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4.0L OHV & SOHC V6 Tech General discussion of 4.0L OHV and SOHC V6 Ford Ranger engines.

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Old 07-14-2011
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What might be the problem?

I own a 97 Ranger V6 4.0 5spd w/ 67K . I received it from my father in-law in 05 when he decided it wasn't worth trading it in for a new truck. He had owned it since 99. He took good care of it, but it always had some rough/high idling and shaking problems. He said he has taken to a couple of mech and they could never find out the reason for it. When i received the truck, I put new plugs, wires and fuel filter in. It didn't seem to help. I'm finally tired of it having this problem and now I'm trying to figure out the reason why it does it. This is why i joined the forum and to see if anyone else had the same or similar problems. It seems that some do. I have read tons of threads on here and other places but still cant quite pinpoint the problem. Since i have joined this forum i have learned a lot about my truck but have not yet been able to fixed the problem, so I'M looking to your guys for some suggestions.

The problem: When I start the truck it seems that it wants to cut off unless i give it some gas. Then it revs up really high and then back down to where it seems like it wants to cut off again (sometimes it does). I guess once it gets somewhat warmed up, the engine revs up really high and back down again and sometimes the engine starts to shake (shakes the whole truck) and sound like it wants to cut off but doesn't.I have no rpm gauge so i can't give you any rpm fluctuation. It seems to drive fine while I'm driving except when i come to a stop at a light or stop sign, you can here the engine idling very high and doesn't stop until I start driving again. Also I have noticed that my Cats get very red hot (like when a blacksmith pulls steel out of the fire before he starts banging on it) and i know this is not normal. Also my exhaust smells like fuel. Everything on the engine is stock (no modding). Since joining this site I have Cleaned the MAF, IAC, and throttle body (which was full of carbon build up). Still didn't help, but needed to be done. I also believe that the reason my Cats are red hot is due to excessive fuel being dump in and settling in the exhaust thus the reason for my exhaust smelling like fuel. I would really appreciate any advice that could be given. Thanks
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Old 07-14-2011
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Hard time starting, rough idle, cats getting excessively hot, smell of fuel in exhaust. Have you checked for a plugged cat?
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Old 07-14-2011
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Vaccum leak. 4.0 OHV are known for intake gaskets.
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Old 07-14-2011
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How did the pulled spark plugs look?
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Old 07-15-2011
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Quote:
Originally Posted by nukedathlonman View Post
Hard time starting, rough idle, cats getting excessively hot, smell of fuel in exhaust. Have you checked for a plugged cat?
That is what i thought, but from looking at this forum everyone that has had problems with red hot cats, it never seems that them being plugged is the problem and that its something else thats making the engine dump extra fuel in and that its just not getting burned up in the engine and thats why its settling in the cats and why they are getting that hot.

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Originally Posted by rolsmojave3 View Post
Vaccum leak. 4.0 OHV are known for intake gaskets.
I have checked for vacuum leaks and did not find anything that seemed wrong or leaking. what or how would be he best way to check if it is a intake gasket leak?

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Originally Posted by nukedathlonman View Post
How did the pulled spark plugs look?
The old plugs to me seem to not look messed up or fouled...just normal average wear on them.
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Old 07-15-2011
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Average wear - I don't suspect a vacuum leak. If they were burned up from excessive heat, then I'd suspect a lean condition (vacuum leak). Any ways, I found a propane torch with a rubber hose attached to it is a good way to check for vacuum leaks. Attach hose to torch, start engine, then turn on torch (do not light) and run the hose along all the mating surfaces of the manifold (upper and lower plenum, where the lower intake meets the heads, where the throttle body meets the upper intake, etc, etc) and vacuum lines. If the RPM's raise, you found a vacuum leak. Other way, stick a vacuum gage on one of the vacuum lines. In this case, though, I really do think those symptoms point to a plugged cat. Testing for a plugged cat is pretty easy too - pull the leading oxygen sensor out of the exhaust system (from the exhaust manifold side - not the rear most one after the cat) or disconnect the pipe after the exhaust manifold - start engine and see how it runs at the point.
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Old 07-15-2011
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If none of those tricks work and your engine is still running rough, I'd do a compression followed by a leak down test.
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Old 07-15-2011
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My plugs with the intake gaskets leaking looked ok also, not white or eroded away. I also tried propane and carb spray to find the leak to no success. I finally got sick of shops telling me its the intake gaskets so I did them and sure enough it was them. Not trying to shut you down Nukedath, but like you just helping him along.
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Old 07-15-2011
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No worries, I don't feel shut down.

I did my Ranger last Sept, and a friends Exploder last week (both were leaking coolant externally at the water ports between the manifold and head), and it's not a fun job to do.

Okay, it's a breeze compared to doing a T-belt in an AWD Eagle Talon TSI Turbo...

