Hello,
I've got an '03 Sienna 3.0L with a low speed acceleration issue. After warm-up, there is a slight low speed hesitation while moving forward between 20 - 30 mph, ... it is very gentle yet can be felt, almost like a very slight bucking/jerking. I've replaced spark plugs, all spark coil packs, MAF sensor, PCV, air filter. I've run several bottles of Techtron. It only happens once earmed up and between 20 -30 mph. Thanks for your help.
buying potluck parts doesn't get you closer to finding the problem. It just makes you poorer.
I would start with a full diagnostic scan with a professional tool. Have one done at your local parts store.
Thanks for your answer. The van hasn't displayed any trouble codes. I will get a scan done as you have suggested.
you mean it hasn't displayed a warning light, right? That doesn't mean there aren't stored faults.
No check engine light. I wasn't aware that the scan tool would sniff out an issue without the check engine light coming on. I will run a scan and check.
the tool doesn't sniff out underlying causes. Humans still have to do that part. But it does access the fault conditions which the vehicle's computer has detected, and can read live data.
Last month the van was putting up exhaust error codes. I replaced upstream and downstream O2 sensors and added a can of CAT cleaner. I reset the codes and they did not return.
The hesitation/studdering is getting worse after warm up. I'm going to put the scanner on the van Saturday morning. I hope it shows something.
Ran the scan tool, no stored errors. Stumped:(
Ran the scan tool, no stored errors. Stumped:(
Looking for codes is just the bare beginning of the diagnostic process. Have you analyzed live data for problems? Checked all modules for errors? That's what a "full diagnostic scan" entails.
I also took the van to the Toyota Dealership Service and they ran a diagnostic scan that cost me almost $400. No trouble found. What is next? I'm out of ideas.
Two things are known
1) the issue occurs only after the van has warmed-up.
2) the issue irst occurred after the van sent a check engine light about the catalytic converter. I had replaced the upstream and downstream O2 sensors and ran two cans of catalytic cleaner. The error code did not return and the van passed Virginia emissions test.