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Rough Idle, Dead Spot & stumble w/ Acceleration. Out of Ideas!!
I have searched far and wide trying to find a solution to my current problem. There's over 800,000 posts on this forum but I can't seem to find something particular to my issue. I've been testing and troubleshooting for 2 weeks now and can't seem to figure out what the issue is.
My truck is a 1988 Toyota Pickup SR5 22re 4WD 5-Speed Manual. EGR delete by previous owner. 4" RC Lift on 33s. Engine has, roughly, 50,000-60,000 miles on it as it's a longblock I bought and installed back in 2018. Studded block, RV cam they put in to match the 260 engnblder cam I had in the old motor and steel backed guide timing chain upgrade.
Ill start with the issue. About 2 months ago, the truck started to hesitate and become somewhat unresponsive to throttle. Very similar and almost exactly as it did when I replaced the TPS last Janurary/February. The only time it would actually have the power equal to the throttle I was giving it was when I would give it full throttle. Outside of that it would buck, hesitate, bog and even choke sometimes. Mainly, it just wouldn't produce the power equal to the throttle it was given. It was almost as if fuel would intermittently shut off. It threw a TPS code as well and I decided to replace the TPS. From what I recall it fixed it temporarily but did not actually cure the issue long-term. I then soldered the TPS harness that I bought from LCE (it was originally put on with butt connecters) and that made it idle a lot better. I originally bought this harness and installed it because I was having TPS issues over the summer. It fixed it at that time. However, soldering it now did not solve my current driving issue. It only got worse from here. I let it sit, as I had ended up buying a new daily (got tired of busting my ass to make it run just to make it to work all the time and want to make it my project anyway). After a little break I decided to go take a look at it and try fixing it again. I removed the throttle body, adjusted the TPS (it was already within spec) and did so 3 more times after with a separate Multimeter with no luck. I found a huge crack in the throttle body boot, replaced that and it helped it idle but the idle is still really rough and the drivability has not improved. After this, it began to actually start backfiring through the intake and still does. It's so bad I can't hardly test drive it or keep it alive that long. I should also mention it gets significantly worse when it warms up. The warmer it gets, the more it missfires, backfires through the intake and stumbles through all rpms in neutral or in gear. I should mention that after putting ANOTHER TPS in this thing last weekend, I drove it and everything cleared up. Throttle response was great but when I parked it, shut it off and turned it over again the issue came back and got worse lol. In addition to what I've already mentioned, I have also done the following:
-Test harness between ECU and TPS (referencing ECU diagrams) to ensure that there was good connection.
-Adjusted timing with terminals jumped and checked timing with terminals not jumped (after adjustment). That has checked out. 8* jumped and somewhere around 12* w/o if I remember right. I did this while it was at operating temp.
-Performed the same test as stated above but with the AFM.
-Hooked up my buddy's cold air intake (his AFM as well) to see if my AFM was just bad but had no luck. (His 22re runs flawlessly. Should mention his is a 89-95 generation, not exactly sure which year).
-Adjusted Valve lash. This helped a little considering the valves were either too loose or too tight. #4 Exhaust valve was so tight it wouldn't even move 180* off TDC. Did not fix issue, however.
-Tested fuel pressure with LCE's fuel pressure guage kit. All is within spec (36psi running & 40psi w/ engine off). No leaks either; pressure held with engine off for 20-25 minutes.
-Replaced TPS again and adjusted it within spec (I think I've adjusted these over a dozen times now).
-Removed air filter from air box to see if maybe the air filter was just bad but had no success.
-Removed the ECU and opened it up to check for any signs of rust, mold or general corrosion and ware but saw nothing. Everything inside looks good. Should mention water is around the floor board though due to a windshield leak that runs down just forward of it (on firewall) but the water has not or does not come in contact with the ECU.
-Sprayed brake cleaner on vacuum lines to check for leaks but only found the leak on the intake boot.
-Replaced coil, plugs and plug wires. This helped as the coil tower had melted a hole through itself but this only slightly helped idle.
