JamesHigdon Posted August 16, 2012 Report Share Posted August 16, 2012 We've got a '94 Ford F-150 that came in on trade running ok that has since gone to hell. The truck ran out of trans fluid a day after we got it, we filled it back up and then a few days later it started missing real bad. I had one of our guys do a tune-up on it (which it needed regardless of the missing) including an Accel cap and rotor, plugs, wires and a throttle body/maf cleaning. No change. We ran a compression test which came out well withing spec. We re-set the timing thinking maybe the kid had moved it when he did the tune-up. No change. We checked for spark and fire to the injectors, all checked out fine. We replaced the ignition control module thinking it was causing an injector timing issue, nothing. I am now getting ready to check the timing of the injector pluses to the sparks per each cylinder and see if any answers are there...any ideas? We've re-run the spark plug wires through looms to keep them away from any cross-fire chances and that made no change. Traditionally if they have compression, properly timed spark and properly timed fuel they run? Link to comment Share on other sites More sharing options...
jwmbishop Posted August 16, 2012 Report Share Posted August 16, 2012 I would run it through a can of pressurized injector cleaner, do a vacc leak check on all hoses etc. - is the vacc gauge steady etc? Hyd lifters - collapsed lifters/worn rockers can play hell on the tune up - even though will crank and give good compression - hows the oil? Link to comment Share on other sites More sharing options...
JUMPSTER93 Posted August 17, 2012 Report Share Posted August 17, 2012 I would run it through a can of pressurized injector cleaner, do a vacc leak check on all hoses etc. - is the vacc gauge steady etc? Hyd lifters - collapsed lifters/worn rockers can play hell on the tune up - even though will crank and give good compression - hows the oil? Does it have a 351 camshaft in a 302? They have different firing orders. Link to comment Share on other sites More sharing options...
Bigdogracing777 Posted August 17, 2012 Report Share Posted August 17, 2012 im going threw the same issue with an 03 f 150 cylinder miss fire on 1 and 3 am thinking injectors are bad. Link to comment Share on other sites More sharing options...
JamesHigdon Posted August 17, 2012 Author Report Share Posted August 17, 2012 Bigdogracing, the newer Ford Injectors are infamous for going bad but don't forget to check the valve spring, they are weak on the newer motors and can pop pretty easily. As far as my problem, I have pulled the injectors out and checked them and they don't LOOK dirty at all. I have also traded injectors back and forth to see if the miss moved with the injectors and it didn't. The motor is stock and ran fine when it came in so it's not a parts swapping issue. The oil looks fine and the truck overall doesn't show any signs of neglect. Yesterday I broke out the oscilloscope and watched the injector wave forms; the duty cycles and periods between injector fire/plug fire where the same (100 milliseconds or about 370 crankshaft degrees at idle) across the 3 not firing cylinders and the ones that where firing (for what its worth 5/7/3 aren't firing). I am also beginning to lean to a mechanical issue in the valve-train; it's possible someone got in it when it was out of trans fluid and over-revved it trying to get it to move...if so the beatings shall commence. Link to comment Share on other sites More sharing options...
4cylfordz Posted August 17, 2012 Report Share Posted August 17, 2012 vein that it passed a compression test I'm going to lean away from the valvetrain being the culprit since a collapsed lifter or a bent valve will usually not make any compression. 1st it was my guess I would check the fuel pressure ( the regulator likes to go out on those years of trucks sometimes) and allot of time a good inj will not oppererate below oe pressure. Link to comment Share on other sites More sharing options...
Bigdogracing777 Posted August 17, 2012 Report Share Posted August 17, 2012 Bigdogracing, the newer Ford Injectors are infamous for going bad but don't forget to check the valve spring, they are weak on the newer motors and can pop pretty easily. As far as my problem, I have pulled the injectors out and checked them and they don't LOOK dirty at all. I have also traded injectors back and forth to see if the miss moved with the injectors and it didn't. The motor is stock and ran fine when it came in so it's not a parts swapping issue. The oil looks fine and the truck overall doesn't show any signs of neglect. Yesterday I broke out the oscilloscope and watched the injector wave forms; the duty cycles and periods between injector fire/plug fire where the same (100 milliseconds or about 370 crankshaft degrees at idle) across the 3 not firing cylinders and the ones that where firing (for what its worth 5/7/3 aren't firing). I am also beginning to lean to a mechanical issue in the valve-train; it's possible someone got in it when it was out of trans fluid and over-revved it trying to get it to move...if so the beatings shall commence. thanks buddy thats a good starting point Link to comment Share on other sites More sharing options...
