1998 SOHC rough idle

[Ricardo Miramontes]

Hey guys and gals,
I have a 1998 4X4 XLT SOHC engine and I have recently noticed that my idle (especially in the mornings) is rough. It seems to do ok after it has warmed up, although it will act up sometimes while at a light signal. There have been occassions where the rpm's drop so much that the engine dies. If any one out there has any clues to this please help me out. If it seems like I post a lot with minor things it's because my Explorer is a daily driver and I depend on it so I expect it to be in good running conditions. Thank You in advance.

Ricardo

 

[Ricardo Miramontes]

Please

Come on guys, please.....Someone has to have some suggestions. Could it be the automatic choke, a sensor, the fuel pump regulator? Anything that you think may point me in the right direction.

Thank You,
Ricardo

 

[mattadams]

never heard of a fuel pump regulator... your probably thinking of a fuel pressure regulator... my guess would be one of two things, yoru altenator, or your fuel pump. One way you could test it is leave your headlights on for a while, then start up your car and see if it has problems recharging the battery (or the more conventional method of just having the altenator tested). Mine has the same problems you described occasionally and I think its the fuel pump, but I've got too much other stuff to fix on it first. Does the whole vehicle shake when its idling low?

 

[Ricardo Miramontes]

you know what???

I have noticed that the voltage gauge is sitting a little lower than before, I can almost recall that I noticed this when the rough idle developed but I didn't think anything of it. The truck does shake when it idles rough. And one other thing, now that you've got me thinking about the voltage, alternator, is that sometimes when making tight turn arounds when the steering is at it's limits is when it tends to die most often. Is that an indication of a bad alternator?

 

[Ricardo Miramontes]

I'm sorry.....

it does shake when it idles low...not rough, obviously if it's idling rough it'll shake.

 

[gijoecam]

Couple of ideas...

I doubt it's the alternator. True the alternator powers the engine when it's running, but when the alternator fails, the engine draws juice out of the battery. You can throw your fan belt and the engine will still run until there's no juice left in the battery to spark it and power the fuel pump, etc. I suspect the idle speed actuator is not functioning properly, or is plugged, maybe the TPS is out of range, so the engine doesn't know your foot is off the gas, or maybe your MAS is dirty, again telling the computer something's wrong. If you're getting poor mileage, it could be the Engine Coolant Temp Sensor is bad... if the engine thinks it's cold all the time, and it's warm, it could be richening the mixture and essentially choking itself out. Best Suggestion? Have someplace run the codes and narrow it down for you.
-Joe-

 

[Ricardo Miramontes]

for some reason....

your reply makes sense to me Joe. I will get my codes read hopefully this weekend. I'll let you guys know. I have noticed a drop in milage as I've posted in here before. This has been the case ever since the beginning of this year, but I don't recall if the engine was idling rough that far back. Thanks guys!!!

Ricardo

 

[Jeff]

Ricardo,

My 97 has started having the same problem you are although it hasn't gotten to the point of dying. The idle is rough, but only at times and the whole truck shakes. The shake is more like a low grade rumble/roll but it is very noticeable while waiting at a light. Yes, it seems to be more noticeable at start up in the morning. Curiously, this isn't an every day event but it seems to happen 4 out 7 days.

I don't know if this is something you're having a problem with but my rough running also feels like I have poorer acceleration. It gives me a feeling that there isn't as much scoot when I step on it as though there is something keeping the truck from getting air.

Finally, this might be unrelated, but there are times when it is running rough that when I step on the accelerator at a light, the truck simply won't accelerate. It is as though it is bogged down. It moves away from the light but not very fast even with the pedal pressed about 1/3 to 1/2 way down. Backing off of the pedal a bit seems to give me back normal acceleration.

This thing is perplexing because it definately doesn't happen every day but it's a bit alarming when it does.

Are you having the same or similar problems? I'd be very interested in seeing what the codes are when you've got them.

 

[withers]

I am interested in the solution as well. I have experienced rough idle in my '99 since I bought it. Sometimes the idle dips below 500 rpm and some shaking occurs. I thought that the idle should be closer to 1,000rpm but I showed to the dealership around 5K miles and they said no codes showed up and 500rpm was ok. Now I have 22K and still experience this occasionly(at stops or just after start up). I have never gotten great mileage either. I get about 17mpg while freeway driving and 15mpg around town. (This was on the stock tires.)



[Edited by withers on 10-06-2000 at 10:07 PM]

 

[slow-demon]

The problems you guys are having with the SOHC engine is related to the intake manifold 0-rings (gaskets). The o-rings are leaking and letting air into the engine. Believe me I have experience with this problem and have repaired many a SOHC engine. Ford came out with updated gaskets for the intake manifold. If you still have warranty you know where you can get it repaired. Hope this helps. Sometimes but not all the time the check engine lite might light up. The dealer can tell right away by watching the O2 sensor readings at idle. Good Luck.

