89 full size blazer problems

[spudglo08]

Hi I have a full size 1989 chevy blazer thats been giving me problems lately.last week it started to run worse than usual.The last couple of months it has run pretty bad,it wouldnt gain speed very fast and bogged down alot especially after start up and if i floored it the truck didnt always go faster the engine would speed up but my tranny wouldnt kick down or something and my ses light would come on and after a couple miles go back off, if i tried to drive it after just driving the truck wouldnt rum right.Then last week it got alot worse.The engine started sounding like it was dropping cylinders and backfireing my injectors started clicking alot and acting weired almost like they were shutting off suddenly and the gas would catch fire coming out of them alot now my tb is covered in black stuff (carbon?).So I replaced the cap and rotor on sunday.That stopped the problems with the cylinders dropping, but my injectors are still acting the same way and all the previous problems ive been having are still there.So yesterday I put a new ignition module in and when i started it up it sounded like i had plug wires crossed so i checked them and they were all in the right place.It was running horribly.It wouldnt idle at all it just stalled out.So last night we decided to drop it off down the road at an exhaust /mechanic guy down the road.So i had to drive it down there.It stalled a couple of times in the yard here at home but once i got out of the drive way and above 10mph the truck ran great no problems or anything until i slowed down and stopped then it ran like the wires were crossed and stalled.So i'm hoping some one can help me because i have no idea on how to fix it.Havnt heard back from my exhaust/mechanic guy yet so someone please help.By the way i have just recently prplaced cap,rotor,plug wires and plugs.And the fuel pump,sending unit and fuel filter in june and just recently prplaced cap,rotor,plug wires and plugs, and have sience found some sort of silicone caulk in the gas tank vent tube and am wondering if any might be in the sock on the pump or the fuel filter on the frame which might be restricting gas flow sometimes,and a cople of weeks ago my temp sensor quit working i think because the guage on the dash doesnt move at all.Please help

[maxwedge]

This type of problem needs on site diagnosis the littany of issues you posted require hands on attention. On a truck that old, there are possibilities with sensors, fuel pressure, blocked cats, the ses lite needs to be scanned. what I am saying is I don't think more than non -specific advice is available in this environment, sorry.

[2000CAYukon]

Temp sensor for the ECM is in the intake manifold near the tstat. Temp sensor for the gauge is in one of the cylinder heads (drivers side on my 90 K1500 pickup). A bad ECM temp sensor can cause it to run rich.

Did you check the dist shaft for play when you replaced the ignition module? The pickup coil and the magnet on the shaft act like points. If the pickup coil is weak and/or the shaft is loose, the truck will not run well.

Has the ignition coil be checked? When mine went bad, I had no power over 2000 RPM.

Backfire can be from too much fuel and/or a restricted exhaust (muffler or cat).

Check for any vacuum leaks, especially the vacuum line to the MAP. A leak there can cause it to run rich. A bad MAP can cause it to run bad and stall. You should be able to search this forum for instructions on how to test the MAP with a vacuum pump and VOM meter.

ECM temp sensor can also be tested with a VOM meter.

Fuel pressure should be between 9 and 13 PSI. If under 9 or over 15, you have fuel pressure issues.

You did not post the mileage but depending on the mileage, the timing chain may need to be replaced. Has a compression test been done?

//2000CAYukon

[2000CAYukon]

Originally Posted by maxwedge

This type of problem needs on site diagnosis the littany of issues you posted require hands on attention. On a truck that old, there are possibilities with sensors, fuel pressure, blocked cats, the ses lite needs to be scanned. what I am saying is I don't think more than non -specific advice is available in this environment, sorry.

maxwedge,
I completely agree with you. Having owned my 90 K1500 for 17 years, I decided to post some of my debugging experience on my TBI truck.

Hopefully, his mechanic will figure it out.

//2000CAYukon

[spudglo08]

well heard back from the mechanic he scanned it and replaced the map sensor and spark control module he said the problem is probobly the distributor so guess i get to spend some more money at napa.Cant be blocked cats because there are not any on the truck the previous owner had a true dual 3in exhaust system put on last year with dual V-force mufflers (off brand flowmasters) thats why if the engine drops cylinders or something like that you can really hear it.And it has 150000 miles on it, thats the other thing he said might be causing it to run this way.Thanks for the help i cant count how many times ive found info here to help diagnose and fix problems on mine and my buddys trucks.

[2000CAYukon]

Pickup coil and/or worn upper shaft bushing is pretty common issue on the TBI engines. Ignition coil is also 18 years old (if original).

//2000CAYukon