My first post here, hope it works. I have a 1991 S-10, 4.3, TBI, 2 wheel drive, stick shift converted to an automatic. It started jerking on me about a week ago. It would only jerk once, about every 5 miles, and each jerk was harder than the one before. Then on 1-20-07 I drove it to the shooting range, it sat for 4 hours. Got in it to start it, and it cranked but wouldnt start. Did a little diag. and found the fuel pump relay was bad. Replaced the relay, and I had no problems with it for about 25 miles the next morning. Went to drive it that night, I got about 3 miles from home and it jerked real hard, 4 miles down the road it jerked again even harder. So I got home and checked the modulater on the distributor, found that to be bad. Replaced it, and pulled out of the driveway, stepped on the gas and it jerked/hesitated. Then every stop sign I came to, when I accelerated it would jerk/hesitate. Got it up to 55 mph and could fell it missing just very slightly. Checked the kv's and they were all within 3 kv's of each other. Asked a shop near by and they said to unplug the egr and drive it. That was no help. Then they said it was the tps. Replaced that, and now when its cold and you put it in drive and just sit there it acts like its missing pretty bad. When its warm and you accelerate from a dead stop it jerks/hesitates, or put it in drive and barely step on the gas while stepping on the brake it acts like its missing. I have 15 pounds of fuel pressure. Aslo I did a tune up about 8,000 miles ago (wires,cap,rotor,and plugs) Also I just replaced the temp sensor just for good measure. I also have sprayed the plug wires with water and found no arcing. Any suggestions. Thanks in advance for the advice.



I thank God for free sites like this!!

I see it’s your first post, so welcome to the message board.

It sounds like you have already eliminated several of the possible causes for the problem.

Here are a few thoughts:
Bad Ignition coil
Water in fuel

I have 15 pounds of fuel pressure spec is 9 – 13 PSI, but I don’t think high pressure is causing the problem.

Have you check the ECM for trouble codes? Do you need instructions on how to pull the codes?

ChevyTech: I put some HEET in a full tank of gas about 3-4 days ago. I used my snap on scanner and got a fuel pump relay code, but I imagine it was from before I replaced the relay. I will replace the coil when I get some money. Is there any way to check the coil?

I agree, the code 54 is most likely an old code, if it starts normally.

Is there any way to check the coil?

Here is a link that shows testing of the coil, but an oscilloscope is a better test and will show what the coil really has for output.

http://autozone.com/servlet/UiBroker?ForwardPage=/az/cds/en_us/0900823d/80/08/5c/0c/0900823d80085c0c.jsp

Edit: the above link is for full size trucks. The link below is for your vehicle.
http://www.autozone.com/servlet/UiBroker?ForwardPage=/az/cds/en_us/0900823d/80/12/a5/8c/0900823d8012a58c.jsp

ChevyTech: I am guessing I use the 2 wire connection port on the coil and not the other conection port, to perform the test. Also what does the link mean when it says infinite reading? Does that mean Ill get an OL on my meter?

I was probably editing the post when you were typing your response.

I am guessing I use the 2 wire connection port on the coil and not the other conection port, to perform the test. They are actually showing three separate tests – the #1,2,3 meters – step 1,2 and 3.

Also what does the link mean when it says infinite reading? Means the resistance is so high that the meter acts like it is not connected to anything.

It is possible that a coil can test good with an ohm meter and still have low output.

It is possible that a coil can test good with an ohm meter and still have low output.

Yes. Especially with the way they are saying to do it.

That link only tells you if there is an open or a short, it doesn't tell you if the coil is actually working right. For that you need to actually know the proper resistance readings of the coils.

The method they're suggesting to test the coil is like looking at your tires to check for pressure. Yes, you can see if they're flat or inflated, but there's no way in hell you can tell if there's 25 or 35 PSI in them. Same with that method of coil testing. It only tells you if it'll work or not. It won't tell you how WELL it's working.

And no, sorry. I don't have a way of telling you what the actual resistance readings are supposed to be. I'd have to find a known good coil and check it.

I was looking through my saved favorites this morning and found this:

http://shbox.com/1/coil_testing.jpg

This seems to be a very common problem with alot of TBI trucks, (both fullsize and S-10's).
I had a 90 S-15 Jimmy that had a similar problem but it wasn't hardly noticable. I sold it a couple years aago so I don't kow if it got worse or not.
Now I have a 93 C1500 TBI 350 and it does the it too.
Mine has a "surge" at light throttle and when you decelerate, (most noticable in town between stoplights or slower speeds).

I've changed just about everything I can think of, but so far the problem is still getting progressivly worse.
Changed;
Complete throttle body
complete distributer, (twice)
EGR valve
EGR solinoid
coil
temp sender
intake gaskets

My next attempt is going to be putting in a new timing chain. My truck has 375K so I'm sure a timing chain sure isn't going to hurt it but I don't know if it will help the surging problem.

I had a similar problem with our '96 S-10 4.3 4wd a couple of months ago. The brake booster had a vacuum leak in the diaphram. Problem was worse when warm, at idle, with foot on brake, then when you released the brake and accelarated, it would stutter, miss, & jerk until it gained rpm. Changed brake booster and it fixed it.
Easy check: Disconnect and plug vacuum line to booster. Do it while your parked tho!! Mine would smooth right out.
Cayoterun

Also pull the injectors out of the throttle body and look for corrosion on them. It does happen. Any moisture in the fuel lines or if it set for any length of time can cause it.

Kevin