Blazer -98 jerking

I have -98 Blazer 4.3l W. It has started to jerk when it's cold. First it jerked when cruising at steady speed, now it jerks also when accelerating.
What I've done so far:
-total tuneup a year ago
-cleaned MAF
-cleaned and checked EGR
I guess to be done is to check fuel line pressure? It starts very well though. Check catalytic converter?
Should I use fuel injector cleaner? Could this be a injector related problem?
What else should I check?

One of the problems with this engine is that the distributor cap gets moisture in it. It is a known problem with no recall that I know of.
Remove the cap and see if you find moisture inside.
Fuel filter is another good one, I would replace that before doing a fuel pressure test as you could get a false reading.
On my blazer I used dilectric paste at the base of the cap where it sits on the distributor and havent had any moisture problems sence.
just a couple thoughts

ok , just bought fuel filter. have to check distributor, thanks, I'll let you know..

Fuel filter replaced. Distributor checked. Fuel line pressure checked. But still jerking. Any other ideas?

Is the SES light coming on? If not, does it come on with the key on and the engine off?

What all did the tune up include that you did last year? What band name parts were used? Some of the aftermarket stuff is junk.

What is the fuel pressure reading and how long does it hold before it leaks down? How far does it leak down?

SES light comes on when ign is on motor not running and is not on when engine is running.
I rebuilt the engine. It was driven without oil. New distributor cap, plugs. I didn't change plug wires anyhow. They may be next in my list?? I sprayed water over the cap and wires in the dark when idling, no visible sparks anywhere.
All parts I used were AC delco and other quality brands.
Pressure is 61psi when pump runs, after that stays 57-58psi.
Jerking happens usually when I cruise steady speed above 100km/h (60miles/h), when accelerating no problem.
How can I test TSP? could this be a problem with it? I noticed that problem usually occurs when 2200-2400rpm, bad potentiometer???

How can I test TSP?

Do you mean the Throttle Position Sensor? I would suspect the spark plug wires before the TPS. When plug wires get old they develop high resistance and may do fine supplying high voltage at full throttle, but don't do so good with low voltage, like at an idle.

Fuel pressure sounds good. I would go ahead and replace the plug wires, no doubt they are probably due and then you can be rule them out. Go with the A/C Delco on the plug wires also.

Let us know how it goes.

changed spark plug wires. didn't help. it jerks now only when I'm cruising steady speed over 100km/h. Could it be catalytic converter? It does accelerate ok though. Transmission related problem? Any other ideas?

http://www.automotiveforums.com/vbulletin/showthread.php?t=607221

Pg 4 finally has my solution. I would concentrate real hard on when and why it is jerking, if you find it is at mid-high rpm and light - lighest load then conclude that it is missing at the highest timing advance and/or the leanest mix.

http://www.automotiveforums.com/vbulletin/showthread.php?t=607221

Pg 4 finally has my solution. I would concentrate real hard on when and why it is jerking, if you find it is at mid-high rpm and light - lighest load then conclude that it is missing at the highest timing advance and/or the leanest mix.
Thanks 534BC,
I think it's jerking when mix is leanest. It usually does this when i have been driven for 10-15 min highway (engine warmed up) and going downhill. I have AC-delco plugs and new wires.
What was your solution? Distributor bushings?

http://www.automotiveforums.com/vbulletin/showpost.php?p=4439961&postcount=65

My solution is a "patch" but it still runs perfect. If yours is the same you would notice it at the exact moment it goes to closed loop AND very light throttle.

Now it does it all the time... Even when accelerating..
Plugs, wires, etc changed. What next? Any ideas?

Took it to the dealer. They diagnosed it. No problem found. :shakehead:shakehead
I've started to suspect that the problem is TCC solenoid in tranny...

Took it to the dealer. They diagnosed it. No problem found. :shakehead:shakehead
I've started to suspect that the problem is TCC solenoid in tranny...

How old is the tranny fluid and filter??

Never changed I guess. I will change those and tcc solenoid this weekend, maybe that helps...

Ok, now finally changed tranny oils, filter, wires and tcc-solenoid. No help, still jerking. I also measured o2 sensors, all of them are going from 0.4V to 0.8V they must be ok. I also took me vehicle to yearly inspection where they measured co2, o2, lambda etc. everything perfect...!

Only thing I haven't replaced or tested yet are injectors. I have two choises:
1. I'll take spider assy to local dealer who can test those injectors and clean them.
2. I buy modified Delco spider assy from dr.injector in ebay.
These days when dollar is so low , dealer will probably charge more from work than a new assy would cost.
Why spider assy is modified? Was there problems with factory installed spider?

Blocked catalytic converter would be shown when emission test was done, wouldn't it??

Or is there any other ideas left?

Pull distributor and rotate gear/shaft one tooth clockwise.

I'm ready to do that next. I'll post back what happened...

I have this exact problem with my 97, did you find a fix for yours yet?

I removed distributor and checked that timing was ok. Put everything back and started it. This was couple of weeks ago. It has been working since.
I don't know where the problem was.
Before this I have changed plugs, wires and fuel filter.
Check distributor and basic timing. Change cap, plugs and wires if you haven't done this yet.
Hope it helps.

thanks.

It is a mystery, my mechanic says these trucks are known for uneven wear on the dis. cap, but he said mine looked OK, changed everything else already. I'll get him to change the distributor just to make sure.

cheers

thanks.

It is a mystery, my mechanic says these trucks are known for uneven wear on the dis. cap, but he said mine looked OK, changed everything else already. I'll get him to change the distributor just to make sure.

cheers
Not much mystery for a good tech/mechanic and proper testing.
Do not try throwing parts at it.
Proper testing is what it needs.
A good mechanic with a engine capable scanner and a fuel pressure testing gauge should be able to pinpoint the problem real quick.
Any check engine lights on or flashing light when driving?
Check for codes and engine running data and do not forget the basic tune up with good AC-delco parts.
It would be best if you started a new thread/post on yours and give us all of the info on it you can.
Year and engine and mileage.
And what all has been done or not done.
MT

I removed distributor and checked that timing was ok. Put everything back and started it. This was couple of weeks ago. It has been working since.
I don't know where the problem was.
Before this I have changed plugs, wires and fuel filter.
Check distributor and basic timing. Change cap, plugs and wires if you haven't done this yet.
Hope it helps.


The timing is not adjustable.
But the camshaft retard needs to be checked and adjusted if needed when dist is removed.
Has it been set or adjusted?

How is the fuel pressure running on the road?

Has it been put on a good engine capable scanner and checked for missfires or lean running condition?

Does the check engine light blink when it jerkes?

Try unpluging the MAF sensor and see how it runs.
MT

The timing is not adjustable.
But the camshaft retard needs to be checked and adjusted if needed when dist is removed.
Has it been set or adjusted?

How is the fuel pressure running on the road?

Has it been put on a good engine capable scanner and checked for missfires or lean running condition?

Does the check engine light blink when it jerkes?

Try unpluging the MAF sensor and see how it runs.
MT
It has been adjusted at least three times now.
Never tested fuel pressure when running on the road; I will do this if it starts to do it again.
I took this car to local dealer who is known to be the best here. They did testing: everything was ok.
No codes or engine light never.

OK, finally problem solved. I changed fuel spider assy with new modified part. Now it runs like a new. No jerking. Fuel economy better. Idling better...
Thanks to everybody...