86 bronco II surging, hesitation, etc..

chris78 · Jun 28, 2018

I have an 86 bronco II with 2.9l. It is hesitating, surging, and shutting off randomly. I had this problem last year. At the time I ended up replacing the Distributor cap, rotor, and ignition control module. I pulled some codes that pointed to the egr system. Then replaced some vacuum lines running to and from EGR, the EGR solenoid, but it didn't seem to help until I replaced the EGR valve. Everything seemed ok, but now its starting again and worse. I've pulled the KOEO codes again and I get 34(o) and 67(o). Also 63(c) and 32(c), which is what was in memory.

My book says 34(o) is "EGR control circuit fault" or "Defective EGR pressure transducer sensor" I guess that is the EGR Sensor? or?
I don't understand what code 67(o) is. I tried unplugging the EGR sensor to see if it made a difference and it did not.

Just wanted to get an idea of what I should do to figure this thing out.

Paulos · Jun 28, 2018

Codes

I get code 67 every time I pull codes with the trans in neutral. Now I always make sure that the AC is off and the trans is in neutral first. It looks like 32 and 34 are related to the EGR valve position sensor (EVP), but I'd probably change the EVP and recheck your codes before replacing the TP sensor (code 63). You might check your PCV valve, crankcase breather, and related hoses for leaks also.

If you figure out what is causing the hesitation and surging please post your solution. I've been trying to figure out what is causing mine to act in a similar way for a while now (it runs rich and all sensors have been replaced, yet no codes other than 11).

chris78 · Jun 30, 2018

11 is system ok! ha.. Maybe its one of the fuel pumps, not sure if they throw codes.

wildbill23c · Jun 30, 2018

I don't think fuel pumps throw codes, but mine was doing the same thing and the fuel pump in the frame rail was bad causing the problem.

chris78 · Jul 3, 2018

So I put on a new EGR Sensor and no dice. Still getting a KOEO code of 34o, defective egr sensor or egr circuit fault. I checked the wiring harness from egr sensor plug and egr solenoid plug back to computer on all wires and everything checks out(eec, sensor, & solenoid unplugged). Checking for ground faults, only the red wire from solenoid read in mega ohms across ground, doesn't seem like a fault to me(eec, sensor, & solenoid unplugged). Is there anyway to check across egr sensor leads? or the solenoid?

I've replaced all vacuum lines on the egr system. What is the box under the intake breather that the red vacuum lines from solenoid go into. Could something be wrong there?

Paulos · Jul 3, 2018

Egr

Did you check the EGR valve (by applying vacuum/suction), and the port that leads from the EGR valve to the throttle body? Over time that port gets clogged with carbon, etc, from the exhaust gasses passing through it.

If you're talking about the box that is directly underneath the air filter housing, it's a vacuum reservoir. If it doesn't hold vacuum, that would be a problem. On my '87 (with a 2.9), vacuum lines go from the front left intake manifold vacuum tree to the front vacuum reservoir port, the rear vacuum reservoir port to the lower EGR solenoid port, and the upper EGR solenoid port to the diaphragm of the EGR valve. The EGR position sensor connects to the EGR port that has exhaust pressure on it. I realize that you may already know all this. When you started this thread mine was throwing a code 33, which went away after replacing the EGR solenoid, so I know this configuration works.

chris78 · Jul 5, 2018

I checked the vacuum box under breather and it looks fine. Re-checked all vacuum lines. Replaced lines and grommet on pcv valve and cleaned checked valve, its fine. I pulled the egr valve and checked it, seems to be functioning I can hear the diaphram move when I suck on the vacuum line. Ports are clean, I pulled the port on manifold for egr and its clean. Engine still surges.

I pulled the egr solenoid and checked the plug to see what voltage the cpu was sending it, I got 13.4v, so I applied batterry to it and there was no click. Got a new one and put on, seems better except it idles high and oscillates. Seems like it wants to surge, and I'm getting code 34o still. I checked this new one with 12v and it doesn't click either. I also tried to blow through it with and with out power and it doesn't matter, seems like its not working either???

chris78 · Jul 20, 2018

I was able to fix the problem a couple weeks ago. It ended up being the way the wiring harness pulling down on the connector for the egr solenoid. Not sure why, but there wasn't enough wire and it was causing some kind of loose connection. I pulled the wires out of the connector and cleaned them up, then pulled back some of the tape freeing up slack in the harness for the connector. Haven't had any problems, smooth running. Funny to cause it doesn't run as hot now, I guess EGR causes engine to run hotter if its always open?

86 bronco II surging, hesitation, etc..

chris78

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Paulos

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wildbill23c

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