KISS_Racing Posted August 18, 2012 Report Share Posted August 18, 2012 Bigdogracing, the newer Ford Injectors are infamous for going bad but don't forget to check the valve spring, they are weak on the newer motors and can pop pretty easily. As far as my problem, I have pulled the injectors out and checked them and they don't LOOK dirty at all. I have also traded injectors back and forth to see if the miss moved with the injectors and it didn't. The motor is stock and ran fine when it came in so it's not a parts swapping issue. The oil looks fine and the truck overall doesn't show any signs of neglect. Yesterday I broke out the oscilloscope and watched the injector wave forms; the duty cycles and periods between injector fire/plug fire where the same (100 milliseconds or about 370 crankshaft degrees at idle) across the 3 not firing cylinders and the ones that where firing (for what its worth 5/7/3 aren't firing). I am also beginning to lean to a mechanical issue in the valve-train; it's possible someone got in it when it was out of trans fluid and over-revved it trying to get it to move...if so the beatings shall commence. I need some help here? Why are you even considering fuel, fuel pressure or injectors? By saying not firing are You saying there is spark but no combustion? When I see the statement not firing I'm thinking You have pulled these plugs and have grounded them and you are not seeing spark. It is most likely my misinterruptation but just wanting to make sure I follow. Link to comment Share on other sites More sharing options...
4cylfordz Posted August 18, 2012 Report Share Posted August 18, 2012 We've got a '94 Ford F-150 that came in on trade running ok that has since gone to hell. The truck ran out of trans fluid a day after we got it, we filled it back up and then a few days later it started missing real bad. I had one of our guys do a tune-up on it (which it needed regardless of the missing) including an Accel cap and rotor, plugs, wires and a throttle body/maf cleaning. No change. We ran a compression test which came out well withing spec. We re-set the timing thinking maybe the kid had moved it when he did the tune-up. No change. We checked for spark and fire to the injectors, all checked out fine. We replaced the ignition control module thinking it was causing an injector timing issue, nothing. I am now getting ready to check the timing of the injector pluses to the sparks per each cylinder and see if any answers are there...any ideas? We've re-run the spark plug wires through looms to keep them away from any cross-fire chances and that made no change. Traditionally if they have compression, properly timed spark and properly timed fuel they run? the older ford EFI system does not have a specially timed injection system. all injectors pulse at the same time. you can essentially flip the wiring harness between injectors if they will reach to test for a bad harness. Link to comment Share on other sites More sharing options...
JamesHigdon Posted August 20, 2012 Author Report Share Posted August 20, 2012 I need some help here? Why are you even considering fuel, fuel pressure or injectors? By saying not firing are You saying there is spark but no combustion? When I see the statement not firing I'm thinking You have pulled these plugs and have grounded them and you are not seeing spark. It is most likely my misinterruptation but just wanting to make sure I follow. You are right, I should have said not combusting or not contributing. I am getting spark to those cylinders but when you pull the plug wire off those cylinders there is no change in the misfiring sequence. Link to comment Share on other sites More sharing options...
KISS_Racing Posted August 20, 2012 Report Share Posted August 20, 2012 I need some help here? Why are you even considering fuel, fuel pressure or injectors? By saying not firing are You saying there is spark but no combustion? When I see the statement not firing I'm thinking You have pulled these plugs and have grounded them and you are not seeing spark. It is most likely my misinterruptation but just wanting to make sure I follow. You are right, I should have said not combusting or not contributing. I am getting spark to those cylinders but when you pull the plug wire off those cylinders there is no change in the misfiring sequence. High resistance in wiring harness? I would ohm out the harness and or check the contacts at the injector to make sure they are not spread to far apart thus causing bad connection. since injectors were swapped around and no change happened it has to be there. Link to comment Share on other sites More sharing options...
