Harder Start When Engine Warm

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I’ve got a 97 LX450. When engine is cold starts pretty quickly and smoothly. If I drive it 10 or 20 miles and get engine to full operating temp, shut it off, then try to restart it, it takes 2-3x as many cranks and kind of stumbles to fire. The idle is just a tad bumpy- but really pretty good. No CELs. Anyone else experience this? Fuel filter is new. Injectors serviced by Witchhunter. Fuel pump and fuel pump relay may be original with 25 years of age and 225K miles- I’ve only owned for about 5 years and maybe 10K miles. Engine is basically new.
 
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Corrosion in the cables, or fuel injectors, a lot of times when I worked on cruisers for living we never sent out injectors unless made to by the customer most time had issues after. Would buy new if it was me. I had a runner that did this and went though lot of stuff came down to once I changed the main power cable to starter no more issues, would always start after it sat for awhile just like you describe.
You can listen to the injectors while running and also look at the rail for any leaking. Just my thoughts

Could also look at some threads of people adding ford starter relay
 

awf

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I’ve got a 97 LX450. When engine is cold starts pretty quickly and smoothly. If I drive it 10 or 20 miles and get engine to full operating temp, shut it off, then try to restart it, it takes 2-3x as many cranks and kind of stumbles to fire. The idle is just a tad bumpy- but really pretty good. No CELs. Anyone else experience this? Fuel filter is new. Injectors serviced by Witchhunter. Fuel pump and fuel pump relay may be original with 25 years of age and 225K miles- I’ve only owned for about 5 years and maybe 10K miles. Engine is basically new.
I’m trying to figure out the same issue on my ‘94 FZJ80. I’ve put in a new FPR, but that didn’t solve the problem. I’m wondering if it might by the ECT sensor, and I think I’m going to have to learn to diagnose fuel rail pressure to do a serious job of running down the issue. From scouring mud, I’ve assembled a list of potential culprits that includes: gas cap, charcoal filter, VCV valve, FPR, ECT sensor, and fuel injectors.
 

awf

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Sounds like a tired starter
The problem some of us are having is that the truck starts fine when cold but then takes a very long crank to start when warm. The starter, battery, cables all check out. I don't think that's the problem. It is something heat-related, and I'm focused on the fuel system or something like the ECT sensor. But... there doesn't seem to be a single or even consensus diagnosis.
 
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The problem some of us are having is that the truck starts fine when cold but then takes a very long crank to start when warm. The starter, battery, cables all check out. I don't think that's the problem. It is something heat-related, and I'm focused on the fuel system or something like the ECT sensor. But... there doesn't seem to be a single or even consensus diagnosis.
I’m leaning toward fuel system on mine. Everything forward of driver seat is pretty much new- including main harness. My ECT is new. Still occasionally takes 2-3x more turnovers to start, and then will sometimes hiccup right before it fires. I’m planning to tackle fuel pump and fuel sock next- based on all the records that came with my truck about 5 years ago, those parts are likely original. After 25 years, probably not a bad idea to replace. I’ll report my findings after I get those replaced.
 

awf

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I am curious about what you find. You seem to be a bit ahead of me. I would say pretty much everything forward of the drivers seat is new, but not yet everything. I explored a fuel pressure issue involving the gas cap, tank, carbon filter, and FPR being the culprit, and feel I've eliminated that. But, if you replace the fuel pump and sock and it solves the problem, I won't be far behind. For the time being, I'm keeping the hunt focused on things affected by heat past the FPR. If I solve it, I'll share.
 

COYS

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The problem some of us are having is that the truck starts fine when cold but then takes a very long crank to start when warm. The starter, battery, cables all check out. I don't think that's the problem. It is something heat-related, and I'm focused on the fuel system or something like the ECT sensor. But... there doesn't seem to be a single or even consensus diagnosis.

Reman Toyota starter did the trick for me. Same symptom - Good luck.
 
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Aug 23, 2004
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I have the same issue. Try turning the ignition position 2 or idiot lights are on for about 10 seconds and then start the L/C. I find it easier to start.
 
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I’m trying to figure out the same issue on my ‘94 FZJ80. I’ve put in a new FPR, but that didn’t solve the problem. I’m wondering if it might by the ECT sensor, and I think I’m going to have to learn to diagnose fuel rail pressure to do a serious job of running down the issue. From scouring mud, I’ve assembled a list of potential culprits that includes: gas cap, charcoal filter, VCV valve, FPR, ECT sensor, and fuel injectors.
All these parts are new on my truck except for injectors which were cleaned, rebuilt and checked out OK by witchhunter. I’ve put a stethoscope on all of them and they all seem to be clicking like they should. #4 and #5 injectors are hard to get at, but I think they sound OK. Hard start when warm (but not all the time) and just a little burble at idle. Tach holds very steady at 650 RPMs on the cluster- never fluctuates. I did notice more crispness / responsiveness in the throttle after changing the fuel pump relay- for whatever it is worth. Another thing I notice is that when I’m parked and try to hold a steady RPM at around 2000-2500 RPM, I feel a slight miss in driver seat- maybe starving for fuel from a weak pump or old sock? So, that brings me back to the fuel sock and pump. I’m not a mechanic but can effectively swap parts and it seems my truck might be starving for fuel at higher RPMs. Don’t notice it when driving, just when revving in park. I don’t put a whole lot of stock in my ultra gauge, but I do have it set to monitor STFT and LTFT. My LTFT is always +8 to +10. STFT is almost always -5 to +5. The fact that long term fuel trim is averaging about +9 and I don’t have any vac leaks that I can detect, leads me to believe it’s not getting the proper amount of fuel. Any comparative STFT/LTFT readings would be appreciated. Mine seem pretty good from what I’ve read. Again, when I get time I’ll swap new parts in the fuel tank and report back. Parts cannon, fire!
 
