1992 Toyota Pickup 4 Cyl PU
01-31-2021, 09:30 AM
#1
Registered User
Thread Starter
1992 Toyota Pickup 4 Cyl PU
New here
I purchased my truck two years ago and have had the following issues since that I hope someone can help with, I currently have two different Haynes books:
1) hard start when warm, cold start is beautiful and idles down properly after 10 mins
2) idle screw is worn down and since I've noticed I have been trying to adjust the idle properly but I can't get it right, started with idle not maintaining and then it stalls. I did notice the screw would vibrate loose so I tried a few tricks from the internet like the teflon tape and added an O ring and it helped the screw from loosening but didn't really help the idle reliably
3) now, when driving on the highway the engine seems to miss at exactly 2500 rpms...no matter how tight the idle screw is or is not. I noticed the truck eventually adjust for the idle screw being too loose or tight so I can't get it to 700 rpms (ideal I imagine). The engine light comes on after I let the rpms drop like when I push the clutch in. I have checked all vaccuum hoses and changed the pcv valve after I noticed it was old. I have changed the spark plugs, alternator cap and all the obvious maintenance things but I can't figure it out.
4) panel cluster/speedometer doesn't work, worked before on and off, fuel gauge was always off by half but the others work fine
I agree with the post about mechanics not knowing how to work on these trucks. I went to one and established company and they didn't even know how to drive standard so they had to wait for someone who could. In the end they could fix it but I was still charged for their time.
I purchased my truck two years ago and have had the following issues since that I hope someone can help with, I currently have two different Haynes books:
1) hard start when warm, cold start is beautiful and idles down properly after 10 mins
2) idle screw is worn down and since I've noticed I have been trying to adjust the idle properly but I can't get it right, started with idle not maintaining and then it stalls. I did notice the screw would vibrate loose so I tried a few tricks from the internet like the teflon tape and added an O ring and it helped the screw from loosening but didn't really help the idle reliably
3) now, when driving on the highway the engine seems to miss at exactly 2500 rpms...no matter how tight the idle screw is or is not. I noticed the truck eventually adjust for the idle screw being too loose or tight so I can't get it to 700 rpms (ideal I imagine). The engine light comes on after I let the rpms drop like when I push the clutch in. I have checked all vaccuum hoses and changed the pcv valve after I noticed it was old. I have changed the spark plugs, alternator cap and all the obvious maintenance things but I can't figure it out.
4) panel cluster/speedometer doesn't work, worked before on and off, fuel gauge was always off by half but the others work fine
I agree with the post about mechanics not knowing how to work on these trucks. I went to one and established company and they didn't even know how to drive standard so they had to wait for someone who could. In the end they could fix it but I was still charged for their time.
01-31-2021, 11:26 AM
#3
Registered User
#1: Check the fuel pressure regulator. The little item on the end of the fuel rail, where the fuel returns to the tank. It has a vacuum line attached. The vacuum line lowers the pressure it maintains during a nice hot start. Prevents "hot soak" problems. Do you have a fuel pressure gauge you can attach to the system? Easiest place is the fuel line to the Cold Start Injector. Put in the jumper to the test connector, B+ to Fp. Turn the key to ON. Apply vacuum to the pressure regulator. The pressure should decrease, IIRC. I'm pretty sure the vacuum line comes from a VSV, which is activated by the ECM, I think. I may well be wrong on that, though.
#2: Get a new idle adjustment screw. It shouldn't change position, IE: where you set it. If it's that worn, get a new one. I think that's the only way you'll get it to stay put once you set it. I believe idle is 800-850 RPM. Once the truck is fully warmed up, the idle speed shouldn't change, if there are no input. No pressure on the gas pedal, no brakes applied, anything.
#3: At anything above idle, the position of the idle adjust screw shouldn't matter. When you talk about the IAS being "loose" or "Tight", you mean screwed in, or out, yes? All that the screw does is set the idle speed when the truck is fully warmed up. I'm pretty sure the "tighter" it is, the lower the idle. Again, though, the IAS shouldn't change it's position at all. Ever.
All it does is set the amount of air allowed into the throttle body when the plate on the TPS is fully closed. Thus, the idle speed. Once again, the IDLE speed. Obviously, it allows air in, even when the throttle plate is opened, but that's compensated for by the ECM. The ECM gets information from the TPS on how far it's open, thus, how much fuel the engine needs to run correctly for that amount of air flowing in, and uses that, among other inputs, to determine how much fuel to allow in. Thus, fuel, plus air, equals engine speed. At idle, IOW, the throttle plate closed all the way, no air allowed in, the idle screw allows a small amount of air in. The TPS has a switch in it that closes when the throttle plate is all the way closed, telling the ECM "use idle fuel amount".