But it's still a pain enough job that I'd hate to see him perform the job and have it turn out to not be the problem.
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Old 07-15-2011
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I just want to say thank you guys for the info. Im not quite sure what I want to look into first. I will check all of those things that you all have mentioned though. I have a busy weekend of other stuff going on, but i will let you all know what i have found and the solution. Thank you all again.
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Old 07-16-2011
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I was thinking just the plastic upper intake gaskets..I should have mentioned that. Very straight forward, less then an hour job.

http://www.explorerforum.com/forums/...d.php?t=171819
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Old 07-16-2011
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I would replace the iac when they get caked with carbon the plunger tends to get striped out making it useless and it could be the intake gasket. As for the over temp on the cats it could be the upsteream o2s are bad but not out of range enough to set a code for it. It could be a number of things like a misfire, bad maf, iat sensor, coolant temp sensor, etc. It's only gonna be hit or miss when replacing parts without testing them. I would get a good service manual and a good multimeter and have at it.
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Old 07-19-2011
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Update: So I decided to try and go the cheaper route and do the upper intake gasket repair on the plenum since it was about $6.00 for some gaskets and just my time to do it. I think i found the problem that was wrong. Here are some pics. The first pic is the fuel injector wires that look like a mouse or something had an acorn party and decided it wanted to chew some wires too. Whatever it was, it just ate the coating off of the wires......So i will probably use some solder and solder it, then shrink wrap it and get some new black wire tubing to help protect it.

[IMG][/IMG]

This pic is the gasket that is below the fuel rail. It looks pretty bad to me.

[IMG][/IMG]

I have to get some external torx sockets to get the fuel rail off now and also some new fuel injector o-rings. Couple of more question though. I did not depressurize the fuel system since I thought was only changing the plenum gaskets....Is there a good way to do that now that it is all taking apart without really getting fuel everywhere? Also, when I replace the gasket under the fuel rail do i need to use any gasket sealant or do i just place the gasket on and then the fuel rail and tighten it to specs of the vehicle?
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Old 07-19-2011
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I don't recall the size, but you can get them off with a normal socket. Put a rag over your hand and depress the test port fitting to let pressure off.
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Old 07-19-2011
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I don't have 12 point sockets, but do I remember that I used an 8mm standard socket to remove the rail. I didn't use any RVT or sealant on mine or friends Explorer - just installed good quality Victor-Reinz gaskets.
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Old 07-19-2011
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Quote:
Originally Posted by rolsmojave3 View Post
I don't recall the size, but you can get them off with a normal socket. Put a rag over your hand and depress the test port fitting to let pressure off.
Ok cool....Is that the thing on the fuel rail with the little blue cap on it?

Quote:
Originally Posted by nukedathlonman View Post
I don't have 12 point sockets, but do I remember that I used an 8mm standard socket to remove the rail. I didn't use any RVT or sealant on mine or friends Explorer - just installed good quality Victor-Reinz gaskets.
I just want to thank you all for the info. I never read in any "How to"....if you were supposed to or not use any RTV or sealant and it never looked like anyone did. Just double checking. Thank you all again so much. I will let you know the end result once it is done.
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Old 07-19-2011
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Yep - there's a Schrader valve stem under the cap like on a tire.
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Old 07-19-2011
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The studs are Etorx not 12 points. Im not sure if the 12 point sockets will work.

My ex does this and it uses coolant so that leads me to believe it has one or more cracked heads. As that is a common issue too.
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Old 07-22-2011
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While cracked heads on the 4.0L OHV Cologne engine is not unheard of, cracked heads are not a common problem like they were with the smaller displacement (2.8/2.9L) Cologne engines.

My engine and my friends engine are no longer losing coolant after doing the lower manifold gaskets. Both where diagnosed with proper inspection and pressure tests. I hope that that is all your problem is, and not a cracked head (or heads).

Your correct in saying eTorx are not 12 points. However 12 point sockets can and do work fine on eTorx. In fact, I do know that a 12-point socket will engage the 6 eTorx points with more grip then a regular 6-point socket. Further, I have used 12-point sockets on 6-point eTorx in the past countless times at work. Safest - use an eTorx socket. 2nd safest - use a 12-point socket or closed wrench. Least safest - use a normal socket and extra care to not strip the head of the eTorx.
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Old 07-22-2011
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I have done lower and upper intake gaskets and swapped the 95 intake for an 00. Coolant usage is the same and getting worse.

I have rounded off an Etorx off with a 12 point before so I bought a cheapo harbor freight set to do this job. The stud I was working with may have been stuck, I ended up using a stud puller to remove it.
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Old 07-26-2011
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Update everyone: So i got everything pulled off and cleaned. Fixed the fuel injector wire that was chewed up by something and got the new gasket put on under the fuel rail. I got everything put back together and started it up. The truck started right up and idled perfectly (no wanting to cut off or the engine revving really high). I just have to take it for a drive now (my life has been so busy lately). I want to THANK everyone for the help and suggestions given. My next project is a coolant flush, but I have some questions to ask before i do that.
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