89 Blazer Surging--Fixed--Page 2 update

[ZJumper]

I picked up an 89 Blazer 350 TBI, 700R4, 4x4 with 95,300 original miles which is bone stock down to the stereo. When I got it, it had a few maintenance issues, but I was more than willing to deal with those to have such a clean, non-beat-up rig. I did all the normal stuff by replacing all the old fluids and filters with new stuff...everything--engine, tranny, diffs, t-case etc.

Here's the problem--it surges. It does it in all the gears, but it very apparent when cruising in say, 1st gear around 15mph, or in 2nd gear around 30 mpg. When you romp it, it will take off pretty good, but if you ease into the gas the power seems to come on in stages. I just can't figure out what the hell is causing this--it's freaking annoying to say the least.

Here's a list of what has been repaired/replaced:

-Cat converter/muffler/exhaust pipe--the stock stuff was trashed
-New fuel filter--old one almost plugged solid
-New Cap, rotor, wires and spark plugs
-TBI torn apart, cleaned everything and put back together with new gaskets etc.
-Checked all the hard vacuum lines and replaced what was bad
-PCV Valve replaced
-EGR Valve replaced(AC Delco unit)
-O2 Sensor replaced

There is no "Check Engine Light" coming on. It starts and idles fine. It accelerates fine when you romp it, but surges when accelerating at a moderate pace or when cruising. Any ideas? HELP!! TIA.

 

[dleroy43]

Mine does the same thing, I have no idea eather Ihave been trying to figure it out for three years.

 

[ZJumper]

When I figure it out, I'll post up the solution. I did quite a few searches and found many similiar issues to mine, but nobody ever posted up what the fix was.

 

[blazerguy 90]

I have a 90 Blazer, when I got it - it was running real bad, I did a complete tune up and that helped a lot, but it still had a noticable miss at idle, I removed and cleaned the EGR valve and TBI, I also replaced the ignition module and all of the vacuum hoses, they were all shot. I also had the exhaust done. all of this helped alot but the miss was still there, this past weekend I replaced the fuel pump and the miss is gone. so I guess with a 149000 miles on the original fuel pump it was starting to die, the new fuel pump made a huge difference, you might consider replacing your fuel pump, its not as hard as it looks.

 

[K30Blazer]

did you notice any improvement with the replaced EGR valve?

 

[350k5]

Mine would to that... its an 84 with a carb... but reading what he said about the fuel pump made me think of it. About a week after I noticed it surging like that the fuel pump went out... so it could be a big part of the problem... or if there is some sort of kink or clog in your fuel line that could be a problem as well. Just some ideas.

 

[tomseviltwin]

-New fuel filter--old one almost plugged solid

Bet your fuel pump is toast. Also, maybe the coil giving up?

 

[ratchetgmc]

i am not the expert on this as some might be; but i do know this. the pulsing of the fuel injectors on a tbi is originated at the distributor. most repairs you have made were good maintanence anyway. with all my old trucks i try to keep parts around that might not be top of the line but work. if it were mine i would swap in a know good distributor to check. i worked as a car mechanic for large dealership for years; honda. this was a practice used by some great mechanics. also related and may check first. the ignition timing. could be fuel pump as others have posted; this is easily checked with guage for pressure. clogged fuel filters do trash fuel pumps.

 

[blazerguy 90]

I didn`t replace the EGR valve, I just removed it and cleaned it and the intake manifold, it wasn`t that bad, but im sure it helped a little.

 

[ZJumper]

did you notice any improvement with the replaced EGR valve?

Nope--no improvement with the new EGR valve.

Looks like the fuel pump needs to be checked along with the distributor and the coil.

What are the specs for fuel pump pressure? If the fuel pump is bad, how big of a PITA is it to pull the tank? How long does it take to R&R the tank/pump? Any quirks to performing this job? How much does a new fuel pump cost?

 

[blazerguy 90]

I just got done changing my fuel pump last weekend, its not as hard as it looks, just take your time. the first thing I did was remove the rear bumper and deflector then you can get to the nuts for the gas tank straps, loosen the clamps and remove the hoses from the filler neck and remove them. the main fill hose is a bit hard to get off, but it will come off. if you have a trailer hitch on your Blazer it needs to be removed before you can remove the tank
(ask me how I know), with the hitch removed next remove the gas tank skid plate, use a floor jack to hold the skid plate up while you unbolt it. with the skid plate out of the way use something between the gas tank and jack to protect the bottom of the tank, unplug the wiring harness to the pump and unscrew the ground wire from the frame, now take the gas tank strap nuts loose and lower the tank enough to reach the fuel lines on the top, there are three lines, remove them and the tank will come out.

 

[dyeager535]

CHECK your TPS. Make sure the voltage changes incrementally with throttle position changes and doesn't have dead spots.

 

[ZJumper]

Today I checked the TPS and it was fine. I was hoping the TPS was going to be the problem--easy fix--but no luck. I was at a loss, so I took it to a very competent mechanic I know. He took it for a test drive and when he came back he said, "I can feel the surge and it's almost like it's not getting the gas it needs." Dammit. He told me to leave it with him and he'd put it on a diagnostic machine and check things out this afternoon.

He gave me a call and told me to come by and that he'd like to show me what's going on. I went to the shop after work and he had it hooked up to the diagnostic machine. We started the Blazer up and he explained a bunch of stuff--way over my head at times--and came to the conclusion the fuel pump is bad. He told me the plugged fuel filter probably killed the pump. Lesson learned here--change the damn fuel filter--it's only about $6 and 5 minutes.

At idle, the O2 sensor was reading fine, but at 2300-2500 rpm the O2 sensor was detecting a flatline lean condition--basically not getting the fuel it needs. Along with the pump being suspect, the timing was retarded 6* and he adjusted it to 0* as per spec. Next Tuesday I'm going to R&R the fuel pump and will post up the results. Thanks fellas.

 

[ZJumper]

OK, for an update. I was gone out of town for about a month and haven't had a change to work on the Blazer.

I changed out the fuel pump and this corrected the lean condition I was experiencing, but it was still surging.

For some odd reason, from the beginning of this problem, I felt it was a distributor issue. Since the problem wasn't getting any better, I went with my gut and pulled the distributor. I figured I'd thrown enough $$ at it, why not another $20 for the ignition control module and $30 for the magnetic pickup. Initial inspection of the ICM was it was pretty dirty and nasty--the connections had a bit of corrosion around them. Pulled the distributor shaft out to get to the magnetic pickup coil--HOLY CRAP!! It's amazing the thing was even running. Dirty, corroded, broken wires, nasty as hell.

To make a long story short, I put the dizzy back together with the new electronics, stabbed it back in the truck and whammo...started up quicker then ever before. Hit it with the timing light to be sure and that was it.

Drove it and the problem is solved. Now...lift, lockers, tires...after I replace the alternator that is crapping out.