I’m at a loss, I’ve been scouring the internet and forums the past 2 months working on this truck I inherited from my grandpa after his passing late last year.
Truck drives great as normal but the idle has always been lumpy once it warms up. I’ve replaced all ignition parts minus a new dizzy, found the exhaust was pinched far back so I chopped it off (about a foot), brand new denzo o2 sensors (both), removed TB and thoroughly cleaned it and the IACV as well as removed TPS and verified it work mechanically and reset and adjusted in spec, sprayed around engine bay and no leaks found, jumpered and timed to 5*. Ive got a new intake boot today I need to throw on it since the old one was barely held together with tape.

I don’t know what else to do. Truck idles great and runs great even but if I rev the engine a bit in gear or not, it stumbles heavily when it returns to idle and mellows out after ten seconds or so, I figured the tps wasn’t snapping back to idle position since it goes away shortly. Only thing I haven’t checked is the EGR as I don’t have a vacuum hand pump to check it, grandpa had it smog her mid last year and passed flying colors so figured egr is ok.

Any ideas that I’ve missed? IACV cleaned, TPS checks out, ignition all new, TB cleaned, o2 sensors replaced ($$$), timing is good. Thanks in advance!

 

Might want to double check that TPS. They are a finicky mess on these engines. Sounds like maybe the TPS is causing issues when the engine goes into closed loop. A slightly out of tune TPS will seem to be working fine when the engine is cold and in open loop. I had the same thing going on, and eventually had to have a tech do the TPS and it was fine ever since.

Not saying your issue is TPS related, but could be 100% from my experience with the same symptoms. Would be the first spot to make sure is OK before chasing other gremlins.

 

I like first posts like this. Enough info, lots of self-diagnostics beforehand, and detailed descriptions. None of the "Hi i have a truk it s broked" tomfoolery. Welcome to Yotatech, I hope we can help you out!

Now then, my 2 cents are: check the CSI? If it's clogged open, might be dumping just enough fuel in? Not sure, it's been a hot minute since I've had my 22R-EC.

 

Have you checked out the AFM at all? I had an issue with my truck about 12 years ago and it would start and idle fine but would fall on its face and stumble when I drove it. It turned out to be the AFM having a dead spot in it and the computer didnt know what was going on. I replaced it with a used one from a junkyard and no more issues.

 

to be honest, I’m nowhere near certain I did the tps correct. I had it off the car when I checked it and slight movements did change ohm values but the one that’s supposed to be around 9k was up at 24.6 so I tried a second (admittedly cheaper and older) multimeter and it showed ok. I’ll give it a second check, thank you!

Thanks man always nervous about getting flamed first post in forums and it’s been a long while since I’ve posted in one lol. CSI was one of my first thoughts as well as all injectors in general, the thought of it being stuck open even slightly causing the deceleration enrichment to be to heavy and causing the engine to stumble when coming to a rest. What would be a good way to test it? Just unplugging wouldn’t work, right? I’d need to get a new crush washer to remove it and see if it’s spitting? Thanks again dude!

I have not. I know MAFs are super finicky and fragile so I’ve been avoiding it, tbh I’m not even sure how to check it minus pulling it off and spraying maf cleaner in there lol. I might go and grab a new tps today just to be sure it’s ok and grab some maf cleaner. Which Supra has the maf we can “upgrade” with? Just in case I have to change it might as well upgrade it, should be smog legal right? (Damn Commiefornia)
Thank you for the suggestion bud!

 

No problem!
I know there's a whole process in the FSM for testing it out, I think it goes something like this: Remove the CSI, spray something (low pressure shop air? cleaner? I need to look that up) into the CSI inlet and check for leaks at the outlet. Then apply 12v across the CSI terminals and check again, seeing if you get stuff coming out this time.

Removing the injector will require some new gaskets, but it shouldn't be that much. This may also get you a chance to clean it if it needs it.

 

Sounds good I’ll order up some gaskets and give it a cleaning. Ive actually wanted to check it because first start of the day takes a solid second of cranking to start but when it’s warm, it fires up instantly.

 

These trucks dont have the usual MAFs, they have AFMs. Does the same job but in different ways.
The MAF has a hot wire that is cooled by incoming air and the computer reads the wire for air flow. It can get dirty and thats why it needs cleaned every so often.
The AFM has a door that flaps open as air is drawn into the intake system. That door has an arm that drags across a circuit board and where it is on the board tells the computer how much air is being drawn in. There is nothing to clean inside of these flappy doors. You can cut the silicone seal open on the black plastic cover to have a look around and see if its corroded inside but they usually are just worn out. There is a procedure to check them with a multimeter if you search around for it.

IIRC The upgrade is from the '82 celica or supra but I wouldn't waste time or money on one if you have a stock engine. I would just get a stock junkyard one and be done, if yours is the actual problem.

 

gotcha, I’ll check and see how exactly you test it out then and give it a whack. Funny thing about spraying carb cleaner around the engine bay, only place I get a small “hit” is near the afm-intake pipe connection. It’s not a big rev but when I spray near there it definitely climbs 50-100 rpm.

 

As I've mentioned in the past, I'm not a fan of the FSM procedure for dialing in the TPS. Here's my write-up of the way my techs did it back in the day when 22RE's ruled the roost.

Setting/adjusting TPS

Set base timing first

1. Get vehicle to operating temp. Then turn engine off.

2. With a jumper wire connect the E1 and TE1 terminals at the diagnostic box next to the engine fuse box.

3. Connect the timing light to #1 cylinder and check that timing is at 5 BTDC. If not, loosen distributer and adjust. Ideally the distributer adjustment bolt should be somewhat centered in the slot ( If the adjusting bolt is at the extreme end of the slot there may be problems elsewhere. )

4. Once base timing is set shut engine off. Leave the jumper wire in place, along with the timing light.

5. Now loosen the two screws holding the TPS. You'll want them just loose enough so you can rotate the TPS.

6. Restart the vehicle and double check timing. It should still be at 5 BTDC.(if not, rotate the TPS counter-clockwise )

Now you come to the actual TPS adjustment

7. With the engine running and the timing light on the crank timing mark SLOWLY start rotating the TPS clockwise while watching the pulley. As you turn the TPS you should see the timing mark suddenly advance several degrees. STOP turning. Now VERY SLOWLY turn the TPS back the other way. As soon as the timing goes back to 5 BTDC stop and tighten the TPS screws. Ideally, like the distributer, the setting should be somewhat centered in the adjusting slot.

What your trying to do is set the TPS right BEFORE the timing jumps.

8. Now pull your jumper wire from the Diagnostic box and remove the timing light.

 

Nice! I’m gonna try it this way for sure, I went and looked at my tps and uh, this might be embarrassing, the tps is clocked completely to one side. I’m damn sure I did it horribly wrong...

 

ok gave that a shot, pain in the ass getting the bottom screw of the tps loose while running lol. It uh, runs better, timing was at 6* so fixed that and idles perfect at 725-750. Same deal though, coming to a stop and it bogs down 200 or so rpms and comes back to 750 after 10 seconds or so. I can’t remember which leads on the tps I tested, it’s supposed to be <9k and it was up at 26k... that’s when I got the older multi out and was able to get it down to 9k or so and called it good, might need to shell out the $100 for a new one and hope for results.

 

I pull the throttle body to loosen that screw. Then pull it again after adjusting the tps to tighten. Pain, but for me it’s faster than trying to mess with in place.