 

[mountaineerman]

My 99 Mountaineer has the same problem. Dealer called it a resonance vibration, and said all the 4.0 SOHC motors have this problem. He said there is no fix (typical response)- and this is normal for this motor. I'm going to try the intake manifold gasket to see if it helps. Thanks

 

[sphaugh]

jeff

I get the exact same thing. I wondered if it may be the fuel filter - not really sure. the manual suggests replacing the fuel filter every 15K.... and I've got 52K on my 99.

I get 20-23 mpg, also - but it's primarily highway driving (surprise!).



[Edited by sphaugh on 10-07-2000 at 06:14 AM]

 

[Jeff]

slow-demon,

You say you've worked on many a SOHC. Is this dealer experience? The reason I ask is because I'm out of warranty (75K) but perhaps there is a hidden dealer warranty that you know about.

Although I didn't mention it before, at idle there is a whistling sound that is very, very noticeable. I haven't paid much attention to it because I thought it was the KKM filter making noise. Hmmm.

What's the repair cost? I don't have time to do it myself and I'm not sure I want to tackle such a problem.

 

[Jeff]

sphaugh,

I doubt it's the fuel filter although my truck acts like it might be. I change mine every 30K as part of religious maintenance. I'd be happy with the easy fix but I think this problem is deep rooted within the beast.

 

[sphaugh]

Jeff,

I have doubts too, but since the filter may be long overdue - I'm doing it today. I bought my explorer with 42K miles - and the previous owner was a MB technician with family he visited often - way up the coast. I had it checked out & it was/is very good mechanically; however the service records (very detailed) shows no activity on the fuel filter. Oil change every 3333, tires rotated, inspections on brakes, etc - but nothing else noted. Just like any used vehicle, you can't be certain.

Anybody have info on cost of replacing the intake manifold gasket? thx

 

[slow-demon]

Ford has a technical service bulletin (tsb) regarding the symptoms you guys are experiencing. I've changed intake gaskets (o-rings) and they are easier to change than the OHV engines. No gasket to clean off and no need to drain the coolant. It takes me about an hour to change them but that is with air tools. What's happening is the o-rings are shrinking and letting excess (unmetered by MAF) air into the engine.
Jeff, the warranty is the 36/36 month warrany. If your out of warrany the length of the repair should take less than 2 hours and the parts should be cheap since they are just o-rings seals.

 

[Robert]

Originally posted by slow-demon
Ford has a technical service bulletin (tsb) regarding the symptoms you guys are experiencing. I've changed intake gaskets (o-rings) and they are easier to change than the OHV engines. No gasket to clean off and no need to drain the coolant. It takes me about an hour to change them but that is with air tools. What's happening is the o-rings are shrinking and letting excess (unmetered by MAF) air into the engine.
Jeff, the warranty is the 36/36 month warrany. If your out of warrany the length of the repair should take less than 2 hours and the parts should be cheap since they are just o-rings seals.

Correct, when I had mine replaced last year the charge to my warranty company was about $125. The shop replaced both upper and lower gaskets and the gasket on my VIS. I had the check engine light but not the rough running. My codes were P0171 & P1074. And, yes while monitoring the short-term fuel trims and injecting propane around the manifold my fuel trims would change drastically. Easy to diagnose with the right equipment and a little help from Ford's TSB regarding the problem. After finding the problem, I took it to the shop to let them replace it under my extended warranty.

 

[JM Dookie]

Wow, my Explo is exhibiting the same exact problems. It idles rough at start up and the idle wavers when stopped at a stop light after the engine is hot. It also has cut off several times after the engine was warm. I have taken it to the shop three times in less than two months and they replaced the MAF sensor twice. One time they told me that it did not show an error code at all. Needless to say I still have the problem but they keep telling me that nothing is wrong. Does anyone think that it could be a vacuum leak? Thanks for the input! I hope we can find a solution to this wide spread problem.

 

[withers]

Anyone know the tsb number? I want to look it up and take it with me to the dealership.

thanks

 

[PaulJ]

Me too

I had noticed this same problem a few times on my 99 XLT. The other morning I left for work, and when I stopped at the stop sign at the end of my street, the idle dropped and the engine stalled. NOTHING would get it running again except me sitting there holding my foot on the gas. I had to call Ford Roadside and have them tow it to my dealer. The guy at the dealership said something about the oxygen intake valve...and also said he is seeing this quite allot.
Am I gonna keep having problems?