Rough idle after getting gas after long interstate drive

[Odyssey 4x4]

The Odyssey has a slight issue that it has had since I purchased it. It starts, runs and cruises excellent. It cruises beautifully and runs great having no problem cruising at 65 mph.The problem is after cruising on the interstate for long distances (longer than an hour drive). Once I stop for fuel it has no issue getting to the gas station, but once I shut it off and fuel it up and restart it, it has a low idle and runs incredibly rough, even stalling at times. If i cycle the key a few times before starting it sometimes seems to help, as well as turning the AC on to bring the idle up. If I am able to pull onto the road and give it throttle it seems to "clear out" and runs basically normal again with no low idle or stuttering. I should also mention it does this after stopping at a grocery store or wherever else, so it is not specifically a result of getting gas, more so just a hot soak issue. 

 

Check engine light is not on and there are no codes stored in memory when checked. I have replaced all of the usual suspects while doing other work and repairs on the rig to make it reliable. New plugs, wires, distributor, injectors, fuel pump, fuel filter, fuel lines, EVAP vapor canister etc. The air flow meter and TPS checked out good under an ohm test. 

 

The problem is somewhat hard to recreate since it requires doing a lot of driving. My next guess is possibly a fuel pressure regulator? Engine coolant temp sensor (unsure if a bad one would trigger a check engine light)? My pops says it sounds like vapor lock. I believe this rig is supposed to have a system that prevents vapor lock using a vacuum solenoid which I tested out as good (although I did not test it under hot conditions). 

 

Anyone got any ideas? Is it worth throwing a new fuel pressure regulator on? 

 

Edit: I just took a look at all engine codes for the 3vze are there is a code for engine coolant temp sensor as well as TPS and air flow, I'd imagine that I would have a check engine light if these were the issue 

 

Edited November 29 by Odyssey 4x4

[MaineJed]

I agree with your pop

[IdahoDoug]

Though I am likely from your Pop's generation and vapor lock was a thing when I owned carbureted cars back then - not likely what's going on here.  Your 1990 will have fuel injection, which essentially eliminated vapor lock in the automotive world with very, very, very few exceptions. 

 

Sequentially, I'd do a smoke test on your engine to see if you have a vacuum leak, which can manifest during a hot start, which is actually an awkward phase of engine operation. You can make one, rent one, or buy one on Amazon pretty cheaply and on an older car with a LOT of vacuum lines, and a bunch of dried out intake gaskets and seals, it's money well spent.  Then, I'd pull the throttle body and physically clean the crud out of it using THROTTLE BODY CLEANER spray (not brake fluid, or carb cleaner, which are too harsh for any sensors you might spray).  Those are my higher probability tests, given what you've replaced. 

 

As for a new FPR, couldn't hurt, but I'd do ONE more thing.  Go through your engine bay using a service manual and find and clean every ground.

 

These are based on that your engine runs fine in all other conditions, which indicates to me your gracefully aging vehicle has a sensor somewhere that's not engaging when it should, or the CPU is ever so slightly acting up.  Those are symptoms of poor grounding, which impacts low draw items like sensors and CPU's first before the ground would eventually draw direct attention to itself by causing something to stop working altogether. 

[Odyssey 4x4]

1 hour ago, IdahoDoug said:

Though I am likely from your Pop's generation and vapor lock was a thing when I owned carbureted cars back then - not likely what's going on here.  Your 1990 will have fuel injection, which essentially eliminated vapor lock in the automotive world with very, very, very few exceptions. 

 

Sequentially, I'd do a smoke test on your engine to see if you have a vacuum leak, which can manifest during a hot start, which is actually an awkward phase of engine operation. You can make one, rent one, or buy one on Amazon pretty cheaply and on an older car with a LOT of vacuum lines, and a bunch of dried out intake gaskets and seals, it's money well spent.  Then, I'd pull the throttle body and physically clean the crud out of it using THROTTLE BODY CLEANER spray (not brake fluid, or carb cleaner, which are too harsh for any sensors you might spray).  Those are my higher probability tests, given what you've replaced. 

 

As for a new FPR, couldn't hurt, but I'd do ONE more thing.  Go through your engine bay using a service manual and find and clean every ground.