KISS_Racing Posted August 20, 2012 Report Share Posted August 20, 2012 Also... Does the 302 in this truck have the pigtail and plug on the distributor? If so, don't forget to pull the plug to check timing. I know, your a shop and I'm sure You know but if your tech hasn't done one it is a common point people forget. I am really leaning towards harness. If I read correctly You have replaced (CM) so only thing left for me is low or no voltage at injector. Do you have access to an injector flow bench? If not I need to introduce You to a close friend here in San Antonio. I have meant to ask you several times just forgot. I have a business meeting tonight around 5pm. I can be available between 4p & 5p if I can help on the phone. Grab my # off the CCM banner and give me a shout around that time if you would like. Mark Link to comment Share on other sites More sharing options...
4cylfordz Posted August 21, 2012 Report Share Posted August 21, 2012 have you checked te fuel pressure? Link to comment Share on other sites More sharing options...
KISS_Racing Posted August 21, 2012 Report Share Posted August 21, 2012 have you checked te fuel pressure? I love learning new things and filing them away for the future. If the truck runs on the same 5 cyl but not on the same 3cyl, I'm curious as to how fuel pressure would only be affected on those same three cyl everytime they are called to fire? Thanks in advance for educating me... Link to comment Share on other sites More sharing options...
jwmbishop Posted August 21, 2012 Report Share Posted August 21, 2012 A marginal injector can "dribble" under less than ideal pressure while the good injectors still atomize well. The dribbled fuel makes for a quenching of the flame front. However above you said you swapped the injectors and the problem did not follow - so again that does point to the harness or module. Doesn't hurt to verify pressure though... as the port floor can cause fuel "fallout" with the same effect - and if ALL injectors dribbled a bit due to low pressure it would show as a miss fire on the worse shaped ports. Link to comment Share on other sites More sharing options...
4cylfordz Posted August 21, 2012 Report Share Posted August 21, 2012 have you checked te fuel pressure? I love learning new things and filing them away for the future. If the truck runs on the same 5 cyl but not on the same 3cyl, I'm curious as to how fuel pressure would only be affected on those same three cyl everytime they are called to fire? Thanks in advance for educating me... Ok. this is what we can determine by verifying the fuel pressure. With this one simple 5 minute test we can determine all sorts of stuff and also rule out the mechanical end of the fuel system. Lets start with the symptoms of low pressure, in this case the engine will typically run and be sluggish, often hesitant with heavy detonation upon acceleration. Symptom #2 is less common but still happens...high pressure, Fuel injectors are nothing more than small electronic valves typically using an electromagnet and spring to open and shut the valve. when the fuel supply lines are over pressured, the injector does not have enough power to close the valve initiating a open stream of fuel to that cylinder often misdiagnosed as a misfire though actually is a foul. the drivers side bank is where the the Fuel Pressure Regulator and the fuel inlet which in the physics this will most likely be the area of the highest pressure in the line so naturally injectors on this side of the motor (minus injector #8 since it is located on the side of the log with more injectors IE 1234&8 vs 567) will most likely fail during high pressure situation as the further you get away from the wide open injectors the lower the line pressure will be letting the other injectors operate more correctly. But before you say well #3 is on the other side let me explain. #3 happens to be located directly underneath the vacuum tree. Often when the diaphragm in a fuel pressure regulator fails raw fuel will be introduced to the vacuum system and thus ending up directly pouring into #3 runner causing the same misfire or fouled plug situation. not saying that it cant be a blown ecm or burned up harness just saying with five minutes and a rent-a-tool you can be extra sure that its not just a bad regulator causing a mystery misfire. I am contributing my knowledge to help out a fellow racer, not be slandered for it. So before you mark my posts as irrelevant to your awesomeness I suggest you think wisely as one day i may have the answer to your question as I treat all of yours with the utmost respect with the intentions to learn something new. Thank you, Dan Link to comment Share on other sites More sharing options...
