No rpms

[Randall008]

Hi,
I’ve got a 1988 bronco ii. Last year, on a hot day it stalled driving about 40 down the road. I replaced the tfi module. Then it started stalling and not starting for a few minutes. I checked the inertia switch. The connection was melted, so I figured I’d replace that. It drove fine the short distance I drove it. Then it started dropping rpms after it is was warmed up. I couldn’t give it gas to accelerate and the transmission sort of felt like the clutch was slipping and the stick was wobbling. It seemed like it was probably fuel so I checked the fuel pump relay. The plastic case was broken with a piece of electrical tape on it and the contacts in the wire harness were corroded. I figured that was a good place to start. Again. It drove fine until it was warmed up and I let it idle for five minutes at a gas station and it did it again. It also idles really low 5-600 rpms when this problem occurs. Engine thermostat is set for 180 degrees and stays there when warmed up, but I do smell a burning smell when this problem occurs (not of gasoline) sorry for a rambling post. Any ideas? Thank you for your help.

 

[Uncle Gump]

I think when it quits... you need to determine if it is a spark problem or a fuel problem.

Carry a spark tester and a fuel pressure gauge with and when it quits... see what's happening.

 

[Randall008]

I think when it quits... you need to determine if it is a spark problem or a fuel problem.

Carry a spark tester and a fuel pressure gauge with and when it quits... see what's happening.

Thank you for the advise I’ll look into buying a pressure gauge and spark tester. I don’t have them at the moment. I’m good with my hands, but by no means a mechanic lol

 

[Uncle Gump]

Thank you for the advise I’ll look into buying a pressure gauge and spark tester. I don’t have them at the moment. I’m good with my hands, but by no means a mechanic lol

You can save yourself a bunch of money doing your own repairs... just need some hand tools to get through a lot of things. To diagnose electrical and fuel system... you just plain need a couple affordable tools. The two I mentioned... a Digital Multi Meter... and a test light. A service manual helps too.

 

[Randall008]

You can save yourself a bunch of money doing your own repairs... just need some hand tools to get through a lot of things. To diagnose electrical and fuel system... you just plain need a couple affordable tools. The two I mentioned... a Digital Multi Meter... and a test light. A service manual helps too.

 

[Randall008]

The car just has low and erratic rpms at idle/when driving as soon as it starts now. I checked the spark. It appears to be the problem. The light flashes erratically. I replaced plugs, wires, distributer cap, and distributor button 3 years ago. I replaced tfi module 1 year ago. I have a second bronco so I swapped in starter solenoid and coil to test these, no change. Any ideas?

 

[JerryC]

What about fuel pressure? Did you check that ?

 

[Randall008]

Thank you for the idea. Fuel Pressure is just under 40 PIS I believe. I swapped out the MAP sensor from an 87 bronco II I have. It works in the 87 so unless the year makes a difference cause of the year or something I don't think its that. Spark seems erratic to me, but it seems erratic when the engine slows down, so I'm guessing its probably because the engine is slowing down and staling rather then causing it. My current theory is the O2 sensor may be bad and giving bad information to the computer about how much oxygen is in the gas. Any merit to this? I'm not sure if these early computers had a factory default or if they were based entirely on the information provided by the sensors, but if its wrong enough, I could see it

 

[Randall008]

I cleaned the idle air control valve with mass air flow sensor cleaner because I thought this could be the problem... it looks to be original to the car, is there a good chance this is the problem?

 

[Uncle Gump]

@Randall008

Lets start over here.

You said it was stalling and wouldn't restart. Now it's erratic idle and spark is erratic when RPM's slow down. How did you check erratic spark when RPM's drop?

Most times when idle speed "wonders" high to low and even stalling... the first thing you need to check is for a vacuum leak.

But honestly... just start over and tell us what it does when you first start it up...

 

[gaz]

Randall,

I would try to get it to act up in the driveway. How many miles on those ignition parts in 3 years?

 

[Randall008]

Basically it’s gotten worse, and I think I may have been linking different problems between last year and this year. I did some work to it over the winter. It was running better then it ever had. Then when it started to warm up outside, it would stall occasionally after maybe 5 miles of driving, or it wouldn’t start right up... a little bit after that, I noticed that I left it running when I went into a store, I would come out and the rpms would be about 5-600. The ride home it would have no power and the stick would be wobbling, then it would sort of surge. Now it can’t leave the driveway because when I start it up it starts shaky, rpms drop to like 400 then it dies after a few seconds and the engine shakes

Ignition components less then 3000 miles

Checked spark with inline spark bulb. It blinks when there is spark