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1990 Ford Ranger Pick-up Malfunction - Ignition System
Question: I think I have a ignition problem.When the truck is ideling there is a slight shudder or hesitation.When driving there is no power on accelerationand the engine runs rough.The fuel pump is new, fuel pressure is fine.The plugs, plug wires, distributor cap and rotor button are all new.Could it be the coil?If it is, how do I check it.The manual I have does not give any specs for 1990 model.Could it be a compression problem? The truck has 216, 000 miles.Also, I replaced the fuel injectors about 15, 000 miles ago.Also, when holding a piece of paper over the exhaust, it makes an intermitent popping noise.
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Owner: another thing, when holding a piece of paper near the end of the exhaust it amkes an intermitent popping noise.ta, ta, ta...ta, ta, ta, ta something like that
Technican: Hello, An ignition problem causing a lack of power comes down to timing. ( what with all you have replaced, little else would be suspect.)
However, a lack of power due to low compression is certainly believable at this mileage. Perform a compression test and see what you get. The exhaust sound you note could be a burned valve. Compression leaking past a valve equals low power.
Compression leaking past a head gasket equals an engine overheat, lack of power, hard starting, coolant building up in the overflow resivoir.
At this mileage if you want to keep this vehicle consider a new timing chain/belt and inspect the cam and crankshaft gears for wear that would call for replacement while you are there.
Owner: Another thing I forgot to mention is that there is a slight oil leakage down onto the exhaust.Would this indicate a head cover gasket problem?I am going to get a compression check device tonight and will let you know tomorrow what I find out.
Technican: Head cover (as in valve cover) gasket allowing a leak is a strong possibility here and would be replaced as part of a valve job or head gasket replacement repair.
Owner: WellI did the compression test and here are the results.What I will do is give each cylinder readings as follows, first stroke then seventh stroke followed by first stroke, seventh stroke after a squirt of oil .1st cylinder, 85, 140-90, 170.2nd cylinder, 85, 160-90, 180.3rd cylinder, 85, 155.90, 180.4th cylinder, 80, 150-90, 160.5th cylinder, 85, 140-90, 160.6th, 85, 140-90, 160. Does this mean that the head gasket is leaking?
Owner: I just got everything hooked back up.When I started the truck back up it ran fine for aprox.10 seconds before the rough idle came back.I'm sure that means something, I just do not know what.Could this mean a bad exhaust valve?Also I noticed that when I close off the pcv valve, which is working, the engine is unaffected.I seem to remember that when I would do this the engine would just about stall.Is this right?
Technican: The compression test readings you sent are good. No reason to suspect problems with head gasket or a burned valve.
Compression rule is the lowest reading cannot be less than 75% of the highest reading. Your engine passes the test by a good margin.
I'm now thinking you have a vacuum leak or a lazy fuel injector spray at idle causing a lean burn misfire.
Have you inspected all your vacuum hose connections carefully for splits, disconnections, etc. at the full run and each end of the hose?
If you can rattle the pcv valve when disconnected/removed from the hose I wouldn't fault it for not stalling the engine when you block it off.
Your injectors are not that old but may have a slight restriction that alters spray pattern and quantity at idle. Can you remove spark plug wires (one at a time) from either end and see which cylinder is least effected? Do you have insulated pliers to avoid a shock from the ignition?
Can you treat the combustion chambers for carbon build-up that would effect cylinder efficiency?
Owner: What do you mean about treating the cylinders for carbon buildup.How would I go about doing this?What would be the best way to check or clean the fuel injectors?
Owner: One thing I forgot to mention is that about 2 weeks ago one of the electric plugs came loose from an injector.When this happened the truck ran very rough, but after I found out what had happened and plugged it back up it ran fine.Could this have damaged it in any way.I came across something that said fuel injectors could be clogged or go bad electrically.How would I be able to tell?
Technican: The best way to clean fuel injectors is to flush them with an injector flush chemical. You can usually find a flush at an auto parts store. It is not the same as a fuel tank addative to clean injectors. They can help you decide the products application to your needs.
Having a fuel injector unplugged for a period will not damage it. Nor clog it. To see if a particular injector is electrically bad you can unplug it and take an OHM reading and compare it to another injectors test (OHM) result. To see if the computer is firing the injector properly you need a test device called a node light. The node light plugs into the injector wire connector and will flash if the command from the computer is getting through (engine running).
To "de-carbon" cylinder combustion chambers you need another product from your parts store. Follow directions on the product. One treatment is not always enough but often does the trick.
Owner: Man you should see these injectors.There were 3 that were totally gunked up at the top.What wouild be the best way to get this stuff out of the screens?Also, when I get ready to put everything back in, how can I be sure which injector plug goes to its proper injector?
Technican: I use a chemical Berryman B-12 Carb and Choke Cleaner and compressed air (wear safety glasses) to clean injectors that are removed.
Your injector wiring harness should go back in place and judging by the length of the wires one can reason which connections go where. If your injector wires are color coded we can get a schematic and match connectors to injectors.
Owner: , Do you add the compressed air to the top or the bottom of the injectors?You are right about the different lengths on the wiring harness, but there are two connectors for each length.The wires seem to be color coded.I don't know if my Haynes manual lists these or not.Maybe you can find these on your end.The fuel rail seems pretty dirty on the inside also.I will try to add cleaner and blow it out too.
Technican: The chemical is in a spray can with a straw to pin point the spray. I use compressed air to blow away what comes loose with the chemical and to dry what I'm cleaning up.
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