89 W100 truck stumbles and pops/cracks wont run right

Got this truck about a year now, ran fine no problems. running it every week lately. last week it started to stutter, hesitate and almost backfire under power and wont make power or shuts off. What could it be? truck has 89,000 miles. Throttle position sensor? idle sensor? anything else throttle body related? it idles but you can hear it not ideling correct anymore. Mostly when truck is warm or hot is when problem is bad, it stalls. if cold does not do it as quickly.


wizard

I had an '89 act like that and it turned out to be the fuel pump.

check your fuel pressure for sure #1. Runs richer when cold so it runs (seems to) better. Supposed to be 14.5 plus minus 1.

Brand new fuel pump installed about 4 months ago.

You did the filter too right?

My dollar says distributor. Had an 87 dakota that the hall effect wheel got loose in its plastic retainer. All kind of whacky problems.

yes, replaced filter. Seems like this only acts up when truck is warm or has been running for awhile.

Unfortunately, the new aftermarket pumps are on the junky side. If it was an airtex or similar, pump in still very high on list. Then check for codes. Then check for ignition health and distributor shaft wear.

Okay, see if I can limp it into Autobone to check for codes

I had a new pump put in mine....lasted a couple months then acted up again. swapped out a used tank and pump and never looked back.

What do you do to fix this distributor problem if it is what it is? Have not taken to Autobone yet for code reading. Replace whole distributor or is there a part you can replace?

Replace the Hall effect pickup plate/coil in the distributor. $20-30. Napa or Rock Auto should have it.

A few years back, had an 88 Ramcharger 4x4, 318 TBI. 70k miles. Same problem. Would just stall after driving, fully warmed up. Sometimes right on the freeway in the middle of traffic! Annoying as hell. Replaced the fuel pump, fuel filter, problem continued. Wait about 15-20 min. after stall then restarts no problem and resume driving. Won't throw any codes. Stumped, I spoke with a Chrysler Tech about it. He said the pick-up coil gets hot and shuts off. Common problem. As I recall, at the time, the dealer parts dept always kept an inventory of those coil pickups on hand. Go figure!

Seen them fail hot here too. Normally, they would not do the intermit misfire, they would heat up and quit like you said. And when the codes come up, I think 12 and 37 are no prob normal.

Right. I don't know if this problem would come up on lower mile, newer TBI's but the pick-up coil failure would rear it's ugly head on higher mileage TBI Rams of the ones I've encountered, around 60k and up. The Ramcharger had 130k when I sold it. The problem never occured again 60k later after I replaced it. I did give the buyer a spare pick-up just in case...

Okay, will keep this on the lists of fixs. Been getting a few different theorys of what is wrong. Will have to try it. What about Map sensor? Someone mentioned that

Well, think may have eliminated few things about what is causing this problem.

Don't think its fuel pump as I plowed the driveway full of snow 2 weeks ago. Ran fine for 1/2 hour. Then noticed it was just starting its problem a little bit when I was done plowing. Started to stumble and not run right. I don't think its the fuel pump.


We replaced the throttle position sensor last week, today was the test for it. Ran down town to post office ran okay. Then after about 25 minutes of running it started to act up, hesitant, coughs, not running right. Turned it off for little over an hour and then starts up okay and runs.

Come to conclusion it is acting up when it gets hot or running for about 1/2 hour. Heat related problem.

Could this be worn out o2 sensor?
Clogged cat? Bad Map sensor? I am thinking of trying o2 sensor first.

I could not get the oxygen sensor busted loose so I put on the new MAP sensor on. This fixed the truck and not having anymore problems. Still going to put the oxygen sensor on, just have to bust it loose somehow to get new sensor on. Truck has 82,000 miles on it. Sensor needs replaced anyhows.

Wizard

Is your truck still running ok after the fix? I have an 88 TBI truck that is doing the same thing. If I looked at it right....the MAP sensor is on the passenger side of the firewall. They're proud of those things at the parts house!