Continuation of the 3.0 issues, surging idle

[AxleIke]

I know I have another thread, but this is pretty specific, and could help someone in the future, as a surging idle seems to be a common issue with a multitude of solutions.

Some quick background in case the other thread hasn't been read.

This is on my brother's 95 4Runner.

It blew a head gasket, and was not covered under the recall. I replaced both.

I also replaced the timing belt, water pump, thermostat, and knock sensor wire.

I had the injectors cleaned, re-o-ringed, and flow balanced by witchhunter.

When it was all back together, it surges at idle. I set the timing (sorta, because of the rough idle, it was hard, but its close).

I then suspected a vacuum leak, but upon hooking up my vacuum gauge to numerous ports, I get 15 inHg on each port, though it surges with idle (expected).

Reading further online, I found that the TPS is a chronic issue, so I tested mine, and it was not acting properly. I replaced it, and set it using an Ohm meter and feeler gauges to the specified settings in the FSM.

More reading suggested a bad VSV on the EGR. I bypassed that, and the problem didn't change, at cold idle or at warm idle.

Its possible that there is air in the coolant lines still, but I'm fairly sure the symptoms wouldn't be this strong, as when I replaced my heater core on my 87, I had air in the lines for a while, but the stumble was very intermittent, and it went away after driving a bit.

The truck drives fine at higher RPM's. Just below 2500, it begins to surge, and it won't idle.

Any other ideas? I know a lot of folks have had this issue, hopefully someone has a trick that I haven't read about yet?

[AxleIke]

Also, I have checked for vacuum leaks with the spray bottle method, using water, as per BigMike from Marlin Crawler. No leaks found with that method either.

[thefatkid]

Lower the idle speed, sounds like your at high rpm fuel cut.

[hunter4runner]

my 95's rpm will move and bounce a lot (300 rpms) when air is in the coolent system. I know you did the tps but when this happens does unplugging it help?

[AxleIke]

Lower the idle speed, sounds like your at high rpm fuel cut.

Sorry, forgot to post up. I have moved the idle screw all the way in, which kills the motor, and all the way back out. I ended up setting it so the truck idles between 1100 and 800. But it still swings around a bunch.

[AxleIke]

my 95's rpm will move and bounce a lot (300 rpms) when air is in the coolent system. I know you did the tps but when this happens does unplugging it help?

Haven't tried unplugging it. I will let it sit idling on a hill for a bit, and see if I can get any more air out of the system.

Good to know. I'll give those things a try.

[AxleIke]

It finally threw a code. Code 52, knock sensor.

[thefatkid]

Whenever I pull the heads or manifolds I replace the knock sensor wire, if not the sensor also. The sensor not so often though. You didn't put any sealant or threadlocker on the threads did you?

[thefatkid]

Does the idle change with the vehicle just sitting without you touching it or is it after using the throttle?

[AxleIke]

Whenever I pull the heads or manifolds I replace the knock sensor wire, if not the sensor also. The sensor not so often though. You didn't put any sealant or threadlocker on the threads did you?

I replaced the knock sensor wire. I did not remove the knock sensor.

[AxleIke]

Does the idle change with the vehicle just sitting without you touching it or is it after using the throttle?

Both. When I first start it (cold) the engine idles low and rough. If I rev the motor, the RPMs will hold at 2k to 2200 or so, until it warms up. Then they drop.

This evening I noticed two more things. One, I opened the heater core and parked on an incline and let it idle for 10 minutes, to eliminate air. After bringing back down, I noticed the coolant was dirty again. Sort of brownish. Looks like a diluted form of what it was prior to the HG job.

However, it was not foamy, so I don't think oil is leaking back into coolant via the HG again, but rather that the heater core was filled with nasty coolant that just got recirculated. Or so I hope. Looks like its time for another flush.

It was not having quite as hard of a time idling after driving it around a bit. However, it was still having problems intermittently, including cutting in and out under light acceleration.

[AxleIke]

Oh, and one last thing. I did notice a bit of a "knock" for lack of a better word. Its not horrible, but its noticeable. Its sort of slow, like something going on with a single cylinder. I ran out of time (town home and quiet hours are at 8), and I wasn't able to isolate it with my stethoscope. Just another piece of the puzzle.

[gasbandit]

Make sure the throttle body is not carboned up causing the throttle blade to stick slightly open. The idle switch in the TPS will not close and you will an over advance timing curve at idle. Your adjusting the air bleed for idle speed right, not the stop screw for the throttle cable linkage? Also make sure your TPS is properly adjusted,timing belt is lined up, and distributor is stabbed correctly. Any of these can cause idle hunting issues. Are you able to set proper timing at idle? Does the knock sound mechanical or is it happening under load, some ping from the lack of a functioning knock sensor? Sounds like you may have a bad knock sensor but the sub-harness is almost always the issue. Oh and how hot did the truck get when the HG's let go?

[AxleIke]

It is somewhat fixed.

The idle is fixed, which turned out to be a timing problem. The engine was running so rough, that I tried to time it, but it was still way off. So, I thought I had installed the distributer wrong. I took it out, and moved it one tooth. I was also seeing two different "timing marks" with the light, which was because the pulley was rusty. After I realized that I could see two "marks" I shut down, and colored in the actual notch with black marker. Once starting again, it was plain as day that I was looking at the wrong mark.

I took out the bolt on the distributer, and advanced the timing enough that the engine ran smooth. Then, I could see the mark perfectly, and adjusted to 10degbtdc, with the short, and it moved to 8 when the short was pulled.

I then shut down, pulled the distributer, and put it back in where it was before. Re timed, and it idled great.

Unfortunately, I still have a knock sensor code, and there is a loud ticking noise, which is possibly from knocking, though I don't know. It sounds like loud valves, but I didn't change anything with the valves. It didn't make that noise before the head gaskets blew. Also, my brother says the truck feels more "gutless" than it did before. (I know, the 3.slow is always a dog, but it seems worse than usual for him.)

Anyway, I was hunting, so I haven't looked at it for a while. I'll get back to it after the holiday.

[Lysmachia]

That is odd there is a ticking, after you had a lot of that cleaned out and machined. I wonder if that ticking was there before but somehow gunk or something muffled it??

[AxleIke]

Maybe, but I doubt it. I think I will head down with a 6 pack and have Brian listen after work. See if we can't figure it out.