#4: Have you checked the ground point under the driver's side kick panel? That might be related to the difficulties with the gauge cluster. Also, pull the gauge cluster, and check for broken wires, or runs, on the circuit card. Use a multimeter to check for a cracked run. Sometimes they're not visibly cracked, but are enough that there's no current flow through them. It can be an incredibly frustrating thing to do, but it might solve your problem. Also, examine the runs with a magnifying glass. You might be able to see a crack that way. Check where the gauges' electrical connections bolt to the circuit board. Any cracked runs, or loose bolts? Any broken or loose wire IN the gauges? Most of them are open enough to see such things.
I hope something in all my rambling is helpful...
Pat☺
#2: Get a new idle adjustment screw. It shouldn't change position, IE: where you set it. If it's that worn, get a new one. I think that's the only way you'll get it to stay put once you set it. I believe idle is 800-850 RPM. Once the truck is fully warmed up, the idle speed shouldn't change, if there are no input. No pressure on the gas pedal, no brakes applied, anything.
#3: At anything above idle, the position of the idle adjust screw shouldn't matter. When you talk about the IAS being "loose" or "Tight", you mean screwed in, or out, yes? All that the screw does is set the idle speed when the truck is fully warmed up. I'm pretty sure the "tighter" it is, the lower the idle. Again, though, the IAS shouldn't change it's position at all. Ever.
All it does is set the amount of air allowed into the throttle body when the plate on the TPS is fully closed. Thus, the idle speed. Once again, the IDLE speed. Obviously, it allows air in, even when the throttle plate is opened, but that's compensated for by the ECM. The ECM gets information from the TPS on how far it's open, thus, how much fuel the engine needs to run correctly for that amount of air flowing in, and uses that, among other inputs, to determine how much fuel to allow in. Thus, fuel, plus air, equals engine speed. At idle, IOW, the throttle plate closed all the way, no air allowed in, the idle screw allows a small amount of air in. The TPS has a switch in it that closes when the throttle plate is all the way closed, telling the ECM "use idle fuel amount".
#4: Have you checked the ground point under the driver's side kick panel? That might be related to the difficulties with the gauge cluster. Also, pull the gauge cluster, and check for broken wires, or runs, on the circuit card. Use a multimeter to check for a cracked run. Sometimes they're not visibly cracked, but are enough that there's no current flow through them. It can be an incredibly frustrating thing to do, but it might solve your problem. Also, examine the runs with a magnifying glass. You might be able to see a crack that way. Check where the gauges' electrical connections bolt to the circuit board. Any cracked runs, or loose bolts? Any broken or loose wire IN the gauges? Most of them are open enough to see such things.
I hope something in all my rambling is helpful...
Pat☺
01-31-2021, 12:14 PM
#4
Registered User
Thread Starter
I expected a short “dont u know” answer so I appreciate the rambling. I’ll give it a gander this coming weekend when I’m more patient. Thank u very much
#1: Check the fuel pressure regulator. The little item on the end of the fuel rail, where the fuel returns to the tank. It has a vacuum line attached. The vacuum line lowers the pressure it maintains during a nice hot start. Prevents "hot soak" problems. Do you have a fuel pressure gauge you can attach to the system? Easiest place is the fuel line to the Cold Start Injector. Put in the jumper to the test connector, B+ to Fp. Turn the key to ON. Apply vacuum to the pressure regulator. The pressure should decrease, IIRC. I'm pretty sure the vacuum line comes from a VSV, which is activated by the ECM, I think. I may well be wrong on that, though.
#2: Get a new idle adjustment screw. It shouldn't change position, IE: where you set it. If it's that worn, get a new one. I think that's the only way you'll get it to stay put once you set it. I believe idle is 800-850 RPM. Once the truck is fully warmed up, the idle speed shouldn't change, if there are no input. No pressure on the gas pedal, no brakes applied, anything.
#3: At anything above idle, the position of the idle adjust screw shouldn't matter. When you talk about the IAS being "loose" or "Tight", you mean screwed in, or out, yes? All that the screw does is set the idle speed when the truck is fully warmed up. I'm pretty sure the "tighter" it is, the lower the idle. Again, though, the IAS shouldn't change it's position at all. Ever.