HiTech Posted August 21, 2012 Report Share Posted August 21, 2012 .ID FIRE IT UP AND SHOOT SOME STARTING FLUID CAREFULLY OF COURSE AROUND THE INTAKE ..... .. ....CHECK THE BRAKE BOOSTER ,,,AND THE CHECK VALVE ... Link to comment Share on other sites More sharing options...
KISS_Racing Posted August 21, 2012 Report Share Posted August 21, 2012 have you checked te fuel pressure? I love learning new things and filing them away for the future. If the truck runs on the same 5 cyl but not on the same 3cyl, I'm curious as to how fuel pressure would only be affected on those same three cyl everytime they are called to fire? Thanks in advance for educating me... Ok. this is what we can determine by verifying the fuel pressure. With this one simple 5 minute test we can determine all sorts of stuff and also rule out the mechanical end of the fuel system. Lets start with the symptoms of low pressure, in this case the engine will typically run and be sluggish, often hesitant with heavy detonation upon acceleration. Symptom #2 is less common but still happens...high pressure, Fuel injectors are nothing more than small electronic valves typically using an electromagnet and spring to open and shut the valve. when the fuel supply lines are over pressured, the injector does not have enough power to close the valve initiating a open stream of fuel to that cylinder often misdiagnosed as a misfire though actually is a foul. the drivers side bank is where the the Fuel Pressure Regulator and the fuel inlet which in the physics this will most likely be the area of the highest pressure in the line so naturally injectors on this side of the motor (minus injector #8 since it is located on the side of the log with more injectors IE 1234&8 vs 567) will most likely fail during high pressure situation as the further you get away from the wide open injectors the lower the line pressure will be letting the other injectors operate more correctly. But before you say well #3 is on the other side let me explain. #3 happens to be located directly underneath the vacuum tree. Often when the diaphragm in a fuel pressure regulator fails raw fuel will be introduced to the vacuum system and thus ending up directly pouring into #3 runner causing the same misfire or fouled plug situation. not saying that it cant be a blown ecm or burned up harness just saying with five minutes and a rent-a-tool you can be extra sure that its not just a bad regulator causing a mystery misfire. I am contributing my knowledge to help out a fellow racer, not be slandered for it. So before you mark my posts as irrelevant to your awesomeness I suggest you think wisely as one day i may have the answer to your question as I treat all of yours with the utmost respect with the intentions to learn something new. Thank you, Dan Wow, so much for saying I was willing to listen and learn! I will now mark you as quick to get pissed when asked to explain your theory... Contrary to what you might hear I have been working on cars for 36 years and yes I to this day learn new things. So much for asking a fellow racer to educate me.... FSAE, My offer stands. Call if you need any help... Link to comment Share on other sites More sharing options...
4cylfordz Posted August 22, 2012 Report Share Posted August 22, 2012 quick to get pissed, I'll have to disagree , quick to defend myself defonintly guilty... however I interpreted you reply as a loaded post (apparently I miss judged the contex clues as a challenge to be graded on rather than a remark of true curiosity). I now stand corrected.... So from now on I want to see only standardized ASE style questions JK. let's call it spilled grease. take it for what it's worth as it is a very possible situation. though with all the master mechanics, ASE certified ASADE certified the respected machinists and shade trees (...allot like myself but I'm more of a micro machinist) that post on here im sure the answer to this fellas problem is just around the corner. Link to comment Share on other sites More sharing options...
