FJ62 Idle/Stall Issue (1 Viewer)

[Britter1]

Hey guys, I've read this board for years, but haven't posted much in the past as I only recently (last month) became a proud FJ62 owner ('88 that I bought off MUD).

This past week, I've noticed some issues when starting the truck, having to crank it a few times before the idle will hold. Earlier today, I was driving at low speed on a neighborhood road and the truck stalled. I got it off the road, but then had to try numerous times over about 30 minutes to get the truck to hold idle and drive. I was able to get it home and read as many only threads as I could find to try to figure it out. Here's what I've done:

- Checked the Fuel Pulsation Damper -- I still have the screw intact and it seemed tight/in place
- Diagnostic Check -- I got the Error 51...which led me to the TPS
- Resistance Check on TPS -- I think I'm running pretty normal. I get a reading (around 12 ohms) when closed and it goes to OL when I open the throttle. I'm checking as per the FSM across IDL-E2
- Did a quick visual inspection of all hoses and connections under the hood -- I haven't done an exhaustive search, but everything seems intact.

After doing the above steps, I didn't clear the Error 51, but the truck does fire up and seems to idle ok. I drove around the block and again had a stall issue. I couldn't get it started (again), but was able to pop the clutch (H55 conversion) to limp home a few feet at a time. I did notice that when I attempted to hit the throttle to up my RPMs it would still stall...like pressing the gas pedal had no effect on preventing the stall.

Edit: I've also discovered that I can prevent the idle down / stall on starting the truck by keeping the starter engaged (turned). If I keep the ignition turned by holding the key it will idle and rev RPMs without issue. The minute I release the key it idles down and dies.

Any ideas? Thanks for any recommendations, this place is awesome!

 

[Britter1]

Update with some additional info after further diagnostics:

I did the fuel pump check and could hear a faint sound indicating the pump was probably engaged (I think). I visually inspected the EFI fuse and did a continuity check on it, it's good. I checked the EFI main relay per the FSM -- when doing continuity checks on the relay, I did get a resistance reading of around 83 ohms across 1 & 3 (I'm assuming that's ok) and zero continuity across 2 & 4. I then applied voltage to 1 & 3 and could hear the relay click. With all that said, it sounds like my EFI master relay is good, correct?

After these checks, I started up the truck. Zero issues with cold start. I let it idle, it seemed a little low, but kept running (better with the A/C load on it). I kept the A/C off and let it idle. After about 5 minutes, as the motor was starting to warm up, it stalled. I tried cranking it again, but ran in to the same problem I've been having -- the motor cranks fine, but immediately stalls. Attempting to add RPMs with the gas pedal doesn't effect it, but I can keep it running if I keep the ignition engaged.

So in summary: No issues with cold start, idle is low, Error 51, and stalls when it warms up. I'm thinking the Fuel Pressure Regulator.

Any ideas? Thanks for any feedback!

 

[MiyamotoMusashi]

Definitely rule out that fuel pressure regulator and the vacuum line. It sounds like a classic symptom of the fuel pressure regulator.

 

[Britter1]

Definitely rule out that fuel pressure regulator and the vacuum line. It sounds like a classic symptom of the fuel pressure regulator.

Thanks, that’s my plan. Am I missing something in the FSM about checking the FPR? I see how to replace it, but don’t see any diagnostic steps to determine if it is bad. Edit: I also reviewed the maintenance history from the PO and noticed that the FPR was replaced (with a Standard Motor Products unit) in 2021. I’m thinking it would be unusual for it to go bad in a year.

From older threads, it looks like a bad thermostat could result in similar symptoms. Does that make sense?

Thanks for any feedback!

 

[toy_tek]

Have you confirmed the timing and valve clearances are correct per FSM?

 

[Britter1]

Have you confirmed the timing and valve clearances are correct per FSM?

No, I haven’t, but I assumed (probably incorrectly) that it was something else given that it cold starts and runs ok initially and only acts up once it starts to warm up.

Could timing and/or valve clearance issues manifest in that way also?

Thanks for your post and any feedback.

 

[Britter1]

Apologies that I’m replying to myself, but I just did some more trial and error testing and think I may be getting a bead on this.

Tried a cold start this afternoon with no luck. I say ‘cold’ as the truck has been sitting all day (in the sun), but I live in FL so it’s 90 degrees here. The truck cranked fine but would immediately stall unless I kept the ignition turned.

I then jumped +B and FP on the diag box and it started and idled ok. I had to feather the throttle a bit and turn on A/C to get a decent idle, but without the jumper, I couldn’t keep it running.

My EFI fuse seems ok (good continuity), I heard the EFI main relay click when I applied voltage, my fusible links look ok to visual inspection, but not sure what else I should look for or test.

Any thoughts on why I can keep it running when I jump the terminals? I’m thinking Circuit Operating Relay (COR) under the passenger side kick panel. I removed mine and it had some water in the housing as I drove in hard rain this week and some rust/corrosion. I tried brushing it off, cleaning the housing. I reinstalled it and it still stalled.

