Hot Start Issues

[Derek Greenwood]

A great deal of my 94 Sport has been replaced but I still have one nagging problem. It runs good and starts great except when its hot and has been sitting for a little while, say 10 minutes. After it has heat soaked for 10 minutes it starts just fine but it is very rich for about 15-20 seconds. Then it clears out and runs just fine. I have replaced the map and the IAC and injectors and the fuel pump and the coil and wires and plugs and heads and... I have been rebuilding it for long trips camping so I don't mind replacing parts that could fail.

Any ideas?

 

[MrShorty]

My first thought with a hard warm start (especially where it is running rich after it does start) is a bad fuel pressure regulator. Run the engine for a bit and pull the vacuum line to the FPR. If there is gas in that vacuum line, the FPR needs to be replaced.

 

[Derek Greenwood]

It only runs rich for about 20 seconds. I have replaced the FPR also.

 

[Derek Greenwood]

In order for there to be a hot start problem it has to be run and then shut off hot and then heat soak for like 10 minutes. Then it runs very rich on start and sounds like it is missing. I used to have a little fuel injected sports car and if I put a couple of bottles of alcohol in the tank it would run great but would miss on hot start up until the hot gas got out of the fuel rail. Then it ran great. This sounds like the same thing but if no one else is having trouble with all of the alcohol in fuel these days then that isn't the problem.

I am sure one of you guys have run into this before?

 

[MrShorty]

Maybe an injector "leaking" into the intake? If you put a fuel pressure gauge on it, does it hold pressure, or bleed down quickly?

 

[Derek Greenwood]

They are rebuilt injectors so that is very possible. I will check it out this weekend and let everyone know. Thanks

 

[mikewilder]

Same here

I am having a very similar problem. Sometimes on a warm start, it is so rich that it almost doesn't start at all. I also notice a slight miss and "surge" at highway speeds. I cleaned the iac, no change. I used to own another Ford with a wierd problem, it turned out to be a shorted intake air temp sensor. Since the sensor was shorted, the computer thought it was very cold outside and did not throw an error code. This one has no error code either.
Any suggestions would be greatly appreciated.
Surely someone has seen this problem and solved it!

 

[Derek Greenwood]

Rebuilt Injectors coming

I had already installed rebuilt injectors but I have bought another set from a more established company and will be putting those in sometime over the next week. Keeping my fingers crossed

 

[Derek Greenwood]

Resolved

I put in the new rebuilt injectors and the problem resolved. Seems the first place I bought rebuilt injectors from just did a bad job. The second set came from a different rebuilder on Ebay from Orlando and they seem to work great. It runs better and so far I haven't had any hot start issues.

On another note I bought a bypass tube for the cat. The cat had been gutted and I can say it runs better with the bypass tube installed. Plus it is quieter. I bought the tube from a seller on ebay as well. It didn't fit exactly right. The forward area of the tube would not fit over the exhaust and I spent about an hour heating and pounding it out. I suppose I could have cut part of the Y pipe that used to stick back into the cat but I didn't want to modify it just in case I had to convert back. Other then that it fit fine and I am quite happy.

Its a good day in Explorer Land!

 

[Tyexplorer]

Derek,
Does this sound familiar? My 94 Ex with 127K has two problems. (not really there are more but I'll keeep it short). After hours of test and observations, I am pretty sure they are releated.
Once the engine is warmed up and then shut off for 10-15 minutes, it idles rough for a minute. Not sure it's flooded or starving. At times I have smelled fuel but found no leaks. It starts and idles perfectly when cold OR if I wait one hour. One hour seems to allow the engine to cool enought for the temperature gage to drop below the "N" in Normal or allow fuel to leak past the piston rings?

The 2nd repeatable observation is when the key is turned with the car warm....you can hear the fuel pump and then a gurgling/bubbling sound in the tank. This can only be heard during a warm state after sitting for 10-15 minutes and the level in the tank does not matter. There is no gurgling sound when cold.

I have replaced two injectors and cleaned the other four and installed a new FPR.

Temperature issue or have I not found the leaking injector? Is your Ex still starting smooth when hot? No pun intended....

 

[Tyexplorer]

More information. Just checked the spark plugs with four older old injectors and they are dry and white as a bone.

 

[Derek Greenwood]

Sounds like you may have found your problem. Since my last post I have had to rebuild my motor. It decided to not run on all cylinders. I believe I hurt it by running it a long time on a trip with what turned out to be a bad O2 sensor. It seems that bank got really hot. Anyway, its all new now and if the final lifter will pump up I will be happy.

 

[Tyexplorer]

I still have the problem of a rough idle after restarting after a 10 minute shutdown. Others have advised to buy a fuel pressure gauge to check the pressure and monitor it for an hour once the warm engine has been shut off.

