MXShea985

I've searched for the last few weeks and haven't found any answers for my problem with this yet.
90 V6 4WD 4Runner- just did HG and valve job, new plugs, wires, cap, rotor, fuel filter, coolant temp sensor and 02 sensor. Swapped VAFM with the one off my truck I know works, wasn't that. It's timed, the cat is new, t-stat is new, fuel pump is good, injectors are good...
It runs great when it's cold but as soon as it warms up it starts running bad at idle. I thought maybe the fast idle when cold was masking the problem, but that wasn't the case. It runs perfectly normal until it reaches operating temp.
I put in the new coolant sensor last week and it didn't change at all.
No CEL no codes
Any ideas? Thanks guys

Kiroshu

did you do the valve job properly? Did you adjust them hot? They have to be adjusted hot if you did them cold i'd say thats an issue too. Prob EGR issue try changing or removing it and see if prob goes away. If its not that then its a temp issue with the computer. It might not be reading proper temp when hot. Possible the computer still thinks its cold when it warms up. If you had a scanner you could hook it up and see if the coolant temp is acctaully showing proper temp. Hows compression? It could be your mass air flow. Did you get the proper one for the truck?

TNRabbit

Most of the time when you have a good run when cold that gets bad when warm, it's masked by the rich mixture when it's cold. When the mixture leans out, your issue shows up. I've found this is usually a vacuum leak. Run an UNLIT MAPP gas or propane torch around ALL the hoses, to include the intake hose, to check for a crack/leak (you'll know when it idles up slightly). They can be incredibly difficult to find by just looking.

MXShea985

Thanks for the replies guys. I forgot to mention that for the first couple hundred miles after the HG/valve job, this wasn't an issue and it was running perfect so I don't think it's the valves. Compression is good and both the 89 truck and 90 4Runner are 3.0's so the AFM is the same.
One thing I noticed is that while it's cold and running good, there's vacuum to the EGR and when it's warmed up and running rough, there is no vacuum there anymore. I don't know if that's normal or not but it's just something I noticed when I was poking around in there.
I will get a hold of a torch and (unlit) check for vacuum leaks. I'll report back with findings.
Thanks guys!

Kiroshu

ok an EGR valve is not supose to open when the engine is cold or at idle or at full throttle. only during driving range or other RPMS other than idle and WOT(Wide Open Throttle). If the EGR opens during the wrong times it will cause issue. Since you have a head job done its possible one of techs crossed or messed up a vaccum line. I think your simplest thing now is to trace vac lines and see if they are all connected and in the right areas and not leaking.

MXShea985

Just finished testing all vacuum lines, intake and EGR stuff with propane and nothing happened.
I read on here that if your TPS is out of adjustment and making it idle bad, you can unplug it while it's idling bad and if it fixes it, you need to adjust it. I unplugged mine while it was idling bad and it was still bad, just a little faster. Does this rule that out? I've heard that it could take up to 70 complete warm up/cool down cycles for the computer to recognize the new coolant temp sensor. I figured it would have immediately fixed it if it was the culprit. Does anyone have experience with this? Also I sent the injectors off and had them blueprinted so those are good. It ran good for a couple hundred miles, cold and hot, so I don't think there are vacuum lines crossed.
What should I do next? I'm going crazy!

MXShea985

Searching the internet and generally googling my problem, I saw some people saying to disconnect the 02 sensor. Supposedly this forces it into closed loop? Anyway, I tried it and no difference.
The RPMs drop under 900 when it's just about warmed up, but not at full operating temp. At this point it still runs smooth...once it gets to that hottest point though it runs terrible.
I appreciate any and all help from you guys. I had an account years ago and learned a lot from you guys. I guess inactivity shut it off..but I'm back! Thanks again...

MXShea985

Still no CEL on but I pulled a code off finally. 41...this is TPS signal, correct?
Does this mean it needs to be adjusted or should it just be replaced?
I'm also starting to fear the problem is beyond the TPS.
The clips that hold the injector wires onto the injectors are broken off and the harnesses slide on and off without needing to press the release clip.
With the engine running and warm, I started pulling wires one at a time off the distributor cap. All of them made a difference except #1...no change. With the engine cold, there was a difference when pulling #1.
Could this mean that the cold start injector is giving it enough to go when cold but once it shuts off, that cylinder isn't firing because the #1 injector wire slipped off?
One slipped off before but it was on the other side where you can see and reach the injector wires and I found it quickly.

MXShea985

Vacuum leak under plenum causing rough idle and brake problems turned out to be injector.

jbcleere

Having the same problem, What and where is the plenum?