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Scobb27

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1988
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I have a 1988 bronco 2 and it is running really weird, it idles not to bad in park but there is still a misfire but as soon as I put it into drive it bogs down doesn't like to go it sputters when I press on the gas and if I stop at a stop sign or street light it dies. I took it to a shop and said it was a fuel problem but cant really rely on them because they didn't know what they were talking about. any help would be greatly appreciated.

List of replaced parts: Fuel tank, fuel pump, injectors, fuel lines, fuel filters, cleaned out the fuel rail, distributor cap, rotor, wires, and the plugs.

shop thinks I need to replace the Fuel pressure regulator what do you think.
 


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huh?

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i think you may find the answer regarding F.P.R. replacement by getting(renting) a fuel pressure gauge and hooking it up to see what kind of pressure your system is producing.

also, as i have read through hundreds of threads here at TRS i have observed that many of the troubleshooters ask for trouble codes. accessing the codes and posting them, along with the results from the fuel pressure test may allow the kickass diagnosticians here to zero in on what's happening with your bronco ii
 

RonD

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1988 2.9l used a Speed Density system for fuel/air mix.
This used a MAP sensor as the main sensor for fuel/air mix ratio.
MAP sensor will be located on the Firewall, usually passenger side behind wiring harness, so hard to see.
It will have a vacuum hose attached connected to the upper intake manifold, that's the easiest way to find it.
It will have a 3 wire connector.
Unhook the connector and check MAP and wires for corrosion.
Unhook vacuum line and check it, very closely, for any leaks.
MAP sensor tells computer how much fuel to add based on engine vacuum, so even a small leak will cause big problems.
MAP sensors rarely fail, not never but rarely.

The '88 was the last year of the two fuel pumps, I think, one in the tank and one in the frame rail under the drivers seat.

Does the vehicle get up to highway speeds and then stay at speed?
If so fuel pressure could be OK
Low fuel pressure/flow usually shows up first as a lack of power at higher speeds/loads, idle is usually fine.

Fuel pressure regulator(FPR) has a vacuum hose attached, remove that hose and check it for gas or gas smell, if there is gas in there then replace FPR.


'88 will have a TFI ignition, these have a 100% failure rate as they get older.
It could be the spark is not advancing and retarding as it should, causing the bogging and stalling.
Good read here on troubleshooting TFI:
http://www.therangerstation.com/tech_library/TFI_Diagnostic.shtml
Download a print worksheet

The computer(PCM) has a preset routine for cold starts.
At startup RPMs should go up to 1,500rpms, then drop within a few seconds to about 1,000rpms, this is caused by the IAC Valve being opened all the way and then closed a bit to set cold idle.
PCM determines cold or warm engine from the ECT sensor, a 2 wire sensor on the lower intake manifold, looks similar to the 1 wire SENDER used for the dash board temp gauge.
Problem with ECT sensor would cause engine to run better cold than warm, OR visa versa, hard cold start but runs fine warm.

Once engine is warming up idle will slowly drop until it gets down to 750-800rpms, warm engine idle preset for automatic.
If your engine doesn't behave this way then that could point to a problem with PCM.


A vacuum leak could cause all your symptoms, it causes a lean fuel/air mix, so lack of power and stalling, might also get some "pinging" sounds.

A clogged exhaust system could also cause your symptoms.
A vacuum gauge is not expensive, and can tell you alot about engine condition and problems.
Read here for troubleshoot tips using a vacuum gauge:
http://www.gregsengine.com/using-a-vacuum-gauge.html
 
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Scobb27

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if I was to get a code reader what brand should I get. I replaced the fuel pressure regulator and still no change. it will not get up to highway speed. it will get to maybe 45. if I press on the gas it bursts and redlines but there is no output from this burst or redline it just makes a loud noise. the shop I had taken it to ran out of ideas and said that they couldn't get any codes off of it. basically they told me that if the car doesn't tell them exactly what's wrong that they cant help. I am going to get a code reader and vacuum tester in the next couple of days any suggestions on brands would be helpful thanks.
 

adsm08

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Test fuel pressure. When you find it is low, replace the high pressure pump.
 


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