I may be forgetting a couple things. At this point I'm kind of out of ideas. I may run a compression test just to be able to say I did it which I'll probably do tomorrow. All I can think of in regards to what the problem might be is the ECU or injectors. Fuel pressure is fine, timing is fine, valves are adjusted, TPS is adjusted, harnesses are good from ECU to TPS & AFM, AFM tested out good, etc etc.
In summary these are the symptoms I'm experiencing:
-Rough Idle
-Dead spot when given throttle. The only way it'll rev up is when I gradually give it throttle or else it'll just suck in a bunch of air (you can hear it pretty good through the air box) and backfire. Most times it'll eventually catch up and the RPMs will go up but sometimes it'll die instead too.
-Unresponsive to throttle or at least only partially responsive (power to throttle ratio is off while driving unless throttle is fully open).
-When you give it throttle it will stumble through RPMs and eventually clear up around 2,500-3,000. When warm it only clears up at 3,000-3,500.
-Backfires through intake.
It currently throw a TPS code and two AFM codes. I believe the AFM codes are from when I removed the AFM to put my buddy's AFM on and the TPS came on at that exact time as well. I have checked for codes religiously so I know these came on within hours of each other. Wasn't getting codes at all prior to issue. I'll clear the codes and check again tomorrow.
Seriously so out of ideas here. Someone help a brotha out
UPDATE: I FINALLY FIXED IT. HOLY GOD THANK YOU. I adjusted the TPS with a 1/2 turn of the throttle stop screw after it barely touches the throttle linkage instead of the 1/4 they call for. It's worth noting that I also bought and currently run a factory TPS from 22re Performance which helped it run better but didn't totally fix it without the 1/2 turn of the stop screw. Something worth noting here is that the 1/4 turn made it super easy to get the TPS within spec, once I turned it 1/2 in total instead of 1/4, it was super finicky and more difficult. Just keep that in mind to anyone adjusting their TPS without any luck.
Last edited by ImJustSaiyan; 03-24-2022 at 02:58 PM.
Reason: Updated information
Might be a good idea. I have some more news though. Checked the injectors using the ol' screwdriver method and they checked out. Did a compression test as well. Compression read as following:
So all is good there... however... when pulling the plugs to run the compression test I noticed some weird orange metallic substance on the plugs. It didn't look like metal flakes but like an orange paint like substance with flakes in it. Hard to explain. I'll post pictures I took off my phone in a minute. I also noticed the same orange substance except kind of milky when releasing pressure from the compression gauge. The fitting that screws into the spark plugs socket had the same weird orange substance. I'll post pictures of that as well.
Last edited by ImJustSaiyan; 11-27-2021 at 02:30 PM.
Still kind of at a loss right now although I believe I've made some progress? I just got back from vacation and immediately began doing some more troubleshooting. I pulled off the TPS for a hundred thousandth million time and to no surprise it tested out fine. When I put it all back together I pulled the negative battery terminal for 5-10 minutes to clear codes, reset the ECU and toy with it some more after. After doing so and once the truck was at operating temp, I messed with the idle screw. When the truck ran fine it would occasionally idle low when cold but all I would have to do to get it to idle around 750-1,000 rpms was hit the throttle once and it would even itself out. It wouldn't do it at the moment but after I turned out the idle screw on the throttle body it would. It began to idle at 1k and I said, "screw it" and took it out for a drive. The first 2-3 minutes I felt 2 very faint 'bucks', the same you feel when you have a bad or out of adjustment TPS. The next 20-25 minutes after were perfect. Truck ran fine. I then let it sit for about 30-45 minutes and took it out again, same things happened except the 2 times it bucked were a little harder and it backfired through the intake. Like the previous time, however, it smoothed out once warm and ran/idled perfect. After about 2 hours of sitting, I drove it home and the same thing happened except I literally could not get it to move. I had to rev the piss out of it (3-4k rpms) just to get it to move when letting out the clutch in first gear. Otherwise, it would bog, become completely unresponsive (like it was suffocating and would die), backfire through the intake and idle horribly. Like all the other times though, it cleared after about 2-3 minutes of driving and ran perfectly.