All it does is set the amount of air allowed into the throttle body when the plate on the TPS is fully closed. Thus, the idle speed. Once again, the IDLE speed. Obviously, it allows air in, even when the throttle plate is opened, but that's compensated for by the ECM. The ECM gets information from the TPS on how far it's open, thus, how much fuel the engine needs to run correctly for that amount of air flowing in, and uses that, among other inputs, to determine how much fuel to allow in. Thus, fuel, plus air, equals engine speed. At idle, IOW, the throttle plate closed all the way, no air allowed in, the idle screw allows a small amount of air in. The TPS has a switch in it that closes when the throttle plate is all the way closed, telling the ECM "use idle fuel amount".
#4: Have you checked the ground point under the driver's side kick panel? That might be related to the difficulties with the gauge cluster. Also, pull the gauge cluster, and check for broken wires, or runs, on the circuit card. Use a multimeter to check for a cracked run. Sometimes they're not visibly cracked, but are enough that there's no current flow through them. It can be an incredibly frustrating thing to do, but it might solve your problem. Also, examine the runs with a magnifying glass. You might be able to see a crack that way. Check where the gauges' electrical connections bolt to the circuit board. Any cracked runs, or loose bolts? Any broken or loose wire IN the gauges? Most of them are open enough to see such things.
I hope something in all my rambling is helpful...
Pat☺
#2: Get a new idle adjustment screw. It shouldn't change position, IE: where you set it. If it's that worn, get a new one. I think that's the only way you'll get it to stay put once you set it. I believe idle is 800-850 RPM. Once the truck is fully warmed up, the idle speed shouldn't change, if there are no input. No pressure on the gas pedal, no brakes applied, anything.
#3: At anything above idle, the position of the idle adjust screw shouldn't matter. When you talk about the IAS being "loose" or "Tight", you mean screwed in, or out, yes? All that the screw does is set the idle speed when the truck is fully warmed up. I'm pretty sure the "tighter" it is, the lower the idle. Again, though, the IAS shouldn't change it's position at all. Ever.
All it does is set the amount of air allowed into the throttle body when the plate on the TPS is fully closed. Thus, the idle speed. Once again, the IDLE speed. Obviously, it allows air in, even when the throttle plate is opened, but that's compensated for by the ECM. The ECM gets information from the TPS on how far it's open, thus, how much fuel the engine needs to run correctly for that amount of air flowing in, and uses that, among other inputs, to determine how much fuel to allow in. Thus, fuel, plus air, equals engine speed. At idle, IOW, the throttle plate closed all the way, no air allowed in, the idle screw allows a small amount of air in. The TPS has a switch in it that closes when the throttle plate is all the way closed, telling the ECM "use idle fuel amount".
#4: Have you checked the ground point under the driver's side kick panel? That might be related to the difficulties with the gauge cluster. Also, pull the gauge cluster, and check for broken wires, or runs, on the circuit card. Use a multimeter to check for a cracked run. Sometimes they're not visibly cracked, but are enough that there's no current flow through them. It can be an incredibly frustrating thing to do, but it might solve your problem. Also, examine the runs with a magnifying glass. You might be able to see a crack that way. Check where the gauges' electrical connections bolt to the circuit board. Any cracked runs, or loose bolts? Any broken or loose wire IN the gauges? Most of them are open enough to see such things.
I hope something in all my rambling is helpful...
Pat☺
02-07-2021, 12:03 PM
#5
Registered User
Thread Starter
Re: Issues mentioned
I finished working on the truck today. I used the jumper wire to diagnose the issues and it returned code 13, code 22, code 31, and code 43. It occurred to me that I hadn't reset the codes since I started experiencing random engine light warnings so I decided to reset it and take the truck for a drive. When I returned I used the diagnostic again and the only code shown was 22 which is for the water temp sensor. I read about the sensor before but a water temp issue just didn't seem to create the issues I was having but now I know it was the problem. I drained half the radiator and removed the old sensor, or should I say it removed itself (plastic and metal pieces sort of crumbled. This was fortunate because the 19 mm deep socket wouldnt reach far enough to ratchet it out. The new sensor fit in the socket perfectly. Anyway, I put everything back together and took it for a long drive and no missing, no engine light, hums perfectly. Thanks for your help...I was really starting to doubt my ability to fix it. I still need to look at the cluster issue. Oh by the way, I ended up changing the fuel pressure regulator just because I had the part already and was going through the motions of what it would take to remove and I bent the little vaccuum tube on the part against the intake.
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2ToyGuy (02-08-2021)
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