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All these parts are new on my truck except for injectors which were cleaned, rebuilt and checked out OK by witchhunter. I’ve put a stethoscope on all of them and they all seem to be clicking like they should. #4 and #5 injectors are hard to get at, but I think they sound OK. Hard start when warm (but not all the time) and just a little burble at idle. Tach holds very steady at 650 RPMs on the cluster- never fluctuates. I did notice more crispness / responsiveness in the throttle after changing the fuel pump relay- for whatever it is worth. Another thing I notice is that when I’m parked and try to hold a steady RPM at around 2000-2500 RPM, I feel a slight miss in driver seat- maybe starving for fuel from a weak pump or old sock? So, that brings me back to the fuel sock and pump. I’m not a mechanic but can effectively swap parts and it seems my truck might be starving for fuel at higher RPMs. Don’t notice it when driving, just when revving in park. I don’t put a whole lot of stock in my ultra gauge, but I do have it set to monitor STFT and LTFT. My LTFT is always +8 to +10. STFT is almost always -5 to +5. The fact that long term fuel trim is averaging about +9 and I don’t have any vac leaks that I can detect, leads me to believe it’s not getting the proper amount of fuel. Any comparative STFT/LTFT readings would be appreciated. Mine seem pretty good from what I’ve read. Again, when I get time I’ll swap new parts in the fuel tank and report back. Parts cannon, fire!
Update- I installed a new fuel pump and fuel pump sock filter. This made a big difference in starting and performance. No longer sputters when trying to restart when engine hot. Now takes 3-4 turns to start any time. It’s peppier on the highway, now, also. However the fuel trims didn’t change much except LTFT did drop a tiny bit when getting after it at highway speed. I was hoping to get LTFT to drop down around 5 or less, but no dice….until today. I spent my lunchtime driving about 20 miles to get non-ethanol gas. My theory was that pure gasoline (non-ethanol) would drop LTFT. It did. $70 worth of pure gas made my highway speed LTFT drop to +5% vs +10% with 10% ethanol blend. So, yes. The ethanol blend crap makes the ECU command the injectors to stay open longer. Mystery solved on my long-term fuel trim. And this reduction in LTFT is including the tank still being about 45% ethanol. Too bad I can’t find pure gasoline in the town I live in.
 
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Update- I installed a new fuel pump and fuel pump sock filter. This made a big difference in starting and performance. No longer sputters when trying to restart when engine hot. Now takes 3-4 turns to start any time. It’s peppier on the highway, now, also. However the fuel trims didn’t change much except LTFT did drop a tiny bit when getting after it at highway speed. I was hoping to get LTFT to drop down around 5 or less, but no dice….until today. I spent my lunchtime driving about 20 miles to get non-ethanol gas. My theory was that pure gasoline (non-ethanol) would drop LTFT. It did. $70 worth of pure gas made my highway speed LTFT drop to +5% vs +10% with 10% ethanol blend. So, yes. The ethanol blend crap makes the ECU command the injectors to stay open longer. Mystery solved on my long-term fuel trim. And this reduction in LTFT is including the tank still being about 45% ethanol. Too bad I can’t find pure gasoline in the town I live in.
Also, I’m going to replace the main cables off my battery. They are original. I need to order the positive cable. The negative cable (OEM) I have. Quick question, on the negative cable (battery side) there are 2 terminals. The negative cable going from the battery on my truck goes into a loom of wires. I can see where the one terminal goes to the block, but can anyone tell me where the other terminal goes? Maybe on the inner fender??
 
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A photo would help.

There is a fender mounted ground strap, about six inches from the battery (-) terminal. The upper ground point is on the inner fender, inside the barrtey box envelope. The lower one is on the frame.
1655295821647.png

(This image is reversed in the parts fiche images, for some reason; it's from the '95 catalog. It should show the (-) lead on the right side of the battery)

There are also a couple on the intake side of the engine and one on the frame on that side. These are all the loose and harness-related grounds:
1655295973701.png
 

Dirt Ferguson

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If you’re planning on replacing all your battery cables, I would highly recommend the set from @Fourrunner


I replaced all my cables with his set, they are very well made and come with good instructions about which cable goes to which location.

Also, some related info in this thread that may help shed some light

 
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