Hoping for some guidance for this novice. Picked up a 1996 E350 that had been sitting for a few years. first thing I did was drop the tank, clean it out and install new fuel pump (don't remember the brand but picked it up at orielly) I also installed a new battery, air filter and serpentine belt. after priming the fuel system by cycling the key it started right away and was running pretty strong. It did have a higher than normal idle and when I drove it shifted gears a little harder than what I thought was normal. The check engine light also came on fairly quickly after starting.

After getting an OBD I scanner I pulled the codes and it was TPS voltage. I pulled the throttle body off and replaced the TPS, TB gasket and cleaned it up pretty good. After reinstalling the TB the van started right up , check engine light didn't come on, and idled great until it started stuttering a little (misfire). I test drove it and it misfired at idle, in drive at complete stop and most prominently when you got the vehicle up to speed and applied very little throttle to maintain speed. The van had plenty of power if you WOT but as soon as you let up and just maintained it would buck her and there. It seemed like it was a vacuum thing but I couldn't be sure. So I pulled the TB off again to make sure the gasket has seated properly and it was good. Then I thought I just got a bad TPS so I got another one with no change. I tested voltage at TPS and it was within specs (around .9 at idle up to 4.5 at WOT. Then I changed the plugs, wires, cap & rotor with no change.

Then I entered the rabbit hole of throwing parts at it. After checking the fuel pressure (35 KOEO and drops to 30 KOER at idle)I have to date changed the IAC, coil, FPR, MAP sensor and the fuel filter again with no change. fuel pressure seems consistent and doesn't drop over time or when the vehicle misfires at idle.

I have read some forums entries that suggest it could be the coolant temp sensor or even the ECM. However, hardly anyone who has experienced similar issues provided any conclusion to the problem. Either they are still battling it or just forgot about bringing some closure.

What am i missing? Timing, EGR, Etc. Dreading having to take this into a shop but it is driving me a little crazy. Any assistance you could provide would be greatly appreciated. Thanks for reading and let the judging began...

 

So while I don't have any conclusions... I have a 1994 with very similar symptoms (351 e4od E350.)

Just got it this weekend and just getting started. Im gonna start with some testing of grounds. Mine is EECIV - are you the old or OBD II? Edit just saw you have the OBD I as well.

The grounding scheme is such that things get goofy if the grounds aren't pristine. old Ford standards - ill be double checking it all.
My PO replaced all the normal sensors with auto zone stuff and no change - so I may open the computer and look for leaky capacitors...

An adventure no doubt.

 

How did the plugs look??? Fouled? EGR valve stuck open?

I would suggest you have a qualified mechanic look at it before you get any deeper into it.. You have replaced so many items, some repeatedly just by guessing. With so many items replaced, who knows if one of those parts are contibuting to the problem.You pulled off the TB to check your new gasket. Did you put another new on on ? Once a throttle body gasket is compressed, it should not be reused.

If you plan on troubleshooting, get the correct scan tool for your 1996 model and put the original parts back on the engine except the plugs, wires, cap and rotor. They are not bad and logically troubleshoot from there.Just because a code is thrown for a sensor doesn't mean it's bad. It's a direction to investigate deeper into that circuit.

 

Thanks for sharing in the adventure. I too will test grounds. I did check the inspect the ECM but didn't see anything obviously amiss.

 

Thanks for your feedback. Plugs looked good with normal light tan color around the tip. I have not tested the EGR yet but it is on my to do list. I did change the TB gasket each time it was removed but just out of habit. I wasn't aware that you couldn't reuse one of those if it had been compressed. Thanks for the knowledge as that's the main reason I am reaching out on this forum.

What exactly do you mean by "correct scan tool". As previously stated I have an OBD I scanner.

As for my original replacement of the TPS, I didn't just change it because of the code. I first ensured it was grounded, checked the reference and signal voltage. Only after it failed signal voltage testing did I replace. The second TPS was not a good choice but it happened and I own it now. That being said I did admittedly threw some parts at it in hopes of finding the problem.

And thats where I find myself now. I will reinstall the original parts as you indicated (minus the TPS) and start from the top. Thanks again for your feedback

 

It is my understanding begining in 1996, OBD 2 was the standard. Where are you plugging in your scan tool. In the cab under the steering column or under the hood, in the engine compartment?

 

It’s under the hood in the engine compartment. I believe this was the crossover year as it has an obd ii connector under the steering column as well but no scan tool will connect .Tried the cheap kind you borrow at Napa as well as my buddies latest snap on

 

If you are able to connect to the computer , please post the code(s) you get.
The 94 will give 2 digit codes and the 96 might give 2 or 3 digit codes.

If the scan tool is not able to communicate with the vehicle computer, check for power at pin #16 of the 96 diagnostic plug, also make sure pins 5&6 have a good ground.

As to the 94,,,,,,,,,,,, if you just got it, how long was the fuel setting in that tank?

If you are getting a high idle speed , you need to make sure there are no vacuum leaks, hoses, intake manifold mounting, and especially if somebody else worked on the vehiclee, they could have mixed up vacuum hoses and you need to verify each one is in it's proper place.

 

Hey bud - made any headway?

I'll be checking my grounds tonight. Once i get the truck back together ill be checking my sensor supply voltages. Good discussion of these here. Here!

I also popped open my fuel computer and have one bad capacitor (super high esr) so am replacing all 3 electrolytics.

Hopefully the computer fix and anything I find with grounds gets me back rolling without the misfire!

 

no progress yet. Probably have to wait until the weekend to tinker around. I’ll be checking out the sensor supply voltages link you posted so thanks for that. I did read on another thread about issues with the ICM. But right now I too need to put everything back together and start the whole process in a much more methodical non part replacing method. Keep me posted