1999 SR5 4x4 5VZ-FE idling low when warmed up
04-01-2010, 01:54 PM
#44
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Thread Starter
Pendrag--listen-- i keep hearing alot of REPLACING and CLEANING--but no TESTING---TEST TEST TEST--guess work wont solve the problem.
OK--think about it like this--the MAF(also air temp sensor) measures the volume of air coming in--TPS tells the engine where the throttle is and what you are trying to do. Together, they calculate engine load and relay that information to everthing else. So, at idle your TPS may be telling it one thing but doing another because it is old and tired--considering all the other stuffs arent broken (That goes back to testing)
You will never really become good at cars unless you learn the basics of problem solving and how to test for those problems!!!
OK--think about it like this--the MAF(also air temp sensor) measures the volume of air coming in--TPS tells the engine where the throttle is and what you are trying to do. Together, they calculate engine load and relay that information to everthing else. So, at idle your TPS may be telling it one thing but doing another because it is old and tired--considering all the other stuffs arent broken (That goes back to testing)
You will never really become good at cars unless you learn the basics of problem solving and how to test for those problems!!!
I'm absolutely with you. I inspected the MAF resistance (see top image below) and I didn't get any needle movement on my ohm meter from the MAF in the poorly-idling (5VZ-FE) truck. I tested from the prongs on the connector, as shown in the Haynes manual, not from beside them as shown in this photo, though.
I next tested the MAF in the other truck (2RZ-FE), and got a resistance of about 3000 ohms - probably fine for a sensor with 157k on it. That should indicate that I was performing the test correctly on both sensors. So am I correct in thinking that NOW the next thing to do is get a new MAF?
If so, what's the best source for a new Denso MAF?
I haven't done the meter operation test (lower image) - is there a reason to with the results of the resistance test?
Last edited by pendrag; 04-01-2010 at 11:33 PM.
04-02-2010, 08:43 AM
#46
Registered User
is there any body in the area you know with the same engine???
Easiest way I know to answer that question is to swap the part !!!!
if your part on the 5vz is the same as the part in the 3vz swap it out, then start it if it fixes the issue, buy a new one if the part is different and you know some one with the same engine, ask them to allow you to swap the part for ten minutes or so, this will answer your question the fastest and easiest!!!
Easiest way I know to answer that question is to swap the part !!!!
if your part on the 5vz is the same as the part in the 3vz swap it out, then start it if it fixes the issue, buy a new one if the part is different and you know some one with the same engine, ask them to allow you to swap the part for ten minutes or so, this will answer your question the fastest and easiest!!!
Last edited by eddieleephd; 04-02-2010 at 08:44 AM. Reason: punctuation
04-02-2010, 09:13 AM
#47
Registered User
Thread Starter
I was hoping that the 3RZ and 5VZ had the same part, but unfortunately they don't. The housing is a little different. Thought I had a good idea there 
I'll test it with voltage applied and post it when I do.
I'll test it with voltage applied and post it when I do.
04-02-2010, 01:49 PM
#49
Registered User
Thread Starter
My brother and I put thin sewing pins through the MAF wires as indicated in the diagram above, and connected them to a multimeter. With electrical power to the MAF, my brother blew into the MAF and we observed the voltage fluctuating.
We confirmed that the MAF's resistance in E2 and THA (the second from the left and center pins on the MAF itself) have infinite resistance (a broken circuit?)
I'm a little confused about these results.
I realise that there are two approaches to probing - one is what we did and one involves slipping the pin alongside the wire going into the connector. I kind of wish we'd done the latter (after having read more about it after the fact), but as thin as the pins were, I don't think we did any significant damage to the wiring, and the insulation basically self-sealed. I mis-read the diagram and didn't realize that we could do the latter approach.
We confirmed that the MAF's resistance in E2 and THA (the second from the left and center pins on the MAF itself) have infinite resistance (a broken circuit?)
I'm a little confused about these results.
I realise that there are two approaches to probing - one is what we did and one involves slipping the pin alongside the wire going into the connector. I kind of wish we'd done the latter (after having read more about it after the fact), but as thin as the pins were, I don't think we did any significant damage to the wiring, and the insulation basically self-sealed. I mis-read the diagram and didn't realize that we could do the latter approach.
Last edited by pendrag; 04-02-2010 at 01:55 PM.
04-08-2010, 02:56 PM
#50
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04-10-2010, 03:18 AM
#51
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Just fixed exact same issue. I replaced, cleaned, troubleshooted EVERYTHING...then ran two cans of fuel injector cleaner in the tank. I didn't notice a difference until about 90% thru the first tank. It began to get sporatic, so I ran another can of FI cleaner...now She purrrrrrrrsss like a kitten now.