Anyone selling a COR I can try? Any other ideas on testing or cleaning the relay? Anything else I should check?

Thanks for any feedback!

 

[LA Z]

“ but I can keep it running if I keep the ignition engaged “ do you mean keep the key in the cranking position?
( I just read your post again, and that’s what you mean )

If that is the case, try bypassing the COR which will turn the fuel pump on and see if it stars and stays running.
Sounds like your air flow meter might be the issue or a bad connection in that circuit. ( see red circle )
The COR gets triggered by cranking or by the air flow meter when the engine is running and the air moves the flap inside.

 

[Britter1]

Thanks! Yes, I meant keeping the key turned.

I will run the air flow meter FSM checks today. How do I bypass the COR? I thought that’s what I was doing when I shorted out the +B and FP in the diagnostics box — when I have it shorted it will start and run.

Can you point me to the location on the vehicle of the circuit in the red circle? Sorry, brand new to 60s, so I’m learning!

Thanks for the assistance!

 

[toy_tek]

Regarding air flow, check all your intake tubing and make sure everything is tight and that you don't have a leak - the rubber tubes commonly crack. This could cause similar behavior to what you're describing.

 

[Britter1]

Thanks. My hoses look pretty good and I can’t see any obvious cracks or disconnects. The PO did replace these in the last year.

I just checked the resistances at the air flow meter connector. For the most part, I they are ok, but some are out of spec — for example, I got 1 ohm instead of 900 on E2-THA.

I also noticed that my connector is missing a contact (the second E2 contact). Pic below

Would the missing contact cause this type of problem? I also noted that the ‘cap’ on the air flow unit (I think it has the potentiometer under it) seemed a little janky, like it had been sealed back in to place previously:

The symptoms have started to crystallize over the past 2 days. I can’t get a cold start or keep it running unless I jump the +B and FP connections on the diag box. I’m still thinking it’s the COR relay. I ordered one from Parts Geek and will source a generic 12V/10A with 5 pins locally to see if it works.

I’m new at these so I haven’t reached the point of frustration yet! If there are any other suggestions, I’ll try it. Thanks!

 

[LA Z]

Your connector only supposed to have 6 pins in it, so that part is okay.
However I would take really good look at your intake hose. ( red circle )

If that connection has a leak ( witch it seems from the white goop around it that at some point it did )
that would explain you having problem with your idle. The air getting sucked in through the cracks would not register on your airflow meter ergo your fuel pump wouldn’t run on idle. ( if the leak is big enough )

 

[Britter1]

Thanks. I’m not discounting your input, but apparently, the white goop has been on the intake hose for a few years (from a couple owners ago). I think I have an additional issue, but to your point, maybe I should attempt to reseal the intake hose.

 

[toy_tek]

Thanks. I’m not discounting your input, but apparently, the white goop has been on the intake hose for a few years (from a couple owners ago). I think I have an additional issue, but to your point, maybe I should attempt to reseal the intake hose.

@LA Z is 100% correct, and based on the pics you've posted, I wouldn't assume *anything* until you confirm it 100%. And don't let that goop take all your focus, check every hose that connects to the intake, even all the vacuum lines.

That's basic troubleshooting. you're doing a good job checking things with the meter, but since you just got this truck you have a bit of investigating to do to ensure the baseline mechanicals are intact as they should be.

"New" used trucks can be frustrating at first, figuring out all the quirks and stuff the PO neglected, most of us have been there. Don't lose focus, you'll figure it out!

 

[Britter1]

Thanks to both you guys, I appreciate the feedback and will continue to go through the truck.

I’ll continue to share what I learn and take any feedback you guys have. Aside from helping me out, maybe this thread will eventually be useful to someone else (once I figure it out)!

 

[LA Z]

There’s a few more things you could check with a test light, if you have one.
If you don’t, I’d suggest you get one for your self because you’re going to need it now that you are a proud
owner of a 62. ( welcome to the club ) They’re great, once you ironed out a few kinks.

While we’re on the subject of a test light, finding a bad connection or a broken wire is easier with an
“ old school ” test light. The ones with a light bulb not an LED or a volt meter.
The light bulb draws a bit of current ( up to 500mA depending on the bulb ) not like the LED ( 2-20mA )
and that current will help identify a bad connection by dropping voltage across it.

Just my .02

 

[Britter1]

Thanks for that tip — yes, I need to get a light and will look for an old school one.

Update on my issue: it was the COR. I sourced a similar relay at Auto Zone (Duralast 20098 60-0198), swapped it in and she fired right up and drove fine. I have a replacement relay on order from parts geek and will probably swap that one in and keep the Duralast as a spare — I’m researching the COR specs, but I believe my Auto Zone replacement may not have the right amperage rating (It’s 10A and I think the factory relay is 15A).

Thanks for the feedback in this thread. I learned a lot about the EFI system in my troubleshooting.