View Full Version : What about the injectors...

05-30-2003, 09:34 PM
What are some signs that one or more of the injectors may be starting to fail. I have increasing difficulty starting it. It turns over well, but it's just taking longer to start. (There is no upshift arrow light...yet. And I still have the bolt holding my HB on.) Other symptoms that I'm having are:

1) A consistent "miss" under moderate to hard acceleration. This generally happens just after I press on the accelerator.

2) An occasional "miss" under low rpm acceleration. This happens between 1k and 1500 rpm under moderate (at most) acceleration. The engine is under a heavier load than if it were to downshift.

It is always as if the engine completely stops for an instant and then continues on as if nothing had happened. I'm not getting any codes relating to this. And the cylinder test passes too. I'm starting to think that it could be related to a fuel issue where I previously thought that it might be an ignition issue. I've put on a new fuel filter, but it didn't help. If it were the fuel pump, I'd have more problems (specifically at WOT) than I'm having now. There doesn't seem to be any fuel "starvation" issues at WOT and high rpms. So that leaves the injectors, or maybe the MAF, TPS or IAC. The latter 3 would have other indicators that would presumably point me in the right direction. Any other thoughts would be greatly appreciated. Thanks.

05-30-2003, 10:41 PM
My harmonic balancer broke after the head broke off of the bolt that goes into the crank to hold the balancer to the crank.The car ran okay but if you were under load like going up a hill,the car would miss and give all kind of problems.Just reach down and feel for the bolt head inside the main drive pulley,mine was broken off fully.

05-30-2003, 11:44 PM
How old are your spark plugs? I had the same symptom on both of my SC's, and both times it was the spark plugs and wires. Went with all motorcraft, problem solved on two occasions.

05-31-2003, 01:10 AM
The bolt is there. I did a visual inspection of it earlier (used a mirror). And the plugs, wires, DIS, Cam Sensor (all OEM) have all been replaced within the last year. (among other things) My initial thought was the crank sensor, but I don't get the up arrow when cranking, yet. That is partly why I'm starting to think that it is the "fuel supply" that is doing it. As I stated before, it only happens once, just after I punch it, so to speak. After that, it runs just fine. I'm thinking that the engine is initially "starving" of fuel until the injectors can catch up. But again, it's just a thought. I don't know too much about this type of stuff, so I'm hoping someone who does can tell me exactly what it is...Yeah, I know, I can keep dreaming. Thanks guys.

05-31-2003, 01:53 AM
It's not the fuel system.

Start at the top of this list and work your way down, by the time you get to the bottom it will be fixed.

Have you had a water pump leak? If so you need to clean the dried residue off the crank sensor and trigger ring behind the dampener. Use fantastik.

Could be the TPS. There are 3 wires. Check the Voltage reference for approximately 5V. Use a digital volt meter to backprobe the TPS signal through the TPS sensor ground. Work the throttle open slowly with the key on and enine off. It should start around .6-.99 volts and increase smoothly and linearly to just under 5 volts at WOT. Any drop outs or spikes in the voltage will indicate a defect.

Remove the MAF electronics from the MAF body and make sure the hot wires are clean and don't have anything stuck on them. Use a light spray of electronics cleaner and don't touch them with anything.

Replace the cam sensor.


05-31-2003, 10:25 PM
Thanks for the info. MAF is clean. I've been checking it regularly hoping it was something like that. I already have a new cam sensor on there too. That fixed my tach problem, but not the miss. I've not had a water leak since I've had the car (just over a year). I do have an oil leak though and now that you mention it, this problem may have started after I went through on of those automated car washes to clean up the underside of my car. Do I have to take off the pullies and HB to clean that up, or can I get to it without taking that stuff off? I've got some engine degreaser that I'm going to use tomorrow to clean up the underside anyway. I'll also check my TPS as well. I don't have a voltmeter yet, but this is a good exccuse to get one right? Thanks for the info. I'm hoping that I'll be able to fix this thing soon. I really want to take it back to the track... :)

06-01-2003, 12:35 AM
Hmmmm, since you haven't had a coolant leak lately it may not be a contaminated crank sensor. As for cleaning the crank sensor I have had sucess using a high pressure hose at a normal car wash. Since you have to clean the crank trigger ring to the method I used was to temporarily remove the belt and spray directly behind the damper with the engine idleing. Run it just long enough to give it a good cleaning and shut it back off.

Since your car passed the balance test it won't be injector related. The IAC isn't a miss maker, only an idle speed control.

It's most likely MAF or TPS. Check the ignition switch for intermetant shorts.


06-01-2003, 12:42 AM
Thanks for the info. I'll still try to clean the crank sensor though. It's pretty caked with oil down there. I'm going to check the TPS too. It just seems that I'd be having more trouble if it were the TPS. Oh well. It won't be too long and I'll have a brand new SC if I keep having to replace all these little things to keep it running! Thanks again.

06-01-2003, 06:57 PM
Cleaned the lower part of the engine today. It seems to have helped significantly. It was not nearly as hard to start and about 20 mins of driving did not produce a single miss. I'm going to further test it later as it was sprinkling here so the roads were wet enough to allow the @$$ end to go all over the place. But initial trials have shown to be effective. Thanks again Vernon for the help.

06-01-2003, 07:19 PM
Very good, I'll guess I'll add oil to my list of crank sensor contaminants. Glad you got it running right again.