My 161k miles 4R has seen a lot of hesitation from idle lately. So far bad items on the engine include finding the ignition was bad (ignitor & coil), and checking vacuum lines. Also did timing belt 2 weeks ago. Each step brings a smoother idle but haven't fixed the hesitation.

Received an code 71 from my computer the other day
so I went through the manual's procedures on checking the EGR valve operation, the EGR modulator, and the VSV associated with the EGR. The one thing that bugs me is the manual does not give a set value (or range) for the EGR gas temp sensor. There's mention of it being tested, but nowhere in the manual does it state what the range is, or a graph of temp vs. resistance. So I just measured across the terminals and had 51k at normal warmed up engine temperature. Unsure if this is a good sensor or not(?) But at the $100+ asking price for a new one, I'll do a lot of research before getting one. If I get another code 71, then I probably should consider it as the rest of the EGR system looks to be working good.

Anyone know what the normal range is for the EGR gas temp sensor?

Anything else I should hunt down for hesitation?
I'll be doing the gas filter this weekend and test the O2 sensor. The EGR gas temp sensor was cleaned and reinstalled - just to make sure it wasn't carbon causing misreads.

- AmigoWA

 

I just had this same problem a few months ago and my buddy had the same thing happen just a week ago, in both cases it turned out to be the EGR Vacuum Modulator. Got a new one, cleaned all the vacuum lines and it runs great and no more check engine light.

 

Just in case someone searches for this, here is some info.

Here is what the manual says for the EGR temp sensor:
69 – 89 Kohms @ 50*C (122*F)
11 – 15 Kohms @ 100*C (212*F)
2 – 4 Kohms @ 150*C (302*F)

I also had the Error code 71, but I am failing SMOG now so I am researching this.

I did find out I had a bad EGR VSV (always off) and the vacuum modulator did not have resistance to air pressure when the engine is on and you blow air into port Q with ports P and R blocked. I swapped in the vacuum modulator and EGR VSV from my 92 4Runner and I have not had the Error code 71 ever since.