It seems like the symptoms arise after about 2-3 minutes of driving and then go away after another 3-5 minutes of driving. Then it runs and idles perfectly for the remainder of the drive. I went to pull codes sense I had cleared them initial to all the driving I just shared and got nothing. No codes to show for the issue at hand even after an hour or more of total driving. All I can think of now is possibly the cold start injector? I know the cold start injector is supposed to help it idle when cold till it's warm, but I don't know for how long and if it's supposed to assist in driving as well? Maybe it's just not putting out enough and the truck only runs good when its warm or when nailing the throttle so the other 4 injectors are picking up the slack?
I've noticed from all of this that the symptoms are worse the longer the truck sits (how cold the motor is) because each occasion the worse the symptoms were correlated with how long the truck had been sitting before being driven again. Here in Washington, it's about 35-50 degrees right now too.
The problems seem to occur when the truck has been running for a certain amount of time? Time is temperature. Check your coolant temp sensor. I had one on a Honda fail but was still within the realm of possibility. It just thought it was -20*F outside when it was 70*. The car would open the IAC and stall or rev up and try to kill pedestrians. Once the coolant temp changed, the car would start/run again.
The problems seem to occur when the truck has been running for a certain amount of time? Time is temperature. Check your coolant temp sensor. I had one on a Honda fail but was still within the realm of possibility. It just thought it was -20*F outside when it was 70*. The car would open the IAC and stall or rev up and try to kill pedestrians. Once the coolant temp changed, the car would start/run again.
Thinking about it, that would actually make sense lol. I did briefly look into it but overlooked the possibility that it could be the issue but that was also prior to yesterday’s findings. I’ll pull it tonight after work, test the resistance and report back. I’ll obviously check the harness as well for any corrosion. Really hope we’re closing in on the problem here. I’d love to spend time working on upgrades and prep for light snow adventures this winter lol
Thinking about it, that would actually make sense lol. I did briefly look into it but overlooked the possibility that it could be the issue but that was also prior to yesterday’s findings. I’ll pull it tonight after work, test the resistance and report back. I’ll obviously check the harness as well for any corrosion. Really hope we’re closing in on the problem here. I’d love to spend time working on upgrades and prep for light snow adventures this winter lol
also make sure your engine is getting to operating temperature..... i.e. you don't have leaking thermostat
The problems seem to occur when the truck has been running for a certain amount of time? Time is temperature. Check your coolant temp sensor. I had one on a Honda fail but was still within the realm of possibility. It just thought it was -20*F outside when it was 70*. The car would open the IAC and stall or rev up and try to kill pedestrians. Once the coolant temp changed, the car would start/run again.
Resistance on the Coolant Temp Sensor clocked at roughly 2,800 in 55-60 degree setting and 300 ohms in boiling water (don't have a thermometer to get exact temp but water boils at 212 F). Not sure if these values are within spec but based off pictures I've found off other threads these seem to be within.
Originally Posted by Blackdoodle
also make sure your engine is getting to operating temperature..... i.e. you don't have leaking thermostat
Engine gets up to temp or at least the gauge shows that it does. Nothing unusual there.
I'm going to pull the cold start injector and give that a visual.
the cold start injector does NOTHING during idle. NOTHING.
it only operates when the key is in the “start” position and the temperature of the sensor is below a defined reading. it doesn’t operate at any other time, or under any other conditions. it is installed purely to enrich the mixture for starting (!!!) the engine.
the cold start injector does NOTHING during idle. NOTHING.
it only operates when the key is in the “start” position and the temperature of the sensor is below a defined reading. it doesn’t operate at any other time, or under any other conditions. it is installed purely to enrich the mixture for starting (!!!) the engine.