 

These are based on that your engine runs fine in all other conditions, which indicates to me your gracefully aging vehicle has a sensor somewhere that's not engaging when it should, or the CPU is ever so slightly acting up.  Those are symptoms of poor grounding, which impacts low draw items like sensors and CPU's first before the ground would eventually draw direct attention to itself by causing something to stop working altogether. 

 

I agree on it likely not being vapor lock, but could definitely be a possibility. I will whip up a smoke tester and see if I can find anything regarding a leak, I haven’t tried that one yet! I have however already replaced 99% of the vacuum lines, maybe it’s the last 1% with a leak! I also replaced intake manifold gasket when I did the injectors. I’ve also removed and cleaned the throttle bottle completely and did that gasket as well! 

 

I’ll also go ahead and start double checking grounds. 

[Odyssey 4x4]

A non productive update. I did a smoke test and found one small vacuum leak but it was on a vacuum line that I had previously replaced, and this hot start issue has existed since I bought the truck so I know it isn't that. After doing a lot of research it appears a few people have battled this issue and still not solved. I am wondering if the issue could be the fuel pressure regulator, but i've read others had no success once replacing. I am also considering a bad engine coolant temp sensor since this can cause all types of weird issues, but this should trigger a check engine light. This 3vze engine has a "coolant bypass block" on the rear side of the motor that houses all kinds of sensors that rely on engine coolant flowing by for correct temp readings. This block can look a bit different depending on year of truck. (not my photo)

 

 

From my understanding the red arrow sensor is for the temp gauge (single wire), green arrow (2 wire) is coolant temp sensor for ECU, black arrow (2 wire) is for the cold start injector, and yellow arrow (single wire) i am not 100% sure. I believe the yellow arrow is possibly for the automatic transmission, something to do with overdrive only functioning once engine is warm? Some also apparently have a coolant temp switch that turns the AC off under hot engine conditions, I am unsure if that's what the yellow arrow could be. Of course these are all in a terrible spot to get to behind the intake plenum on back of engine.

 

 

There is also a coolant bypass pipe that runs underneath the lower intake plenum and gives the passage way for the coolant to make it to this rear coolant bypass sensor block. I have read that someone with this issue has found their coolant bypass pipe completely clogged. Once cleaned it resolved their issue. Of course this is another headache of a job having to remove near the entire top of the engine to get to it! 

 

(not my photos but showing the coolant bypass pipe)

 

 

 

 

At this point I'm not quite sure what route I am going to take. I will probably just enjoy the camper for the winter and pull the engine apart once it warms up again in Florida and makes camping not so fun. 

[Ssunrader]

Might try readjusting the throttle position sensor.

[IdahoDoug]

If you have badly sludged coolant lines, then yes - perhaps worth dealing with that bypass pipe.  But fully blocked?  I think that guy was not being truthful.  Never ever seen that.  His sludge looks SOOO bad he clearly had a lot of engine oil in his cooling system, though.  That can coat sensors and cause them not to accurately measure the coolant temp by insulating the sensor for a period of time.  So, if your cooling system has been very badly neglected, I'd suggest you do a proper detergent based flush, backflush, etc which is not hard to do.  However, you definitely seem to take care of your engines and I don't think that is your issue.  Worth doing, I suppose.

 

The idle control valve is actually a good call.  I had an 88 Toyota Supra I restored/rebuilt fully a couple years ago and its TPS had begun malfunctioning.  I replaced it pretty cheaply, and the adjustment for it seemed daunting when reading the instructions, but in practice was actually pretty easy. You can adjust your existing one and thereby verify it's proper functioning, or simply get a new one and install it, eliminating another variable.  Happy to assist with the knowledge I gained, and suspect another Toyota EFI system from the same era would just be an easy variation on the theme I learned. 

 

Those sensors are 35 years old now and perhaps the one that your EFI system needs is slow to react.  Consider replacing them if they're all in a convenient spot. Toyota parts are very reasonable and from your things done and symptoms, I still think a slow sensor is your issue because it smooths out.  And on a hot start, money says it's a temp related sensor like those pictured.  

[Scott iv]

Different engine(22re) but the same niggling problem here. Comes and goes under the same circumstances mentioned. When I had the head off I also took the bypass pipe off and there was no blockage. I also replaced all of the vacuum lines and it runs better than ever except for the inconsistent hot idle. Interesting it effects both motors. 