04-14-2010, 10:33 AM
#52
Registered User
Thread Starter
Okay, so as you'll recall, I tested the MAF resistance (appeared to be bad) and the MAF functioning (appeared to be ok), leading me to suspect a bad MAF sensor. I replaced it today with a remanufactured one from autozone, but I had no improvement in the low idling issue. Guess mine was ok after all. I went back and did the MAF resistance test as shown in the diagram on pg 2 of this thread on the new one, and also got infinite resistance on the circuit I was supposed to test. Maybe the diagram is incorrect?
I went back to the engine and unplugged the TPS while it was running at operating temp, and got little to no change to the idling issue. Makes me suspect the TPS now. I'm going to see if they'll let me return the MAF and pick up a throttle position sensor ($50) and see if that fixes things. I'm a little fed up with this issue.
I went back to the engine and unplugged the TPS while it was running at operating temp, and got little to no change to the idling issue. Makes me suspect the TPS now. I'm going to see if they'll let me return the MAF and pick up a throttle position sensor ($50) and see if that fixes things. I'm a little fed up with this issue.
Last edited by pendrag; 04-14-2010 at 10:43 AM.
04-14-2010, 04:21 PM
#55
Registered User
Thread Starter
This is the 3.4L / 6 cyl truck.
After seeing no change with the new MAF, I replaced it with the old one. This afternoon I put on a new TPS, but without improvement, unfortunately. I'm out of ideas.
After seeing no change with the new MAF, I replaced it with the old one. This afternoon I put on a new TPS, but without improvement, unfortunately. I'm out of ideas.
04-15-2010, 06:32 AM
#57
Registered User
Pendrag--if i were out in Georgia i would come out and give you a hand (not the clapping type) 
.
Have you checked the harness for continuity?--any broken wires anywhere?--wish you had some scan equipment so we could see what was going on with the other sensors.
I know times are tough--but it makes things a lot easier and cost alot less in the long run...
I am sorry hear you are having so many issues--Tell you what--I'll go to the bar for you......
.Have you checked the harness for continuity?--any broken wires anywhere?--wish you had some scan equipment so we could see what was going on with the other sensors.
I know times are tough--but it makes things a lot easier and cost alot less in the long run...
I am sorry hear you are having so many issues--Tell you what--I'll go to the bar for you......
04-15-2010, 12:39 PM
#58
Registered User
Thread Starter
No, I haven't done the coolant temperature sensor. How does it affect idling speed? I'm not saying it doesn't; I'm just curious.
I replaced the plugs with Denso K16TR11's as suggested in the haynes manual.
04-15-2010, 01:40 PM
#59
Registered User
the Ecm looks at the signal from the temp sensor and a few other things to decide how much fuel to give, Usually the temp sensor is attributed to a high idle when warm but can also do the opposite saying it is hot.
the only other real suggestion I could have was from cpate
Just fixed exact same issue. I replaced, cleaned, troubleshooted EVERYTHING...then ran two cans of fuel injector cleaner in the tank. I didn't notice a difference until about 90% thru the first tank. It began to get sporatic, so I ran another can of FI cleaner...now She purrrrrrrrsss like a kitten now.
I always feel that cheaper parts are where to start beings they can never hurt but only help!! and that would be the coolant temp sensor!!
It is really hard to diagnose these kind of issues and know what to replace,
could be simply bad flow on the injectors which FI cleaner would help with if not cure.
and it could be a bad connection on the coil... with out and codes to work from it is really hard to tell which is why I suggested burping the IAC valve...
improper reading at the front o2 sensor or at the maf could be culprits along with fuel pressure but no code means a lot of circles to run in and some times even with a code we get it wrong! TEST TEST is the biggest part of it and as you mentioned some times parts test faulty but are actually ok, or other times there are multiple parts contributing to the same issue...
so This is part of the reason that I pm'd you my number figuring we could meet some where and easily swap parts till we found a cure I do have an old engine sitting in the yard and 3 coils in my tool box so those are easy and that is the easy cheap way...
the only other real suggestion I could have was from cpate
Just fixed exact same issue. I replaced, cleaned, troubleshooted EVERYTHING...then ran two cans of fuel injector cleaner in the tank. I didn't notice a difference until about 90% thru the first tank. It began to get sporatic, so I ran another can of FI cleaner...now She purrrrrrrrsss like a kitten now.
I always feel that cheaper parts are where to start beings they can never hurt but only help!! and that would be the coolant temp sensor!!
It is really hard to diagnose these kind of issues and know what to replace,
could be simply bad flow on the injectors which FI cleaner would help with if not cure.
and it could be a bad connection on the coil... with out and codes to work from it is really hard to tell which is why I suggested burping the IAC valve...
improper reading at the front o2 sensor or at the maf could be culprits along with fuel pressure but no code means a lot of circles to run in and some times even with a code we get it wrong! TEST TEST is the biggest part of it and as you mentioned some times parts test faulty but are actually ok, or other times there are multiple parts contributing to the same issue...
so This is part of the reason that I pm'd you my number figuring we could meet some where and easily swap parts till we found a cure I do have an old engine sitting in the yard and 3 coils in my tool box so those are easy and that is the easy cheap way...
