I'm a new member and really hoping someone can help me out here.

I've got a '92 bronco XLT 302 e4od. The truck is all stock with 119,000 miles on it. About a week ago I went to start it and ran into some issues. It fires up but immediately begins a rough idle (worse when cold starting). The idle drops and tries to catch itself a few times but usually stalls. If I help it along with the throttle I can keep it running...but even revving it and letting it come down on its own results in unsteady idle and stalling. The transmission is also shifting very hard...mainly 1-2 gear. CEL is on and throwing code 27 (vss), 18 (timing/spout), 44 (smog pump) and 107 (no definition). Here's what been done...
New distributor, cap, rotor
New tps
New iac
New icm
New ecu
So far nothing has made a difference. I've read about the VSS but most of the symptoms indicate speedometer, odometer, cruise control and 4x4 issues and I'm not experiencing any of those. I'm at a loss now so any help is greatly appreciated!!! Could the VSS still cause the issues I'm having?

 

Welcome to FTE!

Let me be the first to inform you will not get a mix of two and three digit codes. It's one or the other. That tells me your code check is invalid. A 1992 Bronco with an E4OD should have three digit codes but there are exceptions to the rule.

Never under estimate the basics. What about plugs and wires?

The VSS will not cause the idle issues but it an contribute to hard shifting. Until you can get valid codes, it's a guess as to root cause.

 

Thanks for the tips! Happy to be here...always been a Ford guy and love Broncos. This is my second.

As for the codes...they were pulled by a local shop. All the searches I've run on explanations for them seem valid with the exception of the 107, which is the only 3 digit code that came up...no idea what that is. From my understanding the VSS can affect anything from speedometer readout to ignition timing through the ICM and SPOUT to ABS function and transmission shift points. From my reading it seems to be something that can cause symptoms in a number of systems? When I had it in the shop they went through the entire ignition...plugs, wires, cap, rotor, entire distributor, ICM, etc. Everything came back good and what they changed out made no difference in the problem.

Is it possible that since I'm getting a code for vss and for ignition timing, that the VSS is malfunctioning in a way that is interrupting engine performance but still permitting the speedometer, abs, etc. to all work?

Also, how many vss are there...I know there is one on the diff but I've seem mixed information about there being one on the transmission somewhere too. Any idea?

Thanks!

 

I believe the TPS for that year has some adjustment. make sure the throttle screw has not been tampered with. the spout connector should be a tiny plug just off of the dizzy. make sure that is in place. its possible the distributor is having problems or the tfi module.

did they check the timing and if so what is it set at?

 

Since you listed two and three digit codes none are valid. You may be going down a bunny hole. Get the proper codes then go from there.

If it is a VSS code replacing it rarely fixes the problem. There is only one located on the rear axle for 1992 and later trucks. It also supplies speed data to the RABS controller. This device is a frequent cause of VSS codes because it attenuates the signal before it gets to the PSOM.

All of the above is FYI since your code check is invalid IMHO.

 

So here is everything I know...

The VSS, tps, icm, computer, iac, and distributor have all been replaced. The shop checked the timing and said it was good but I'm not sure where it's set. The plugs and wires look old...haven't changed them yet. The codes that I have were pulled by a shop, but I've just ordered my own code reader so I'll run them again when it arrives. I've read a number of threads about the PSOM, but other than the transmission shifting hard I'm not having any other symptoms.

Right now the truck fires right up when cold, but as it starts to idle down to its normal idle speed it begins to misfire and develops an unsteady idle until it eventually stalls. Once you're able to keep it running long enough (usually 3-4 starts) it seems to stay running with the occasional stumble. The CEL is on through all of this and stays on but there is no ABS light staying on and the O/D indicator works normally.

I'm at a loss now...just got this truck and have already sunk a chunk of money into it. I've heard nothing but good things about these Broncos and f150s....but I'm getting really frustrated with the conflicting information from shops, online articles and generally just not having any success. I will recheck the codes but in the meantime...is there any other component that would affect both the engine and transmission how I've described that hasn't been replaced yet? Beginning to get desperate.

 

I would say you have multiple issues. Old plugs and wires can definitely cause idle and driveability issues. Any shop worth a hoot would have replaced them, but nowadays the keyboard jockey mechanics start replacing expensive "computer" parts instead.

You could start with the basics yourself by pulling the plugs and inspecting them. Since they look old, have a new set of Motorcraft copper plugs ready to go in. Unknown plug wire age? replace them with good quality replacements. Do not skimp like Duracrap brand but no reason to go the other direction and mortgage the house.

Another item to not take for granted are the distributor cap and rotor. Verify if they are new as well.

Then you can tackle the conflicting code issue.

 

I can understand your frustration, but just think of it this way; by replacing some of these original parts, you are taking care of it, and technically shouldn't have to worry about for a long time. You'll learn more about your specific truck and feel more confident in the long run. These older trucks are obviously a lot easier to work on compared to newer vehicles, so if you are able to, do some repairs on your own to avoid getting hit hard by shops. There's massive amounts of information and help for these trucks on these forums and the internet in general. Also, if you don't have one, you might want to pick up a Haynes repair manual for your Bronco, as it's an extremely good reference for information and repairs.

 

Thanks for all the info everyone. So after changing out the VSS and the MAP sensor everything seems to be back to normal. Never would've thought one sensor could cause so many different issues but I guess I'm all the wiser now. Probably going to change out the plugs and wires for good measure anyway.

 

Glad to see your leap of faith may have paid off. Invest in your own code reader for the toolbox instead of relying on a shop to pull erroneous codes. You probably won't get lucky the next time.

 

I've actually already purchased one...should be here next week. Trying to avoid a repeat like this. On a related note...I've read that Ford was transitioning from 2 digit codes to 3 digit codes in the 91/92 model years. Is it possible for a 92 to have a mix of 2 and 3 digit?

 

right on, glad you got this fixed.

 

No, there is not a mixture of two and three digit codes. It's one or the either. The most accepted date for the transition is 1991.

FWIW...my 1992 F350 w/5.8L engine and E4OD displayed three digit codes.

One more time: You will never get a mix of two AND three digit codes. It's two or three period.

One caveat..some aftermarket code readers interpret the separator flash between the KOEO test results and stored code display as Code 10. This is completely wrong and does not constitute an exception to the rule, it's only an observation for an aftermarket code reader.