4runner w/VN V6 idle/throttle issues

[Wooks]

Hi, I'm looking for some help with a problem I've been having.

I Had issues with my VN V6 fitted 4runner, It started to splutter and miss under load. I pulled the intake, rockers and crank case off suspecting a bent push rod, loose rocker or similar.

Swapped out the timing chain as it was getting pretty slack and the tensioner was very worn.
I discovered the lifters were all gummed up and didn't spring like they're supposed to, so replaced those.
Cleaned the whole thing, molly greased the machined surfaces and re assembled.
Took the injectors out and had them professionally done as they were mucked and not spraying right.
changed the oil, new filters (air, fuel and oil), reset the ECU and crossed my fingers.

It now idles ok (but fast) from a cold start and runs significantly quieter untill it starts to get to temprature, it then begins to splutter, miss and eventually stalls.

The current theory is that the Idle Air Control (IAC) valve has become mucked/filled with something during the cleaning process and I'll pull it out on friday and give it an inspect/good clean and cross my fingers again.

So the question is, has anyone had a similar issue if so how did you resolve it. Have I overlooked something that also causes these kind of problems.

Thanks

Wooks

[PGS 4WD]

Idle speed motor won't cause a splutter and miss, certainly it could cause a fast idle, if the TPS is faulty then it may not identify idle throttle opening and will not slow down. The miss and splutter is when warm and under load? I'd be considering a faulty coil or DFI. Generally if lifters are pumping up and causing a miss it is relative to rpm not load (unless boosted) and worse when the oil is cold/thicker, It is common on LPG engines for the valves to recede causing weak spring pressure and lifter pump up, recifying the heads rectifies this it is not a lifter fault. You should also look at the codes and check the MAP voltage, if the miss under load is due to a faulty MAP or MAP hose blocked with oil scum the problem is generally worse cold not hot.

Cheers

Joel

[404HZS]

Check the crank sensor

Common fault on the commo motors

[Struth]

Your fast idle can be caused by the IAC and as I found recently it can also be caused by a slightly tensioned throttle cable. Mine was ok as far as the throttle returning to closed but just that smidge too tight so it would not return to closed fast enough under normal driving conditions, so the TPS didn't see a proper closed throttle position.

I relaxed the cable and mine now returns to a normal idle when I pull up within a second or two.

Don't know about the miss though, so many things can cause that, but in my experience a lot of the time it can be traced to the ignition system, normally the secondary system but can be on the primary as well. Have you had your ignition module tested?

Cheers

[Wooks]

Thanks for the suggestions guys.

IAC valve and seat black with muck, same with the in and out ports. Cleaning those now.

Found a MAP line that would connect to an auto gearbox that had been plugged up for use in the manual 4runner.
Plug was missing. I think this has cause a vac leak and the resulting splutter/stalling.

Hopefully will get it all back together wednesday, will post results.

cheers

[pricey bandit]

If it doesn't already have one, fitting a ECM light is the fastest way to know if its got any fault codes coming up. Your problem could even be the coolant sensor.

[highersurf]

the miss splutter and stall when warm could be a faulty voltage signal to the crank angle sensor from the ecu. done it to mine 4 wks ago i ended up having a new ecu module for it put in. ran like a dream after that.

[Wooks]

Yeah ECU is looking like a good candidate, do you mind if I ask you what it cost?
and was there any manual/auto related issues? most vn's are autos and mine is a manual

cheers

[highersurf]

off the top of my head the unit cost 280 plus labour cause i was stuck 3000 km from home. but its was a brand new item try getting a ecu from the wreckers out of the commodore you need and try that or borrow a mates one if you can. didnt have any auto issues as the ecu on vn's is stand alone setup and the t700 auto is one was the last used without a computer. shouldn't make any difference weather its auto or manual. i wanted to put a manual in but was already setup for auto.