Hey all, driving a friend's spare / beater '01 EX while he's out of town. I notice these symptoms: once the engine is warmed up, pressing the accelerator gently to medium does not increase the RPM. It's the same accelerating from a stop, or at any speed. Doesn't seem as bad when engine is cold.
What it does do: while I am pressing the pedal, RPMs stay at 800 with no response. Then it'll suddenly "catch up" to pedal position, jump to 2k and accelerate. Then drops down to 800 again...even though I'm still pushing the pedal...however, if I push the pedal hard / far, it will track and accelerate fast as it should (to 2k or 3k).
I read some other threads and initially suspected a sticky / dirty throttle, or throttle cable. But I can move the throttle fairly easily by hand, and the cable movement when pressing the pedal (engine off) seems smooth with no binding.
Also of note, but maybe unrelated - the TCS light comes on and stays on with similar timing as this starting to happen. CEL is on, haven't taken it to get the codes checked. It does idle a bit rough, too, when stopped - to me it seems low, like it might die (although it hasn't). But it *doesn't* surge while idling.
Any clues with these specific symptoms? Thanks in advance!
Almost sounds like a timing problem, perhaps a worn or slipped timing belt.
But, just a wild guess.
Checking the codes could be a big help. I believe places like Auto Zone will do it for free.
Buffalo4
One simple way to take the wheel sensor out of the situation would be to see how the engine performs when stopped, in Park and also in Drive (stopped, with the brakes on). I'm pretty sure the wheel sensor will not be causing a problem there, and you can see if the RPMs / throttle cable / etc. all behave as smoothly as they should.
If the engine is good in those tests, but bad when driving, you will probably have moved suspicion away from the engine / throttle, and towards the transmission / wheel sensor / etc.
The comment on lack of surging while idling suggests that you've thought about the IACV. And I'll say that even though a lot of aspects of this problem do NOT sound like IACV, it might be wise to keep that in mind as you go.
Don’t discount John’s suggestion. I’ve seen some very odd behavior when a wheel sensors out.
Now I do not understand the timing belt comment. That seems to be unrelated. I would verify simple things first. Check oil level and more importantly the transmission fluid. If low you can get odd acceleration.
Back to the wheel sensor. The sensor will tell the computer to back off if it thinks there is slipping. That very well could be your root cause.
the throttle body has a computer module right on it. it controls the throttle electronically. if it goes bad I did see one seller on ebay with a replacement module but normally you have to replace the whole throttle body. it was like $20-30 on ebay I think. that could be your problem if nothing else works
The TCS light is "traction control system." If a wheel speed sensor is acting up and the computer thinks a wheel is stopping or skidding it's going to reduce the power and possibly even apply brake to other wheels. Even though it's a mechanical throttle it still has a computer that takes the inputs from everything, including throttle position sensor and wheel speed sensors, and decides what to do. If it thinks there is a skid happening it's not going to let you apply power. I've seen wheel speed sensors dropping out and causing issues just like this.
That's where I'd start. If the engine runs fine otherwise, this will have nothing to do with engine timing. You need to check for codes but Autozone isn't going to cut it. You need a scan tool that can read the ABS system, as well.
There are many situations where the computer will override the gas pedal/throttle mechanism, not by rolling back the mechanism (not possible) but by modifying other engine control parameters to reduce engine power output.
Thanks for all the thoughts y'all! I finally got the codes checked (this is a work vehicle to haul used laundry machines) and there's a bunch...
P0171 fuel metering too lean
P0131 H02S-11 (bank 1 sensor 1) circuit low input
P0132 H02S (B1) S1 circuit high voltage
P0401 EGR insufficient flow detected
P1739 3rd pressure switch failure
P0170 fuel metering B1 out of spec
I also checked the oil, it was at the fill line...er...hole so I added 1/3 of a quart which now I'm realizing is probably too little for the 4.65 quart capacity. (I'm so new to auto care, mostly have been riding a bicycle for the past decade). Will add more today.
Opinions? EGR valve, can I clean it? Replace? O2 sensor also? I unfortunately don't have maintenance history, might be able to glean some info when my buddy is back in town. I am considering purchasing the vehicle from him, but it obviously depends heavily on what needs done.
I imagine the EGR issue has something to do with the fuel metering error codes, but it also seems like I should try checking the wiring for the 02 sensors (at a minimum). Any other advice is appreciated.
John, thank you. After careful re-reading of this thread, I'm going to try the suggestions of putting the car in park (or drive with the brakes on) once the problem starts, and seeing if it doesn't happen. Will report back.
Update: the problem persists regardless of whether the transmission is engaged (I drove till problem started, put car in park, tried applying accelerator and the engine doesn't rev, then spikes to 2k, then drops and almost dies. Same in drive with brakes on).
In addition, putting the van in park, turning the engine off and then on again will "reset" the problem. It only occurs after the car has been driven for 3-5 minutes.
I'm going to try cleaning out the throttle body, since that seems easy enough and would be good to cross off as a possible cause. I'm very open to thoughts on what else to try....!
I would start by inspecting the spark plugs and find out when they were last replaced. That alone can give you an idea of the running condition, excess carbon build up could mean to much fuel equals possible o2 problem, white ash build up they are running hot equals probable egr system issue. Furthermore one main concern is your p0730 code tell tail sign of the infamous transmission problems this generation experienced, easy 2500 to 3500 fix.
I found the Throttle position sensor on ebay. this one has the best reviews. it looks exactly like the rest except the metal bands that hold the bolts together look a little different and the bolts look different so I think it is actually not manufacturered exactly the same. if you get the other ones some reviews say the voltage is unstable for the 1st gear shift/ fluctuating voltage due to poor quality so if you do get the other ones instead of this one don't freak out if you get arractic shifts/ voltage fluctuation, just buy another one and it might be fixed with a good one. like I said this might be made different from those https://www.ebay.com/itm/173319879242 I'm gonna get this as a backup, it's only $12 you might as well swap it out just to test it, TPS do require you adjust it before it works right though. probably google or youtube it
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