Ford Van multiple cylinder misfire
302 Sequential fuel injection: Lab scope shows the coil not firing several random cylinders at a time. Pip signal to module has good scope pattern. Spout in or out makes no difference. Outout to coil drops out randomly. Coil and module getting 13 volts steady. Vehicle came from another shop. Has had full tune up, two distributors, a reman PCM, two gray modules and one Black module. Still running like crap. Ran a jumper wire from module output terminal to coil but no help. The module uses pip signal to fire coil . With spout out, PCM is not involved. Anybody has any suggestions?
Are you sure that you have good terminal tension at the coil primary connection?
Signal out of the module drops out at the module. Coil terminals look good.
“Drops out” meaning it goes low or high? The module pulls the primary to ground so if the module missed a beat, the primary would stay high. Going low suggests a module issue (which I see you've ruled out), a momentary or intermittent short to ground (which you've also ruled out unless you did an overlay instead of a completely new wire), or loss of ignition power to the coil. Based on…
I’m guessing this has a TFI module attached to the distributor? If so, make sure the correct screws are being used as I think one screw grounds the module to the distributor body.
This has a TFI module, but it is remotely mounted by 95 IIRC. It's on the firewall on the driver's side.
Hi Robert, “Has had full tune up” means go back and verify all work. What is the fuel pressure and quality? Any history? Has this thing sat in a back yard for years, now they want to resurrect it? “Outout to coil drops out randomly”? What is Outout? First impression: This favors the ignition switch on the column coming apart. Fords of the era had lots of problems with that. The housing would…
Scope shows good voltage at the module so I wouldnt think its an ignition switch…Will try a little pressure on the module harness.
We have checked firing order, compression, coil KV, fuel pressure, ran a temporary new wire from modlue to coil,
That era Ford was known for bad connections at the coil. I use to keep pigtails for that on hand. Tom
Will remove and tighten terminals to confirm… Connector tab broken off ( of course!!) but tight fit on terminals. evan used jumpers to confirm good connetion during testing.
Hi Robert, Did you confirm the distributor cap firing order rotation and wire locations. Sounds stupid, but I have had them towed in before due to incorrect firing order. I also recommend you pull the cap and watch the rotor while the engine is being cranked. The not firing several random cylinders at a time could be a jumped/ jumping timing chain or the teeth on the camshaft for the…
Firing order correct per Alldata. Would run okay, hard to get it to skip in shop , not a dead cylinder skip while straining under load but is getting worse. Lab scope shows PIP signal from distributor perfect so I wouldnt think its a chain issue. Distributor replaced twice so drive gear is good.
Hi Robert, Thanks for filling in some of the blanks… “still running like crap” is a pretty broad term. Not criticizing, just trying to help you home in on possible problems. Have you monitored coil power (+) with a test light while under load? The PIP is the trigger (-). A skip under load at or just above idle can indicate a sticking EGR valve. Disable/block off the EGR and see if that…
Random misfire so cannot pinpoint any cylinder. PIP scope pattern shows a group of two or more in succession not getting ground signal to coil from module. EGR has been unplugged as well as spout to eliminate a PCM involvment. Still have my OTC 4000e oftware so able to run self test but only had one code (PIP signal)when it arrived two weeks ago. Was erased before I got involved but no codes…
From all your testing, it really can only be an IC modules issue. These are fairly simple animals. I used to run Fords in the old days…carried a spare ICM in my glovebox for really hot days! I suppose you could check coil current instead of voltage as a way to determine load capacity, and eliminate that issue…I would be surprised if you could even get a Motorcraft, that hasn't been produced…
Trying to better my chances by ordering throught local Ford dealer but i agree totally.
Try disconnecting the transmission range sensor and see if it runs any better. I have seen several Motor Homes of that vintage that had corrosion in the connector and it would back feed the PCM ground and cause all kinds of running issues. Usually a new sensor and pigtail would fix the problem but a few did wipe out the PCM as well.
Worth a try but I thought that was an E4OD issue…
We just repaired one of these vans for a different issue with fuel pump that turned out to be a broken ground strap from body to frame, probably not related to your issue but is possible? I have been a tech for more than 40 years & have never seen this ground issue before now. Good luck
Recently had a Bronco of that era, long crank time, random misfire and poor power. Original test of the coil passed, easy 1" spark, but finally put a new secondary coil on it and she runs great. My belief is intermittent internal shorting.
It has neen replaced already but as we all know, faulty parts are becoming the norm. If module doesnt fix it, I may throw another coil at it. Hate guessing but sometimes reduced to just that. Old bossman used to say “ Columbus took a chance…”
If the PIP and SPOUT signals are good and never fall out, but the coil stops firing, the problem is most likely the TFI.(assuming your coil is good as well as power and ground remain constant) I had a 90ish F150 in here with 3 aftermarket distributors(3 different brands) and it would still display the same symptoms(misifring, random stalling) All ignition components were replaced multiple times…