Engine stall at 3000 RPM

[SVOMark]

When accelerating at low rpms and without a lot of boost car runs well. At 3000 RPM under 10-12 psi boost its just like the gas get shut off. It studders hard.

Car has been setting for a while (2 years or so) with half tank of gas. Filled tank up with 93 octane and put in a can of seafoam. Still same problem. Thinking fuel filter, fuel pump???


Its an 85.5 with a few mods - valve kit and adjutable boost controller. Its the one in Pats pic!!!!

[MikeFleming]

What does it do after it stutters? Does it recover immediately at a lower RPM setting? Or take 5-10 seconds? Will it rev at a lower power (boost level) to a higher RPM?

Fuel flow, VAF hose collapsing, lifters pumping up (due to weak valve springs), etc. - all can cause the symptom you're describing.

[BrianM]

Stick a fuel pressure gauge on it and see what you get. May very well be the fuel filter or pump. New ignition parts (properly gaped plugs, Motorcraft wires, cap and rotor) would also be a likely possible cause.

Edit: The guru beat me typing and has other ideas. Take his advise first.

[SVOMark]

After it stalls the rpms drop and no matter how much the throttle is open and it decelerates. When it gets to about 2000 rpms it will run again until it hits 3000 rpms again. It's a pretty violent drop in rpms. Under low boost <4 psi it runs great until it gets to 3500 rpms and then it drops out again. It just seems like its not getting gas.

[MikeFleming]

Fuel flow or valve springs. STOP driving it and get a fuel pressure gauge on there.

[SVOMark]

Hows the best way to hook up the fuel pressure gauage?

Runs much better after filling up the gas tank. As the gas is used it runs worse.


Fuel flow or valve springs. STOP driving it and get a fuel pressure gauge on there.

[TheSVOTrust]

Before you start tearing into it.....

What was the condition when parked? Ran, Ran great, was not running perfect so we parked it etc etc.
When you TRIED to start (just now after nap) What did you do? But a battery in and crank? KNOW you had bad old gas but got running, started hard, ran rough or "just wouldn't start"?

IF this was a good running car - then getting that old gas should have been your first effort (drop tank)
NOW - you have 50% old gas and 50% new gas with stuff it in! (that doesn't equal good gas)

Mike is correct with 2.3 EFI T/C's in that is comes down to fuel pressure/octane and spark. We will assume your fuel is bad (can say your injectors aren't gummed up without seeing) can we assume your plugs and wires are good too? IF SO - address the fuel and then see where you are. IF NOT, address the fuel then change the plugs and wires

Mark

[MikeFleming]

The 85.5/86 models have the square intake and there is a Ford Schraeder valve on the fuel rail, slightly forward of the dip stick tube. You will need a Ford-type adapter.

[SVOMark]

The car has run fine the past few years. It doesn't get driven very much. But this is the first time it has not run right.

After putting in a new battery the car started much like you would expect a car to start after sitting for a while. After it turned over a few times it started right up.

Thanks guys. I put a gauge on it this weekend.

[Patrick]

Runs much better after filling up the gas tank. As the gas is used it runs worse.

BINGO!!!

There's a crack in the fuel hose between the pump and the fuel pump bracket. When the fuel level drops below the crack, the pump spews the gas out of the crack and back into the tank, rather than going to the engine. Been there, done that. We went through this together at the Best Western parking lot in Richmond Ky with Gyrhead's car when you and I met the first time.

[Stinger]

BINGO!!!

There's a crack in the fuel hose between the pump and the fuel pump bracket. When the fuel level drops below the crack, the pump spews the gas out of the crack and back into the tank, rather than going to the engine. Been there, done that. We went through this together at the Best Western parking lot in Richmond Ky with Gyrhead's car when you and I met the first time.

You got it...that's exactly what I thought when I saw that information.

[Desert Patina]

If its okay, I'm having the same problem so I'll go through and answer the questions already asked...Description:at 3000-4000rpm it maintains steady power all the way up to the stock 8psi boost. The needles are all stable and happy.


Between 4500-5500 it feels like it is stuttering, with some violent bucking / stalling as it approaches 5000+. For each stall, it only lasts a bit less than a second, enough for the RPM's to drop back into the low 4000's or even below 4000 where the power returns with a vengence.


Also just as the car enters boost, it seems to retard just slightly until the PSI picks up. This is slight, but I thought I'd mention it in case it is related.


