I bought a great looking but poor running Ranger. The engine is a 4.0, it idles rough and does not seem to have much power. I pulled the plugs, they looked decent, they had ware, but still should have ran alright. I checked the compresson, 120-150psi on all cylinders, I thought I might have a blown head gasket, or warped head. There are not signs of water in the oil or moisture in the exhast, or running hot, but it does run rough. How can I test for sure, to find out if the head gasket are heads are not the problem. The engine is a fairly new Ford creat motor, it would be a shame if it had internal engine problems.

Thanks

 

I don't know other than a compression check, but the efi engines have alot of sensors that tend to be the cause of a rough running engine than anything else. Not saying that it is the cause, but is worth checking out. A lot of times they will throw a code, 1990 is pretty old, but I'm sure still should be able to be read with a code reader to make sure. Also my 84 2.3 was running rough, couldn't figure it out, turned out to be the intake gasket. Squirted starting fluid around the intake manny and it started reving up. Changed the gasket and it smoothed right out. Others should be a long with some idea's as well.

 

A bad head gasket would show up in one of the tests you've done already. It could show up as water in the oil or vise versa, or low compression on one cylinder or continuous water in the exhaust. Also there could be a leak of water or oil around the edge of the head where it meets the block. You say none of these are showing up, so your heads should be ok. Some other things to check would be the ground wire from the engine to the body. Make sure the wires are in good condition and that all connections are clean and not rusty or corroded. Also check for vacuum leaks. These leaks can make an engine run rough at all modes of driving. Vacuum hoses should fit snug on all fittings and the hose should be soft enough to make a good connection. Shouldn't have cracked, split or brittle hoses. Also rubber vacuum caps should be in good condition. Some of the earlier 4.0's had problems with lower intake gaskets leaking or even the upper intake gaskets leaking where it mates to the lower intake. The thin upper intake gasket can split and break apart and you won't see it except in worse engine performance. You could try the test that Wendell mentioned with starting fluid being sprayed around the split line of the upper & lower intake and around the lower intake where it meets the heads with the engine running. If the rpm goes up then there's a leak at one of the gaskets. Let us know what you find.

 

Thanks for the replys.

I replaced the valve cover gaskets today, the upper intake was not torqued correctly, nor were the valve covers. Someone must have replaced these before, there was a mound for RTV and gaskets were finger tight to over tight. I am hoping the upper intake seal might have been the problem, I still have a few more things to reinstall before it will be ready to crank.

Is the torque 84 in lbs on the upper intake?

Thanks again for the replys.

 

Book I have shows 15-18 ft lbs which is 180-216 in lbs for the upper intake. Certainly sounds like you may have found the problem. Let us know how it goes.

 

Thanks for the replys, but I still do not have it completely repaired. I took the truck to a machanic, he said the intake manifold was leaking, and one of the injectors was almost completely clogged. He did a fuel injection service on it, and retorqued the intake manifold. The truck runs better, but still has a miss. I have not driven the truck enough to see if I am lossing coolent.

The temp guage does something strange, when driving the temp will go between just below 1/2 way to about 1/4 for a few minutes, then back up, then back down. Any ideas?

How do you use the cooling system pressurizing test tool? I would like to test the cooling system for leaks.

The mechanic said there is not a problem with the cooling system holding pressure, but he also said there was nothing wronge with the transmission. When the transmission shop opened the transmission there was a lot of broken parts, it needed a complete overhaul with hard parts. So I have a hard time taken the machanics word that there is nothing wrong with the engine, not to mention it still has a miss.

 

It could be one of two things with the temp gauge. There may be some trapped air in the cooling system. These sometimes have a hard time perging the air because the upper hose on the engine is higher than the radiator. Best way I found for mine was to fill the radiator to just below the cap neck when it's cold, then drive on the freeway a short distance and watch the gauge to see if it settles down. If not then I get it back home and let it cool down so I can take the radiator cap off to add more coolant up to the same level, then drive to check it again. Sometimes when air is in the system you can hear a gurgling sound over by the heater core when you first start the engine after sitting for a while. The thermostat is the other thing that could be acting up when it trys to work. Maybe it's sticking as it moves or something. Even if it's a newer one it may not be working well. Be sure to get a good brand name if you replace it. The pressure tester will let you pressurize the system while the engine is off to test for leaks at any part of the system that has a connection or gasket. Head gaskets, intake gaskets, all hose connections, water pump shaft seal, radiator tanks etc. The system does not have to be cold when doing the test. Put the tester on the radiator in place of the radiator cap, then pump it up to the pressure rating that's on the radiator cap. If no leaks show up any where right away, then you could let it sit ten minutes or so to see if any do show up. If none show up, you're done. If any do show up, at least you know where it is. Other parts of the ignition system could be breaking down after getting warm or being used for a little while to give you a miss. Might be a coil pack or plug wire or plug. If you don't know when the plugs or wires were changed last you could replace them and see if it changes anything and at least you would know those parts are good.(Stick with Motorcraft plugs and wires if you can.) If the miss is still there after you replace these, then you might get the coil pack tested for breaking down.

 

look at the sender connector up by the tstate housing make sure its tight on the sender as this will cause it to wqonder up and down. Agree witht he post above by stan, I always R&R plugs wires fluids filters when I buy a used vehicle make a lot of difference as you know where things are. Also make sure to change the fuel filter if you had a blocked injector, more than like ly you will need to pull them and clean/replace as the in vehicle cleaners dont really work all that well. Plus they are fairly inexpensive to clean once out or put in remans. Flush the fuel lines well while you have it apart.

 

Thanks for the replys, I am slowly getting the truck back in order.

Question?
Someone told me my rough idle might be cause by a faulty ignition control module. How do you test this part? My coil pack was a little out of specs, I replaced it and the idle improved a great deal. This is an expensive part to replace if that is not the problem.

The truck runs better, but I still have a slightly rough idle, one mechanic said the 4.0 engines do not idle smooth, there is nothing that I could do.

Will a ignition control module cause a motor run fine at 1000+RPMS but idle rough below 1000 RPMS?

Thanks

 

the best thing is to get to a shop who has a computer to hook up insteead of the code reader. that would be the biggest help for you instead of replacing parts trying to find the problem. I know this may be an acceptable way, but it is a PP troubleshooting technique.

Snapon has a computer that reads the codes, find an indy shop or even the dealer if all else fails. could even be a bad ECM, maybe a bad MAF sensor.

 

Check that the spark plugs wires are in the right firing order.My 4.0 idles smooth .

 

Well.... I still have gotten the engine problems corrected. The old motor had ran very hot in the past and putting any more money into it was a lost cause. I had a new Jasper 4.0 installed and have had more problems with this one than I had with the one in the past. The new motor started to run hot before I left the repair shop's parking lot, they replaced the thermostat. The engine started to burn coolent within 100 miles, the shop pulled the heads and Jasper sent new ones. The engine started to burn coolant again within 2000 miles, pulled heads again, found a poor repair job done to the heads Jasper had sent. The last time Jasper sent new heads, they were aftermarket castings, really looked like some quality heads. When the new heads were installed, for some reason the rocker arms would not adjust out correctly, and the top-end sound like it was coming apart. When I picked the truck up the last time, the repair shop claimed they could do no more, so now I am totally screwed over. The best part there is only 20 miles on motor, and it's buring coolent again.

There is not a single shop that wants to work on it, because Jasper only pays $50hr. When I spoke to Jasper, they claimed that they can not make a repair shop work on the engine, there is nothing I can do.

What can I do?

 

you a AAA member? have a state consumer advocate? go to the Better Business Bureau ? that is all I can think of