KISS_Racing Posted August 22, 2012 Report Share Posted August 22, 2012 quick to get pissed, I'll have to disagree , quick to defend myself defonintly guilty... however I interpreted you reply as a loaded post (apparently I miss judged the contex clues as a challenge to be graded on rather than a remark of true curiosity). I now stand corrected.... So from now on I want to see only standardized ASE style questions JK. let's call it spilled grease. take it for what it's worth as it is a very possible situation. though with all the master mechanics, ASE certified ASADE certified the respected machinists and shade trees (...allot like myself but I'm more of a micro machinist) that post on here im sure the answer to this fellas problem is just around the corner. Thanks Dan... Unlike benchracing when it comes to helping people I'm like you I'm serious and it was not my intention to challenge You or anyone that you'll are wrong. I hadn't heard of such a thing and wanted your take. I know on boosted (supercharged or turboed) vehicles fuel pressure is a must. We have had vehicles begin to go lean and found it wasn't lose of fuel pressure although you would see the gauge going down, but instead the wire going to the fuel pump wasn't big enough to carry required current at higher volume. We would add a jump box or battery charger with a wire at the pump and not have an issue. Imagine trying to explain that and get people to buy into it... Put in a bigger gauge wire and a relay then problem solve. Some of the most fun I have on here is in this section. Mike, myself, You and others helping people with issues they can't figure out. Mike will tell you we have gone months on one issue as people have time to work on the vehicle. Thanks again for explaining. Mark Link to comment Share on other sites More sharing options...
JamesHigdon Posted August 23, 2012 Author Report Share Posted August 23, 2012 Long few days...this mess just keeps getting deeper besides that. We pulled the valve cover today to find no bent pushrods, no broken valve springs and all rockers...well rocking. We tested the fuel pressure with two different gauges and it's in spec. We have pulled the SPOUT plug when setting and checking the timing as per Fords instructions. I have leaned towards the injectors but changing them from one cylinder to another didn't make the miss-fire move and we have now checked injector pulse with both injector lights and an oscilloscope...hell I even pulled the injector plugs and cleaned them while making sure the pins where tight in the cavities. Tomorrow we start over. We are rechecking compression on all cylinders, checking spark timing/ordering/strength with the 'scope, checking injector pulsing (can anyone confirm if this motor fires all the injectors at once, that seems wompy but who knows with early injection), the checking exhaust manifold temps to see how big our power balance issue really is. My plan is to run one cylinder totally unhooked (plug wire), let the motor fully cool and then hook that cylinder back up to see if it's totally dead or just weak. I may throw 3 injectors at it if nothing else shows up with the thinking being a weak injector plus a weak cylinder may mean a weak injector will fire on a better cylinder. If nothing then Mark I will be calling!!! The worse part is this was a trade in so it's basically a big lump of misfiring cash sitting in the shop! Link to comment Share on other sites More sharing options...
4cylfordz Posted August 23, 2012 Report Share Posted August 23, 2012 what firing order are you using? 1-5-4-2-6-3-7-8 ? Dont forget that in 1994 the 302 in the f150 and Bronco got a new rolla cam and the 351w firing order that came with it 1-3-7-2-6-5-4-8 Link to comment Share on other sites More sharing options...
KISS_Racing Posted August 23, 2012 Report Share Posted August 23, 2012 what firing order are you using? 1-5-4-2-6-3-7-8 ? Dont forget that in 1994 the 302 in the f150 and Bronco got a new rolla cam and the 351w firing order that came with it 1-3-7-2-6-5-4-8 <Hitting Like Button> Link to comment Share on other sites More sharing options...
JamesHigdon Posted August 24, 2012 Author Report Share Posted August 24, 2012 what firing order are you using? 1-5-4-2-6-3-7-8 ? Dont forget that in 1994 the 302 in the f150 and Bronco got a new rolla cam and the 351w firing order that came with it 1-3-7-2-6-5-4-8 The truck is an early '94 as is the motor, the core support however is out of a truck with the later roller cam 302...it runs GREAT with the 1-5-4... firing order but the 1-3-7... listed on the core support was wrong! Thank you A TON for the suggestion as well as everyone else for the tips. This situation ended up being a GREAT lesson for our new tech fresh out of highschool as he now knows a ton of diagnostic procedures PLUS that you can't always believe what you read on the core support! Thanks again everyone!!!! , 4cylfordz, I'm going to find you at a track sometime and fund some of your favorite beer or food! Link to comment Share on other sites More sharing options...
KISS_Racing Posted August 24, 2012 Report Share Posted August 24, 2012 Racers helping racers! I love it... Link to comment Share on other sites More sharing options...
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