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View Full Version : Odd "stumble" in the Taco


bgoodheart
09-04-2012, 09:50 AM
I didn't come up with anything in the search, so I'll throw this out to the experience of the group.

On the way out to Ouray, the truck started showing a slight "hiccup" at about 2000RPM (+/- 200 or so). I wouldn't call it a stutter, per se. There is no noticeable RPM drop (at least on the tach), but you can feel yourself lean forward as is the brakes were momentarily engaged. The whole thing is about a second long.

On the trail, I didn't seem to have any trouble, mostly the issue seems isolated to steady throttle position on flat roads.

Nothing about the "stumble" is violent, but it is certainly noticeable, and it happened too many times to count on the way home from Ouray.

I initially thought I had some bad gas on the way to Tincup, but the fact that I went through a couple of tanks during the trip seems to rule that out. May run a little Seafoam through it just for grins.

The truck has almost 93K on it. It is a 2004 Tacoma DC, 3.4, Auto. Always Toyota parts and service intervals. Plugs are in good shape, MAF is clean. Maybe a plug wire or a coil? RPM-specific symptom makes me think it isn't fuel related, but that could be wrong.

Any ideas?:confused:


Thanks,

BJG

SteveH
09-04-2012, 11:49 AM
I'd sure check for pending OBD codes, if there is no MIL showing. I agree that it sounds more like a coil than a fuel issue. Changing the fuel filter might be good insurance, at the age/mileage you have, too.

bgoodheart
09-04-2012, 01:53 PM
Thanks Steve. My code reader doesn't read the pending stuff, but I've got an appointment to stop by a buddy's shop and have a look.

Another thought is the TPS. Not sure how often those go out, but it does seem to happen only with light pedal pressure and around the same amount of travel. Agreed on the FF. Will probably pick one up and change it just for good measure.

corsair23
09-04-2012, 03:05 PM
No help on a Tacoma but on an 80 that symptom has been linked to a cracked air intake hose or chaffed wiring (in a big loom) causing intermittent shorts (usually when power is applied that "torques" the engine and moves stuff around).

Knowing nothing about Tacomas I don't know if you might have any similar items as above :hill:

baja1d
09-06-2012, 08:57 AM
Thanks Steve. My code reader doesn't read the pending stuff, but I've got an appointment to stop by a buddy's shop and have a look.

Another thought is the TPS. Not sure how often those go out, but it does seem to happen only with light pedal pressure and around the same amount of travel. Agreed on the FF. Will probably pick one up and change it just for good measure.

Had this same issue on my Tacoma. It turned out to be too much oil on the K&N filter that saturated the TPS. At least that's what the mechanic said.

bgoodheart
09-06-2012, 03:42 PM
Thanks Trav, no K&N here, and I haven't ever had one. You're right though, it is a lot like what another buddy's Taco did with oil on the MAF and a gummed up throttle body from his K&N. I clean both (MAF and TB) every 15K or so, but I'm definitely going to pull them apart and check. I found the resistance specs on the TPS, so I'm going to pull that off and throw the meter on it too.

SteveH
09-06-2012, 05:01 PM
Motor magazine had a story where cheap Chinese air filters give off fuzz that contaminates the MAF, just as excess K+N oil would, so sometimes these problem are not only K+N related.

bgoodheart
09-06-2012, 06:11 PM
Huh, thanks Steve. I used Toyota filters until I put in an AFE Pro Dry last year. Have to do a "fuzz" check.

TIMZTOY
09-06-2012, 10:12 PM
have the codes pulled to see if there are any "easy outs". if your on the south side swing by my shop and ill read the computer for you.

well your approaching the magic 100k mark. and at 100 the timing belt and plugs are due.
if they haven't already been replaced id highly suggest doing it now (denso ). your issue has many different areas of possible failures, expectually with 100k. approaching. but before worrying about anything. id do all maintenance first. then see if the issue is still there.. if so then you have a issue that requires diag.

bgoodheart
09-07-2012, 11:00 AM
Thanks Tim, I did all the maintenance already. All Toyota parts. Did it a little early because I was in town and it was convenient, so everything has had a few thousand miles to settle in. Had the codes checked on Tuesday. Not a thing there, and nothing pending. I'm going check the relevant sensors this weekend and see what I come up with. I'll put an update in this thread if I find anything good.

subzali
09-07-2012, 11:07 AM
You might try buying a coil pack and substituting it one by one through all the cylinders and see if that helps. It may be misfiring but not enough to throw a code. Not a bad thing to have as a spare anyway, at least with a 2UZ-FE...

bgoodheart
09-07-2012, 12:17 PM
Not a bad idea at all Matt, thanks.

