Help diagnosing engine problem

[BroncoII4Life]

My '86 'co II 2.9l has been giving me trouble for the last two weeks. I will be cruising along and then the whole vehicle starts bucking/surging, engine runs rough sputtering and if I give it any throttle the RPM's drop and engine dies. Engine temp rises at this time too, sometimes the radiator boils over for a good 5-10 mins. At first I could wait a minute and coast down the road until it returned to normal but now I have to shut it down and let it cool. Now I can't restart it until it cools.

I found no codes on the computer but I did find the distributor was loose causing the timing to vary. Got that tightened down and still had problems so I replaced the dist head and rotor arm(they were looking rough). Got the timing dialed in with a timing light. I found a busted grommet around something similar to the PCV valve. the PCV valve is on one side and this unknown thing is on the other. I replaced the grommet but i'm unsure what that unit is and how important it is. I pulled the thermostat out and boiled it on the stove and it appears to function. The radiator is new,and the water pump is new. Fuel pressure is good. Fuel filters are fresh.

I'm starting to think the fuel pump could be going but press looks good every time i check it. ? I've done some research here and now i'm considering the TFI or the EGR or could my 02 sensor cause this? Should I replace the whole distributor next? would an intermittent dist failure cause overheating?

I've got a lot of things to check has anybody got ideas on what to check / replace first?

[Ranger Dave]

do a leak down test on the cooling system, converter plugged up??

[BroncoII4Life]

I can assure you the converter is not plugged, that was fixed awhile ago. I'm betting the O2 sensor is toast do you think that would cause problems once warmed?

Leak test? no leaks on the ground. Do you think I cracked a head which would leak into oil or exhaust? my oil is clean and up until the boil over I have not had to add any coolant.

[oneway]

leak down measures compression and blow by. Not leaks on the ground.

[Ranger Dave]

leak down measures compression and blow by. Not leaks on the ground.

no it doesnt and yes it could

quote-(do a leak down test on the cooling system)-quote

[drofman]

sounds like plugged exhaust to me, might want to check it. does it sound like am vacuum cleaner out the exhaust pipe when driving? are you using coolant beside losing it when it overheat?

[BroncoII4Life]

I pulled off my EGR and it was full of carbon. I had to drill out carbon in the the metal vacuum hose connector before replacing the EGR. I also had to pull off the throttle body to ream out more carbon gunk with a piece of bailing wire. While I was at it I replaced the O2 sensor and now I've got 100 miles with no problems.

[KRE]

My '86 'co II 2.9l has been giving me trouble for the last two weeks. I will be cruising along and then the whole vehicle starts bucking/surging, engine runs rough sputtering and if I give it any throttle the RPM's drop and engine dies. Engine temp rises at this time too, sometimes the radiator boils over for a good 5-10 mins. At first I could wait a minute and coast down the road until it returned to normal but now I have to shut it down and let it cool. Now I can't restart it until it cools.

I found no codes on the computer but I did find the distributor was loose causing the timing to vary. Got that tightened down and still had problems so I replaced the dist head and rotor arm(they were looking rough). Got the timing dialed in with a timing light. I found a busted grommet around something similar to the PCV valve. the PCV valve is on one side and this unknown thing is on the other. I replaced the grommet but i'm unsure what that unit is and how important it is. I pulled the thermostat out and boiled it on the stove and it appears to function. The radiator is new,and the water pump is new. Fuel pressure is good. Fuel filters are fresh.

I'm starting to think the fuel pump could be going but press looks good every time i check it. ? I've done some research here and now i'm considering the TFI or the EGR or could my 02 sensor cause this? Should I replace the whole distributor next? would an intermittent dist failure cause overheating?

I've got a lot of things to check has anybody got ideas on what to check / replace first?

The Trigger within the Dist, as well as the TFI board on the outside of the Dist will cause all the problems you are having, to include frying the C/Converter and O2 senser. The temp the Dist. lives in, is much higher than what was known, before the electronics were built. If you elect to R&R the parts yourself (very easy by the way) be sure to install the heatsink paste correctly. Units that see cooler ambent temps may never see a problem, but those that drive in the south, where A/C is required most of the driving time have seen higher TFI issues. Some have installed 2" air ducts from the R/S grill area to termanate at the Dist. which has greatly reduced TFI problems in hotter areas. This was a Recall then a Class Action Law Suit many years ago. The replacement parts of today are better suited for the true temps at the Dist area.

[BroncoII4Life]

Thanks, its all starting to make sense. Did I mention the Cat caught my floor on fire about 2 years ago so I put a new one in. That probably burned out my o2 sensor. Overheating led to a whole chain of heat related failures that I am still tracking down to this day.

[KRE]

When a part fails there are two things that one has to find, before correcting the issue.

The first item found is easy the effect, the harder item to find is the cause. If the cause is not corrected the effect will happen again.

Failure analysis is a dying art, and parts stores want it to go away quickley, they prefer for you guess with your wallet. Alot of wrench shops are moving in this direction as well, because it's more money in their pockets as well. I've done "Shop Failure analysis" for many Mfg's, which means I've hosed iron to see how shops preform/rate when the job is completed. You would be shocked at some of the findings.

[forman621]

I think i may have had the same problem. is it a 5 speed? maybe just try replaceing the gear oil with some fresh gear oil. it actually made a difference to mine.

[BroncoII4Life]

My gear oil is fresh my diff exploded the spider gears so I put a new diff in.

I have just about rebuilt it one piece at a time.