Answers to previous questions...


Q. What does it do after it stutters? Does it recover immediately at a lower RPM setting? Or take 5-10 seconds?
a) It seems to recover pretty quickly.


Q. Will it rev at a lower power (boost level) to a higher RPM?
a) Yes, it seems to be a combination of high RPM and boost that stalls. High RPM at low boost, and low RPM at high (8psi) boost sounds more like occasional missing than stalling at worst.


Its all new gas, and I've put more than 100 miles its on its third tank of gas since having the tank washed, putting in a new head gasket, TFI, radiator cap, plugs and wires, ignition coil, and both fuel pumps and filter.


It also seems to do more when the temperature outside is warmer.


Many thanks!

[TheSVOTrust]

Knowing all the work that has been done - I would question the plugs!

Wrong type installed out of box (platinum)
Too wide a plug gap (anything over .030)
One damaged by a friend helping you (and you don't know it)

Mark
P.S. Admin (read Mike) want to split this thread? I know he will let us know how it goes!!
Best thing about forums is we can use it for all the cars (you know how they hate wrong plugs)

[Desert Patina]

Thanks.

As it turns out, while driving it home tonight (where it passed smog!) it happened again, at low rpm and relatively low boost. (Not even WOT).

So when it works: Smooth progressive pedal when the engine is warm
when it bucks like a bronco: jumping on the throttle when the engine is relatively cold

All the above still applies.

Oh, and for the record they are Motorcraft copper plugs.

The only components of the ignition I didn't replace is the PIP and rotor (I have them, just waiting to do it when I have the time to press out the distributor shaft).

[TheSVOTrust]

They are good plugs if gapped down. I want to say they are .036 out of the box.
You can always plug just #1 get a look (condition of burn).

Sound's like the ECC-IV is pulling out timing (like it should) but because it is reading knock, poor octane or lack of fuel.
(Spark and Fuel can feel like the same issues)

IF the rotor is really bad (that could be the spark issue) Are you pressing out shaft because the car had a different distributor than stock 84/85 (common to have a 86 style) ?

Anyway I REALLY think you are close !! (done so much so far) Sometimes I have people check their work (I've seen everything from wrong firing order to poorly set up timing) But with Barrett Jackson so close I'm hoping I can just stop by!
I know Doug in Glendale expects a visit!

Mark
P.S. I wish i could find the guys in Mesa that I went over to to get their SVO running (after weeks of talking on the forums) I tired and tried to explain how to set up timing without a cover -but I think they just held out until I said "I'll be there this weekend - how is 1PM?" They drove it for the first time that afternoon!

[Desert Patina]

You are always welcome for a visit.

For the most part it is there, I have it smogged and ready to register today. It drives really well, only bucking when I kick it while its cold. I'd buck too if it were me.

I'm going to start tying things down in the engine compartment. The battery and VAM are loose, (so is the ECU for that matter). Time to tidy things up and see if that helps.

As for the distributor shaft, I'm working off of a howto on the internet. It actually just hammers out the shaft, if that isn't needed then everything is that much easier.

[Desert Patina]

I hope it is just the flopping VAM, but I do have some reason now to think it is.

It did run badly, and then I cleaned the VAM (but it was already clean) and it ran great. But not just that, when I pulled the codes today it said 54, which I think meant VAM is missing. When I unplugged and then replugged in the VAM, the error code disappeared.

The only thing I could do today for the VAM was to tie it down with a wire tie.

[Desert Patina]

Well, at the end of the day it appears the problem was the belts.

I just replaced the Power Steering that was removed long ago, and replaced the belts. The car drove worse and worse until it finally died (I thought it was gas, so it died just as I pulled up to the pump).

After a jump, it died again about two miles later. The headlights were flickering, and all of the missing issues and retarding was at its worse.

After a recharge of the battery, and a ride home where it was driving badly again, I though about a 3g alternator replacement.

But then I remembered that the belts were new, and still bent. Its likely that they were relaxing, and the alternator pulley was not spinning as well.

Sure enough, on closer inspection, the belts were pretty loose. With a crow bar's help, I tightened them back up. Now... now there is no missing at all.

Considering that the 3g will up the voltage in the system, I'm contemplating that swap still. But in the mean time its running better than ever.

Oh, and tethering down the VAM seemed to make things better also.