the air flow meter, but these are pretty tough so I'd wait on that until after eliminating the coils and the igniter as possibilities. Other than swapping out the igniter I know of no test for these. There are continuity/resistance tests for the coil & pick-up coil in the IG section of the service manual, but for an issue like yours I'd prefer to swap out the entire distributor with a good used one for troubleshooting. If that's not an option, then do the tests per the manual. The problem I have with this is the intermittent nature of your issues. For all you know they could be triggered by heat, condensation, or only mess-up under load, so to totally eliminate these as possible culprits I'd feel better with swapping parts. Good luck with your troubleshooting and please report back with how it goes. Tim

[EZHIKER]

My 4wd auto is running better than ever. The ignitor was not working properly. Swapped it out and saw immediate improvement. I also, replaced the crappy autolite plugs with mismatched gaps with platinum plugs, the plug wires that had excessive resistance as well, new cap & rotor, replaced a few hoses while I had the engine cover off. Power is good and economy as good as ever. Very nice.

[NEC]

That's great to hear you are running again. Maybe I'll try my spare iginter and see if it helps my mpg. FWIW, in my experience Toyota coils can be tricky to diagnose. You can find a batch of 5 cars at the local wrecking yard and all the coils will test out of range for primary resistance if you go by the specs in the book, however they will function perfectly when used in real life. On the other hand, when a coil starts to go bad it often tests good on the resistance test but fails after heating up for a while ie driving for a bit. I have several "diagnostic" coils I have pulled from vehicles because they would quit after warming up. Whenever I suspect a coil is at fault I install one of these as a test and see if it at least runs for a little while...

[timsrv]

When my coil failed I swapped igniters 1st just to see if that was it. It wasn't, but what's funny is the van wouldn't fire at all with the old igniter, but would run with my test igniter (but just barely). Then I swapped distributors/coils and it ran like a million bucks. So there is such a thing as a weak (but good) igniter...........at least varying degrees of how "hot" one can be.

Glad you got her fixed. Tim

[EZHIKER]

I was prepared to try another distributor/coil (next) as I did not think an ignitor could go south without complete failure. I Just finished the 1st leg of a road trip (600 miles), the van was flawless 21-22 MPG. I'll be raodtrip 4-5K miles over the next 2 months visiting family, climbing mountains, fishing, etc. I always travel with tools, but I sure am glad to have sourced the issue before finding myself away from my parts bin.

I read some information suggesting Diagnostic code 11 was bogus? I have been unable to clear this error code. Perhaps, I should recheck my TPS adjustment? Any thoughts?

This TV Community is Awesome!
Thanks so much.

[timsrv]

In my experience code 11 usually equals a bad or failing TPS. I've seen so many bad TPS units over the years, that I almost consider replacing them as routine maintenance. My rule of thumb is: "If it's got over 100k miles, and I don't know history...........it gets replaced". Of course adjusting correctly is critical. I've posted basic instructions for that here before and in several places over at TVP. I'll be doing that job again really soon, and plan on doing a more detailed step-by-step tutorial. Tim