I looked around so hopefully this hasn't been covered before...

If I drive around town my 93 351W 4x4 auto sounds and feels like it has a flooded cylinder or a miss or something.

After 5 miles of highway driving it starts to run pretty well. 5% throttle still seems to be a bit messy but hard on the throttle is fine.

After 50 miles or so. It runs like a dream. But if I pull into town and go stop light to stop light a bunch times it starts to run like crap again.

It used to run like it had a miss all the time. Then I replaced the FPR and TPS and a tuneup and it got to the point that it was fine on the highway and only took 5 minutes or less of driving to clear it up. I heard that high fuel pressure would cause the cylinders to flood at idle and would need to run for a while to get the plugs firing well which seems to fit what I have.

I replaced the FPR with a BWD not FoMoCo since it was 1/4 the price but could that be part of it?

Any ideas folks?
Dano

 

PULL CODES

check the fuel pressure at the rail, also pull vacum line going to fpr to see if gas is present. what spark plugs are you using? whats the timing set at?

 

Insufficient EGR Flow is my only code. No fuel in the FPR line, good vaccum. I dont notice any difference in idle with it dis/connected. Not sure if it should. Havent touched timing since I have owned it. Motorcraft plugs.

Will have to get fuel pressure gauge to do that part.

 

with fpr vacum line pulled and engine running the fuel pressure should jump up to 60+psi.

 

Is that just for the 351 engines? All the SBF EFI systems I've worked with say 40 psi is the fully loaded pressure.

Also, if you have a weak pump, it may maintain 40 psi at idle, but under load, it could lose pressure because it can't keep up with the flow rate.

Does your truck have the TFI ignition module mounted to the distributor? Those things can fail due to the excessive heat they get exposed to in that location. This is a well known problem, and here is a fix I recently implemented:

https://picasaweb.google.com/eycchu/87MustangEngine

 

I was going to get a replacement FPR just in case that was the issue when I decided that I would pull the battery cable to reset the fuel map ( I was told that every time the battery is pulled it resets the fuel map), up to this point I havent disconnected the battery. The first time I drove the truck around town it was great. After that it runs like crap.

After I start the truck it runs OK for a few minutes then garbage after that. Idle is terrible whereas before it was OK. 5% throttle is great, everything else is garbage. Sometimes I can ease into the throttle and get 30-50% throttle with no issues.

Before my idle would be normal for 10 seconds, then really low/bogged down for 10, then up, down, etc. My AC wasn't on or any of that. Now its constantly feathering between 800-1000. When bringing home 1800 lbs of shingles in the bed I was running 3k RPM (OD turned off) I was losing speed on a normal Iowa hill.

Boy this is fun. Going to probably look at a fuel pressure guage in the coming days once things slow down.

 

check your idle air control, its on the throttle body. mine was bad it kept fouling plugs to much fuel dump not enough air at idle

 

You must pull codes and report back. this way your not chasing ghosts.


the fpr should maintain 38-42psi of fuel. when the vacum line is pulled the fuel pressure will increase a bunch in some cases up to 60psi.

 

Alright I pulled the codes again. The 332 is the insufficient egr flow that I mentioned previously. I am not too worried about the 628. I got a hard shift 1-2 code when the truck was running rough a year and a half ago. Went away when the poor running went away. Seems like the E40D shift quality is tied to how well the engine is running.

332 (R,M) EGR did not open/respond during test or if memory code, did not open intermittantly - EVR or PFE

628 (M) Excessive converter clutch slippage - Transmissions

I have been looking around for ways to test my IAC. One test was to get the engine warmed up and then kick on the AC. If the engine bogs down rather than idling up then thats a sign of a bad IAC. My engine definitely bogs down about 300-400 rpms when the compressor kicks on. Another was to disconnect it while idling and if the truck died then the IAC should be good. It didnt die but came pretty close.

Thanks

 

pull the IAC and give it a good cleaning, worth a shot.

what size tires are you running? when was the tranny last serviced?

 

I am running 31 x 10.5 on 15in rims. I put a new filter and high mileage fluid in the tranny a little over a year ago, only a couple thousand miles ago. This was done after the 628 code went away but it did help smooth the trans out even more. Fluid level is holding fine and looks clean.

I am going to pull the IAC and give it a good cleaning and look over.

Got off work early, found the leak in my pool after a month long search for it, I got a feeling this is my day.

Edit: Cleaned the IAC, idle is running much better now. Still flutters a bit but kicking the AC on doesnt bog the engine down any more. Under load the engine is running better but still not good. I havent had a chance to drive a distance to see if its running like it was before/good yet.

 

you may consider buying a new IAC valve then. what is your timing set at with the spout connector removed? it should be at 10* and could be bumped to 11 or 12* for a little added spunk.

 

Looks like a new IAC is in my future. I am going to pickup a timing light and fuel pressure gauge tomorrow after work.

I took the truck for a spin earlier and it idled pretty good. Took off great. A "miss" here or there but tons better. Then after a few miles of being on the throttle is was back to its old self again. Seems like its flipping how its acting. But I have some good things to check out. Thanks for all your help guys.

Dan

 

So i picked up a new IAC this weekend. Put it in and man the truck drove amazing. No miss no nothing, I was loving it. I drove it about 10 miles, stopped for a few minutes and went home. As soon as I started the truck to go home it started the whole miss thing again. It cleared up while making the 10 mile trip again the next day but is still there occasionally.

I got cheap when I found the fuel injection pressure tester was $100 at harbor freight but I have a timing light so I will get to that once I get some time.

Looks like I need to try and get my hands on a pressure checker. I do have a cylinder pressure checker, maybe I can fashion a fitting to connect it and test that way.

 

I'm not sure if you've checked this yet, but the TFI ignition module is known to overheat on the Windsor type v8s (302 and 351). So it starts showing up once the engine warms up, and can get really bad in stop-and-go traffic, but may get better moving at highway speed due to more air flowing through the engine compartment.

I recently relocated mine from the distributor to the inner fender on my 87 Mustang while trying to diagnose a backfire problem. It was probably not the problem in my case, but I know a lot of people who have had the problem, as there was a class action suit against Ford for it. I think Ford settled case with the provision that they will pay for the repairs that owners have had to make:

Ford TFI Module National Class Settlement | The Center for Autosafety