[Odyssey 4x4]

5 hours ago, IdahoDoug said:

If you have badly sludged coolant lines, then yes - perhaps worth dealing with that bypass pipe.  But fully blocked?  I think that guy was not being truthful.  Never ever seen that.  His sludge looks SOOO bad he clearly had a lot of engine oil in his cooling system, though.  That can coat sensors and cause them not to accurately measure the coolant temp by insulating the sensor for a period of time.  So, if your cooling system has been very badly neglected, I'd suggest you do a proper detergent based flush, backflush, etc which is not hard to do.  However, you definitely seem to take care of your engines and I don't think that is your issue.  Worth doing, I suppose.

 

The idle control valve is actually a good call.  I had an 88 Toyota Supra I restored/rebuilt fully a couple years ago and its TPS had begun malfunctioning.  I replaced it pretty cheaply, and the adjustment for it seemed daunting when reading the instructions, but in practice was actually pretty easy. You can adjust your existing one and thereby verify it's proper functioning, or simply get a new one and install it, eliminating another variable.  Happy to assist with the knowledge I gained, and suspect another Toyota EFI system from the same era would just be an easy variation on the theme I learned. 

 

Those sensors are 35 years old now and perhaps the one that your EFI system needs is slow to react.  Consider replacing them if they're all in a convenient spot. Toyota parts are very reasonable and from your things done and symptoms, I still think a slow sensor is your issue because it smooths out.  And on a hot start, money says it's a temp related sensor like those pictured.  

 

 

Ill swap the sensors out on the coolant bypass block in summer, like i said, it's a real pain in the neck spot to get to them and the upper and lower intake plenum need to come off so i'll do the dreaded knock sensor/wiring harness at the same time. My coolant is all new and when I did the flush the old coolant looked just fine, so I too find it hard to believe my bypass pipe is blocked. If it were, I'm not sure any of the sensors would work at all, especially my dash temp gauge. My TPS tested out good when I pulled it off and cleaned the throttle body and lines out as well. It may be worth rechecking it, but it' somewhat difficult to diagnose considering it's only during extra hot engine conditions after interstate drives. For example, it may test out good cold but once hot will it test out of spec? I'm not sure, and I think that should trigger a check engine light as well. 

 

I've always kinda figured I may end up doing a 3.4 swap in this truck so I never wanted to dump a bunch of money into the 3.0. The 3.0 3VZE gets a lot of hate on the internet as the "3.slow" and one of the worst toyota engines made, but I gotta tell you, it cranks my RV along just fine. It's funny that it's known as being a slow and sluggish engine when just on the truck platform, not even considering an RV!  If I don't mind watching my fuel gauge drop quickly I have no problem keeping up with traffic leaving red lights and cruising around a majority of the time, as well as cruising on the interstate at 65 mph no problem. The only place is struggles is steep grade roads which I have found true with my other Toyota RV as well and is really to just be expected considering I'm driving a 35 year old truck with a house built on it up a mountain. I know the 3.4 would have a decent amount more power (something like 40 hp I think), as well as a better engine design and OBD 2 system, but for now I'm going to stick with the 3.0 as it seems to do just fine. Perhaps if I lose a head gasket or some other big failure I'll start actually considering a 3.4 swap. 

[WME]

Do a voltage check on the fuel pump cold vs hot.

[Odyssey 4x4]

45 minutes ago, WME said:

Do a voltage check on the fuel pump cold vs hot.

 

That has been replaced as well! 

[WME]

3 hours ago, Odyssey 4x4 said:

 

That has been replaced as well! 

Maybe so, but bad voltage will still make a new pump run poorly.

[IdahoDoug]

This is kind of basic, but what about your oxygen sensor?  They can be heated with a torch and tested with a simple multimeter.

[Odyssey 4x4]

10 minutes ago, IdahoDoug said:

This is kind of basic, but what about your oxygen sensor?  They can be heated with a torch and tested with a simple multimeter.

 

also new lol

[IdahoDoug]

Well, I'd check engine bay grounds, then, and critically your engine computer's ground(s).  As a former vehicle planner for GM and Lexus, I know the hot start is one of the most demanding engine management conditions and where issues commonly exist, and then sort themselves after a short period of running.  The engine computer is super sensitive to proper voltage and grounds, so perhaps start with any grounds on or near it?  If it's easy, remove the cover and gently blow compressed air across the circuit boards to see if metal dust over the decades is starting to form circuit bridges where none should exist?

 

Sticky wicket.