My surging/running down issue has returned on my '86 2.3l Ranger. I thought it was electrical, when things improved with the new ignition switch, but lately it's hard to get out of 2nd gear before the engine surges then starts to lose power. a poke of the gas pedal starts the who cycle over again. I pulled codes but it's hard to tell what the reader is saying either 33 and 34 or 334. The good thing is all the codes point to the EGR system. Can anyone suggest a diagnosis tree to determine if the valve is bad or the sensor is shot? They are both not cheap so I don't want to just throw parts at the problem. Thanks for any suggestions or comments.

 

Have you looked through the Emission System links, in the "Tech Info" thread atop this forums index page????

If the EGR valve isn't rusted & falling apart, its usually a problem with the rubber vacuum lines being dryrotted, carbon has plugged the feedback orifice below the EGR valve, or the hose running to the PFE/DPFE sensor, or the sensor itself.

Try again to get & post up the code Number/s your getting, as they can often give clues that'll narrow down our trouble shoot.

 

Good advice by paw paw. Older EGR systems break down mechanically (bad hoses, stuck EGR valves, holes in EGR metal tubing, etc.) and can also get plugged up with carbon.

Your '86 will spit out 2-digit codes. CLICK HERE.

 

The system used has two solenoids over by the air cleaner box, and plastic tubing with rubber ends/corners for vacuum source and EGR diaphragm operation.
The solenoids allow vacuum to the EGR, the computer 'senses' the position, and then the solenoids 'hold' the vacuum at whatever position the computer demanded.
To check for an EGR problem, I'd check the diaphragm for leakage by applying vacuum from another souce, stoppering the source, and see if the EGR went closed.
To check for the opposite, where the EGR seems to stick, or the pintle valve leak gas when it was supposed to be closed, plug the vacuum line to the EGR with a golf tee. If the engine runs without bucking and so on, maybe that is the problem.
The two solenoid operated valves can be checked for operation & leakage also with a vacuum source, gauge and 12 volt supply.
tom

 

^ + 1, I like tomw's test ideas.

 

Thanks Tom. I've been reading up on the system as pawpaw suggested. I know I replaced the two solenoids when rebuilding, the old ones were so beat I could not reinstall em. At the time I had no idea of their function, but hooked them up as the originals. That having been said, I took the EGR valve off and inspected it. The interior was still clean and shiny, which leads me to suspect the diaphragm less. I did find a lot of moisture where the valve is bolted to the manifold and one of the two bolts was on the verge of being loose. I replaced the gasket and reinstalled the valve. If a test drive yields no joy, I will begin to test the vacuum system and for a stuck open EGR. Also, some of the stuff I read mentions as sensor called a DF something or other that uses a differential between two ports on the EGR tube to measure the flow of exhaust gas. Would an '86 have such a sensor? I don't remember any tubes coming off the EGR tube. Thanks for the tips and suggestions.

 

I do not think the 86 had the DPFE sensor. Unless it was a radical change from the 85.

The codes are two digit. I don't have a decoder ring handy, so don't know what yours indicate.

I had a bucking or trailer-hitching in mine. Thought it was EGR as it went away when I plugged the vacuum line with a golf tee. Replaced with new. No such luck.
Days later, in the early AM, had rough running. Looked under the hood at the light show from the spark plug wires. Replaced the wires, and no more chugging. Don't know if there were any codes.
tom

 

If the codes you posted are valid, they suggest that the PFE sensor has a problem. So maybe begin your trouble shoot by having a look at it, its electrical connections, wiring, the plumbing to the PFE sensor & its operating voltage.

EDIT: When you removed the EGR valve, did you look in to see if the exhaust gas feedback port orifice located below the EGR valve, was clear of carbon deposits???? That port clogging up is a common EGR exhaust gas feedback to the PFE sensor problem. The line carrying the exhaust gas to the PFE sensor is also known to plug up with carbon, especially if the engine is using some oil.

Keep us posted on your EGR system trouble shoot.

 

Tried plugging the vacuum line where it entered the EGR. Got a nice high idle and good shifting at first, but later on another drive it began surging and dying again. Is it possible the sensor on the EGR valve is defective and the computer is trying different fuel amounts to get the response it wants? Thought that had it licked, now back to the drawing board.

 

We aren't supposed to have EGR feedback at idle, so there shouldn't be any vacuum on the line TO the EGR valve at idle. If there is vacuum on the line that connects to the EGR valve at idle, something is likely wrong with the PFE sensor.

Your codes say that something isn't right at the PFE sensor, so using your repair manual, or the link Rockledge posted, to check it & its electrical connections & interconnecting tubing out.

Again, did you check the orifice below the EGR valve, to see if it, or the interconnecting tubing to the PFE sensor is plugged with carbon????

 

I know this works on semis not sure about on cars but a lot of times when egr issues ar suspected we'll put egr in test mode by inactivating it by removing electrical lines going to it. U could try removing vac lines when engine is cold, egr should be closed when engine is cold at see if with egr off if runs better. Will have chk engine lite on, due to ECM knowing egr is not active, but can be useful for troubleshooting

 

If your idle changed, then you have either 1)a vacuum leak or 2) a leaky EGR valve or vacuum valve {solenoid valve}. There should be no vacuum for EGR at idle.
Did you try the golf tee test?
Read your codes again, and take the time to determine what actual code you have. The 33 & 34 codes indicate a position problem with the EGR. It didn't respond to an 'open or close' command, as sensed by the position sensor. The sensor is a variable resistance potentiometer that changes value as the valve opens and closes. The computer expects the value {resistance} to change as the valve is commanded to move either open or closed. The other possibility was the vacuum was not being maintained, and the position was not as either remembered or commanded:

(O) = Key On Engine Off test (R) = Key On Engine Running test (M) = Memory code

33 ALL - (O, M) EGR did not open/ respond during test or if memory code, did not open intermittently

34 EVP - (R) EGR did not respond properly during test EVR - (O, R, M) EVP sensor is/was high PFE - (O, R, M) PFE sensor is/was out of range

Does your EGR system have a PFE sensor? If not, you can rule it out.... Heh.

Anyway, you can rule the EGR in or out by plugging the vacuum source and testing for a while. If the problem reoccurs, it is not the EGR.
tom

 

WOOOPS, I see we're talking about an 86, not 96, so if your EGR valve has an EVP sensor attached to it, check it out as outlined here in the site link Rockledge posted.
Fuel Injection Technical Library » EGR Valve Position sensor (EVP)

 

Good, we're on the same page now. The only sensor is the EVP. I ordered a new one and will try it soon. tomw: tried the golf tee( a wire nut actually) and no joy. I also made a "no flow" gasket out of a soda can for the EGR valve and the poor performance was still there if not worse. I'll let you know if the EVP switch helps. Thanks for the continued advice.

 

If you blocked the port, and tried blocking the vacuum with no difference, then the EVP will have no effect either.
You have the problem with the EGR disabled totally. The EVP just reports the position of the EGR valve. Who cares the position when it cannot flow any gas anyway?
I would look further afield for your problem cause.
tom