Hmm. That’s unusual then because I can hear it clicking continuously as it runs while it’s cold. Are you positive it isn’t supposed to be on after the truck is running while cold? If that's the case, then that might explain why it runs like crap cold. When I pulled the plugs they were wet and it keeps backfiring through the intake when cold. Eventually after driving it through its bucking and hesitation, it eventually clears up and runs fine. Maybe that's because the CSI finally turns off? Could the backfiring through the intake be from the CSI pushing excess fuel through the intake? When reading about backfiring through the intake I often only read that its due to a lean mixture, but other places will say it could be either or; lean or rich. Wet plugs would indicate rich which could be due to the CSI not turning off.
UPDATE:
The clicking at the CSI is still there even when disconnected. It clicks faster as I rev the motor but there's no way it could still be clicking with the harness disconnected from it. Moving on I guess. It does seem like its running lean. When I start it it'll idle perfect at 750 rpms but eventually finds it's way down to 500. Initial throttle will choke it and sometimes kill it. More often than not it'll just choke, bog down to about 100-200 rpm and then catch up. Seems like it's taking forever for fuel to match the amount of air that's being put into the motor. As I've mentioned, this went away yesterday after a couple minutes of driving each of the 3 times I went out to drive it. When it does decide to catch up and move up through RPMs it stumbles (or misfires?) till about 1,500-2,000 rpms and then clears up.
Last edited by ImJustSaiyan; 12-09-2021 at 08:26 PM.
Are you positive it isn’t supposed to be on after the truck is running while cold?
100%.
and it doesn't "click" like the cylinder injectors. it opens once, sprays a continuous stream during the "key start", and turns off as soon as the key is released. the "regular" injectors all open and close at the same time, injecting a portion of the fuel needed for each cylinder during the 4 strokes of the cycle.
Resistance on the Coolant Temp Sensor clocked at roughly 2,800 in 55-60 degree setting and 300 ohms in boiling water (don't have a thermometer to get exact temp but water boils at 212 F). Not sure if these values are within spec but based off pictures I've found off other threads these seem to be within.
Engine gets up to temp or at least the gauge shows that it does. Nothing unusual there.
I'm going to pull the cold start injector and give that a visual.
it would be more meaningful to know what the resistance measures at the time the problem is occurring. As i said, mine failed within spec. It just went wacky in the middle of the range.
it would be more meaningful to know what the resistance measures at the time the problem is occurring. As i said, mine failed within spec. It just went wacky in the middle of the range.
I can do that. I see what you're saying now. That would make sense. Just unsure of what the resistance is supposed to be, but I can report back. I had my grandfather come by and look at the truck. He's a retired mechanic of 35 years and he thinks it's a fuel issue. Fuel pressure is fine and everything else tests okay so from there we've narrowed it down to the injectors. Unless they've been rebuilt before I bought it then they have 280,000+ miles on them so they may just be worn and gunked up. I'll check the resistance on the Temp Sensor and report back still. Unfortunately, I just haven't had the time to work on it the last couple days. Hope to wrench on it tomorrow.
Originally Posted by wallytoo
100%.
and it doesn't "click" like the cylinder injectors. it opens once, sprays a continuous stream during the "key start", and turns off as soon as the key is released. the "regular" injectors all open and close at the same time, injecting a portion of the fuel needed for each cylinder during the 4 strokes of the cycle.
Well, as mentioned above, I had my grandfather come by and we think it might just be narrowed down to the 4 injectors. It's hard to say but everything tests out fine and he couldn't find any vacuum leaks either. May just suck it up and send mine in to get rebuilt. Hopefully that fixes the issue.
Last edited by ImJustSaiyan; 12-13-2021 at 08:13 PM.
it would be more meaningful to know what the resistance measures at the time the problem is occurring. As i said, mine failed within spec. It just went wacky in the middle of the range.
unless I’m messing it up, I’m not getting a resistance reading when the truck begins to idle like crap. Just checked and it’s reading “1” which I’m assuming means open
Here's the manual page for the ECT. http://web.archive.org/web/201311071...40engineco.pdf Make sure your ohmmeter is on a high-enough range. If you're trying to measure 4k ohms (48° F) on the 200 ohm range, you should get the over-range indication (which on your device, is probably "1").
replaced the ECT and still didn’t fix anything. Decided to have the injectors rebuilt and it helped a ton with idle and throttle response. Still had a backfire through the intake but checked timing and saw that was out. Jumped the T1 & E1 terminals and set it to 5*. It sat around 12* without the terminals jumped.