 

[RustySJohnson]

Rough Idle when warm - Very common

I still have the problem of a rough idle after restarting after a 10 minute shutdown. Others have advised to buy a fuel pressure gauge to check the pressure and monitor it for an hour once the warm engine has been shut off.

#1 Vacuum leak
#2 Intake gasket leak
#3 Dirty injectors (#1 when rough idle after warm)

Note: This is assuming you've covered all, but not limited to the basics:
-fuel pressure OK, filter's good.
-plugs wires OK
-engine's firing on all cylinders
-Not a sensor issue, TPS, IACV, MAP.
-Clean air filter and no leaks on intake tube.

http://www.explorerforum.com/forums/showthread.php?t=374394

My advice for what it's worth, service the injectors. Either clean/rebuild them yourself or get a reconditioned set, whatever you're comfortable with. The process of servicing the injector's will solve the other major contributors to this problem and net you better mpg. Replace all the vacuum connectors, and intake plenum gaskets.

Injector service kit:
http://www.bonanza.com/listings/Fuel-Injector-Service-Rebuild-kit-6-Cylinder-Engine-Bosch/52065711

Off the shelf vacuum connectors, buy two of these:
http://www.autozone.com/autozone/accessories/Dorman-AutoGrade-4-pcs-soft-elbow-vacuum-tubing-connector-assortment/_/N-25ry?itemIdentifier=426018&_requestid=739106

All my first Gen Explorer's had this problem, I've helped a couple members solve this. I'm not sure if it's the injector's, or just the combination of fixing intake and vacuum leaks combined with serviced injectors, but I've had success 6 of 6 times on the 4.0 motor's.

 

[Tyexplorer]

Does the fact that the warm rough idle goes away after revving the engine help narrow down the possible problem parts and areas to check?

Also, neither link is working. Are these old part numbers?

I really appreciate the help. I hope to get this car running smoother and then send it away with my son to school this summer!

 

[RustySJohnson]

Does the fact that the warm rough idle goes away after revving the engine help narrow down the possible problem parts and areas to check?

Also, neither link is working. Are these old part numbers?

I really appreciate the help. I hope to get this car running smoother and then send it away with my son to school this summer!

Revving it up fixes it? Yes, that's one of the trademarks. Links fixed (I copy pasted shortened URL).

 

[Tyexplorer]

Thanks for the confirmation and the updated Links.

I checked the vacuum at the intake manifold octopus and it read 20 inches Hg at idle and drops as it should when revved.

There are alot of vacuum lines in the 94 Ex....is one more notorius than the others for small leaks? Like trying to find a needle in a haystack.

Thanks again.

 

[Xeek]

so im having this exact issue. 10-15min after shutting it off and trying to start it it may even stall. or just miss until i rev it up some.
turning the key on i hear the fuel pump, then bubbling coming from the engine bay, then it stops.

so i changed the injectors with a matched set i had in my exploder with new orings, new intake gaskets, exploders old fpr, and tightened the lower intake down(was slightly loose..)
now it misses ALL the time. absolutely no power anymore

 

[RustySJohnson]

Bubbles

so im having this exact issue. 10-15min after shutting it off and trying to start it it may even stall. or just miss until i rev it up some.
turning the key on i hear the fuel pump, then bubbling coming from the engine bay, then it stops.

so i changed the injectors with a matched set i had in my exploder with new orings, new intake gaskets, exploders old fpr, and tightened the lower intake down(was slightly loose..)
now it misses ALL the time. absolutely no power anymore

The bubbling noise is most intriguing. I'm running possible causes through my head, but can't come up with anything helpful. Well..... a few jokes come to mind, but let's stay focused.

Bubbling sound? Are you sure it's coming from under the hood? Could the sound be traveling through the fuel lines from fuel tank?

Give us more details on the loose intake gaskets. Did you forget to tighten them down, or reuse the old ones?

 

[Xeek]

i dont hear the bubbling anymore. i dont remember what thread i saw it in, but it was the exact same thing as this threads about and someone said they hear bubbling and its due to the hot fuel in the fuel rail with dirty injectors. i need to find it again.

as far as the intake, i only replaced the fuel rail and upper intake gaskets, since i was doing injectors. while i was there i tightened the lower intakes bolts. i think all of them mustve gotten 180* turn before i ruled tight again.

old injectors all read 17-18ohms. the set from the exploder was 14-15ohms. so none "failed", i just think they were dirty.
im thinking i may have bent a plug wire when moving the intake around before i unclipped them from the holder. or the fpr/ac/airbox vacuum line may have come apart. octopus has everything on it, 100% sure of that.

ps, how the hell do you hook up a newer design pcv?? i have a stock on that points straight up, the autozone fram one is an L. the tube on the intake simply will not line up cause of that. i will get a picture tomorrow