I have a 91 regal on a John deer chassis with 460 and on my way to trip it started idling rough and bogs if you give it to much gas I'm looking for the spot to hook up a scanner to see what the problem is

You might consider running some Red Line Fuel System Cleaner through it first. There are lot of good similar products on the market, but RL has delivered the best results for me.

AND----------------Welcome to the forum

It was all of a sudden never ran bad before has to be something simple blows black smoke like its running rich but it efi

Our T-bird has gone from smooth as silk to barely running a couple times. Plugs and wires both times.
It's a Ford thing.

I have a 460 and it did the same thing as you described 3x. The first time the loss of power wasn't too bad.

1st time it happened the EUL light came on too. I traced that to a bad oxygen sensor. 2003 Post - Click here

2nd time the same EUL light came on - So, without testing, I changed out my Oxygen Sensor and promptly wasted my money. I traced it back to a bad EGR Valve Position Sensor 2009 Post - Click here

The 3rd time it didn't trip the dash idiot light but it was exactly as described by you. This is probably the problem. My intank fuel pump was failing/weak.



Here is the link to that post, another problem from 2009

When you do figure out what is wrong, update this thread so we know what happened.

When troubleshooting fuel injection systems, I always check fuel pressure. Fuel pump, fuel pump relay, and pressure regulator together provide stable fuel pressure to the injection system.. Mechanical failure in the fuel delivery system often does not set an error in the CPU, but the engine knows! Bill NY saw this apparently and I had a similar problem with my Ford Ranger in tank pump.

During cranking there is usually a fixed amount of fuel being delivered, until engine starts and computer takes over. If it fires while cranking your injectors and spark modules are probably OK.

To keep it running, the computer actively senses several inputs to decide how much fuel to deliver. This is the normal "closed loop mode" If critical input sensors fail the computer will go into "open loop" mode (limp-in mode), set an error code (hopefully) and deliver an over rich mixture until corrected or all plugs foul.

Your symptoms could be due to a defective MAP sensor, a defective oxygen sensor, or a bad throttle position sensor (or maybe just a wire that fell off one of them) I have had all of these fail at one time or another on my Ford vehicles.

Check the harness condition for all the sensors you can find.

Check fuel pressure.

Check for error codes (sorry, not sure where your diagnostic plug is located.)

My in tank pump is new so is filter though this don't mean anything

Does your coach have an idiot light that says EUL on it? What is your data tag number? Maybe you're close to mine in the production run. Here is the tag from my 1991 commercial conversion.

9102 3709 33S-12


When you turn on the ignition, do you hear the fuel pump running in the tank?

Perhaps you have a bad fuel pump relay. Mine is mounted behind the right side headlight bucket and was hanging upside down causing road spray to get into the contacts. Your coach should have that relay in the same spot - there are two of them mounted there. The other one is the ECM Relay.

If you don't hear the pump running, or you have weak fuel psi, perhaps you're not getting full current under a running load to the fuel pump. Maybe this is why you needed to replace your fuel pump before?

Your fuel pressure is prob OK (hopefully!) since system has been serviced. Check those relays! Sounds like you're running rich... (limp mode?) Good reason to try and get codes now.

My Ford knowledge is based on cars, not trucks. Early 80's used the MCU system, late 80's they went to the EEC-IV system until about 1994, then on to the OBD-1 and OBD-2 systems, and on and on. I'm guessing you have EEC-IV?

The MCU and EEC-IV systems had similar diagnostic plugs (one or two) found in various locations around the engine compartment, usually about 4-6 wires. One of these was the STI (self test input) when this lead is grounded, the self test mode is activated. Another wire is the STO (self test output) which alternates from 5 volts to ground to flash the error codes. The error codes are 2 or 3 digits depending on system type.

Here is the EEC plug on my 94 Ranger, driver side behind battery:



The plugs themselves:



Simple code scanners used to be common. In a pinch you can use a ground jumper and a voltmeter to read them.

The newer OBD (on board diagnostic) systems have far more sophistication and require proprietary software to access in some cases... dealer only!

See if your owners manual has any info or maybe stickers on engine, firewall, etc.

Since your symptoms were sudden and severe, I don't suspect oxygen sensor. Bad wire, or MAP sensor is #1 suspect for me, then maybe throttle position sensor? Don't forget to look for vacuum leaks (esp to MAP sensor!) Good luck

TROUBLE CODES Here, at this link, are the 2 & 3 digit codes:
.

quote:

Originally posted by Steve VW:
My Ford knowledge is based on cars, not trucks. Early 80's used the MCU system, late 80's they went to the EEC-IV system until about 1994... I'm guessing you have EEC-IV?

I'd bet the house on that one. Mine is a 91 and it is EEC-IV

That setup on my Barth is located next to the ECM and Fuel Pump Relays. It's right behind the passenger's side headlight.

I had an Econoline with the last year of the OBD1 diag system which was very limited in what it told you. The van would go into retard modeand hardly no power. The mechanic could not find any codes. Well, one day I saw that some plug wires were routed thru a heat shield and it turns out they were cross-arcing and putting it into timing retard mode. Simply wrapping insulation around those wires before putting them that close teg in the heat shield fixed the problem. But, that probably has nothing to do with this.

Tom Taylor

Hey everyone thanks for all the help! It ended up being a plastic vacuum line that melted shut, it's the one that runs to the map sensor!! Once again thanks for all the help