It idled great and everything after. Throttle response was better than it has ever been and idled better than I’ve ever heard it before. Then the minute I left my driveway it stopped responding to all throttle unless it was slammed to the floor. This was only when I started letting out the clutch. It jumped, jolted and bucked really bad for about 2-3 minutes and then cleared up. Then drove fine. Once I got home after driving for awhile, it idled like crap again. Now I’m inside and just about to go to bed lol. I don’t know what to do now.
I did finally pull a code when I went to set the timing. Code 41 which is a TPS circuit code. Open or short somewhere?
replaced the ECT and still didn’t fix anything. Decided to have the injectors rebuilt and it helped a ton with idle and throttle response. Still had a backfire through the intake but checked timing and saw that was out. Jumped the T1 & E1 terminals and set it to 5*. It sat around 12* without the terminals jumped.
It idled great and everything after. Throttle response was better than it has ever been and idled better than I’ve ever heard it before. Then the minute I left my driveway it stopped responding to all throttle unless it was slammed to the floor. This was only when I started letting out the clutch. It jumped, jolted and bucked really bad for about 2-3 minutes and then cleared up. Then drove fine. Once I got home after driving for awhile, it idled like crap again. Now I’m inside and just about to go to bed lol. I don’t know what to do now.
I did finally pull a code when I went to set the timing. Code 41 which is a TPS circuit code. Open or short somewhere?
An intermittent wiring fault as you suggest could definitely make it behave that way. I'd agree your next move is to take a really careful look at that harness and make sure it's completely pristine.
An intermittent wiring fault as you suggest could definitely make it behave that way. I'd agree your next move is to take a really careful look at that harness and make sure it's completely pristine.
I may check the resistance from the VTA/IDL/E2/VCC ports at the ECU end of the harness while it's plugged into the TPS on the other vs measuring resistance AT the TPS itself. Could indicate whether the resistance readings are making its way to the ECU correctly. That may not come up 100% though as it is intermittent so it may show a false positive, so to speak. Going to do all this today and see if I can narrow down the issue. TPS is brand new, set correctly and I'm still getting a code, so it has to be the harness. Only other thing I could think of is that the pigtail that I got of LCE and soldered onto the harness to plug into the TPS could be messed up, but the pins look fine, and it has a good connection. I've also double checked to ensure I soldered the correct wires together. Will be back to report what happens lol
Got a weird reading at the ECU side of the harness when testing the TPS like that. Read infinite with the IDL contacts but everything else read fine. Only time it read any resistance was without any feeler gauges. I went to test the TPS AT the TPS while it was still on the truck to see if it was out of adjustment or if the IDL wire is just screwed up and it read the same. I then removed the throttle body and tested it... it tested fine off the truck. As of right now it's back together and tomorrow I'm going to go through and test the TPS from the ECU side of the harness again and see if I get something different. I'm wondering if I just had the feeler gauge on there weird or if my multimeter is just too cheap because it seemed to be acting up a little at first. I may just remove the throttle body to get the feeler gauges in there easier and do it that way. Regardless, the CEL code pulled a 41 which is "THROTTLE POSITION SENSOR SIGNAL--OPEN OR SHORT IN TPS SIGNAL". It points at the TPS Signal/Circuit, TPS and ECU as the probable causes. I'm attaching a picture which includes both the ECU Harness wiring diagram for the truck and ECU pinout. Yellow is everything associated and directly connected to the TPS and light blue is anything that branches off lines that directly connect to the TPS. I figure this is relevant as something that branches off a direct connection to the TPS could be the cause too? Might help anyone following brainstorm more ideas. More information the better... right? I did not tear too deep into the harness as I figured that might be a last resort option. I'm really hoping there's a way to find any electrical issues through a multimeter.
11-26-2021, 10:48 PM
