Tin Soldier

I finally got the new engine installed (22RE 1994 stage 1 performance). It fired up nicely but is surging from 800 rpm to 2500 rpm or so. I figure its a problem with the TPS, but I'm not quite sure. I put the TPS in the exact position when I rebuilt the intake. I did not mess with the distributor, assuming that the mechanic put it in the right position for gross adjustment and startup. Timing will happen later, need smooth idle.

I have to believe the surging is a common issue, so maybe someone here can point me in the right direction. I plan to slowly go through the TPS adjustment process on 22RE Perf website, but I'd like to know if this is a simple issue with new engines.

Thanks

Odin

Quite common, in fact so much so a search world have likely revealed hundreds on the same surging idle subject. Since it's a fresh install I'm going with the most likely and one of the most easy to fit.

If there's a large air pocket trapped in the coolant system it will expose the coolant temperature sensor and sent the ECU the wrong information. The result is a surging idle. The process......



Make sure the engine is very cool to dead cold so you won't get injured by coolant if there's any pressure in the system when removing the radiator cap.

1. Turn the heaters blower fan to off!
Slide the heaters temperature control to full hot
(only step one so you won't forget)



2. Fill the coolant overflow bottle to the full mark.



3. Jack up the front end as high as you can get it and place it on jack stands.
The reason for this is that air always wants to travel upwards and by placing the radiator up as high as you can it allows the air to escape easier.
No jack or jack stands, drive to the steepest incline or hill and proceed.



4. Remove the radiator cap and start the engine.
4a. Check coolant level.
If coolant is low fill it to about 1/2 inch below the start of the filler neck.
You'll be adding more so having it right up at the top isn't important and can keep the splashing down and conserve coolant.



5. From inside the truck wait till the engine temperature is allowed to get off of the cold mark on the gauge.
5a. Have someone hold the throttle open for you at 2500-3000 while you observe what the coolant is doing.
If you're alone go back under the hood and hold the throttle open by hand until the engine is about 2500-3000 rpm.
Hold the throttle open until you finally see water start rushing about in the radiator a few times.
That's the thermostat opening and allowing the flow of coolant.



6. When the thermostat opens you'll likely see the coolant level drop because air is being purged from the system.
Refill the radiator as described in step 4a. (1/2 inch below bla bla bla)



7. Staying clear of the fan squeeze the upper radiator hose at it's tight bends while holding the throttle open.
It will help to get any trapped air moving along to the radiator where it will be purged from the system.



8. Repeat steps 5a-7 for roughly 20+ minutes always refilling if it needs it.
Keep an eye on the temperature gauge and don't let the engine go into the danger zone.



9. While the engine is running fill the coolant to the top of the filler neck and screw the radiator cap back on.



10. The next few times you go for drives always pop the hood and check for leaking hoses, leaking radiator, and make sure the overflow bottle is still at the full mark.
If any leaks are found fix them ASAP.
Try to find dry spots to park over after a drive. When you're about to get back in look at the ground under your truck for leaks.
It's important not to have any leaks in the cooling system so it can regulate the temperatures correctly and if enough air gets into the system you'll be back to having a surging idle.

Odin

Some other causes:
You mentioned you haven't checked the timing.
On mine when I started advancing the timing I eventually got surging along with it.
When I backed it down to got rid of the surge.

TPS setting
Vacuum leak
High idle speed

Taken from toyotanation's FAQ section
Idle surging:
This is also discussed in the FAQ, but I put it in here because it's one of the most common, if not the most common oddity people run into when they buy one of these trucks, because either the previous owner or the new owner has messed with the idle speed. The idle speed bouncing/surging up and down is fixed 90% of the time by setting the idle speed down. If the idle is too high, the computer will engage/disengage a fuel cut when you push the brakes, causing the idle to bounce. With the engine fully warm it should idle at EDIT: 750 rpm +/-50. Too much lower you will be bogging, too much higher your idle will start to bounce. If by chance this doesn't fix the idle surging, check for vacuum leaks.


.

Odin

Also since FIPG or RTV is always an issue in the coolant system have a look at this.

Tin Soldier

Yeah, Its easy to get lazy on the searching when everyone is so helpful. This is great. I am the PO, I have owned this truck from the day I bought it new in 94. There has been very little messing around with TPS, or timing or anything else for that matter. The distributor was just placed on 1TDC by the mechanic who rebuilt the engine. Presumably that's enough to keep the idle from surging, we'll see.

Coolant level sounds like its the most likely cause right now for the surging idle. I'll do as you have pointed out and get the air out.

BTW - 22RE Performance has a good write up on new engine startup. Been following that, but no info on surging idle, but certainly a good bit on getting your coolant full and filling the whole system, heater core included,...

Excellent info. Thanks very much.

Odin

Don't trust that until you've seen it.

I think you were adjusting the correct screw for idle but just to make sure the image circled in red is where you adjust the idle speed.
Some people make the mistake of adjusting the very small Idle Stop Screw (down further on the throttle body) which throws the TPS adjustment off. I found mine way off a couple days ago.

Tin Soldier

Anyone know if there is a way to mimic the proper voltage on the temp sending unit? I'm pretty darn sure I have all the air out of the coolant system. I ran the engine with the ridiculous surging for 15 to 20 minutes, nice way to break in the new cam shaft, right, at from 800 to 2500 rpm every few seconds? Hopefully that didn't ruin it.

If I can mimic a decent temp in the engine and the thing still surges, then its something else, like TPS, or one of the umpteen vacuum lines.

Also, can codes tell me what the problem is?

Tin Soldier

I removed the throttle body because I couldn't get the surging to cease. I tested the temp sensor and the cold start sensor, all good, I then set the throttle stop appropriately and removed the TPS. I realized that I installed the TPS wrong when I rebuild the air intake system. I placed it on the other side of the tabs on the throttle plate, so at low throttle the plate still didn't close. Anyway, I tested it and placed in right and now no surging. Well not serious surging. I suspect the temp sensor surging is more like what I experienced until the thermo opened. Tested that also. The surge is light and almost not noticeable, but now its gone after warming engine. Set at 750 rpm and now i need to get Power Steering working. Frothy.