TIMZTOY
09-07-2012, 08:36 PM
i have 6 coils from a yoda either 3.4 or 4.0 .. i highlly doubt its a coil issue though. does it always misfire or only under load, cold, hot, cruise, highway, city..

bgoodheart
09-10-2012, 03:45 PM
Well, I did a thorough clean of the MAF, the TB, and the intake. Ran some Seafoam through for good measure as well. I read somewhere that there is a "cleaning" procedure for the TPS that involves 100 full-travel cycles of the accelerator pedal. I did that too, figuring it wouldn't hurt anything to try.

The problem is still there, though the cleaning netted me some improved throttle response. I'll take what I can get, I guess.

Tim, I notice that it happens more often than not around 2K or so, generally with light throttle pressure, but sometimes with my foot out of the gas altogether.

I'd say it was the TPS if it didn't do it without any throttle at all. I read a forum post online somewhere with almost identical symptoms caused by slight wear in one of the plug boots (that didn't manifest itself in a continuity check or any other tests). I don't have any heartburn replacing the wires at nearly 100K, so I think I'll head that route first. Haven't had time to put the TPS on the meter, but I'm starting to think that isn't the issue.

TIMZTOY
09-10-2012, 05:47 PM
Vacuume leak !

bgoodheart
09-10-2012, 07:01 PM
Looking for one...

TIMZTOY
09-10-2012, 11:49 PM
There are about 4 good ways to check for vac leak
•starter fluid / brake clean / carb cleaner, with truck running and spray
•Vacuume gauge hooked up and watch the needle and #
•smoke the motor with a smoke machine and look for leaks
•watch short trim fuel #'s on scan tool

rover67
09-11-2012, 01:19 AM
Did you go through deep water in ouray? Make sure none of the plug wires are worn or have water under the boots.

TIMZTOY
09-11-2012, 10:05 PM
Did you go through deep water in ouray? Make sure none of the plug wires are worn or have water under the boots.

thats a good point. pull the plugs, but mostlly check the porclin for cracks and burn through

bgoodheart
09-12-2012, 07:08 AM
This thread describes exactly what my truck has been doing: http://wew.ttora.com/forum/showthread.php?t=13283

I have found no evidence of a vacuum leak, but I have not had the time to troubleshoot the rest thoroughly. I'd be fine with the TPS going bad, but I haven't gotten a CEL, which normally accompanies it. I'm really hoping it isn't the APPS, since the part, unlike the TPS, is only available as part of the complete TB (~$800).

No deep water, but I still need to pull the wires and plugs to inspect. Plugs are only a few thousand miles old, but wires are original.

bgoodheart
09-12-2012, 09:05 AM
Talked with Derek at Stevinson this morning. He couldn't find where the TPS is available as a separate piece for my truck, noting that I would need to buy the TB assembly. He showed four of those sold in the recent history on his computer. The low, low price for the TB? $1100 retail. Let's hope the troubleshooting points to something else :eek:

MountainGoat
09-12-2012, 10:56 AM
Talked with Derek at Stevinson this morning. He couldn't find where the TPS is available as a separate piece for my truck, noting that I would need to buy the TB assembly.

That doesn't sound right B.J. I am pretty sure that we had Joe at CTS here in Conifer replace the TPS on the :Princess:'s 2000 4Runner 3.4 last fall. I can dig through my receipts and let you know this afternoon. If you need it I can probably get you the part number.

When her truck first started stumbling it turned out to be coil packs going bad. We replaced one and shortly after that another went south, so we replaced them all. That was more of a stumble off idle. Many months later it developed a miss similar to what you describe. Pretty sure that was solved by replacing the TPS. Although it was throwing codes each time - misfire code on the coil packs and fuel trim code on the TPS problem. Also, as a data point, her truck has over 200K on it. :hill:

bgoodheart
09-12-2012, 05:12 PM
Thanks Dan, I think I may have found something. Though the 03-04 Tacos have a unique electronic throttle, I think the TPS is the same. Not sure on the 4Runner. I do know you can get the TPS for the 01-02 3.4 Taco. A friend with a shop looked it up and ordered what we think is the right part. Also realized I transposed lines on my service records, and didn't do plugs when I thought I did. Will pick up a set from Derek tomorrow.

bgoodheart
09-14-2012, 08:54 AM
Well, no dice on a replacement TPS. My P/N is 89452-35030. No replacement available, and Toyota specifies a new throttle body as the replacement. That's a bummer!

Changed the plugs and wires last night with Toyota parts. Cleaned the APPS and TPS connections while I was in there. I need to do some flat highway driving to see how things are behaving, but it feels like the stumble is still there.

bgoodheart
10-12-2012, 09:03 AM
So, just to close this one out... I did some more testing and the issue seemed to be with the APPS. Picked up a low-mileage throttle body from Oleg, and and things are back as they should be.